Blown head gasket question

[JOHN SCHUTTE]

I have been tearing down a k301 12hp and it has the typical blown head gasket. Tonight I am going to have the head machined because it is warped. My question is how much material can be removed from the gasket mating surface before piston and valve clearences become an issue? I would like to increase the comp. ratio to try to get a few more hp. This engine will be used in a stock/stock modified class and as a worker at home.

[ol'George]

Originally Posted by JOHN SCHUTTE

I have been tearing down a k301 12hp and it has the typical blown head gasket. Tonight I am going to have the head machined because it is warped. My question is how much material can be removed from the gasket mating surface before piston and valve clearences become an issue? I would like to increase the comp. ratio to try to get a few more hp. This engine will be used in a stock/stock modified class and as a worker a home.

Well back in the day,
I would use a little modeling clay or putty to check the valve to head clearance.
I'd put a little goober on the heads of the valves the put the head back on with the gasket and just snug the head down with 2-3 bolts, and roll the crank over 1-2 revolutions by hand and see what you have.
Then you got an idea how much you have to play with, before the valves make contact with the head.
But I'm sure somebody will chime in and tell you you can take so and so many thou's off.
In flathead days maybe .050 was good but you never knew if the po already took some off.
So the clay method is a good check to prevent the valve from getting intimate with the head

[JOHN SCHUTTE]

Thanks for the info ol'George! Do you think some of my girls play-doo would work instead of clay? I was hoping there was a "magic" number to shave off, but like you said, you never know what the PO has done.

[steve59]

Originally Posted by ol'George

Well back in the day,
I would use a little modeling clay or putty to check the valve to head clearance.
I'd put a little goober on the heads of the valves the put the head back on with the gasket and just snug the head down with 2-3 bolts, and roll the crank over 1-2 revolutions by hand and see what you have.
Then you got an idea how much you have to play with, before the valves make contact with the head.
But I'm sure somebody will chime in and tell you you can take so and so many thou's off.
In flathead days maybe .050 was good but you never knew if the po already took some off.
So the clay method is a good check to prevent the valve from getting intimate with the head

.050".....max

[Yosemite Sam]

Sand it flat with a piece of wet and dry sandpaper on a piece of glass.

[JOHN SCHUTTE]

Droped my head off this morning at the machine shop. Going to cut it .030".

[hotya100]

John,
Some of the stock pullers up here feel that as long as you can catch a fingernail on the inner and outer surfaces of the gasket area that is all you need.

Larry

[JOHN SCHUTTE]

Larry, I thought about cutting it .040", but I didnt want to take it down to far for a few reasons. This motor next year might end up back doing yard work. Considering this machine work is FREE, I could always cut it some more if needed.

[JOHN SCHUTTE]

Thanks to everyone who posted some information! I just got my head back and it looks great. They ended up taking .020" off to true up the surface even though I wanted .030 (it was free, I can't complain). While we are on the subject, are copper head gaskets good and if so where is the best place to buy them?

[Pop's]

My puller has 25 off but my other yard worker and puller combo I am running at 20 which seems just right for yard work. Little yard worker has plenty of torque.

Pops