header selection help

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pontiacgp

blank
Mar 31, 2006
29,270
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Kitchener, Ontario
So you are sayin these heads aren't any good. I tried to post a link to them but it wouldn't work. Just do a search for them on summitracing.com

Chevrolet Performance Fast Burn Cylinder Heads 19300955

Those are the heads that's on the Gm 604 crate racing engine. We had that engine in a few of our cars and that is a good head. You should easily have over 400 hp as long as you have a decent cam but if you want to switch those heads out for something else I will gladly take them off your hands...I can't help you out with a header choice though case we used schoenfeld headers
 

Mike buttafuoco

Apprentice
Sep 27, 2016
86
51
28
Carlisle, pa
Absolutely, I got a little carried away. Unfortunately in our positions we are limited by space, price, and what is available. Make your calculations and buy the closest thing you can afford/find.
I don't think you got carried away. "That's a question a child might ask, but not a childish question."
 

Mike buttafuoco

Apprentice
Sep 27, 2016
86
51
28
Carlisle, pa
And just a little food for thought: the general idea is a large primary tube header will give you better flow at the top and the smaller tube will give you better torque on the bottom. (Not in every case) but remember something too, hot air moves faster than cold air. The larger tube will theoretically cool the exhaust gas faster and thus move the spent fumes slower. And you guys gave me verbal diarrhea!
 
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bertscova

Greasemonkey
Jun 27, 2015
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I agree with you pontiacgp. I did a lot of research on heads before choosing these.
wiseco flat top pistons, scat crankshaft, Cast Steel, 3.750 in. Stroke, 6.00 in. Rod, Each. by our calculations should be around 10.5:1 compression ratio
this is the cam
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=189&sb=2
all put to the ground with a monster 700r4 and a moser custom 12 bolt with 4.11 gears
and Im looking at these headers Hedman Husler Race Headers 65218
 
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Bar50

Royal Smart Person
Jan 1, 2009
1,180
870
113
Tulsa, OK
Swapped from ported Vortec to AFR heads on a 350 in a bracket car G-body....it picked up 0.7 of a second in the 1/4.
 

Clarmo

Master Mechanic
Jan 29, 2016
267
460
63
Ottawa, Canada
The diameter and length of the primary tube is THE singe most important part of your exhaust system, followed by diameter and length of your collector. This is determined mostly by your cam profile as well as your stroke and bore. This is a good calculator to get a good idea as to what you need as long as you know all the specifics of your exact cam profile and where your engine is supposed to make peak torque. I've had some extensive conversations about this with an experienced racing mechanic who has worked along many of the legends in drag and motorcycle racing.

http://www.wallaceracing.com/header_length.php

You could have 1.5" headers on a 450-500hp motor and it wouldn't make a difference. The OP was looking for a header that fits angle plug heads and mentioned 1-3/4 long tube headers. NOT NEEDED. A set of shorty headers that fit properly with angle plug heads and a proper flowing exhaust will support well over 500hp in a "street" car any day.
 
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383_GrandPrix

G-Body Guru
Sep 9, 2016
678
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Quebec, Canada
You could have 1.5" headers on a 450-500hp motor and it wouldn't make a difference. The OP was looking for a header that fits angle plug heads and mentioned 1-3/4 long tube headers. NOT NEEDED. A set of shorty headers that fit properly with angle plug heads and a proper flowing exhaust will support well over 500hp in a "street" car any day.

Can you make 500 hp on 1.5" headers? Yes. Do you need an optimised exhaust for the street? No. My only point is that if you want to get the full potential of your motor the size and shape of the header will be the most important part of your exhaust system. Everything after the collector is parasitic. How much of an effect it has depends on size and shape of the exhaust and how efficient your header is. We don't all need the perfect exhaust to make peak power but understanding the science and dynamics of it can be helpful.
 
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bertscova

Greasemonkey
Jun 27, 2015
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Let me clear some thing up. I have to use headers with a primary tube of atleast 1.75 or the header tubes will be smaller than the exhaust ports on the heads. And i know that wouldnt be good for hp.
 

383_GrandPrix

G-Body Guru
Sep 9, 2016
678
1,310
93
Quebec, Canada
Let me clear some thing up. I have to use headers with a primary tube of atleast 1.75 or the header tubes will be smaller than the exhaust ports on the heads. And i know that wouldnt be good for hp.

So with the calculations I made based off the valve diameters and cam specs you have, a header with 1.75" dia x 30" long primaries with a 3" collector will be pretty much perfect. As for the flange shape; a D port flange is ideal but you can get away with an O shape flange, as long as it's 1.75" inside dia. Now it's just a matter of finding one that will fit over the angled plugs, unfortunately I can't help you there.

Also, from what I've read these seem like nice heads, I think you made a good choice. I'm willing to bet you won't have any of the problems I'm having with my E-street heads, but that's a whole other can of worms. -_-
 
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