Timing and Dieseling

Posted by: snowman4839

Timing and Dieseling - 08/22/10 06:19 PM

I'm trying to adjust the timing, idle mix, and stop my 250 from turning over backwards when I turn it off (diesel I think it's called). The factory says 33 degrees on the dwell and TDC for timing. I've tried setting it at 0 and 2 degrees advanced where it doesn't diesel much if at all but the mix screw has to be about 1/8 of a turn out of completely in for it to run well. Then when I set it to 4 degrees advanced, about a 1/4 of a turn is where it's best. But once I set it past 2 degrees advanced, it starts to diesel a lot. I've set it to somewhere around 12 degrees advanced (just a guess) and then I can turn it out about a full turn for it to run well. I've rebuilt the carb twice and double checked everything on the second rebuild. I've resealed the manifolds with a new gasket, replaced the internals of the dizzy and set the points to 30 degrees.

What should the timing be set at before it starts pinging? I use 87 octane.

Someone mentioned before that I needed to use an idle solenoid but I don't see how that helps. What's the point of the idle solenoid if I have an idle screw?
Posted by: snowman4839

Re: Timing and Dieseling - 08/22/10 06:58 PM

Also before I rebuilt it, the best mix was about 2 and a half turns out when it was 2 degrees advanced.

I also have the stock jet I had in it before I rebuilt it.
Posted by: Ken

Re: Timing and Dieseling - 08/22/10 07:19 PM

Sounds like your idle speed is set too high - that is what an idle solenoid does, it drops the idle stop to shut off fuel when the ignition is shut off.
Posted by: Ron Golden

Re: Timing and Dieseling - 08/22/10 07:22 PM

Dieseling is caused by the engine idleing too fast (throttle open too far). Advance the timing, then adjust the idle mixture screw for the best (smoothest) idle, then set the idle rpm lower.

The distributor mechanical advance, vacuum advance and carb idle adjustments respond together and any one of them can effect the idle and throttle response. Sometimes you have to modify one, or all, of them to get it to run right.

Ron
Posted by: snowman4839

Re: Timing and Dieseling - 08/22/10 07:23 PM

As expected, I just went out and moved the timing advance with a screw driver and it sped up.

It wasn't idling very fast, maybe 750

But wouldn't advancing it more than 4 degrees be dangerous to the engine and cause pinging?
Posted by: tlowe #1716

Re: Timing and Dieseling - 08/22/10 07:34 PM

I know you are new to alot of things mechanical. We never quit learning.
How exactly are you setting the timing?

It should go something like this.
1. Pull vacuum line from distributor and plug the carb end of hose.
2. Start engine and check timing with light. It should be idling and the timing # should be between 6-10 degrees BTDC.
3. When hooking vacuum line back up , the timing will go higher, maybe 20 ish.
4. Adjust idle back down to 750 RPM with idle screw and adjust mixture screw for highest idle and then bring idle back down with idle screw to 750.


Start with that. Tom
Posted by: snowman4839

Re: Timing and Dieseling - 08/22/10 08:05 PM

 Originally Posted By: tlowe #1716
I know you are new to alot of things mechanical. We never quit learning.
How exactly are you setting the timing?

It should go something like this.
1. Pull vacuum line from distributor and plug the carb end of hose.
2. Start engine and check timing with light. It should be idling and the timing # should be between 6-10 degrees BTDC.
3. When hooking vacuum line back up , the timing will go higher, maybe 20 ish.
4. Adjust idle back down to 750 RPM with idle screw and adjust mixture screw for highest idle and then bring idle back down with idle screw to 750.


Start with that. Tom


Well i'm not knew to mechanics, just to actually working on a car

I pulled the vacuum line but forgot to plug the carb.

I can't really read the timing marker though. I see an 'A' at one end and a '0' at the other but I can't see marks in between. Is 'A' 8 degrees or 4 or what?

When I hooked the vacuum line back up when it was idling, It actually went a little retarded.(toward the 0 and away from the 'A'.

I tried turning the screw out 2 and a half turns and then I set the timing in increments from super-retarded to super-advanced and it never did start.
Posted by: tlowe #1716

Re: Timing and Dieseling - 08/22/10 08:12 PM

There should be more #'s and dash marks on the timing indicator. Maybe take some time to clean it and look at it close with a light.
The 'A' stands for advanced, same as BTDC. That is the way the timing mark should go when hooking up the vacuum line.
Posted by: snowman4839

Re: Timing and Dieseling - 08/22/10 08:36 PM

Alright, I wire brushed it a little more and found some marks. Assuming that each one is 2 degrees. I set it to 8 degrees which is just before the A.

I also just tried the vacuum advance again and I checked the idle without it, plugged it in, and then checked it again and it was either the same or retarded a degree.

I also looked at the vacuum advance and I'm not sure if it's working correctly. At idle it doesn't look like it's doing anything and as soon as I give it maybe 200rpm more than idle, it engages fully. When not idling, it then either stays at the fully advanced position when opening throttle or it sporadically moves back and forth between full open and off when changing throttle position. Does this mean that the mechanical springs are off or something? Isn't it supposed to engage gradually as you increase the throttle?
Posted by: Ken

Re: Timing and Dieseling - 08/22/10 08:56 PM

Vacuum advance comes in when the engine vacuum picks up - doesn't matter what the engine speed is - the induction system will be subject to vacuum whenever the motor is not loaded - so off idle vacuum going to full stroke of the vacuum actuator would not be unusual at all.

