Header size for big cube FI?
Thread Starter
Safety Car
Joined: Mar 1999
Posts: 3,608
Likes: 180
From: Toronto, Canada
Header size for big cube FI?
When building a 400 + ci motor with about 14-15 psi what header size would you recommend? I have a set of ARH 1 3/4 and would like to resuse them with my future build. How do my current headers compare to Kooks 1 7/8? Would I be giving up 10-15 rwhp or is the margin less than that?
Former Vendor
Joined: Dec 2006
Posts: 2,239
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I would say that you very well could be giving up 10 to 15 rwhp. You have a lot of exhaust to expel from the larger cubic inch engine. If you can afford to do so, the switch to the 1-7/8 headers will indeed help. Bob
Premium Supporting Vendor
Joined: Aug 2008
Posts: 1,964
Likes: 37
From: Deer Park NEW YORK
You're definately gonna need the bigger system with that setup we can build you exactly what you need. give us a call in the shop with more specifics and we can spec something out for a repeat customer
Former Vendor
Joined: Mar 2008
Posts: 2,279
Likes: 1
Why build a 400 cube motor? A 347 can make 700 easily with your 1 3/4's? Now you have to sell your headers spend another 2k for 1 7/8's, the another 2.5K for better heads and another 1K on a better intake to feed the 400 cube motor.
Just forge the 347 or go 364, add eight ribs and turn up the boost-700 is easy and more than enough-you seen how easy it was to make 650 right?
Just forge the 347 or go 364, add eight ribs and turn up the boost-700 is easy and more than enough-you seen how easy it was to make 650 right?
Race Director
Joined: May 2003
Posts: 12,725
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From: ECS : WTF did you break now and HTF did you break it this time
um.....I'm with Arun, just go 346...
I have stock 243 heads unported, ls6 manifold, ECS blower cam, kooks 1 7/8ths (came with the car....prefer teh AR's on my other one honestly) with cats, 2.5 inch exhaust, into a stock C5 catback chopped at the mufflers with some junk bullet mufflers and bends.....
car has dyno'd over 800 at the wheels with 93 and meth.
you really don't need to spend the money on a 402, heads intake etc. its easily an extra 5 grand to start over the forged 346 that will just make you break more parts and equate to more tire spin.
I have stock 243 heads unported, ls6 manifold, ECS blower cam, kooks 1 7/8ths (came with the car....prefer teh AR's on my other one honestly) with cats, 2.5 inch exhaust, into a stock C5 catback chopped at the mufflers with some junk bullet mufflers and bends.....
car has dyno'd over 800 at the wheels with 93 and meth.
you really don't need to spend the money on a 402, heads intake etc. its easily an extra 5 grand to start over the forged 346 that will just make you break more parts and equate to more tire spin.
Former Vendor
Joined: Mar 2008
Posts: 2,279
Likes: 1
um.....I'm with Arun, just go 346...
I have stock 243 heads unported, ls6 manifold, ECS blower cam, kooks 1 7/8ths (came with the car....prefer teh AR's on my other one honestly) with cats, 2.5 inch exhaust, into a stock C5 catback chopped at the mufflers with some junk bullet mufflers and bends.....
car has dyno'd over 800 at the wheels with 93 and meth.
you really don't need to spend the money on a 402, heads intake etc. its easily an extra 5 grand to start over the forged 346 that will just make you break more parts and equate to more tire spin.
I have stock 243 heads unported, ls6 manifold, ECS blower cam, kooks 1 7/8ths (came with the car....prefer teh AR's on my other one honestly) with cats, 2.5 inch exhaust, into a stock C5 catback chopped at the mufflers with some junk bullet mufflers and bends.....
car has dyno'd over 800 at the wheels with 93 and meth.
you really don't need to spend the money on a 402, heads intake etc. its easily an extra 5 grand to start over the forged 346 that will just make you break more parts and equate to more tire spin.
