[kman400]

I have a newly rebuilt 400 that runs OK but has very little bottom end torque. It’s a 69 YS block 30 over and stock 62 heads with valve job and springs. New pistons brought the compression down to 9to1. I’m pretty sure of this number although it was the first time I had checked an engines CC,s. The intake is a Performer as is the carb (600CFM). The cam is a Comp Cams XE262H with a 218 IN. and 224 EX. @ 050 and a total lift of 462 IN. and 470 EX. with matching lifters. Degree wheel was used during install along with a new stock harmonic balancer. Stock exhaust manifolds and a new Gardner exhaust system installed…a little restrictive. 400 trans with stock, used torque converter and 293 open rear end. Cam break-in appeared uneventful, temp never broke 190, oil change after. With 300 mile on engine compression check ranged from 155-160 psi. One concern the vacuum at idle is only 10in HG. Timing is set at 14 degrees initial and 20 degrees mechanical for a total of 34 degrees. MSD ignition system including distributor, no vacuum advance. The car runs and drives great, it just a dog off the line/ stoplight. If nailed at a stop it will chirp one tire for just a second. It seems to pull pretty good after that thought. I know its not a 13 second setup but I think there should be a little more. Any help would be greatly appreciated.

[kman400]

I have a newly rebuilt 400 that runs OK but has very little bottom end torque. It’s a 69 YS block 30 over and stock 62 heads with valve job and springs. New pistons brought the compression down to 9to1. I’m pretty sure of this number although it was the first time I had checked an engines CC,s. The intake is a Performer as is the carb (600CFM). The cam is a Comp Cams XE262H with a 218 IN. and 224 EX. @ 050 and a total lift of 462 IN. and 470 EX. with matching lifters. Degree wheel was used during install along with a new stock harmonic balancer. Stock exhaust manifolds and a new Gardner exhaust system installed…a little restrictive. 400 trans with stock, used torque converter and 293 open rear end. Cam break-in appeared uneventful, temp never broke 190, oil change after. With 300 mile on engine compression check ranged from 155-160 psi. One concern the vacuum at idle is only 10in HG. Timing is set at 14 degrees initial and 20 degrees mechanical for a total of 34 degrees. MSD ignition system including distributor, no vacuum advance. The car runs and drives great, it just a dog off the line/ stoplight. If nailed at a stop it will chirp one tire for just a second. It seems to pull pretty good after that thought. I know its not a 13 second setup but I think there should be a little more. Any help would be greatly appreciated.

[Engo]

More ignition advance needed in my opinion. Try bumping it up to 18 or 20 degrees initial and see what happens. 34 total is also too little. I suggest at least 36 degrees, but 38 degrees or even more are probably better. Maybe need too adjust the advance curve in the distributor. A vacuum advance would help also.

[Blue '66]

I think the 2:93 rear is too high for the cam you have.You need at least 3:23-3:36.A free flowing
exaust would also help.Since you have spent the
money on Gardners'exaust,the cheapest would be
to put on better mufflers,walkers,flowmaster,ect.
I prefer walkers.Good luck!....Eric

[firebird72_4-ME]

Number 1 what is it in? A tuna boat or a firebird(weight of car)? I ran a 400 in a 1980 bird and it had a comp cam High Energy 268 that ran the same way. I agree with the guys above.TO HIGH OF GEAR IN THE REAR.That is what is killing you the most.You need headers to breathe.Now what will help you the most (other the 373 posi in the rear)Is a B&M 2000+ hole shot converter.Get those RPM's Up.You can spin a 400 (unbalance)up to about 6100-6200 between shifts.

[David Jones]

The outlets on my stock 69 exhaust manifolds measured only 1 7/8 inches. I don't think your car can breathe. As for the rear end, what kind of car are you looking for? Highway cruiser or dragster? Shorter rear end would help in acceleration off the line but make things busier on the highway. 3.23 or 3.55 would be good middle ground choices. Are the Gardner pipes 2 1/4? They would with different downpipes hook up to some Ram Air III manifolds. Look to spend some more money. That you can count on.

[ May 15, 2002, 02:11 PM: Message edited by: David Jones ]

[Half-Inch Stud]

you said: "Stock exhaust manifolds and a new Gardner exhaust system installed…a little restrictive. 400 trans with stock, used torque converter and 293 open rear end. "

aside from a potentially bottled EXHaust system.

I think the stock converter may have a stripped sprag....real dog off the line when then the converter doesn;t convert. You will see and feel great responses with a 2800-3200RPM 10" converter installation.

