Turbo primary size dilemma
Thread Starter
Staging Lane
Joined: Apr 2006
Posts: 62
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From: Saint Clair Shores Mi
Turbo primary size dilemma just as I was going to v band my truck manifolds I came across set SW turbo headers for great price. They have 1 3/4 primaries and 2 1/2 collector for a 2 1/2 hotside all of which I read was good for my 5.3 Billet S480, LJMS cam motor....got the headers and they look incredible nice quality.
Measured the primaries and they are 1 3/4 OD but have an 1 5/8 ID. Researched more and many header manufactures go by OD....so the question is...will the 1 5/8 ID work for my S480 build which should be about 900-1000hp?
again...many of the 1 3/4 turbo headers on the market are all OD...so I would need an 1 7/8 OD to get the 1 3/4 ID if that's needed.
Measured the primaries and they are 1 3/4 OD but have an 1 5/8 ID. Researched more and many header manufactures go by OD....so the question is...will the 1 5/8 ID work for my S480 build which should be about 900-1000hp?
again...many of the 1 3/4 turbo headers on the market are all OD...so I would need an 1 7/8 OD to get the 1 3/4 ID if that's needed.
Last edited by deputydog; Jan 21, 2019 at 06:50 PM.
Thread Starter
Staging Lane
Joined: Apr 2006
Posts: 62
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From: Saint Clair Shores Mi
Last edited by deputydog; Jan 21, 2019 at 07:55 PM.
My 5th gen camaro Huron kit had log manifolds with 1.5” ID primaries and just under 2” ID vbands. On my SBE LS3 I made 817rwhp/758rwtq @ 16psi. Down stream exhaust design (post turbo) will be more critical.
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Smaller diameter that will still flow enough volume at max rpm is most desirable for turbo spool. I am pretty sure you could have 1.5" ID primaries and (2)2.125" ID pipes feeding the turbo and make 1000hp.
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Staging Lane
Joined: Apr 2006
Posts: 62
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From: Saint Clair Shores Mi
Thanks for replies....the exhaust port on my 243 heads measure 1.570 wide and 1.175 tall, so im good with the ID of my headers being 1.625. The ID on my 2.500 stainless tubing for hotside is 2.370. Guess I just assumed ID when people recommend 2 1/4 or 2 1/2 hotsides or 1 3/4 or 1 7/8 headers....was concerned for awhile....not even worried about my 2.500 hotside being to big now knowing it's actually 2.370. The headers do concern me a bit but I'll run them. if I did it over would got 1 7/8 so ID would be 1.750.
TECH Fanatic
Joined: Feb 2015
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Side note - not all 4 primaries flow at the same time. Collector could be reduced to 3.5 sq in. (~2.125") Amazing to see collectors that look abnormally small on high end headers.