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

[TurboRagtop]

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!

 

[evelrod]

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

 

[thruthefence]

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.

 

[evelrod]

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

 

[swall]

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.

 

[IceStationZebra]

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

 

[turbomotor]

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.)