The mechanical advance that comes in does come in as a function of engine speed and is completely independent of the vacuum advance function.
Posted by: snowman4839

Re: Timing and Dieseling - 08/22/10 09:06 PM

well I'm confused as to why even when I set it to 8 degrees advanced, it still only works when I have the idle mix is 1/8 out.

EDIT: I also just tried again and i can see how the timing gets way advanced when the vacuum kicks all the way in. I'm just confused because the mix is way off and it doesn't run very smoothly either.
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/22/10 09:59 PM

Is it possible to find or borrow another carb to fix your problem?

MBHD
Posted by: snowman4839

Re: Timing and Dieseling - 08/22/10 10:02 PM

well the point is to get this one working. I'm going to get the 4 barrel setup I told you about in the turbo build thread soon but I want to figure out the problem with this one. What's the point of having a defective item if you don't learn from it?

I just took out the idle mix screw and blew out the passages with compressed air and I saw some gas some out the top and saw some mist come out of some other part. Put it back in and it didn't do much. Might've added a half a turn out for best mix
Posted by: snowman4839

Re: Timing and Dieseling - 08/22/10 10:35 PM

Would something like metering rod adjustment or float height make a difference?
Posted by: panic

Re: Timing and Dieseling - 08/23/10 06:51 AM

What's the point of the idle solenoid if I have an idle screw?

What is your purpose: to get the correct answer, or to discuss the subject?
Posted by: Ken

Re: Timing and Dieseling - 08/23/10 10:05 AM

Snowman -

Tom's procedure is pretty good and should help you make progress.

Once you set the idle mixture screw to where the motor runs decently leave it alone and get your timing squared away - then adjust the idle speed screw for optimum idle speed and double check timing.

You should have no problem getting a 500 - 600 rpm idle speed unless you have a really lumpy cam and the motor will shut down nicely with the idle speed set this low.
Posted by: tlowe #1716

Re: Timing and Dieseling - 08/23/10 04:43 PM

I think the symptom of no vacuum advance and then it all comes in with another 200 rpm sounds like a vacuum leak. That will throw idle mixtures way off and produce no vacuum advance at low idle.
When idling to set timing with vac line off, does the line have vacuum? It should. Tom
Posted by: snowman4839

Re: Timing and Dieseling - 08/23/10 06:24 PM

Alright I made a video of what is happening to my advance when I rev the engine. http://www.youtube.com/watch?v=S--xJZM6tyc

Should I just re-re-rebuild the carb?

I tried Tom's method and the only problem with the procedure is I have to set the mix first and there's obviously something wrong with it because it runs best with an 1/8 turn out.

I set the timing pretty well because it barely pings on occasion

EDIT: Alright now this is just more F'd up than before. Now the idle mix screw doesn't really affect the idle at all and I just sprayed everything down with penetrating oil to find vacuum leaks with no success.

I also just looked at the advance and it doesn't move at idle whether it's plugged into the advance port on the carb or not

The last thing I was thinking of is the idle tube fits into the hole very loosly. If I remember correctly, it was pretty tight before. Would this let in extra gas?
Posted by: Sam Welch

Re: Timing and Dieseling - 08/23/10 07:00 PM

Does the dizzy need a new vacuum advance?
Posted by: snowman4839

Re: Timing and Dieseling - 08/23/10 07:10 PM

I'm not sure. Does it? look at the video. Is that how it's supposed to work?
Posted by: panic

Re: Timing and Dieseling - 08/23/10 09:05 PM

the idle tube fits into the hole very loosly. If I remember correctly, it was pretty tight before. Would this let in extra gas?

What's an idle tube?
Posted by: snowman4839

Re: Timing and Dieseling - 08/23/10 10:52 PM

http://www.walkerproducts.com/_pdf/rochester1barrel.pdf
page 16. Part 25

It's a small constrictive tube that sits in the fuel bowl that is supposed to suck in the fuel for the idle circuit.
Posted by: RichardJ

Re: Timing and Dieseling - 08/24/10 12:17 AM

Your vacuum advance is working properly.
You even have it connected to the proper port on the carb.
The correct port is called ported vacuum, which means the port is above the throttle blade. This port will have very low or zero vacuum when the throttle blade is closed. When you open the throttle (give it gas), this port will have vacuum and pull the vacuum advance, advancing the timing. Also, if you have everything out of adjustment and the idle speed screw is holding the throttle blade TOO far open, you will have vacuum on that port. This causes incorrect idle speed, incorrect idle timing and dieseling.
Many people incorrectly connect the vacuum advance to a manifold vacuum port that has vacuum at all times except of course WOT. Some people think they have to have vacuum advance at idle, BUT they have made other changes to their advance curve to compensate.

When you set or check the timing, pull the hose from the vacuum advance canister and plug the hose. Leave the other end on the carb and plug the hose at the canister.

As Ken said, idle speed should be 600 not 750. You can idle it down around 500, but make sure the oil pressure doesn't drop off when that low.

Set the idle mixture screw to X turns out. Yes, I said X turns. X turns out is the point where the rpm stays the same when you turn it out, but the rpm's drop off like rock when you turn it in. This is called lean roll.
This isn't a fixed adjustment
Use a tach for the mixture adjustment. When the mixture screw increases the rpm, use the speed screw to slow it back down. Finetune the mixture screw again.
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/24/10 06:38 AM

RichardJ,

Well spoken.

I was concerned he had the vacuum advance hose connected to full vacuum @ idle which someone stated that was the correct way to hook it up.


