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Old 05-16-2010, 10:34 PM
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Pontiac 400 HP help

First of all I'd like to say WOW! Great board!! Can't believe I didn't come across this before!

A little about me...

I know some basic stuff, but I'm no mechanic. I can do an oil change, change water pump, radiator, hoses, cylinder heads, intake manifold, etc.....but I'm not the man that should be messing with this kind of thing.

I've got a 1978 Pontiac Firebird Trans Am that is nearly restored. I basically want to turn this into a street legal machine! Here's what I have so far. Guys, I am open to any and all advice. If there is anything I'm missing here, let me know!! Goal is 350-400HP.

Specifics of the engine:

-Pontiac 400 short block (bought this just last week, rebuilt and looks great!)
-Edelbrock Cylinder Heads
-Edelbrock Intake Manifold idle-5500 RPM
-Edelbrock carburetor #1406 600 CFM
-Edelbrock waterpump, don't want this bastard overheating.
-Hooker competition headers, ceramic, ran me about $700
-Flowmaster muffler with dual exhaust....

With all of this on, what am I looking at so far? Stock HP is 220.

I'm looking into buying a Lunati camshaft, P#60901LK. Good or bad move in your opinion?

Opinions, suggestions? Thanks in advance, look forward to hearing from all of you!

Edit: Been reading up on some things, and I'm thinking I should have gone with a 650 or 750 cfm carb.....Would a 600 do me any good at all with my goal of 350-400 HP?

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Old 05-16-2010, 11:03 PM
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I would have started with a 455. Always start with the biggest motor that will bolt into the bay unless you're building for fuel mileage.
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Old 05-16-2010, 11:04 PM
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Quote:
Originally Posted by techinspector1
I would have started with a 455. Always start with the biggest motor that will bolt into the bay unless you're building for fuel mileage.
I would have, but the stock was the 400. It had a ****ed up bearing on it, so I just bought a rebuilt shortblock since I already had most of these parts
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Old 05-16-2010, 11:13 PM
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OK, figure your static compression ratio first. You need 5 values to figure it. Cylinder volume, combustion chamber volume, head gasket volume, piston crown volume and piston deck height volume. If you'll post some measurements, I'll figure the volumes for you. For instance, how far down in the bore is the piston at TDC (piston deck height). What's the bore on the short block, standard or 0.030" over or what?
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Old 05-16-2010, 11:15 PM
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Quote:
Originally Posted by techinspector1
OK, figure your static compression ratio first. You need 5 values to figure it. Cylinder volume, combustion chamber volume, head gasket volume, piston crown volume and piston deck height volume. If you'll post some measurements, I'll figure the volumes for you. For instance, how far down in the bore is the piston at TDC (piston deck height). What's the bore on the short block, standard or 0.030" over or what?
I'll have to get all of the ratio's. I really have no idea, I just know that the guy who does the work says the compression on the new block is great and everythings in order. It's bored 0.030 over I believe.
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Old 05-16-2010, 11:20 PM
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Let us know which intake manifold you have - maybe the Performer?

Then which Edelbrock head you have - either the 72cc or the 87cc?

Was the shortblock done by an engine rebuilder or a private party? Also, just a quick question on what the tops of the pistons look like - two eyebrows, four, or eight?

Then finally what you expect out of the engine, and what performance level you would like to be at. In other words, just cruising around, a few burnouts leaving the local drive-in, or possibly more serious power.
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Old 05-17-2010, 12:12 AM
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Quote:
Originally Posted by lust4speed
Let us know which intake manifold you have - maybe the Performer?

Then which Edelbrock head you have - either the 72cc or the 87cc?

Was the shortblock done by an engine rebuilder or a private party? Also, just a quick question on what the tops of the pistons look like - two eyebrows, four, or eight?

Then finally what you expect out of the engine, and what performance level you would like to be at. In other words, just cruising around, a few burnouts leaving the local drive-in, or possibly more serious power.

I went with the higher power 87cc. The short block was done by a private party. He's always done amazing things. Rebuilding engines, carbs, etc. I'll have to check the pistons out and let you know tomorrow.

As far as power goes, I'd be happy with 350-400. Eventually I want to make this a pro-street car with two carbs, a blower, etc. I figured this would be a good place to start though!
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Old 05-17-2010, 08:54 AM
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With a zero deck and 0.041 head gaskets, you're about 9:1 compression ratio. While CR isn't especially critical on a Pontiac 400/455, it still has a bearing on camshaft selection.

