Inliners International Forums General Discussion Hi Performance My '78 250 cid build

Just filled up the tank tonight after many of my upgrades or reconditioning. It was right on "E" and it took a little over 18 gallons, while the specs say the tank is 21. I got 20.3 mpg in mostly highway driving. And that's without finishing the exhaust, replacing the distributor cap/rotor or springs yet.

Sounds great!
How are you calculating your mileage?

MBHD

I fill it to the top at the same gas station each time, then take the miles driven and divide by the number of gallons I put in until full.

BTW, I don't know who recommended the BWD distributor cap and rotor, but I ordered them along with the a plug wire retainer and coil cover. The coil cover and retainer are factory black, but the cap and rotor were the same gray that the factory rotor was molded in. The picture was black like the stock cap, but the part is actually factory rotor gray. Looks different from stock, but doesn't shout aftermarket part.

I recommended the cap, sorry on the color, I just said to get one w/brass terminals.
When you glance at the cap pic it does look black, but if you look at it a bit longer you can see it's actually grey.
http://shop.advanceautoparts.com/p/bwd-s...distributor+cap
Guess you could paint it?

MBHD

S'okay, looks kind of cool. It would look odd if it were one of the bright red or bright blue aftermarket caps on an otherwise stock engine. I'm also going for a resto-mod look too, so it wouldn't be period correct for the bright colored caps as I remember them first popping up around in the '90s. They may have been introduced in the '80s, but I don't remember seeing any of them back then. I'm waiting on my 8mm spark plug wires still, so I'll put it all on at once when they come.

After talking with Jay, he convinced me that my stock coil should be serviceable and should supply plenty of spark for a street application. So I switched it into the new cap. Here's what it looked like:

New cap/rotor, coil cover, wire retainer, plug wires, and wire looms (spark plugs were already gapped and indexed) on my rebuilt distributor. Haven't had time to experiment with installing new springs and vacuum advance yet.

Looking sharp!

MBHD

Thanks, just going for restored stock look for now so I can pop the hood and not be embarrassed by a rusty greasy mess underneath. Only items under the hood I haven't replaced or rebuilt now are the starter, power steering, EGR, EFE and the engine itself. I'm going to be playing around with advance settings and plug gap to see what is optimal. I may look into changes I can make to the mono-jet besides idle mixture as well.

That looks great! I am getting inspired to clean and paint also! It looks so nice when the hood is open. Jay 6155

Clean look under that hood. Nice. Your mileage is about what I got on the highway in my truck, right at 20 MPG.....but if I decided to go much above 55, it dropped off.

Well mine was 20 mpg in mainly city driving, I haven't checked highway driving yet. I'm figuring that will be better yet. But I suppose the aerodynamics and weight of the truck versus the Camaro make a difference. 55mph makes sense, that was the national speed limit then and the gearing and tire size would have been designed to make peak efficiency around that speed. It's 70mph in Illinois now, so the 2.56:1 rear ratio (which they used in the smaller V8s with TH350 in '80 & '81 too) that was used on the last year of the 250 in '79 (which switched to the 292 SD head & intake/exhaust too) would be more efficient at the modern highway speed.

I read an interesting series of articles on the "deadly sins" of GM on the cars that lead to its decline. I think it was the Vega article where the author described the super wide range 3spd manual (3.50 1st, 1.89:1 2nd) as an overdrive 5spd manual with 2nd and 4th gear missing. That kind of makes sense from my experience with it, as first gear gets you across the intersection, but it bogs a bit if shifted to the 1.00:1 ratio before 40mph. With the 2.73:1 high ratio in the rear end, the overall drive ratios are similar the T5 in 1st (with 3.42:1 rear ratio), while the third gear falls somewhere between the 4th & 5th OD gears. So my seat of the pants experience kind of agrees with that author.

Yeah, I am running a 3.73:1 rearend. It was awesome for hammering it while cruising in 3rd at 50mph and feeling it pull like it had a purpose. I got a free '71 2spd slushbox from a nova which I'm going to use until I get bored and go back to a manual. My saginaw was tired and shifting on the column was killing me. A freebie was just what the doctor ordered.

Ah, column shifter. Mine is on the floor. I've never had a manual on the column, only automatics. What a pain.

Does it have a stock knock sensor?

