Talked to an old hand about fitting tolerances and it messed with my head

I was bitching about a 1/16 gap on a header flange last Tuesday and this 60 year old fitter said he leaves 3/32 on purpose for heat expansion. Made me wonder how many times I've been too tight on stuff that needed room to grow. Any of you guys leave extra gap on high heat joints or am I overthinking this?

2 comments

2 Comments

kimreed10d ago

Jumped in on an exhaust job last month and the same thing came up. I was gonna cinch it all tight but the old timer stopped me and said leave a hair of space on the collector flanges. Sure enough after a few heat cycles everything bedded in perfect. I've definitely been guilty of cranking down on manifolds and ending up with warped flanges or even cracked bolts down the line. Now I leave a little wiggle room on anything that sees real heat, even on header wrap jobs where I used to pull it super tight. Your mileage may vary but I bet you've saved yourself some headaches by leaving that gap.

vera_murphy9d ago

Funny you mention header wrap, because that stuff has a mind of its own too. Pulled it super tight on a customer's Jeep exhaust a few years ago and it actually started to rot out the pipe underneath because of trapped moisture. Had to cut it all off and start over. Now I just do a light snug on the wrap and let it settle naturally after a few drives. Same idea with those flanges yeah, over tightening just sets you up for grief later. Also learned that lesson the hard way on a header install where I snapped a stud and spent the whole afternoon extracting it. Sometimes the loose approach is the smart one, even if it feels wrong at first.