I think he needs to get that electric idle solinoid to work & that usually will kill the engine when the ignition key is turned off & really closes that throttle blade.
That should stop the dieseling.

He has a stick shift car/manual trans,500 RPM might be a bit low RPM for idle?

MBHD
Posted by: panic

Re: Timing and Dieseling - 08/24/10 08:59 AM

Ouch, thanks - I had a similar problem with a tube coming loose and floating around in my Buick Quadrajet!
Posted by: panic

Re: Timing and Dieseling - 08/24/10 09:10 AM

500 seems OK to me, if the cold idle speed is stable and the OP shows at least 10 psi.

In addition to the actual factory curb idle solenoid, which are pretty expensive new, you can bodge almost anything to work from another brand - all you need is to place the plunger (when extended) in-line with your existing idle stop screw, and slightly higher to raise the speed when the solenoid is hot.
You can use the really cheap (like $10.) 12 volt commercial surplus parts, but you want "push = hot" (not pull, unless you can make new linkage on the other side), and "continuous duty" since it will be hot whenever the key is on.
Here's a good pull type: https://www.surpluscenter.com/item.asp?item=11-3179&catname=

Now, the solenoid plunger is your new idle speed adjustment; if it's not threaded you can move the entire solenoid, etc.
Lower your original idle speed screw several turns, since it's now the "no air, anti-diesel" position with the ignition off.
Posted by: snowman4839

Re: Timing and Dieseling - 08/24/10 05:35 PM

alright well I'll look into getting a surplus idle solenoid

I just made a video of all the things I'm doing and what my engine sounds and runs like. It runs so choppily and I still don't have any idea what's going on. Just let me know what else you want me to film and I'll put it on. I just want it to run smoothly and have a smooth transition when I stop on it.

http://www.youtube.com/watch?v=FJOGxOfoiwA
Posted by: snowman4839

Re: Timing and Dieseling - 08/24/10 05:56 PM

Just looked at a cylinder firing by using a timing light and it seems to be constantly moving back and forth 50 rpms at idle.
Posted by: vanherk1

Re: Timing and Dieseling - 08/24/10 06:17 PM

I watched your video. Is the concern currently only with what you perceive as rough running? It will likely never run as smoothly as a newer fuel injected vehicle, if that is a basis for comparison. My 85 Jetta with mechanical injection runs smoother than my 64 GMC with a carb. That aside, have you ruled out mechanical issues-has the engine been rebuilt ever? If not, could there be cylinder sealing issues, or a burnt valve, or even a wasted cam lobe? Have you gone back to basics? When I diagnose a vehicle at work for driveability issues, even with a scanner, the basics apply. Do the cylinders have sufficient compression? Correct fuel pressure and volume? How strong is the spark? Is the coil on its' last legs? Check with a spray bottle filled with water and spritz the plug wires-you may have voltage taking the path of least resistance, i.e. to the block, instead of the plugs. Hope this doesn't cornfuse you more.
P.S.-When checking for vacuum leaks, I like brake clean. While much more flammable, it does have less surface tension, doesn't leave residue, and therefore is more easily ingested by a vacuum leak.
Posted by: snowman4839

Re: Timing and Dieseling - 08/24/10 06:30 PM

Well I'll try to go get some brake cleaner tomorrow then. It runs pretty rough as compared to idling at 800 or so. Is that just normal? Once it gets above 800 it just smooths out because you just can't feel the little bumps or is it because there aren't any bumps because the stronger suction makes the mix more constant and therefore stable?

No it's never been rebuilt but it only has 18,500 original miles on it. Some grandma used it to drive to church and the store iirc.

If you'll listen correctly, do you know what the whistling noise is in the video? It's very annoying and I can't hear it coming from any particular place

I also remember that it's run more smooth as silk before. I just don't remember what RPM it was idling at.
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/24/10 06:45 PM

I like to use starter fluid to check for vacuum leaks,but is very flammable.

MBHD
Posted by: snowman4839

Re: Timing and Dieseling - 08/24/10 06:52 PM

well brake fluid... starter fluid... i'll just check what's at autozone tomorrow

Also even when the engine is warmed up, if I floor it, it dies and then stutters to life. Is that just the idle set too low?
Posted by: vanherk1

Re: Timing and Dieseling - 08/24/10 06:55 PM

You might be just hearing air being pulled into the carb. 18, 500 by a grandma is almost as bad as 185,000 by a leadfoot. If that motor only saw city miles, there could be some carbon buildup internally. If the engine sat for a long time without being run regularly, there are other potential issues, like a valve sticking in its' guide, or stuck piston rings, or even corrosion on valve seats that can cause cylinder sealing issues. You're positive the odometer's correct? Also, one other note, don't always trust the rpm's shown on a (cheap?) tach-they can be inaccurate. 800 is a bit high, especially with an auto trans. Again, basics. Document changes as you go along, and go through things methodically. My last post is bare bones to getting something to run right. In response to your first question, the engine makes less suction, or vacuum, at higher rpm, and as rpm increases, the the mechanical defect usually is felt less exactly because the engine is turning faster. At least, that's what I think.
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/24/10 07:02 PM

I thought it is a manual trans car?
500 rpm seems a bit low for a manual 3 speed & poor rearend gearing.

