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How to repair stripped threads in exh. manifold? (Turbo app.)

How to repair stripped threads in exh. manifold? (Turbo app.)

How to repair stripped threads in exh. manifold? (Turbo app.)

(OP)
Who has direct experience (successful experience preferred) repairing stripped threads in a cast iron exhaust manifold?  This is a very high-heat turbo application so please don't use the word Loctite anywhere near your recommendation. :-]
I want to hear specific experience with Keen-serts vs Helicoil inserts, stainless vs. alloy steel, that kind of input is what I am after.

Thanks in advance!

RE: How to repair stripped threads in exh. manifold? (Turbo app.)

I've been staying with Heli-coil, for quite some time now...I have a repaired sparkplug hole in a cylinder head that I did in 1969 and it's still just fine. Avoid the cheap "imitation Heli-coil" knockoffs.
My "post retirement" job of repairing commercial air compressors would have been nearly impossible without Heli-coil.  Keep in mind that the "corner auto store" does not carry anything near the complete line of thread repair supplies available from Heli-coil. Google can be your best friend here.

Tried several of the preformed inserts and, since most required some form of locking compound, I found them lacking in stability and longevity, not to mention $$$.  Not my first choice.

Rod

RE: How to repair stripped threads in exh. manifold? (Turbo app.)

Rodger the genuine product comment.

I foolishly bought a sack of 1/4-28 "Helicoil-Like" inserts on ebay; about every second one broke the tang off as soon as it went into the repair- and this ain't my first rodeo, helicoil-wise. You'd think at my age I would know better.

RE: How to repair stripped threads in exh. manifold? (Turbo app.)

Quote:

You'd think at my age I would know better.

Only if you are a LOT smarter than me...I seem to be the master at repeating my mistakes!!!

Rod

RE: How to repair stripped threads in exh. manifold? (Turbo app.)

Whatever the merits of the "Keen-cert" type, they require a bigger hole than Helicoils. You can find yourself not having enough material on something like a casting.

RE: How to repair stripped threads in exh. manifold? (Turbo app.)

A little of topic, but I replaced the turbo on an Allis 426 diesel engine once. I was dreading the job because I knew the bolts holding the turbo to the manifold where badly rusted, but to my surprise the bolts went all the way through. I just had to cut the nuts off with my Oxy-Acetylene rig and all done.

In short, if you can use a through bolt it will make life easier the next time you have to take the turbo off. I wish all designs  were like this.

ISZ

RE: How to repair stripped threads in exh. manifold? (Turbo app.)

Turboragtop:

Cast iron is not a good material for high temp manifolds as it goes through a phase transition at about 900C.  See link below:

http://en.wikipedia.org/wiki/Iron

Use a high silicon ductile cast iron (silicon raises the temperature of the phase transition) or iron-nickel alloy like ni-resist to avoid the phase transition that plays havoc on fastener retention.

Make sure your keen-serts (I prefer keen-serts to helicoils for high temp application, but do not have solid data to back up opinion) are made of a material with a similar CTE characteristic.  (Be careful - CTE not constant with temp.  I have been bitten by this in a high temp fastener application.)  

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