Inliners International Forums General Discussion Engines Everyone who's running a 500 cfm Edelbrock....????

I was wondering if any of you guys had the spec's on the metering rods your running in your carbs on 250/292's.

I put a Clifford 4brl manifold and a 500 CFM Edelbrock on my 250..........I didn't want to fiddle with it until I finished the truck the engine is in and tried it on the street. Well, I finally took it for a drive today, It was idling rich, I knew that from running it here at the house, but right in the middle of the rpm ran it seemed like the power was killed and it didn't have anything left from their on up as it, and it didn't have the power the stock setup had. I was wondering what you guys might think the cause is..........Too much fuel or not enough? Ignition Timing? If I bought the spring/rod kit for this carb would it have what I need to tune it right? Or do I need other rods/springs?

I am a newbie to tuning a 4brl :rolleyes:

I am pretty sure you can buy a jetting/metering rod kit that Edelbrock makes.
I see P.A.W. sells kits.Several ones.
www.pawengineparts.com

I bought one when Carter used to make them.
What type of build do you have?
Stock, big cam????

Engine is stock for the moment other than those pieces.........Not sure where I want to head yet.

If you are running your stock cam with that carb and intake then thats definately part of the problem. I would try and eliminate some of the possibilities you mentioned before you try to tune the carb, that way you know what direction to tune in. If you were getting way to much fuel it would likely smoke some or color the plugs. I would look into the timing or mabye too little fuel. Just a guess though.

Personally ,I would sell the Clifford intake or take it off for now & install a Offy intake.
Much better throttle response.

I don't think the setup is the problem........Fuel issues are my thoughts by the way it is acting.......I might try some larger rods in it. Seemed like it is running rich......I thought maybe one of you guys may have been running a similar setup and could point me in the right direction as far as what metering rod to run. I do know it is rich on the low end, probably on the high side too......I guess I'll have to play with it.

I run a Clifford myself and they don't make the same low end torque as the Offy, they are set up to flow big air so the advantage they have is in higher rpm range. I love the Clifford, it gives the engine a totally diferent sound than the offy when you are at high rpm. As far as the fuel goes you may be right, the setup you are running is often too rich, still it is better to know you are too rich and then go leaner than to go leaner on a hunch when you may already be lean. So far we only know that the idle circuit is rich.

I think it is easier to jet the carb w/a Offy intake.
A few guys here has simular problems running a Clifford intake until they put heat to the manifold .
What jets are in the primarys now?
What are the metering rod numbers?
Try going two steps leaner on the primary jets to see if it runs better/leaner.

You are not going to hurt it if its too lean.
Unless you just have it wide open for a long period of time.
Even then ,it probably won't be too lean because your secondary jets are probably too rich also?

Go & put some leaner jets in the primary side.
Put the car in park ,bring the RPM's up to say 3000 & see if it surges up & down in RPM,or it feels hesitant to go higher.
If it does surge ,you are probably too lean.
Go back one step richer in jets (higher number)try it again.
Every engine runs different so it is hard just to tell someone these jets are perfect, run these.

The metering rods should have three steps in them.
Skinnyist, is your wide open throttle. middle is your mid throttle position,fattest is your idle.

You can measure these rods w/a mic, or a dial caliper.
So if you want to run leaner @ idle (the fattest part ,try & get a rod a little fatter ,a few .002-.005 range .
Metering rods are going to be more $$ but it is easier to take out & put back in.

Also keep im mind that the spring you choose for the metering rods can really effect how rich or lean you are. If you have a strong spring installed but have low vacum off idle you will likely be way too rich way too early. You may need weaker spring. The calibration kit has several springs to chose from. Good luck

Get the Edelbrock tuning kit mentioned.In addition to PAW or Summit, any auto supply/ speed shop who sells Edelbrock carbs should be able to order one for you.It has instructions that will help you decide which way to go. Sounds like to me changing the spring to a lighter spring would help.While both intakes do have different tuning characteristics on the upper end I have found the low speed tuning very similar on both Intakes. Once the carb is dialed-in,I think you will find changing the timing a degree or two one way or the other will make a world of difference. Paul

Guys, I bought the carb used off a running SBC.........It came with a spring kit, but doesn't have metering rods.