MBHD
Posted by: tlowe #1716

Re: Timing and Dieseling - 08/24/10 07:51 PM

Don't have a 69 book, but do have a 71 book. Idle should be at 550 rpm. I would set it for 600.
The whistle could be a # of things.
#1 Vacuum leak (also causes weird fuel mixtures and missing)
#2 Exhaust leak. Had a guy bring a street rod to me. Said the new crate engine had a rod/ main knock and wanted it fixed. Turned out being a exh donut on sanderson headers. Sure sounded bad.
#3 put the air cleaner on. It is calculated into the mess by GM engineers.

By veiwing the vid, here are a few things. Slow down with the taping. I was trying to look at things in detail but you would not stay still long enough. Things like the firing order.
Your vac adv seems to work good. I like to see these inlines get 20-22 degrees adv idling. 8 degrees fixed plus whatever the vac can adds, which is around 15-20. My book says the 250 adds 23 degrees with 16" vac.
Is the timing vacuum port live at idle( sucking) or only when revved up alittle? I bet it needs it. Tom
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/24/10 07:54 PM

The timing port is working as it should,you do not hook it up below the throttle blade & produce full vacuum thus giving full advance @ idle.

MBHD
Posted by: tlowe #1716

Re: Timing and Dieseling - 08/24/10 08:20 PM

Why coundn't that be a option? My engine is very happy with 25 degrees at idle.

SBC and BBC use manifold vacuum for their dizzy's all the time.

I am going to have to check out one of those monojets to see the porting. Tom
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/24/10 08:30 PM

It's most likely 118,00 miles ,dont think grandma burned up the clutch in 18,000 miles.


MBHD
Posted by: RichardJ

Re: Timing and Dieseling - 08/24/10 09:25 PM

snowman, lets go back to the video and start all over. Just exactly where do you see 29 degrees dwell?? Between the focus and the jiggling, I couldn't read which scale was for 6 cyl dwell and I don't see a 29 anywhere. Try that again. The 33 deg and the video.
That meter has a low rpm scale that will be much more accurate than the incar unit.
Explain the deal with the duct tape on the manifold vacuum port that has nothing to do with the vacuum advance. Duct tape is not at all reliable for pluging vacuum ports when there might be suspicion of a vacuum leak. Get a rubber cap for it. Again, explain the deal with that port. Why isn't it capped? what was it used for if it was?

This engine should have "ported" vacuum for the distributor vacuum advance. It is sometimes called "timed" vacuum as "Mean buzzen" referred to it as.
We ask you pull the vacuum hose to the distributor and plug that hose so that there was not a vacuum leak while you were checking the timing.
Your video shows that you did not??????
Posted by: snowman4839

Re: Timing and Dieseling - 08/24/10 09:31 PM

Yes I'm positive about the odometer. The driver seat is in way to good of condition and the pedals aren't worn enough for 185,000.

How will I know if the problem is internal like valves sticking or stuck piston rings? Inconsistent compression test?

Should I take the head off and clean out the ports and clean out and reset the valvetrain?
Posted by: snowman4839

Re: Timing and Dieseling - 08/24/10 09:42 PM

Alright my dad helped me finally set everything fairly well.

Checked the dwell and set it to 32.5 degrees which is what the Chilton's book says to set it to

Set the timing to 4 notches advanced. I'm not sure if each notch is a degree or 2. Any more advance causes backfire when I gun it (WHY?!?!?!?!) which is strange because it didn't do that before when I had it around 8 notches advanced. I plugged the vacuum advance when I did this.

I then checked the mix and plugged the vacuum nipple and timing advance nipple. Set the mix (best is still 1/4 out which is still puzzling). And it runs pretty well now.

The duct tape was a rudimentary vacuum port plug. Now I just use a rubber hose plugged with a screw.

I set the idle at 750 or 700. It is supposed to be 700 according to the sticker on top of the radiator shroud.

TO BE CLEAR... there is NO vacuum advance when the car is idling. it engages at around 1000 rpm while my idle is et at 700 or 750.

It's a manual trans car. 3 speed on the column with what I believe to be a 3.23 open diff.

I'll make another vid tomorrow when it's light out and show you guys how well it runs now. I'll also go over the dwell setting, rpm (on the engine analyzer, not on my little tach), carb mix, firing order, etc...
Posted by: vanherk1

Re: Timing and Dieseling - 08/24/10 10:25 PM

Poor valve train condition can be noted with a vacuum gauge, which would show erratic engine vacuum.
Posted by: vanherk1

Re: Timing and Dieseling - 08/24/10 10:26 PM

My mistake.
Posted by: JimW

Re: Timing and Dieseling - 08/25/10 02:17 AM

Snowman,
If you want to try another carb, then send me a PM and I'll send you one. I have my original monojet, rebuilt, that worked great before we began our build (you can buy it, try it, or send it back depending on how it works out).

Removing the head is a great idea if you have the time and the money to go over the head. But if you are concerned about a mechanical internal component issue, then I would recommend a compression test and cylinder leakage test when the engine is cold and again when the engine is hot. The tests are cheaper than head work (especially if all of your problem is either fuel delivery or ignition related.)

Good luck

p.s. - think HEI
Posted by: Titen

Re: Timing and Dieseling - 08/25/10 09:07 AM

'Ported' vaccuum advance is a product of the emmission laws, before the later '60s all vaccuum advance was full manifold vaccuum, either taken from the intake manifold or a carb port on the engine side of the butterfly.

The ported vaccuum is to defeat the vaccuum advance at idle, this, along with retarding the initial mechanical timing was supposed to lower the combustion temperatures, thus lowering NOX production.

