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Dreaded exhaust manifold bolts


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I am considering attempting to install new exhaust gaskets and possibly replacing the exhaust manifolds themselves(as I know the center section has cracks.)

I have started to bath all the bolts with Kroil, which I understand is the best thing to use.


What are thoughts on doing this job; I just want to get a feel for it before really attempting it.


Thanks in advance,

C Drake, Potomac, Md.

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Penetrating Oils


Machinist's Workshop Magazine (March/April or May/June, 2007) actually tested penetrants for break out torque on rusted nuts. They arranged a subjective test of all the popular penetrants with the control being the torque required to remove the nut from a "scientifically rusted" environment.

*Penetrating oil ..... Average load*

None ..................... 516 pounds
WD-40 .................. 238 pounds
PB Blaster ............. 214 pounds
Liquid Wrench ..... 127 pounds
Kano Kroil ............ 106 pounds
ATF-Acetone mix....53 pounds

The ATF-Acetone mix was a "home brew" mix of 50 - 50 automatic transmission fluid and acetone. Note the "home brew" was better than any commercial product in this one particular test. Our local machinist group mixed up a batch, and we all now use it with equally good results. Note also that "Liquid Wrench" is about as good as "Kroil" for about 20% of the price.

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Another thing that is helpful, if you can do so easily, is to apply the ATF / Acetone mixture when the seized parts are warm (not hot, as the penetrant will flash off prematurely).  As the part cools, the penetrant will be be drawn into the threads.  As EmTee suggested above, the more cycles the better.  If the car is running, you could start the engine to warm up the manifold, then apply the ATF / Acetone penetrant and allow to cool.

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I don't know what year your car is, or how original it is. My 1940 had brass exhaust manifold nuts on steel studs, as well as the connection between the manifold and the exhaust pipe, had brass on steel. The brass nuts are extremely soft and you will round them if you use the wrong wrench. I don't know if they were original, the car had the engine replaced in the 1950's so who knows. My 1917 has the original carbon steel nuts and they came right off without even using penetrating oil.

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