Should I try them first? Would they help the issue if I am rich on the top end, or through the entire power band?

I didn't touch the carb when I bought it because I wanted to try it first and go from there, but I figured it would need help.......I am going to pull it off and write down all the #'s and mic the metering rods.

Just wanted to thank you for your help so far, the manual Edelbrock supplies doesn't explain much to someone like me who hasn't played with carbs other than rebuilding the stockers and you guys sure make understanding the setup alot easier.

You have a stock cam, so I would think your vacuum @ idle is about 18 inches or so ?
So I would think even the stiffest springs would not cause it to run rich.
Changing the metering rods is the easyist to do.

If you really want to dial it in,, you could buy a wide band O2 reader.
I use the Innovate LM1 works great.cost 300-350 range.

If you have a vacuum gauge run a line inside your cab and watch it while you drive. I believe the stock Edelbrock spring starts to lift the rods around 6hg. You may find out in the end that you need to change rods jets and springs. Thicker mertering rods is as good as any place to start. Just take your time and make sure you only do one change at a time. If it gets better then keep tunning in that direction. That way you won't get too confused. Even when used on the V-8's they are designed for most carbs are almost never perfect right out of the box.

I had a similiar problem when running my edelbrock 500 cfm on my Clifford intake on my 250. I bought a metering rod kit and springs and tried all combinations of rods and springs and jets, but still the motor would bog badly when I put my foot in it. The solution was to replace the Clifford with a heated Offy. The throttle response is much better and so is the gas milage. I also went to a one stage leaner rod. I agree with Diesel Dan in that the Clifford had a much better sound, but the Offy performs better on the street.
Al

This is why I'm always telling guys That the OFFEY Is more for lowend to MId range Which Is VERY good for the street/Daily drivers.
The Clifford is more for Mid to Upper Rpm. Especialy when running a stock Or close to a stock cam.

I see 2 problems. The first one is what everyone else mentioned and the Clifford manifold is just not going to work well on a stock 292. The second is how the fuel is being handled by the carb. Since it came off a small block Chevy that narrows it down to something between a 265 inch and a 400 inch engine not even considering any performance work done to it so is the carb "as is" as it came out of the box, or has it been tuned by the previous owner? Either way you need to begin with the factory Edelbrock set up and then follow their tuning charts in the manual. The manual can be downloaded from their web site.
Generally speaking from all my experiences with those carbs about all you need to change on the primaries for a stock 292 on a decent manifold is the metering rods and maybe the springs when the rods are right. But if the carb has been changed by the previous owner you really should go back to square one before attempting any tuning because the booklet begins at that point. I have run the 500 on as small as a 200 cube Chevy V6 with only rod changes and of course secondary jet changes.

Heat might help the Clifford somewhat but I don't believe it is the real answer in your case.

Guys this Clifford is heated..........Carb was on a 305(I thought it should have been tuned pretty close from a CI point of view), but I guess I was wrong.

It starts/idles great in the cold(was in the low 30's here this morning when I moved it to get a tractor out)..........Other than it running rich at idle I'd say it is ok there.......If I got the dead spot out of the top end I'd be happy. From what I can see I'll order a rod kit and go from there. I got the Clifford on and I really like the look of the whole setup when I pop the hood, and don't want to get rid of it

TP, I'm on the 67-72 truck board and have the same truck! I'm running the Offy manifold (non heated) with a stock out of the box Edelbrock 500 carb. I tried jetting down, I tried changing the rods, but it all made it run worse so I went back to the stock configuration. I took it to the DEQ and I was well within specs and it runs like a champ. I would be happy to guide you to stock carb specs and I even have my old rods and jets if you want to try those. Check your timing and make sure it's properly set. Also, make sure you use a vacuum gauge when setting your carb. If you need help with that, just ask. Again, I'd be happy to help-just PM me through the other board. We'll get you up and running!

Thanks Brad, I may give you a yell when I get back to work on it..........Been busy picking corn at the moment, so I haven't had enough time to do more than look at it when I leave in the morning and come home at night in my Cummins powered truck.

I had the timing set as the book spec'ed it, but it didn't seem right so I turned it a tad more and it seemed to run better. I need to play with it more. My book called for 4 deg. BTDC........But I have heard everything from that to TDC.......Where do you have yours?

