912 cylinder head damage

[bigbrotherjohn]

I need help from you guys once again.

One of the combustion chambers on one of my cylinder heads was damaged by the previous owner. A washer was accidentily dropped into the carburetor and found its way into the cylinder. This resulted in some pretty deep gouges in the head. So what I did was grind off enough material from the head so that it was smooth and the gouges were gone. This required removing about 2cc's. The heads were cc'd pretty well before this whole mess and were at ~60.5cc's. Now what should I do. Should I remove 2cc's from the other heads, and lose compression (about a quarter point, couple horse power). Would it be possible or advisable to use JB Weld or something like it to put new material on the head so I can keep the compression up?

[C. Clark]

I would leave well enough alone, JB weld won't work, and messing with the other heads is, in my opinion unnessesary and risky. put it together and drive....or is this some tricked out race car?
Chas.
69/912

[bigbrotherjohn]

this car is a 200hp beast and I need all the compression I can get. just kidding.

I think matching the heads and leaving it is probably the best thing to do. A few calculations and it looks like the losses will only be 2-3 horsepower with lower compression.

[C. Clark]

Why I responed was because when I cleaned up all my leaks I removed the heads and replaced the rubber washers which were the major problem. Anyway one of my heads had a similar situation as you discribed, my car runs fine with the dings, gives me and the 912 something in common......
Chas
69/912

[jac912]

Hey Guys ... why would "cc'd" the heads reduce compression? Are you saying that Material is removed from the heads to make the valves closer to the piston at TDC or does it make internal volume greater? Can't quite envision this. Thanks for the education.

[cgarr]

the goal is to get the chambers within .01cc of each to do this you would have to find the largest one then match the others to it. I removed alum from the chamber to match not the sealing surface. you can then set you CR using copper spacers under the cylinders, some even shorten up the cylinders to increase the CR, Just remember to maintain the correct deck height.

cg

[eb61636]

Don't run the heads unless all the chambers are all the same volume.

Don't run the heads with the dings in the chamber, the high points from where the material got pushed up is a stress/heat riser.

You should bring all the chambers down to the same volume, if it is 62ccs, so be it, it will run and you can maintain the compression ratio...you may have to flycut, but not much.

If you had 60ccs before and now you have 62, that is fine...do the math and flycut to bring your compression back.

erik.