Hello

I'm look for a few suggestions, I recently decided to build up a Pontiac 400 out of a 79' TA. I have pretty much decided on all my mods but I'm still torn when it comes to camshaft selection, I need a hydraulic lifter cam that will be ok to run on the street and have enough low end to get me around but still haul serious a$$ on the quarter and smoke any ***** on the street. I know the 400 has serious power potential, so how much do you guys think I can put out.

My mods are listed below:

-Pontiac 400 block bored .030 over
-10:1 comperssion with forged pistons
-Edelbrock Performer RPM intake
-750 cfm Holley double pumper
-Ported Heads
-Roller rockers
-2,800 stall convertor
-3.73 in the rear
-TH350 Tranny

Well those are the mods.....anyone with a suggestion for a cam will be greatly appreciated.

Thanks

 

Bandit,

COOL! Another person who hasn't given up on the venerable Pontiac blocks! With a stout bottom end like that, you can safely make plenty of power on two bolts, for sure.

With only 8.1:1 compression the 400 already makes 325 lb/ft of torque, so maintaining the torque to "get you around" shouldn't be a real problem. You're already going to have around 406 cubes, and 15cc domes should keep the compression around 10:1 in stock heads.

One thing to consider is that the purpose of a different cam profile is to change the head and valve flow. Soem of the change can be done with the valves themselves, and the relatively large chambers of the Pontiac heads can accomodate some pretty impresive valve sizes.

You also need to realize that you are using some really short installed height springs on the stock heads. This can be a limiting factor in cam selection unless you plan to machine for different springs (I would). The reason Pontiac used such large valves to begin with is the lift limits of the valve train. If you install taller valve springs, you can have the best of both. It's fairly easy to install 2.25"/1.90" BBC valves in the Poncho heads and get another 0.200" of spring area without machining. The 11/32" BBC valves are easily found, and can really help the flow with lower valve lifts. If your guides are really worn, you can ream up to the 3/8" stem sizes and still use the later BBC valves in the same seat sizes - cool, huh?

With 2.25/1.90 valves, you can get way better flow than 2.02/1.60 SBC heads with a lot less lift. The valve open area gets really large, really fast. The mildly short stroke of the 400 is also going to want to be very RPM freindly, so consider tighter springs to control the larger, heavier valves at higher RPMs. Get in the BBC-building frame of mind, and realize that you are working with a larger block than the SBC. This should clear your mind of any of those "learned limitations" and "standard procedures" for the SBC.

With all that in mind, you would need to concentrate more on the duration and timing numbers than the lift specifications of a cam. To support flow at higher RPM, I would suggest checking the Comp XE284H profile. 240°/246° - .507"/.510", 110° LSA. If you don't mind a little idle lope and Honda-frightening noise at idle, this might be worth looking at, or call Comp for their input on that or any other cam selection.

Frankly, with a similar cam profile, that compression, the right port design, larger valves, an original design Performer RPM, and supporting exhaust and converter, I would be disappointed if you didn't make 360+ at the rear wheels. Since the crank output should be approaching 450HP with conservative timing and tuning, you shouldn't need any boost or oxidizer to spank plenty of "sporty" cars on a regular basis.

If you slide this into an original '79 TA, you should have respectable performance. With this engine wedged into the smaller, lighter ThirdGen chassis, you could really turn some heads

Here, Horsey! Come and get it....

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Later,
Vader
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"Let the bodies hit the floor!"
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