The 72 cc heads would have given you 10.3:1 CR. There isn't "higher power 87cc", this is a measurement of the combustion chamber. The port and valve sizes are the same between the 87cc and 72cc heads.

Usually, the 72cc heads are for the 400 cid range engines, the 84cc heads are "right" for the 455, giving about 10.2:1 or so w/FT and zero deck.

All that said, you can exceed your 400HP goal w/ease. With the 87cc heads and all. But NOT w/the OEM cam, obviously.

You can take advantage of the better flow of the Edelbrock heads w/a 750 cfm carb and an RPM intake (the shaker hood scoop, won't be any more ), along w/a good cam and your good exhaust system.
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Old 05-17-2010, 09:43 AM
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i personally like the 400's better than the 455's the difference is larger mains in the 455 and less than a .5" stroke (which you can buy a eagle 4.25" stroke crank for 300 bucks compared to the 455 4.21" stroke) bore is pretty much the same +/- .01 (virgin blocks)

ditch the intake and carb. 600cfm is too small, and your 5500 rpm intake (performer) is nothing more than a stock replacement, it may be good off idle, but wont help with higher rpms.
my advise is to get either a rpm performer or a holly dominator (craigslist price 50-100 bucks) i <3 open plentums. cut intake &PORT MATCH!!! use brass shim material to block off heat cross over. get a mec. secondary 750 dp, you can jet up n down from there if needed.

im not a fan of the edel heads, but they do work well!
make sure the valve springs match the cam

no offence but... that aluminum waterpump isnt going to help, if you dont install your devider plate properly. there are tech articles that explain this in detail, but basically you bolt the devider plate to the waterpump and bend the inlet hole so that the sheet metal is .125" or 1/8" away from the pump veins.

there are many many tricks that i could tell you, but i want you to be staring @ my tail lights
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Old 05-17-2010, 02:56 PM
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Lots of good feedback here! Much appreciated! So I'll just swap out the carb and get a 750cfm, and a performer intake manifold. That I can do this week. But as for the cam, what should I go with? With an OEM cam I'm not going to get anywhere like you guys said--so what would be a good camshaft to put in? Price doesn't bother me. I put $700 into the exhaust headers. I just wanna be able to get up and go
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Old 05-17-2010, 02:58 PM
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Quote:
Originally Posted by cobalt327
With a zero deck and 0.041 head gaskets, you're about 9:1 compression ratio. While CR isn't especially critical on a Pontiac 400/455, it still has a bearing on camshaft selection.

The 72 cc heads would have given you 10.3:1 CR. There isn't "higher power 87cc", this is a measurement of the combustion chamber. The port and valve sizes are the same between the 87cc and 72cc heads.

Usually, the 72cc heads are for the 400 cid range engines, the 84cc heads are "right" for the 455, giving about 10.2:1 or so w/FT and zero deck.

All that said, you can exceed your 400HP goal w/ease. With the 87cc heads and all. But NOT w/the OEM cam, obviously.

You can take advantage of the better flow of the Edelbrock heads w/a 750 cfm carb and an RPM intake (the shaker hood scoop, won't be any more ), along w/a good cam and your good exhaust system.
Since the shaker hoods going to come off, what will be showing? The air filter and all? Eventually I want a blower on this beast, dual carb too
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Old 05-17-2010, 03:15 PM
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You need to post some pics for us to see , Love to see the 78.



Cole
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Old 05-17-2010, 04:35 PM
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Quote:
Originally Posted by cobalt327
You can take advantage of the better flow of the Edelbrock heads w/a 750 cfm carb and an RPM intake (the shaker hood scoop, won't be any more ), .
Hey Cobalt, what is the clearance differance between a performer and the rpm intake, Just courious i have the performer on my 78 with a Pontiac Q-jet carb.
And to the OP show your pics.

Cole
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Old 05-17-2010, 06:27 PM
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Quote:
Originally Posted by eloc431962
Hey Cobalt, what is the clearance differance between a performer and the rpm intake
I'm not sure, but enough that w/o a drop base for the shaker (Butler has them), it will not fit w/the RPM.

There is at least one single plane intake that will work- the Tomahawk.
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