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Old 02-09-2004, 03:40 PM
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400 pontiac performance?

I can pick up a 400/4 speed from a 78 T/A for an insanely low price (you'd all hate me if I told you) Is there anything special about this engine? i.e. 4 bolt mains, better casting etc. I was told it had some really good heads. I did some research and came up with "6x-4" something or other. What does this mean? I'll be going through the engine soon, I'd like at least 300 horsepower, can I get this with just bolt ons? Like camshaft, headers, intake manifold, good carb etc. Oh, and I was told that the only difference between it and a 455 is the crankshaft, can I just swap the crank and get 55+ cubes or is there more to it than that? Thanks!

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Old 02-09-2004, 03:55 PM
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not a pontiac guru but

I think all the pontiac blocks are the same, 326,389,400 and 455. If you change cranks you will need 455 connectiong rods too. And I don't know about these other people but bolt on HP is the best way to go as far as I'm conserned!


Tazz


Rat Rods Rule!
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Old 02-09-2004, 04:55 PM
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The motor in your car (assuming it is original) does not have 4- bolt mains. I believe the SD-455 were the last blocks to have 4-bolts (correct me if im wrong).

Pontiac made two kinds of 6X heads. One being a 6X-4 and other being a 6X-8. The 4's were generally used on 350's and some high-performance 400's got 'em but only in the TA. The 4's have a 92cc chamber (roughly). Giving a stock 350 7.6:1 comp. and a 400 around 8.2:1 comp. (not really that high-perfomance!). The 8's were mainly used on 400's and 455's. These chambers are around 98cc. Giving a 400 7.6:1 and a 455 8.2-8.5:1. They are a decent flowing head from the factory but nothing to celebrate about. With proper porting and polishing, they can be woken right up. However, you could use some 4's on a 455 and get like 9.2-9.5:1 comp.

And finally, the really difference between 400's and 455's is the crank, the journals are .25" bigger and the bore is 4.15" instead of 4.12" You can use the 455 crank in a 400 block if it is ground to 3 inch mains or you could get a shim kit.

300 horses is not a problem from a 400 with a few goodies. Hope this helps!
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Old 02-09-2004, 05:03 PM
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This is definitely not the original engine for my car The whole mess is going into a 79 Camaro. How much can I expect to gain from raising the compression? Can I get 300 horses using the stock compression, maybe with a thinner head gasket? I want to reuse the stock pistons as well. How much power can the 2 bolt mains take? And how much power can my 4 speed tranny take? I'm not sure what kind it is, it's whatever came factory in a 78 TA.
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Old 02-09-2004, 05:13 PM
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you realize that a chevrolet 400 is not the same as a pontiac 400 and that you will have to do some fabricating to get this to fit in it!
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Old 02-09-2004, 05:22 PM
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You're gonna put the 400 in a camaro? Why not keep it in the TA?

Anyway, for power by gaining compression, a good rule of thumb is a 4% increase per point of compression increase. So if your motor is puttin out 200 ponies with 8:1 and you increase JUST the compression to 9:1 you will get roughly 16 horses. Not a whole lot. Different factors such as other performance parts will alter the numbers but generally 4% per point of compression. Assuming you have 7.6:1 comp. 300 horses could possibly be had at the flywheel if you use the right parts. Most likely power will be in the 270-280 range depending again on parts. DO NOT use a thinner gasket to raise comp. It will not gain much and your quench distance will be off.

2-bolt mains can take more power than people think. High power and torque in an engine that is driven on the street and raced occasionally is not what kills a 2-bolt. Constant speed and constant high cylinder pressure is what will kill 'em. That's why nascar has to use 4-bolts. Its because of the constant 6-8,000 rpm use. So, unless you are building an all out race 8 second engine, a 2-bolt will be more than enough.

The tranny that car most likely has is a borg-warner T-10. It is a pretty strong unit. It will definately take 300 horses.
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Old 02-11-2004, 11:07 PM
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The TA motor mounts should connect the 400 to the Camaro subframe just fine, since the Firebird & Camaro use the same subframe. Here's a link to some Pontiac performance stuff:

www.pontiacstreetperformance.com
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Old 02-12-2004, 12:09 AM
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RPM limit on a 400 Pontiac with stock rods and stock rod bolts should be kept around 5,600 RPM. Replacing the rod bolts with some good ARP stuff will up that limit to about 6,000. But in either case the limiting factor are the rods and not the mains. The main caps are very beefy and the main cap bolts are 1/2", and it has been stated that the 2 bolt bottom end is good for up to 600 horsepower before you need to worry. Remember that it is the Pontiac torque that hauls the mail.

There has been some very fast cars using race prepped 6X heads. Have them milled to bring the compression up to around 9:1. Another way to look at Bandit's (correct) statement about 4% for each point of compression, is don't get carried away with raising compression too far, because it won't help the horsepower that much - and if you get it too high and have to retard your timing, you will loose much more.

Keep the stock intake and the Quadrajet, get a set of Doug's Headers, and do some gasket matching and a little port cleanup. Drop in either a Pontiac 068 cam or something along the lines of a Comp XE268H or a little smaller.
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Old 02-12-2004, 05:13 AM
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Is the stock intake really all that great? From my experience with chevy's, the factory manifolds are always the first things to go. I was budgeting in an aluminum manifold. Lol, I know it's not the same as a chevy 400. It's waaaay bigger. What kind of custom fabrication am I looking at??? I was thinking just use TA parts instead of Camaro parts.
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Old 02-12-2004, 05:34 AM
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As long as your stock Pontiac intake does not have provisions for EGR it is a very good manifold. Pontiac intakes do not have the same problems as Chevy's.

A stock Pontiac intake and quadrajet will work as well as an Edelbrock Performer. The only difference is the weight.
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Old 02-12-2004, 07:36 AM
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or if you want to step up to the plate you could turbo charge it and make some real power take a look at this link
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Old 02-12-2004, 08:24 AM
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Or you could make it look like mine...
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Old 02-12-2004, 08:25 AM
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Quote:
Originally posted by 455Turbo
Or you could make it look like mine...
haha... Does that thing make 300 horses?
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Old 03-15-2004, 06:33 AM
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I KNOW MY TRANS AMS QUITE WELL AND 3OO HORSES ISNT GOING TO HAPPEN WITH JUST 6X HEADS YOU WANT CASTING NUMBER 614 12 OR MAYBE 13 ..SOMTHING FROM AN EARLY RAM AIR BUT THE HEADS ARE NOT GOING TO GIVE YOU MAX HP WITHOUT THAT HIGH LOBE CAM ..6X ARE JUST STANDARD 77 - 81 TRANS AM HEADS....614 RAM AIR HEADS AND THAT BIG LOBE CAM WILL GIVE YOU WELL OVER 300 ..AND 614 REQUIRE ROUND PORT EXHAUST MANIFOLDS..ADAM

THE CRANK BIT IS RIGHT TO THE 455 CAM IS STROKED MORE BUT BORE SIZE IS THE SAME...614 HEADS ON A 455 WOULD GO LIKE THE WIND.
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