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Header Flange to Primary Transition

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#1 BayAreaZT



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Posted 04 January 2016 - 04:06 PM

It’s been a while since I’ve posted here but there’s always good technical knowledge on this board.  This is not Z related but a header question in general.  I’ve got a set of BMW headers that doesn’t have consistent flange to primary pipe transitions.  There are gaps between the primary pipes and the ID of the flange where ideally it should be flush (welded on the backside).  Most of them are close to flush but the worst gap is about 1/8”. 


My question is should I go ahead and use them as is or should I attempt to fix the gap?  Can a high temp metal filler be used to fill the gap?  I don’t really want to go that route but maybe someone has it before and has some feedback.  If I have to weld to fill it I’d rather send the headers back.  I’m sure the gap will have some effect on flow and performance but would it be enough to not use the headers?  Keep in mind I’m not looking to extract maximum power out of the exhaust setup.  I’m mainly wanting to get rid of the factory headers that have the cats built into them.



Dale A.
'71 240ZT *SOLD*
"Things should be done as simple as possible, but not too simple."

#2 johnc



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Posted 05 January 2016 - 08:14 AM

Weld up the gap and grind it down smooth.

----- John Coffey, Fabricator at Benton Performance, LLC

#3 seattlejester


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Posted 05 January 2016 - 02:25 PM

I agree, although I might be a little concerned about it pulling or twisting or something. On a few eBay headers I had like that the gap area thinned out and wore down and broke/cracked over time. I'm not sure how it is held on the back/outer side, but I would be a bit concerned unless the manufacturer can tell you otherwise. 

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