For those from California that are old enough to remember the 'NOX Device' mandate for pre '66 cars when the smog checks started (this entailed disconnecting and plugging the vaccuum advance, retarding the timing, and putting a 'NOX' decal on the air cleaner) you know about the crappy running, overheating, and other problems this caused. The mod usually lasted long enough for an inspection then was put back to normal by the owner.

That being said... Snowman, if you are not going to fix your curb idle solenoid, you can rig a throttle stop the same height as the solenoid would be when extended, then your butterfly will be correctly aligned in the venturi (after backing off your curb idle screw and setting it correctly of course) then your mixture screw should be back to normal function.

I am a believer in full manifold vaccuum advance and running as much initial advance (like 10-12 degrees) as makes the engine happy, however, the smog carbs are jetted and calibrated for ported vaccuum so that is what you should probably do.

I have been working on cars for over 50 years, all I can say is this is what has worked for me.

Tim
Posted by: snowman4839

Re: Timing and Dieseling - 08/26/10 05:36 PM

Vanherk1
I'll try to get a vacuum gauge from autozone. I'm hoping they loan them out but I might have to buy one.

JimW
I'll try to see if autozone has a cylinder compression tester also because the one my dad has doesn't fit into my spark plug threads.
Now that I think about it, I have to start driving to school in a month and I still need to fix my glass channels, weld in a replacement strip of metal for a rusted through part in the back channel, clean and primer, reseal, and put the windshield and back glass in.
I'll keep working on my cab but if all else fails, I'll PM you. I don't want to waste your time

Tim
I'll try to rig a idle solenoid setup. I just want to see if it overruns when I get all of my settings correct

NOW FOR MY FINDINGS...
I just went out and I must admit, I feel retarded. It turns out the PCV hose that goes into the middle runner of the intake manifold didn't seal all the way around (even though I had a tightened clamp on it) so I just put a rubber suction cup upside down on it and it sealed off completely. The other problem was the vacuum nipple (not the timing advance nipple), wasn't sealed off completely either. I used a screw inside of the rubber vacuum hose which I thought would seal it off. I did a test (put my mouth on it sucked, and see if it would hold on my tongue) and it turns out it didn't hold hardly anything. I just took out the screw and clamped it closed. So now no vacuum leaks!

I also took out the coil and cleaned off the dirt and grime and whatnot to make sure it wasn't grounding out. It didn't do much

I then set the advance to about 8 degrees advanced. The best mix is still 1/4 turn out though. It will now idle relatively steadily at about like 400 or 450. It still rocks a bit though every few seconds WCHIH IS REALLY ANNOYING. It just seems like it just doesn't fire for a split second every few seconds and just sends a vibration through the car. And it does this from 450rpm all the way through 1000rpm
Posted by: snowman4839

Re: Timing and Dieseling - 08/26/10 05:38 PM

I'll also try to post a youtube video of my progress, how it runs, and what's happening and what I've done.

I know I told you guys I'd do it yesterday but I've had school and driving school which is 9 hours out of my day so sorry about that.

Something else I'm also somewhat concerned about is a fair amount of white smoke comes out of my PCV valve on the front of the engine coming out of the valve cover. Is that burning oil or is that normal?
Posted by: tlowe #1716

Re: Timing and Dieseling - 08/26/10 06:33 PM

The white smoke is condensation steaming off. That stuff will accumulate in your motor if it does not get hot enough to steam out. It can cause corrosion and your oil to break down. Excessive idling and multiple cold starts will make it worse. You will be fine once it gets driven regular.

Glad to see the progress. Keep it up. Tom
Posted by: snowman4839

Re: Timing and Dieseling - 08/26/10 07:20 PM

Thanks Tom.

The other thing is that even after all my discoveries, it still backfires when I floor it. It is set at factory dwell, 8 degrees advanced, and the mix is still pretty good. But when I floor it, it sputters and either dies or it backfires through the carb. I can't understand why it would do this because it didn't do this before I adjusted the dwell, timing, and mix. I guess I have to just play with the settings? or is there a specific reason for it doing that?
Posted by: Ron Golden

Re: Timing and Dieseling - 08/26/10 08:03 PM

The stumble/backfire on hard acceleration is caused by not enough accelerator pump "shot". In other words on hard acceleration the engine gets a gulp of air before it gets fuel. This results in a lean condition and the engine will stumble or backfire. The accelerator pump is suppose to supply extra fuel on hard acceleration to eliminate the lean condition.

With the engine SHUT OFF, look down into the carb throat then open the throttle quickly. You should see a solid squirt of fuel.
Sometimes you can adjust the carb linkage to increase the pump
"shot".

Let us know what you find.

Ron
Posted by: snowman4839

Re: Timing and Dieseling - 08/26/10 08:25 PM

Haha well... I just got in it. It was already warm from working on it before and...

NO BACKFIRES AT ALL??

I just floored it about 12 times from idle (450rpm) and it didn't backfire once... maybe my cap on the middle runner was loose and it caused lean misfire? I'm not sure.

I definitely knew that my accelerator pump was working but I just double checked it anyway. Yah there was a nice healthy pump of fuel.

What's the best way to keep that middle intake runner closed? That PCV tube with a clamp obviously doesn't work but I don't want something as permanent as JB Weld.

Lastly it still rocks at idle WHICH REALLY BUGS ME. So hopefully when I test the compression and manifold vacuum, I'll see problem.
Posted by: RichardJ

Re: Timing and Dieseling - 08/26/10 11:16 PM

If you idle it down too low, you will not have sufficient oil pressure. Without having a oil pressure gauge to know, you need to get it up to 550 to 600.

