Advice - How to wake up my '72 400 2bbl

[jpdog357]

I have a '72 Lemans, 400 2 bbl. Body, interior, etc. is rock solid and great but the factory 2bbl low hp 72 400 needs to be woken up a bit. Just for street driving from corner store to 150 mile trips.

For the time being I am on a pretty tight budget so I am thinking carb, intake and maybe headers. Not sure if I will go as far as cam and heads are financialy out of the question.

Can I get some advice on some options that would work with stock heads and cam? I think the flow on these engines is pretty low and don't want to over carborate.

Jason

[super]

A carb and intake change will definitely wake up the 8.-2 compression 200h.p. 400.

Depending on your budget, try to pick up an early cast iron 4-bbl. intake. These intakes work well and won't break the bank. If you plan to do a lot of street driving, a quadrajet carb will be the way to go too. An early dual-plane intake, such as a 1968 model, flows good and would be ideal for street cruising. (Jim Hand did extensive research on these intakes and proved his theories at the track.) Hit the local salvage yards and good luck. If you can not find one, give Lee Jay Ruwwe and call. (573)732-4966. He deals with many Pontiac parts and probably would have what you need. Great guy!! Shipping may be the only thing that would rise cost considerably.

If you choose to run an aftermarket intake, I would suggest an Edelbrock Performer. They are very affordable (around $185 to $190) and offer dual patterns for carbs. You can run a stock quadrajet or a carb such as a holley or demon. A 650cfm carb would be more than adequate. Add a carb spacer to pick up additional low-end torque.

What type of exhaust system do you currently have? A 2 1/4" or 2 1/2" dual exhaust system would work well with the 400. The 2 1/2" system would be a good investment if you choose to further modify the 400 in the future. I would also suggest running a crossover on your exhaust system. An X-pipe will generally generate a little more power, but a H-style crossover will work good too. I have installed some x-pipe systems and they are a little trickier to work with. Try to run a low restriction muffler. Dynomax, Hooker, Full Boar, and Flowmaster all make good performance mufflers. I enjoy the two-chamber Flowmasters I run on my Pontiac. The give a good rumble at idle and sound great at higher RPM.

Headers would be a good investment too. The stock log-style manifolds you are running are very restrictive.

What type of gear ratio are you running? What kind of MPH do you cruise at? A different gear ratio might not be a bad investment. You will definitely get the bang for your buck. Pontiacs make good torque, so a guy generally does not have to get carried away with gears. 3:55? Good all around gear and available in cars such as yours. Still have the stock 10-bolt?

If the engine runs good, does not smoke, etc. I would not disturb it. Gets some fun and enjoyment out of it.

Jeff

[Larry]

Jeff really knows his Pontiac performance.. all good advice.
I built the 400 in my Lemans wagon years ago (cam, heads, headers, Holley, etc. and while it really pulled, I just couldn't smoke 'em (at all! even when non-posi). Enter a 2800 rpm stall converter.... the single MOST difference I think I ever made in a car. If you can afford this item it will really make a lot of difference.
I don't know the measurement of the 2800, but don't let anyone talk you into the "classic" 9" Vega converter... unless you want to "pedal" it through town pumping the gas pedal!
You might not notice the extreme difference I did because my 400 had come out of a '70 full-size station wagon and it had a torque converter as big as a steam boat steering wheel.
Perhaps someone knows what an equivalent PMD converter might be that you can pick up OEM instead of from a speed shop.
Keep us posted on how you do.
Larry

[super]

A torque converter can be one of the single most important upgrades too. If you are interested in tearing in to your Pontiac a little further, this would be a good investment.

From experience, I have a 1974 Trans-Am with a 455 and automatic. I had made quite a few upgrades that only yielded minimal performance. My car was stuck at the low 13-second 1/4-mile mark for a long time. Out of the hole, my T/A lacked the low-end torque it needed to get the heavy T/A going (It had the torque, it just did not have the proper tools to put it to the ground). I was running a stock converter at the time. For about the first 100 feet down the track, the car would not pull as I thought it should. At about the 100-ft. mark, around 3000 to 3500rpm, it felt like I was getting ass-ended by a semi-truck.

I was so dissapointed with the T/A's low-end performance, I opted to purchase a new stall converter. I took about 2 1/2 hours out of a Wednesday to complete the job. I purchased my converter from Doug Herbert Performance(800-444-7373). Pro Tech Engineer was the brand of converter I decided to run. My good friend had ran and tested the converters and had good success with them. The price was affordable too.

I took my car to Gateway International to test the new set up. My cars best time to date was a 13.16. The first pass I made was incredible. It felt like the 455 was trying to tear my helmet off. The first pass was a 12.78. GREAT!!!! I finally made it in to the 12's.

.38 of a second better on E.T. As the evening went on, I took almost a 1/2 second off the T/A's time with a converter.

Doug Herbert offers several Turbo 350 and 400 converters. They range from $89.00 to $199.00. I would have to agree with Larry. A converter with about a 2800 stall speed would really wake up the 400. They offer a 2200 to 2600 stall (11" converter) for $179.00. The 2700 to 3000 stall runs $199.00(10" converter).

I know you had discussed a possible cam change. Keep in mind this can be an expensive adventure. Cam, lifters will usually lead to valve springs, valve locks, retainers, etc. It adds up fairly quick. You may dump far more money in to your heads than they will ever be worth.

If you do decide to keep the 400 mostly stock, I would run a 2 1/4" exhaust system. A 2 1/2" system would probably hurt the 400's performance. Bigger is not always better. If you do plan on making some major changes quickly go with 2 1/2".

Good luck with your Poncho. Let us know what your results are.

Jeff

[jpdog357]

Thanks for all of the great feedback and recommendations.

Frankly, I am not all that mechanical and its great to get your feedback and knowledge.

Its approaching cruising time up in Canada and I am thinking of buying an Edelbrock manifold/carb combo and work on cleaning up the engine bay a bit as everything is 'as is' stock in there.

Anything much more than that will probably happen next year.

My next dilemma is finding a limited slip rear end for it. The stock slip differential is already giving my right side too much of a work out.

Thanks again,

Jason