I think I have mine at about 10* BTDC IIRC, but I'm running HEI. You can only go to about 4-6* with points.

I pulled the carb off today to go over it entirely.........Float was a tad off(Maybe causing the rich problem at idle), and I found that it has the stock rods in it(#6552) and jets are stock(.086" main #1423). I also moved the pump rod one hole towards the carb body, to see if it helps my hesitation on the top end.

My question is the setup springs.......I did get a set of them with the carb, and the ones in it now seem pretty weak. Would weak springs cause the lack of power on the top end? From what I can see in the manual, a stiffer one would help hold the metering rod up. What do you guys think?

Weak/ soft springs are for when you have low vacuum produced from your engine. So it will be on the idle part of your metering rods.
What is your vacuum @ idle.
If you have stiff springs, as soon as you get low vacuum signal, your metering rods pull out of the main jet quickly causing it to get rich quickly.
When you are floored, you should have no vacuum,causing your metering rods to pull out of your main jet.
When you take the metering rod cover off,, does the little piston attached to the metering rod touch the cover?, Does it pop up out of the hole?

Now, if you take the metering rod cover off & you see the piston down in the hole,, then the spring is probably cut. Should replace them (springs).

Your hesitation on the top end??? Explain the what is happening.
I still think the problem really is the intake manifold is too big ,causing the carb not to get a strong signal.
I have both intake manifolds, been there done that.
An Offy intake will help trmendously.
That being said,,
switching to three side draught Webers, that my friend is going to be a day & night time difference. But reguires a lot of jetting & tunning.

springs aren't cut, but they don't pop out of the hole by much(not enough I can grab onto to pull them out).

On the top end, power is not instant.......It comes on slowly and in turn the engine fells sluggish. Like I said, moved the pump rod one hole, maybe that will help when I stand on it.

If the Clifford is a top end manifold shouldn't it be preforming the best at WOT?

The Clifford is a top end manifold and if you gave it a few thousand more RPM you would not have a power problem. But you are using it at low RPM. I agree with Hank, your carb just cant get a strong signal under load at WOT.

Sounds like the springs might be cut?????? Not sure?? I would think they should pop up so they would be easy to grab? Anyone???

Top end comming in slowly, that is your counterweighted secondaries. You can cut some weight off, but that should be performed by someone that knows what they are doing.

Reason they do come in slowly is because the Clifford intake is so BIG (very slow velocity)

Now if your engine was bigger(or you have high compression) you can get away w/it.

If your combonation is all set up perfect for a Cliffod, then yes it is for more top end,(like a high stall converter 3500+, high compression etc,) but you loose so much bottom end, for the street,,, it is not worth it.

You would be surprised what that little OFFY intake can do over a Clifford intake.

I plan on punching this little 250 and bumping up the compression ratio.............Since I am a machinist, I have thought about a little Turbo more than once. Thought the Clifford would be best suited for it when I cross that bridge. And I thought I could run it on the stock engine until I get the other block I have laying around built up but from what I see you guys are saying it won't function............So here are some more questions.......If I bought a Offy, would it preform with the 500 CFM carb on this stock engine? Are the Offy's water heated?

I put the carb back on the truck this afternoon and tried it.........Idles alot better, but still bogs when you tramp on it. If I could get that to get a tad better I could live with it.

The Offy intake will perform much better.
I think you bolt up the Offy direct to the exhaust manifold, just like a stocker.

Sure, if you turbo your 250 w/EFI ,yes the Clifford would make more power for you.

It idles better,,,what did you change???

I reset the float, and put the softest springs in I had..........It actually idles really good now.

I have a set of Clifford headers on this engine.......With the Offy fit with them?

How radical of a cam would I need to put in to keep the clifford? It probably would be easier/cheaper to just pop a cam into it and keep the Clifford? Or would CI/Compression issues still make it sluggish?

I really don't want to buy a Offy, and only run it for less than a year. Any idea on what I could do so it preforms OK for now?

I think there are clearance issues with the Offy and Clifford headers(I am not positive though). If you post your vehicle wieght, trans type, and gear ratio there a few guys here that might be able to steer you towards a good cam. Running the headers, the Clifford, and the 4 barrel with the stock cam and engine is never going to be "right" but try disconecting the carbs secondaries and see if it get's a little better in the top end.