You capped off the vacuum source on the intake manifold for the PCV system and now the engine smokes. Connect the dots.

That rubber hose on the front, side of the valve cover looks short, but it should have connected into the carb air cleaner. Is that not correct?

At idle the PCV system should have a slight vacuum on that hose, drawing fresh, filtered air from the carb air cleaner. Air enters the engine through that hose, collects the crankcase fumes that you saw, goes through the PCV valve into the intake manifold and the engine burns the fumes.

If the PCV hose is bad, replace the hose.

You say it idles best when the mixture screw is 1/4 turn out. What exactly happens when you turn the screw out an additional 1/4 turn?? What exactly happens when you add another 1/4 or 1/2 turn to that and it is at one full turn out????
Posted by: snowman4839

Re: Timing and Dieseling - 08/26/10 11:44 PM

 Originally Posted By: RichardJ
You capped off the vacuum source on the intake manifold for the PCV system and now the engine smokes. Connect the dots.

That rubber hose on the front, side of the valve cover looks short, but it should have connected into the carb air cleaner. Is that not correct?

At idle the PCV system should have a slight vacuum on that hose, drawing fresh, filtered air from the carb air cleaner. Air enters the engine through that hose, collects the crankcase fumes that you saw, goes through the PCV valve into the intake manifold and the engine burns the fumes.

If the PCV hose is bad, replace the hose.

You say it idles best when the mixture screw is 1/4 turn out. What exactly happens when you turn the screw out an additional 1/4 turn?? What exactly happens when you add another 1/4 or 1/2 turn to that and it is at one full turn out????


Alright well why would it matter if the valve cover has vacuum if it is vented into the air cleaner assembly (where it would have slight vacuum anyway)?

It gets too rich when I turn it out and the engine slows (and dies if I turn it out more). If I turn it in, the engine leans and almost dies (unless I turn it in all the way and then it either runs awfully or dies).
Posted by: Titen

Re: Timing and Dieseling - 08/27/10 09:11 AM


'Alright well why would it matter if the valve cover has vacuum if it is vented into the air cleaner assembly (where it would have slight vacuum anyway)?'

Snowman, It is becoming apparent that you are not familiar with the way all the systems work and interact with each other, and are not willing to take the time to learn.

The PVC (Positive Crankcase Ventilation) system, takes filtered air from the air cleaner (the larger hose), which is drawn thru' the engine and regulated by the PCV valve, into the intake manifold (the smaller hose), or base of the carb in some applications, thus purging the oil and combustion bypass fumes into the intake and burning them in the engine, thus eliminating the blow-by being vented into the atmosphere.

This process is engineered by the auto manufacturer, regulated by the PVC valve, and the carburetor is calibrated to take this extra air/fume flow into consideration. Just removing the hoses and plugging them, without realizing the effect, doesn't accomplish your goal.

The same goes with the carburetor. The anti-dieseling solenoid was put there because in order for the engine to pass the pollution standards the compromises needed (retarded timing and leaner fuel/air mixture) caused the run-on when the engine was shut off. So this solenoid, which when energized, positions holds the butterfly in the correct configuration for normal operation, was incorporated to shut the throttle plate (butterfly) completely allowing the engine to die in a dignified manner without bucking and snorting when the ignition was turned off.

By just removing it, or allowing it to stay in the non-energized position, you don't have a stop for the idle speed screw to properly locate, which in turn is more than likely responsible for your mixture screw adjustment problems.

You will not cure the run-on without fixing everything back to factory stock, or getting another model carburetor that you can work with. I have tried redoing these carbs, it is not worth the trouble.

If it ran smoothly before you fixed it, there is probably nothing major wrong that you cannot figure out. Just go step-by-step on what you did and it will come to you.

Please read thru this post a couple of times before thinking I am being a jerk, I'm just trying to help.

Good luck,

Tim
Posted by: RichardJ

Re: Timing and Dieseling - 08/27/10 10:14 AM

What is with this continuing discussion about an idle solenoid?

He has not mentioned any dieseling or run-on since the very first post.
The videos are not great, but I cannot see that it ever had one. It's a '69 and the only emission system visible is a PCV system.
I don't recall any '60s engines with idle solenoids other than small displacement engines with Air Conditioners. They operated only when the AC was on to keep the engine from stalling at stop signals because of the then high compressor loads..

Idle solenoids were common in the late '70s when the engines had multiple EPA mandated emission systems and brand new engines couldn't run without one.
Posted by: Titen

Re: Timing and Dieseling - 08/27/10 11:42 AM

This discussion has been going on since June and is spread out among several topics. If you want to get the big picture do a search for topics by snowman4839, read all the posts and maybe you can come up with an answer to his dilemma.

Tim
Posted by: panic

Re: Timing and Dieseling - 08/27/10 12:23 PM

His dilemma is rather obvious, and encouraging his "eagerness to earn" is called "enabling".
Posted by: snowman4839

Re: Timing and Dieseling - 08/27/10 04:13 PM

Titen - I am VERY willing to learn. I wasn't trying to say that you're a jerk, I'm just asking a simple question. I'm not very familiar with PCV, I know that it is the pressure that slips past the pistons that needs to be vented out of the crankcase. Hence crankcase ventilation. I'm sorry if I came off rude.

RichardJ - Yes you're right. I haven't mentioned my dieseling since the first post because when I've had my mixes set well, it caused little to none. I'm thinking it was because of the air/vacuum leaks. But I should have fixed that. The engine originally did have an idle solenoid however but there's more about it in my video.