H.I. Stud

[kman400]

Thanks for giving me your time and experience. Should have mentioned it, I have a 68 GTO. As for purpose it’s a weekend driver. I’m stationed at Edwards, AFB CA…two hours from nearly anywhere. At some point I would like to change the rear gears to 3:36 as suggested by Eric. For now I will mess with the timing and pickup a new torque converter. The wife real like the sound of the exhaust as is, I would not mind a little more rumble. I can’t change the pipes, I’m pretty sure my financial advisor would discourage against. With 2” pipes before the mufflers and 2¼” after would a muffler change be worth it? I think a torque converter is first on my list, any suggestions? Something inline with 3:36 gears and a mild budget. Any comments on the low vacuum, the manufacture said the cam should have good vacuum. I had the original carb and manifold at first and it was the same…10in HG at idle. Anyone recommend a better cam for this engine, just a thought. Again Thanks for the help.

[2FAST4U]

You can get a 2.5 Flowmaster exhasut kit with 40 series mufflers that would KA* for less than $300

But agree lower gears would help alot; with more advance

KA= Kick A$$

$$= SS

[WARPed]

With what you have to work with I agree with H.I.S., a converter will give you the most bang for the buck and least amount of effort. Gear would be the best overall fix but will cost more to make the changeover. Besides the converter is “broken” right?

[GTOPhil]

Kelly, first things first. 10 inches of vacuum is way too low with that cam. I run 13.5 with my UD 221/230. I suspect a vacuum leak which could be contributing to your problem. Even with your gears and somewhat restrictive exhaust, you should be able to roast the tires from a standand start.

[Half-Inch Stud]

with 2 hours from anywhere, I'd consider keeping the gears in and going to a 27" or 28" tire.

Also, you can spray WD40 around the intake flange during idle to see if the engine stumbles bad due to a vacuum leak at the gasket.

H.I. Stud

[kman400]

2FAST4U the problem is not so much the money (not that money is not a problem) as it is chucking the new system I already have. I don’t know why I put that “broken” torque converter back in…easy fix thought. I think GTOPhil is right about low the vacuum being a problem. I have checked the engine top to bottom with no luck. I have changed the carb and the manifold still no change. H.I.S. it’s funny you should mention taller tires in the rear, I really liked the 68 GTO in this months HPP, 14” front and 15” rear rally II. Thanks…Thanks for everything.

[PONTIAC DUDE]

You do realize that basically you have a "Stock" motor with a very mild cam. (218/224 is in the what they call a hair above an RV pulling classification) and no gear in a tank.
So don't expect vast power gains. But; 3.55 gears/posi and a 2200 convertor. 700 DP Holley will really help.

Try setting your timing with a vacuum guage and see if the vacuum come up when you advance the timing. Hummmmmmmmm.

[ May 17, 2002, 07:33 AM: Message edited by: PONTIAC DUDE ]

[critter]

What Dude said. I think you're strangling this thing on both end. You need a bit more than a 600cfm carb and the exhaust needs to be opened up. The gears are killing your performance. What about a set of 3.08s? A bit more gear and still highway friendly? It might work.

[GTOPhil]

I really think you need to make sure your combo is optimized before you go spending money on things like gears. Verify that you don't have a vacuum leak. Check out the distributor curve, automatics like a lot of advance early. I would shoot for the advance to be in by 2500 RPM. Now, once you get these 2 items sorted out, then you can make a rational decision as to where to go next. I have a little bit different opinion as to the 600 carb, as I think it is fine for your application. I don't think you would notice any seat of the pants difference with a larger carb with your mild cam.

[GTOPhil]

BTW, I am running an L88 type convertor which gives me a few hundred RPM additional stall speed and it works great. My combo is a little different from yours, but not by a huge amount. I run the UD 221/230 with Q-Jet by Cliff and headers with #16 heads and 9.25 CR. Rear is a 3.36 peg leg (soon to be changed).

[Nickv]

Check your timing first to make sure it's on the money. Then adjust the carb mixture

My feeling is you should be able to burn rubber pretty easy with that motor.

I had a 72 350 lemans with 2:73 rear. With headers, 600cfm carb and performer intake and it was very easy to burn rubber with it from a dead stop.

[kman400]

Dude, I understand this mild combination could be a contender at the RV Nationals. I agree the suggestions above would help improve performance. I still believe the stock exhaust system is adequate to support a 250-300 HP engine. I tried the original Q-jet and manifold, it was no better. I had a stock 100,000mile + 350 Lemans, signal exhaust, 273 cogs and a 2 barrel carb; no it was not fast but it would bald a tire from a stop. I just want a little of that Pontiac torque that I used to have with the Lemans. I can’t help think that there is something wrong with engine. Should I be concerned about low vacuum or forget about it and work with what I have? With everything the same except for the gears and a mild converter, would a cam change help? GTOPhil the L88 converter is there a part number or is it just referenced by L88.