I have a '68 Chevy C/10 stepside with a 292, Edel-1404, Offy intake and Clifford headers. The Offy intake is a close approximation of the stock cast-iron intake but in aluminum alloy. So it bolts right up. It has a deck which will accept a base plate for a 4Bbl squarebore carb. Carb heat is not provided, but may be added onto the bottom or between carb and manifold. The Offy intake will fit with the Clifford headers with minimal adjustment. Since I live in Tucson, I don't use carb heat.
My 292 is modified: Bored .030 over, Badger cast pistons, 1.84" (307) intake valves, Crane 260H cam, and Rhoads hydraulic lifters.
I now use an Edelbrock 500 CFM 1404. My carb set-up is Stock main jet (.086), #1452 (.070 x.052) metering rods, and Yellow [4" Hg] springs. The springs have the same function as power valves on Holley carbs.
I passed AZ emissions a couple of weeks ago on the 2nd try with minimal leaning of the carb.
The truck is my daily driver, isn't great on gas mileage, but is quick and nimble in traffic, and will move on the freeway. It roars at 2500 RPM.

If you post your vehicle wieght, trans type, and gear ratio there a few guys here that might be able to steer you towards a good cam.

I second that, if you have a automatic trans, you would need a higher stall torque conveter. Like 3000 RPM+ w/a Clifford intake,stock compression even w/a cam ,stock or little bigger. Still, you would need a high stall converter.

Vehicle is a '72 K-20 Chevy Pickup(7500 lbs GVW).........SM 465 granny gear 4-speed with 4.55 gears in the diff's.

Can we stay with the Clifford and make it work fairly simply. Like I said, I'd like to play with another 250 inline block I have in the future, when time allows, but would like to have a working truck will I work on that, then I can just play engine swap for acouple days and have a useable truck again without it setting.

With the low gearing, I do need the top end as well as the low end I come to love in the 6.......

While I am at it, Thanks for all the help you have given me so far. I am like the lone ranger around this town, nobody else has or wants a 6 and help is non-exsistance for something like this setup.

Ebay Item number: 300042882453
You can use it for a while, then sell it later & get your money back????
Here is another one,,,Item number: 230044896519

With the Offy ,you will gain power everywhere.
Yes,even over the Clifford also!!!!

You can find them used,a Offy intake that is.
You will gain more bottom end & better top end w/a Offy intake w/your particular combo you have right now.
Place a want add for a Offy intake.

I tried what Diesel Dan suggested this morning while we were waiting for a seal for the head on our combine. I disconnected the secondarys and it definitely made a huge difference, still a tad rich, but atleast it is driveable and when you tramp on it, it goes. Could I swap in some different rods to lean it out a tad and run it like that, essentially as a two barrel and not hurt anything??

Crazy I know, but would save the $$$/hassle of swapping parts.

I know that we all sound like a broken record about that Offy, but it really will give you more torque and HP in that heavy Chevy, both in the low and topend. Still it's good to hear you found a way to get her to go, yes can probably get it even better with some tuning and no it won't hurt anything runnig as a two barrel.

Yeah, I know..........But I can't see shelling out the dollars for another intake to run for a short period, plus I'd have to build yet another box to move the air cleaner because of the different carb mounting locations. Not to mention, project money is tight, have a plasma cutter on the way, and I just found a nice South Bend Lathe that is going to find its way here. Oh well, gotta have the tools to play with the toys as they say.

Thanks again guys.
Tyler

Check your fuel pressure also. The Edelbrock carbs like about 4-5 psi. Make sure the automatic choke linkage isn't keeping the secondary from opening. Manually lock/tie the choke open and drive it again.

Another thought: Look up Edelbrock's web site and download the complete tech manual for your carb. It will show you exactly which jets and metering rods to change.

I have the manual in paper form already..........Also, carb is manual choke.

I haven't pulled any big hills lately because I haven't driven the truck more than acouple miles each day, but I think I got the problem licked. So far its working pretty good........Hopefully, Sunday I take it for a run up in the mountains again and see how she works. She how much fuel it sucks up too