 Quote:
His dilemma is rather obvious, and encouraging his "eagerness to earn" is called "enabling".

Well I'm SORRY if my attempts to learn are aggravating you. I just want to speak to people who know about these types of engines and while my questions may sometimes be elementary, the few sentences that you guys type give me a thousand ideas.

I made a new video of my progress. http://www.youtube.com/watch?v=JzJME-XLUW4

EDIT: And I'll be able to provide more information and not seem nearly as stupid when I'm able to drive. I'm basing all of my results on it idling in the garage.
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/27/10 04:38 PM

You just need another carb, so you can adjust the mixture screw.
Turning the mixture screw more than 1/4 turn out & the engine will die,,,your carb is messed up.
Get another one & try it out.
Go to a junk yard & find one,ask members here if they have one for sale,borrow,, etc.

MBHD
Posted by: snowman4839

Re: Timing and Dieseling - 08/27/10 04:40 PM

I understand that buying another carb would fix my problem. I just want to understand what is wrong with the one I have.
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/27/10 04:53 PM

Thats fine,but in your case, you should have 2 carbs,one to play with & 1 ,not to mess with,so your ride will be ready to drive @ any time & have no down time.

Basically saying,practice on things where it does not matter if you mess it up.


MBHD
Posted by: RichardJ

Re: Timing and Dieseling - 08/27/10 05:48 PM

That idle solenoid may have been on the car, but it is hardle likely that it was original. Look on the Walker Products link you posted, pdf page 17, Rochester 1-ME,1-MV. Part #1 is the solenoid, #2 is the solenoid spring and straight to the left is a threaded hole in the carb body.

Here is a picture I found, of one with an electric choke just above the solenoid. That is how original solenoids were mounted.
[img]http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=523294&stc=1&d=1260657481[/img]
( Sorry picture won't load. Must be protected )

What is wrong with the carb you have?? Good question.

Everything you have read about adjusting the carb mixture screw needle, said to lightly seat or turn the needle until it lightly bottoms and then back out 1 1/2 turns or some number. The important word here is lightly.
The carb body is very soft. If the needle is seated too many times, it can damage the seat. If the needle is seated too tightly, it can damage the seat. If the needle spring prevents you from feeling when the needle has bottomed out, you can damage the seat.
I fear "Mean Buzzen" is correct and that 1/4 turn is saying the seat is badly damaged.

I would do one thing before I bought a new carb. Spray "Carb & Choke Cleaner", all around the intake manifold and carb base to make absolute certain there are no more vacuum leaks.
I like carb cleaner much better than brake cleaner or starter fluid. It's not as messy, not as flammable, cheaper, and isn't as hard on paint.
Posted by: tlowe #1716

Re: Timing and Dieseling - 08/27/10 06:09 PM

Snowman,
Good job! It sounds great. Sorry to hear about the tach/ dwell meter. We have all been there. Better it than you!

I think Titen is fine with you being on here, I am. He just is one ornery old cuss. (JK)

With the work you are learning lots. It is good to get a grasp on how the different systems work together, even on a old car like this.
For a 15 year old, I am impressed.

Main thing is, when you start driving that car. You will be watched likea hawk, that car will stick out like a sore thumb compared to modern stuff (both good and bad). Cops will remember it. Be safe with it.
That engine runs good, wait till you test drive it before getting any carb. I have lots of never to be used 1 bbl carbs.

Also be sure to look over all the brake lines on that 40+ year old car ( both metal and rubber ones) they will kill you or someone else. Tom
Posted by: snowman4839

Re: Timing and Dieseling - 08/27/10 06:45 PM

richardJ - Alright. I've been waiting to find the time to go to autozone and try to buy some type of solvent to test for intake leaks.
By "seat", do you mean the end of the needle? or the threads that the needle screws into or what? If it is the latter, then I guess I would need to get a new throttle body in which case, I might as well get a new carb. If you mean the end of the needle then would understand the problem because I would've smashed the end of the needle and then it wouldn't make a complete seal.

Tom - Thanks. I'll definitely keep my wits about me when I first start driving. The cops in my city are notorious about profiling teens and blacks.
I'll try to give the brake lines a look-see next time I get the chance.

I made another video on what I'm doing to adjust the carb but now that you guys mention that there's probably a problem with the mix screw seat, that sounds more like the problem. http://www.youtube.com/watch?v=-h3Y0rGEUSs

After the video, I blow out all of the passages with 120psi of compressed air, adjusted the metering rod all the way down, and then put the top of the carb and it started overflowing??? I'm confused as to why because I didn't touch the float besides pulling it out to work on everything else and put it back in. I got it to stop overflowing by bending it to where I'm pretty sure it doesn't even allow the needle to allow fuel in but why would it have done that? Could I have damaged the needle seat threads or something?
Posted by: Ken

Re: Timing and Dieseling - 08/27/10 08:29 PM

snowman - if there is any debris / dirt in the float needle seat, it will not seal.

If you do not have a GM manual for this engine / carb - you would save yourself a lot of headaches by getting one. It will show you how to measure / adjust the float height.

Kudos for digging in and working on this at the ripe old age of 15 - I was tearing apart quadrajets and working on small blocks when I was your age and I learned a lot but like you - often didn't have good instructions or know the proper processes and I managed to dork a few things up along the way.

If it were me at this point - I would be saving for a new carburetor for this motor - there are lots of options and your best bet is to buy a new replacement model that has good instructions and a good reputation for performance and reliability.
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/27/10 09:47 PM

I think your carb "idle tube" being loose will cause your engine to be rich. Not good.

