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Gary_Ash

How to straighten a warped tube header?

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When I welded up the carbon steel tube header for my 1937 Studebaker straight 8 to be used in my Indy car replica, I didn't have sufficient clamping of the 3/8" steel plate that the tubes got welded to.  As a consequence, the mounting plate has a slight curve to it, resulting in a gap of about 1/8" at the center of the manifold between the plate and the block.  The outer ends are touching the block.  With nuts installed on the studs, I can pull the flange flat, probably enough to seal with a gasket.  However, that leaves a lot of stress in the header.  I'm thinking of shrinking the tubes at the ends to pull the flange flatter.

 

I've got a spare engine block, can tighten the manifold flat, then heat a tube section of an inch or so until it's at least bright red with an acetylene torch.  This should soften the steel and make the tube try to expand in length, but since it it restrained by the rest of the manifold, the tube should get pushed together.  Once the tube cools, it should be shorter than before.  If I do both outer tubes, the flange should be flatter.  If I can get the gaps to be 0.030" or so, I can get the flange machine flat the rest of the way, or maybe that would be OK for just cinching up the nuts.

 

Do I need to do this or will just starting the engine (eventually) and running it for a while do the stress relief I need?  Any other suggestions?    

megaphone_on_engine.jpg

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Can you take it off, make a jig of some kind, and pull the center slightly past straight and see if it relaxes straight (does that make sense)? That flange should be flexible enough to take a little bending.

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Gary,

I've done this a couple of times back in the old days.

1.cinch her down  good and snug with all bolts.

Use a "rose bud" torch head and heat the big tapered tube all round between header pipes 1&2, 3&4,5&6.

I would do 3&4 first and cinch her down while the pipe is still red.  Then do 1&2, then 5&6.

REPEAT above and chinch her down tight and let sit till room temp.

This is better done with 2 people. One on the torch and one spinning wrenches.

 

We did this on a Valiant slant 6 years ago when we built a set of headers and intake using 3 Jag S.U's out of some scrap pieces from a Midas Muffler shop in town.

 

Mike in Colorado

 

 

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Plate being 3/8 maybe it could be machined.

You would still have a quarter inch left.

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Machining the back side is an option, but not a full 1/8".  The tubes were pushed into the holes in the flange leaving a little less than 1/8" for a lap weld. 

I've read a little more on "flame straightening":  https://www.boconline.co.uk/en/images/Fundamentals-of-Flame-Straightening_tcm410-113398.pdf

A little of that and a little of Flyer15015's technique and we might get it done.  I love playing with fire!

 

I looked back on how I assembled the header, see that I had only bolted down the flange at the ends, not in the middle.  And, the flange was bolted to a 2x4, probably not stiff enough to resist the steel bending, anyway.  Once the pieces were tack welded, it came off the 2x4 so I could lap weld the tubes to the flange in back.  This is how we learn (too late). 

 

megaphone_pieces.thumb.jpg.742931e1271479331a27ca187928da06.jpg

 

1324475044_megaphone_with_fittedtubes.thumb.jpg.06ae90f7abf88d8a8cd6d2a82713dcf8.jpg

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Sure is pretty.

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