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Discussion Starter #1
I've just been looking over my original exhaust manifolds for a 1993 6.5. I have enclosed picktures of the mating surfaces after I have wire wheel brushed them and used just a touch of a metal file.

My question is how would you treat reinstalling these manifolds? I've read many differing opinions on using gaskets or not,.Mine didn't have a gasket and seemed to work fine, however I'm up for the latest recommendation. I am tempted to have these exhaust ports machined, Is that a reasonable option?

Thanks for your experience. :)
 

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With a part like exhaust manifolds the shops will usually just hit them with a belt sander and since you have them off I would have it done. It will take them less than 5 minutes each so it shouldn't be all that expensive. Its not like there is a complex setup to mount them in a machine.
 

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With an exhaust manifold you are just looking for a fairly smooth finish that is only flat on one side and you don't much care about all the other angles. With a head or intake you are worried about how each surface relates to other surfaces so you need it held and set up properly before you do any work which can take longer to do than the actual machine work.
 

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Discussion Starter #5
With an exhaust manifold you are just looking for a fairly smooth finish that is only flat on one side and you don't much care about all the other angles. With a head or intake you are worried about how each surface relates to other surfaces so you need it held and set up properly before you do any work which can take longer to do than the actual machine work.
I appreciate that. Do you have any opinion on whether to use a gasket or not? Thanks for chiming in.
 

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I prefer no gasket. Great results from honing by hand on glass w/ #60 (3 sheets lengthwise spray adhesive on plate glass) but it usually takes at least 30 minutes per. On he other hand it is a great workout and you do not need to go anywhere. Yours look pretty rough so having a shop do them would be ideal.

-edit- also... wire wheel the heck out of the studs and clean the holes with a thread chaser of sorts, then apply anti seize liberally.
 

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Discussion Starter #7
You must have been reading my mind. I've been wire wheeling all bolts and studs that I can reuse, and chasing all holes and threads around the engine. Unfortunately none of the manifold to head bolts are usable (they are rusted beyond use). I do not want to tell you what I had to pay for OEM bolts, the price for some of the bolts is akin to gold.
I had wire wheeled and filed those exhaust port mating surfaces, but like you I thought having a machine shop resurface would be necessary. I don't realize how old I am till these machine shops give me their prices for that. I thought 60$ apiece a stretch. I did find someone to them for 2/3 that though. Thanks for responding. :)
 

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I use a large platform belt sander , the main thing is to get down to fresh material and flat, the exhaust bolts are a speical thread pitch from the factory, and they can still be purchased Bolt - GM (10137539) | GMPartsNow , and no gasket, orange HIGH temp silicone is all that is required...
 

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I'll resurface them for ya free just pay to ship them both ways....
What a kind offer. Thank you very much. Unfortunately I didn't read this till today and since my last post I already had them done. You said just to use the high temp red silicone and no gasket, and I appreciate that advice. I had been thinking about using a copper based silicone or spray and no gasket. Thanks again for your offer sctrailrider, and hope you have a great week.:)
 

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So out of curiosity I've always heard any sort of RTV or sealant on exhaust is a No-No. With exhaust coming out around a thousand degrees I would worry that any sort of silicone that would maintain somewhere around 1 or 2 thousandths of an inch body when applied would burn up and leave one or two thousands of an inch gap later.

I am not saying this doesn't work but I have never used anything unless it's a physical gasket to make up for imperfections in flatness.

Is there any sort of documentation that anyone can point me to to change my perspective? Thanks!
 

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So out of curiosity I've always heard any sort of RTV or sealant on exhaust is a No-No. With exhaust coming out around a thousand degrees I would worry that any sort of silicone that would maintain somewhere around 1 or 2 thousandths of an inch body when applied would burn up and leave one or two thousands of an inch gap later.

I am not saying this doesn't work but I have never used anything unless it's a physical gasket to make up for imperfections in flatness.

Is there any sort of documentation that anyone can point me to to change my perspective? Thanks!
As long as it's a high temp sealer it should work just fine
 

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I didn't use anything either, just took a large file and went across two ports at the same time. Seemed to seal up as far as I know.
 

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Don’t machine them you will never get them to fit properly. Even a new one can be difficult. Any minor leak will cause it to crater and become major. Just replaced my right side one.
 

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Don’t machine them you will never get them to fit properly. Even a new one can be difficult. Any minor leak will cause it to crater and become major. Just replaced my right side one.
Not sure I understand how taking material off would cause them to not fit... I mean... as long as you remove material evenly in the original plane you should be good. I removed ~.055 by hand on sand paper/glass. 2 different motors. Worked like a charm. Maybe if they were really badly warped and then you would need to massage the ears to properly align the bolts but still just machining should not mess things up unless the cut it out of plane. Now taking the exhaust manifolds towards the motor means the turbo/intake gap will be slightly tighter but all should be well within working margins.
 

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Discussion Starter #16
Thanks for chiming in guys. I did have a machine shop surface the manifold last week.

To add fuel to the fire, the machine shope told me that most people don't know that you should have brand new manifolds surfaced before installing (for what ist's worth).

Here's another one: exhaust and muffler shop I've used off and on over the last 15 years - I asked him what he uses for a sealer for direct applications - he said "use THE RIIGHT STUFF, it works great" - I asked him if it was a high temp sealer - he said he didn't think it was a very high temp sealer, but that it works excellent. Anybody else heard of this?

I am now taking a block of glass and 60 wt. metal sand paper and cleaning the turbo mount. I'll let everyone know if I have a problem with clearances. Thanks again for all your excellent insights :) .
 
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