Knock sensor? Not on a second gen Camaro. I think the first knock sensor on a Camaro was with the third gen '83 L69 engine (maybe the '82 LU5 first).

I also just changed out my stock HEI advance springs with the Accel white springs after the last fill up. Noticeably peppier. I filled up today and it was 20.2mpg. That's with the stock fan reinstalled while I work out electrical issues with the electric fan. The previous upgrades are a K&N air filter, ram air intake, performance HEI cap with rotor, 2.25" exhaust with turbo muffler and catalytic converter removed.

do you have a part number on that coil?

do you have a part number on that coil?

No, that's the factory coil. It has a number stamped on the top of it, but that doesn't appear to be a part number.

Haven't done a project update in awhile. Finances put it all on hold for a few years. I have my '77-'81 Z28 cat-back exhaust for awhile now, but I only hooked one tailpipe up to the muffler that the previous owner stuck on the header pipe. This temporary setup fell apart last year, and I've got the full cat-back installed now, but I'm still having difficulty getting the old muffler off, and looks like I will have to rent a saw-zall and cut it off. Then add the 2.25" to 2.5" adapter to the 2.5" pipes I have to take the place of the missing catalytic converter. The Y-pipe on the Z28 system is meant to bolt to a bracket on the catalytic converter with a gasket, so I haven't decided yet how to connect the pipe to it.

Got the muffler off now. On the side facing up was the stamped Thrush logo, so it was a nice muffler but I was unable to save it. It was stuck on the old header pipe and I had to cut it off with a Saw-zall. Unfortunately I had already installed the Z28 cat-back pipes and resonators, so now trying to fit the connector pipe between the stock header pipe and the Y-pipe connect is tough. I'm waiting until light tomorrow to try and scissor both ends together with the pipe in-between. (And waiting for the feeling in my arms to come back.) When I get it done, I will try to post a video to show how it sounds.

I put a 3-blade clutch fan off a truck 250/292 on the water pump for a temporary fix while I finish wiring for the electric fans. Put a new battery in it too.

I haven't taken the time to read all five pages of this thread, but I'm a litle curious. Do you still have the 3 speed trans in the Camaro?

Yeah, I don't blame you. A lot of it is speculation and throwing ideas around, and some of it is correcting errors, so it's not really worth reading all of it. i should post another summary of what I've done and what I plan to do. Yes, the stock '78 3.50:1 Saginaw 3spd is still in place. I've been shopping for a Saginaw 4spd and will probably stick with a 3.50:1 1st gear. i definitely need the extra gear in there. 1st gets you across the intersection, but 2nd is a huge kick from that, then it revs pretty high before I hit cruising speed at 35 to 45mph when I can then settle into the direct drive gear. Splitting that middle gear into two would really smooth out the acceleration steps.

Sorry, my smartphone died over a week ago, and I couldn't get a video of the new exhaust up. I'm adding an adjustable vac-adv and up the initial from 6 to 10 degrees. So I will probably shoot the exhaust vid after I tune everything.

Motor looks sharp! Hope to see a video of the new exhaust sometime.

Tuned up the Camaro after installing the Accel adjustable vacuum advance and setting initial advance to 10 degrees, up from stock 6 degrees. Got about 20"HG on vacuum when adjusting the idle speed screw. So I did some video with my new cat back dual resonators:

[img]http://i1109.photobucket.com/albums/h434/Lifeguard2005/th_IMG_0302_zpsezapjrww.mp4[/img]

Then took if for a ride in the rain. As I put new wipers on, replaced the washer motor, and sealed up some rust holes in the header panel vent that was leaking inside. So it is now rain and car wash proof:



Will probably play with timing with the new adjustable vacuum advance. And I need to change all fluids and oil filter.

List of what I've done so far:

Stock 250cid with integrated head, stock 3.50:1 3spd, 2.73:1 open rear gear.
Stock 2.25" exhaust to cat, 2.5" straight and flex pipe for cat replacement, 2.5" to dual 2" pipe with dual resonators and dual 2.25" tailpipes '77-'81 Z28 stock cat-back exhaust.
New HEI cap and rotor with spark plug wire cap retainer, 8mm replacement wires.
Properly gapped and indexed spark plugs.
red springs from Accel HEI distributor spring kit.
Adjustable vacuum advance with maximum 20 degrees of advance.
Upped mechanical advance to 10 degrees initial advance.
three blade later model Chevy truck 292 clutching fan (replacing with electric fans soon)
new battery
K&N air filter in stock air cleaner
New plastic duct work added to opening directly behind the left turn signal and giving it a secret Ram Air Intake.

