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Old 12-05-2012, 08:28 PM
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Shrunken SBC Exhaust Manifolds

This isn't the first time, so I know I'm not the only one to run into SBC 350 exhaust manifolds shrinking. Same manifolds, same heads, same sides, but the holes don't line up now. Engine has been out since early summer. Will they shrink more the longer I leave them off? Left side went on after it learned some new words, but right side doesn't even look like it will listen. Have tried my six-pound coaxing wrench, but it be cast iron so got the result I expected: zip. I don't think the gas wrench will help any, either. Cold when took em off, cold putting them back on, and again, cast iron. Maybe the heads grew, but that's scary. Think last time ran into this, had to use different manifolds, but that was long time ago and had plenty around to try to fit then and don't think even used manifolds off 350, might have come off 400. Does anyone know the cure ? Thank you.

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Old 12-05-2012, 08:44 PM
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At my shop I had an exhaust manifold stretcher I think you can buy them still ! Your manifold didn't shrink it warped and its common! Usually the studs brake or come out very tight when removing the manifolds because they were warped while on the engine Before tear down, and it isn't noticed by people till its assembly time! You should have them machined flat too sometimes there is a twist with the warp that wont let them seal!

My tool is a "Lyle 31000" exhaust manifold spreader

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Old 12-05-2012, 09:17 PM
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Thank you painted jester. That makes perfect sense. This engine obviously been overheated, probably more than once. Pulled the engine out of 94 P/U I got real cheap, and found the engine to be so bad, I couldn't even use the original block. So, new block, crankshaft kit, other stuff to convert from tbi to carburetor. Should have just bought a rebuild. Would have cost less. Am surprised the heads aren't broken (and maybe they are, and I just don't know it yet). Thanks again for the tip. Am thankful the cylinder heads aren't growing. : )
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Old 12-05-2012, 09:56 PM
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Bet its cheaper to get a used manifold than to have them machined.

Also block hugger headers are very cheap these days. Jet hot cloat if you want them to last and not rust but then they wont be cheap any more.
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Old 12-06-2012, 12:29 AM
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Quote:
Originally Posted by fasteddy_1947 View Post
Am thankful the cylinder heads aren't growing. : )
Haa!

I'd say to make one using a heavy turnbuckle, but it might cost as much as the whole tool!

Look the manifolds over carefully. It's not at all unusual for them to have hairline cracks. Finding replacements shouldn't be a problem unless they're, well, a problem!

OEM Chevy exh. manifolds


The spreader will work good on some manifolds:

Not as good on some:

And not at all on others:

Lisle p/n 13000:
Good luck.
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Old 12-07-2012, 09:12 PM
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Yes. I never figured that the manifolds could warp while on the engine. They weren't binding when I took them off. The engine had been seriously abused in the past, so the warped manifolds were just another indication of it. Considered trying bend the right one out to where could get a bolt started, but don't know where to try to correct it in relation to the center ports. Think probably between the center and forward ports, as rear and center flanges bolted up (a little tight, but didn't cross-thread), and with my luck.. . Anyway, a quick trip over to the U-pull auto parts store and warehouse corrected the problem and I found a bunch of other stuff I need. I just thought maybe someone would have a quick and easy (or magic) fix, but there I go trying to think all by myself again. Thank you all for the input, and on we go to the next puzzling development for a highschool dropout trying to reengineer a machine that took hundreds of college trained automotive engineers to design and build. : )
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Old 12-07-2012, 09:17 PM
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Quote:
Originally Posted by fasteddy_1947 View Post
Yes. I never figured that the manifolds could warp while on the engine. They weren't binding when I took them off. The engine had been seriously abused in the past, so the warped manifolds were just another indication of it. Considered trying bend the right one out to where could get a bolt started, but don't know where to try to correct it in relation to the center ports. Think probably between the center and forward ports, as rear and center flanges bolted up (a little tight, but didn't cross-thread), and with my luck.. . Anyway, a quick trip over to the U-pull auto parts store and warehouse corrected the problem and I found a bunch of other stuff I need. I just thought maybe someone would have a quick and easy (or magic) fix, but there I go trying to think all by myself again. Thank you all for the input, and on we go to the next puzzling development for a highschool dropout trying to reengineer a machine that took hundreds of college trained automotive engineers to design and build. : )
Use studs and washers and bronze or brass or stainless nuts


Jester
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