From what info I can gather, it seems with long tube headers 1 1/2" primary tubes are the way to go on a "warmed" up motor with 2" coming out from the collectors??
Header question
- Thread starter Bert Poliakoff
- Start date
Mike Goble
Well-Known Member
I would go with a 1-7/8" collector for each bank, with those going into a 1-7/8 x 2" parallel merge collector, like a JMD . Invert a 21101 Hedman 2-1/2" x 2" collector reducer to expand the tube out to 2-1/2" and run 2-1/2" tube all the way out.
Unless I am missing something in your response, which I am known to do, what size primary tubes? I have been playing on the internet, and see pretty much the same thing. 1 1/2" primaries/. There is also a reference to Ray Korman saying 1 1/2 for a motor up to 300HP
when i spoke directly to Gere Stahl, he referenced discussions / dyno testing with Ray Korman and stated that below 250 hp - 1 3/8" primaries. he said that you needed a real fire-breather to make sufficient use of 1 1/2". as Gere said more than once - bigger is NOT always better.
Mike Goble
Well-Known Member
It was my assumption that you were starting with 1-1/2" primaries. If you are going with 1-3/8" primaries you should use a smaller collector, like 1-3/4" into a 1-3/4 x 1-7/8 2-into-1 merge collector. A common mistake in header designs is a collector that's too large for the primaries. You can read up on this at Headers by Ed or Burns Stainless.