Sounds good!

A little side by side with yesterday and on the car lot when I first saw it:





I've got another video of the idling that is longer and Photobucket doesn't seem to like it so I'm trimming it to get it uploaded and shared.

BTW, stock SAE-net horsepower is 110hp @ 3800rpm, and 195ft-lbs @ 1600rpm. The Z28 numbers with the exhaust is 15hp over the LM1 option, and 10ft-lbs more torque. So maybe I'm at 125hp SAE-net and 205ft-lbs now. Or maybe more with the intake and ignition timing changes, along with the clutch fan.

Oh, finally got the next two parts up:

[files deleted]

It's glitching for me, won't play without pausing every second. I s it doing that for others or is that just me?

Ok, I just deleted them, it wasn't just me they definitely were corrupted. I'll re-trim and post them again.

I accidentally uploaded a 2nd copy of the first part and this works fine for me:

[img]http://i1109.photobucket.com/albums/h434/Lifeguard2005/th_IMG_0301_zpsd2cbxmeu.mp4[/img]

Ok, here's my videos of how my exhaust sound. Dual resonators, no muffler, no catalytic converter:

[img]http://i1109.photobucket.com/albums/h434/Lifeguard2005/th_IMG_0301_zpsd2cbxmeu.mp4[/img]

[img]http://i1109.photobucket.com/albums/h434/Lifeguard2005/th_IMG_0301-2_zpsk5fe7unv.mp4[/img]

[img]http://i1109.photobucket.com/albums/h434/Lifeguard2005/th_IMG_0301-3_zpsqvmrg0su.mp4[/img]

[img]http://i1109.photobucket.com/albums/h434/Lifeguard2005/th_IMG_0302_zpsezapjrww.mp4[/img]

Driving around with the red springs in the HEI, I didn't have any issues so tomorrow I think I will try one red and one blue. I just saw on the packaging that they recommended red springs for big blocks, blue springs for V6 and small block, and the white springs for racing.

now that i have the initial advance adjusted to 10 degrees like the automatic, and I have the adjustable vacuum advance on, I can start turning it in little by little until I get some pinging and rattling. Starting at full out, 20 degrees advance, no issues yet.

Spark plug gap will be played with too.

Not sure if there is any advantage to adjusting initial idle speed on the carb from 800rpm up or down? The auto equipped 250cid had a lower idle speed with a higher initial advance.

Took some pics of the engine again today when i moved the Camaro from one side of the garage to the other:

Apparently Photobucket no longer lets you post your pics from there on forums ("3rd party hosting) unless you pay them $400 per year. Not going to happen, so all my pics from this thread and any others I posted in are inaccessible. I am looking for another pic hosting site, and will try to re-post anything I posted before. This is why if a forum allows storing pics on there, I've done that in the past. What a pain.

looking forward to the re-posted pics and videos. I'm using flickr for pics now if that helps.

Yeah, I was waiting until I finished all the maintenance and repairs on it currently before giving it a wash and polish for some new pics. Then making a new thread to post from my new pic account. Start fresh.

Indeed. They sprung this change on their users last summer - lots of forums and web commerce sites have been affected: BBC News
Apparently their advertising dollars are drying up. Nothing is really 'free' . . .

You should check with your ISP. Mine is with earthlink. Each email-box includes 10MB of webspace - with up to 8 email profiles (on the master account) that's 80MB. It's not alot but if one takes the time to crop images and lower the resolution one can get photos down to 50-100K each. And it's a paid service so images are online until one chooses to take them down.

Yeah, I got another pic hosting site right afterwards. I forgot the name of it. I'm waiting until the snow melts this week and I finish getting all my little things done and a bath to do some fresh pics and make a new update. Most of the forums I post on will host pics and I should have used that before now.

Almost all of my pictures here went away when Picasa (Google) did the same thing. The pics are still there but not where I posted them. The HAMB apparently does it's own hosting. You can post there from your desktop. That would be a good feature for the new website. Thanks for the ISP tip.