IIRC,float adjustment is not taken from the bump on the float,just the flat area.

Carb rebuild instructions should show pics,no?

Needle & seat had a piece of debree & caused your carb to overflow w/fuel.

MBHD
Posted by: JimW

Re: Timing and Dieseling - 08/27/10 10:56 PM



Needle & seat had a piece of debree & caused your carb to overflow w/fuel.

MBHD [/quote]

X2 - hopefully it will clean up with carb cleaner and the overflow problem will be over.

But that problem brings up some food for thought. Any car with a carb can have the 'overflow' problem - do you have a fire extinguisher in the garage? I'd even advise to keep one in the trunk, mounted of course, once you get it on the road. I'm sure that some/many/most of the guys helping you out on this forum have had a carb fire at some point. And the straight six GM with carb directly above the exhaust manifold is susceptable to a problem.


I'd hate to see you have a disaster, especially with that Buick - that is a GREAT car in GREAT shape ;\) - I love Buicks (I'm working on a '64 Wildcat presently.) I've been looking for a Skylark or Special, but none of them in Northeast look like yours.

T Lowe is right - drive like an adult and be safe, and do me a favor - get an extinguisher.

Be safe and think HEI!
Posted by: snowman4839

Re: Timing and Dieseling - 08/28/10 06:42 AM

That's what I thought. I just rubbed off the end of the needle and put it back in and it stopped overflowing (but the float adjustment probably stopped the flow as well). I remember that happening a few times.

Don't worry, I'm quite experienced in carb fires. I've had one notably large one where I was actually freaked out enough to run and get the fire extinguisher. We keep one in our pantry which is about 7 steps from me standing next to the car to be in front of and takes about 5 seconds to get.

I've looked at the rebuild instructions and the exploded diagram is good enough for disassembly and reassembly. It's just that the directions for float and metering rod adjustment and whatnot are not very clear. I get the general idea of what to do to adjust it but the picture they provide to help you further isn't clear. I'll try to get a picture of it on here.

For those of you guys suggesting HEI. Don't worry. That's in my gameplan. I have a thread called "Snowman Turbo Build" or something that MBHD started in the turbo section which lists my projected mods. Why are you guys suggesting this so much? Does it just provide a more stable tune or more accurate and consistent spark or what?

I'm not going to buy another single barrel because I've also listed in that thread that I"m planning on getting an offy 5416 (4 barrel intake) and a 500cfm or 600cfm 4 barrel for my turbo setup. If it gets bad enough to where my Rottenchester monojet becomes unusable, then I'll just try to get the offy/4 barrel setup to work. It's just depressing to me because I wanted to keep all of the stock things on my car in working order in case I wanted to return it to stock. Now the carb is out I guess...
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/28/10 08:16 AM

A better fire extinguisher (less messy) are the Halon type .
They do not leave a corrosive chemicle behind that you need to clean up when used.

Halon type extinguishers cost more but a lot less mess.

The HEI is suggested so much because it is a better distributer than points.
Creates a hotter spark,pretty much maintenance free,no crossfireing w/that large distributer cap,more water proof (when steam cleaning engine) etc.

When the points distributer shaft bushings & shaft wears,that will make your dwell change,dont have that problem with dwell change w/an HEI.

W/an HEI, you just get more consistant spark.

I run an HEI on my Syclone & so far run up yo 25 psi,w/no spark blowing out yet,but I do run an MSD 6 box,I am sure that helps.

I always ran .035-.040" gap & ran up to 22-23 psi,never missed a beat.
It's not only till now I will close the plug gap to roughly .026",just because I will be spraying a lot of methanol & am increasing the boost pressure.

I have the gap now @ .030" injecting meth & running 23-24 psi & it has not missed yet,just want to play it safe.


MBHD
Posted by: snowman4839

Re: Timing and Dieseling - 08/29/10 11:20 AM

Alright. That's what I thought HEIs did.

Now onto the carb (again). I just completely removed the idle tube and it would still run as if it had the idle tube in there. I'm pretty sure gas is getting around the idle tube hole in the bottom of the fuel bowl instead of actually being pulled through the idle tube which is making it run wayyyy rich.

My dad's friend came over yesterday because he's going to reproduce a very unique emblem that goes on my dad's car but there were less than 500 originally badged and they don't make repros. I got to asking him about the carb and he cleared some stuff up for me and I was doing mostly everything right. I told him about my idle tube problem and he said that since he can use a machine shop (i'm not sure if he owns one or works at one or what), he'll produce another idle tube that fits snuggly into the orifice. Hopefully that'll seal it up and fix the idle mix problem. If that doesn't fix it, I'll just try to get a new idle mix screw.

I'm still confused as to what you mean by the seat? I replaced the NEEDLE seat, the needle, and needle seat seal because they came in the rebuild kit.
Posted by: Mean buzzen half dozen A.K.A. Hank

Re: Timing and Dieseling - 08/29/10 11:51 AM

Just go get another carb.
Tlowe offered you an assortment of carbs to you,probably for a good price. Quote:" I have lots of never to be used 1 bbl carbs"
Post #60084

Another member here offered to send you a working carb.

Throw that junk carb to the side (& play w/that to your hearts content) & use a known working one.

Sometimes,a carb will just go to junk after a simple rebuild.
Caused from a simple piece of debree stuck in a passage that just will not come out no matter how many times you carb dip it,blow it out w/compressed air,,believe me ,it happens.

My two cents thrown.