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Old 04-20-2004, 11:48 AM
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so im debating

ive been debating for some time now how to get some more hp from my pontiac ..so ive got a standard 400 from 1976..which is sluggish right..so i got an eagle crank to stroke it to 468 ci i think and i brought a extreme cam kit 477 intake lift 480 exhaust lift in the kit with timing chain and all that and ive had my heads ported polished and my valves faced 3 angle cuts..ive got a 500 holley carb...SO HOW MUCH HP CAN I EXPECT or what else can i do to get some more apart from forking out a grand on heads.

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Old 04-20-2004, 12:34 PM
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I've got a program that I crunched some of your numbers in, and the way it is, you'll get approx. 235.1 hp @ 3500 rpm, and 379.4 lbs torque @ 2000 rpm. These are just rough questimates.
I would get a little bit bigger carb though. At full throttle a 500 cfm won't keep up, you'll be starving the engine. I would go with at least a 650 cfm or so carb.

The only other horse power gains I could suggest would be run an electric fuel pump instead of a cam-driven mechinical, and go with an electric cooling fan, and an electric water pump if possible. That could put it up around 242 hp.
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Old 04-20-2004, 01:19 PM
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your carb is killing you, you need an 800 or larger.

K
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Old 04-20-2004, 01:24 PM
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Like killer said, carb WAY to small. Need a good 750 or higher.
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Old 04-20-2004, 01:26 PM
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I third that motion for a bigger carb, its a 468ci not a small block. Killerformula is problably right 800cfm + ..



Ben
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Old 04-20-2004, 01:34 PM
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It's a small block putting out around 250 horsepower, 800cfm would be a huge overkill in my opinion. Try a 650cfm.
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Old 04-20-2004, 01:41 PM
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You will be making more than 250HP with that combo.

I have the specs on my Bro's fresh rebuilt '77 400ci

Fresh block bored .030 over
Heads 3 angle port job
Flat decked
CR of approx 9.5:1
Stock Quadrajet 850CFM
Edelbrock Pontiac Performer Intake
Comp Cams, not sure which grind #, but approx .480 lift, not too lumpy.

Probably forgot a few things, but anywhoo, when we ran all the data thru Desktop DYno it gave us 380HP, 420ft-lb.

YOu're gonna want a bigger carb on there if you plan to bring it over 4000RPM.
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Old 04-20-2004, 02:28 PM
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Quote:
Originally posted by 69elcaminoss
It's a small block putting out around 250 horsepower, 800cfm would be a huge overkill in my opinion. Try a 650cfm.
I think maybe you misread guy. He's building a 468 motor, he's going to need much more than 650!

K
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Old 04-20-2004, 03:09 PM
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Quote:
Originally posted by killerformula
I think maybe you misread guy. He's building a 468 motor, he's going to need much more than 650!

K

I was just going off of Jhayman's calculations.
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Old 04-20-2004, 03:16 PM
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yeah those calculations are way off, the HP is wrong too IMO.

K
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Old 04-20-2004, 04:17 PM
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some good replys there cheers. i like the electric fuel pump idea and big carb ..carb is easy..can i jet my other one or is it a new one and electric pump di i have to get a block plate for the old one

i did suspect haymans was a tad off i think ive current ly got about 200 hp all that cant only give me 30 extra specially with a cam lifting high seventies...how would ram air iii heads go down i can get some for 600 is this a good price
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Old 04-20-2004, 07:20 PM
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jhaymans calculations are WAY off. A typical stroked 468 pontiac will put out at least 400 ponies at the flywheel depending on heads, cam, etc.

Go 800 or bigger.

69elcamino, this motor is not a "small" block nor is it a "big" block
Pontiacs are the same block size 326-455. I have yet to see a 468 cubed small block by the way.

Expect HIGH compression with the ram air 3's on a 468. Go with some Edlebrocks. Performance straight out of the box.

Here, check out this 455 build up. This should give you an rough idea of the power you can be puttin out:

http://www.carcraft.com/techarticles...ont/index.html
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