view of the primaries


view of the secondaries

I was wondering if anyone had any detailed specs on the older 2 piece 4-2-1 header. I'm mainly looking for primary tube diameter, secondary tube diameter, and any details on what the actual exit diameter is. As we all know, different companies use different collector designs and sometimes they're not always a 2.5" OD all the way through as explained by John from Hytech.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">HyTech's John Grudynski in Tuan's header article on HV
I have done some more research on the JDM verses the Mugen versus the Spoon. The JDM has smaller primaries than the Mugen or Spoon.
They are 42.6mm outside diameter, the Mugen and Spoon use 44.8mm outside diameter primaries. The JDM has a 2.125 I.D. exit size, not the 2.5 in. that everyone thinks. It does expand up to 2.5 O.D. but it has to pass through a 2.125 diameter exit to get to the 2.5 diameter. The Mugen has a 1.875 I.D. exit diameter. The Spoon has a true 2.375 I.D. diameter exit.
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^ That was in reference to the newer 4-2-1 Spoon header with much longer primaries and very short secondaries as pictured below:



I imagine that the specs between the older 4-2-1 and the newer 4-2-1 that John G. is talking about are different. Any info is greatly appreciated. Thanks.