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Old 09-27-2004, 01:56 PM
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need HP suggestions

hey guys, i have a 1978 trans am with a 400 ci motor and a turbo 400 tranny. i have already bought some speed pro "power forged" pistons which raised the compression ratio to 10.25:1. i would really like some help to build my engine (as far as part suggestions). seeing as how i have bought the pistons if you could name pretty much everything else that would be great performance for a low cost ($3000 +/-) total. i was thinking about the performer RPM kit that edelbrock offers and i also considered stroking the engine. everything is fare game except N02.

thanks a lot



PS i would really like it if i could find all of the stuff on jegs.com since i have delt with them before thx

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Old 09-27-2004, 02:20 PM
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This is my friend I was referring to before on my "approx hp output" thread.

We are open to ideas to get some good power out of the 400, so please hook us up with suggestions.
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Old 09-27-2004, 05:53 PM
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lol come on guys help me out
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Old 09-28-2004, 01:31 AM
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The specs for the pistons we have already purchased are:

400ci Stock-Type Piston, .030'' Overbore
Piston Dia.: 4.150''
Piston Top: -6.7cc Dish, 4-Valve Reliefs
Pressed Pin
Comp Ratio: 10.24:1 w/69cc Heads, 7.16:1 w/114cc Heads
Ring Grooves: 5/64'', 5/64'', 3/16''


The block is bored over to fit them. We are basically asking you to fill in the parts to give the maximum power output. Also, what does the .030" overbore bring the displacement to?

Thanks for the help guys.
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Old 09-28-2004, 02:23 PM
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400 pmd over bore

.030 will bring a 400ci to about 403 ci .060 = 408ci
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Old 09-28-2004, 08:33 PM
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What are your goals? Will this be a street car? Highway driving at all? What is your goal for power output? Where do you want your powerband to be?

Start with specific goals. Then work from there.
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Old 09-28-2004, 08:42 PM
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it will be mostly street but strong in the 1/4... (duh) and it will be driven on the highway but not raced on it... i am aiming for as much power as i can get, i would like around 500 RWHP if i can... i have about 3000k to spend so it has to be a lot of bang for buck
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Old 09-28-2004, 09:17 PM
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Thats a lot of power for a street car. So your looking at buidling something closer to 600hp at the flywheel. 600hp naturally aspirated is going to cost $$$ and isn't going to be especially comfortable driving on the street.
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Old 09-29-2004, 04:19 AM
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I've built my Pontiac 455 to run as a street/strip car. My goal was mostly weekend use and 3 - 4 drag meets per year.

I'm still running it in after a total rebuild but aimed for approx 450 hp.

This was based on advice given in the 'how to build horsepower' book by David Vizard. I recommend that you get a copy. His crude rule of thumb for street driven cars is 1 hp per CI.

I have read elsewhere that the edelbrock RPM combo on a 400 (heads, intake, cam, carb) will give 422hp with headers and good ignition etc.

Hope that helps as a starting point - but I think if I were you I would think carefully as one of the other posts said about what your goals are. Don't be afraid to keep refining your goals as you gain more info. It took me a good 6 months of thinking about what I wanted and research to get to the point where I started tearing the engine down.
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Old 09-29-2004, 11:35 AM
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hi. i know just about SQUAT BABY about building pontiacs but it seems like with over 10 to one that you definitely need aluminum heads but your getting them anyway. if i was you i'd go to www.performanceyears.com and order that book by jim hand. read it then you'll be a pontiac guru
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