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What Size Primary For Twin Ls1?

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Old Oct 26, 2004 | 10:20 AM
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Default What Size Primary For Twin Ls1?

I am building a set of twin turbo headers for an LS1. They only needto make about 1000 fwhp max. I am assuming a 1 3/4 primary is adequate? What wall thickness? What are you 1000 hp guys using? Thanks.
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Old Oct 26, 2004 | 02:17 PM
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They only needto make about 1000 fwhp
Lol!

I love this forum!
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Old Oct 26, 2004 | 02:23 PM
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good luck finding somebody saying that many other places...
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Old Oct 26, 2004 | 02:31 PM
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1 5/8 should support that from what I've read.
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Old Oct 26, 2004 | 02:51 PM
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Right now my motor that I sold makes 650 on pumpgas alone! With unported heads! 1000 horse with a twin turbo setup is nothing compared to that. That is a 350 hp increase from what can easily be done on motor only! Granted I will be using an ls1, but I am looking just to double the hp it will produce on motor and was asking for other people with the same setups to give advice on what they use, not some comments messing up my thread. So unless you have an answer to my question, don't comment. Thanks.

Also, Besides primary size and wall thickness, anyone who has built twin headers already, how many of what bends did you go through, I am trying to figure out what to order. Thanks.
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Old Oct 26, 2004 | 05:11 PM
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FWHP what the hell is that? I know what RWHP is.

Get 8 U (or is it J) bents from Stainless this is 16 90degrees bents witch should cover u but u never know how many times u will make a mistake.
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Old Oct 26, 2004 | 05:35 PM
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ask y2khawk
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Old Oct 26, 2004 | 06:17 PM
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Originally Posted by smokinHawk
ask y2khawk
how many cubic inches are you planning on? I've got a 380" motor and 1-3/4 primaries, but I think 1-5/8 would work too.. My last motor was close to 1000 fwhp and it had 1-5/8 primaries..
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Old Oct 26, 2004 | 06:24 PM
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mine are 1 3/4" 0.065 wall

348 cu in, guessing 1100+ at the flywheel
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Old Oct 26, 2004 | 06:41 PM
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Great, thats what I wanted to hear. So you figure about 8 U-bends... What radius? What did Y2KHAWK end up using as far as bends? I am just gonna whip together a cheap ls1 with some billet rods and some dished pistons over the winter. I am going to try to build a 1000 hp pumpgas 347" motor. I had a 427" motor that was identical to Monty william's motor that had 2 pt-52's and made 1200 hp on pumpgas. Now I will just try with smaller cubes. I am planning on trying 8:1 or less compression to see how far pumpgas will go! Figured it will be a good winter project. Thanks for the replys.
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Old Oct 26, 2004 | 07:37 PM
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Originally Posted by goober35
FWHP what the hell is that? I know what RWHP is.

Get 8 U (or is it J) bents from Stainless this is 16 90degrees bents witch should cover u but u never know how many times u will make a mistake.
fwhp is fly wheel horse power
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Old Oct 26, 2004 | 07:38 PM
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where can you get the stainless steel tubing to make the headers at?
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Old Oct 27, 2004 | 05:15 AM
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i think Harlan go this at burns stainless. there are other mandrel bend places as well, i think even summit and jegs have them.

http://www.stainlessworks.net/ a sponser here has them to
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Old Oct 27, 2004 | 09:59 AM
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1 5/8 primaries is fine. We have stangs making 1200+rwhp with those primary sizes.

Jose
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Old Oct 27, 2004 | 09:22 PM
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I just finished fabricating mine for my TT427 Chevy 2 project. They are .065" 321 1 3/4" tubes. I would stick with 1 3/4" over 1 5/8". If you run over 14.7 psi of boost you effectively are doubling the displacement of the motor. That equates to a lot of exhaust to relieve.

Just make sure your turbos are properly sized for the displacement and primary size!

I bought all my material from BURNS STAINLESS as well. Nice stuff!
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Old Oct 27, 2004 | 09:30 PM
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How much tubing did you buy exactly?
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Old Oct 28, 2004 | 11:58 AM
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I actually used less material then what I bought. I think I ended up using 8 2.5" CLR U-bends, 3 4.0" CLR U-bends and about 6 pieces of 24" long straight tubing.

The merge collectors are where the big money is!
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