jtranger

After removing the heads for a valve job, I noticed some of the head bolt threads pulled up or lost their countersink. The block is still in the car and I would like to countersink the holes while in the car.

You will see the photo that the middle cylinder has no countersink in the 2 o clock and 7 o clock locations, along with the 12 o clock location on the other cylinders. I assume this was from over tightening by the PO and may have contributed to the head gasket leak between the middle cylinders.

I assume I will need a countersink bit to sink the holes. Sears makes several sizes 5/8, 1/2, 3/4. Which size would I use and what are the instructions for doing this countersinking as I have not done it before?

Can this be done by a novice with the engine in the car? Thanks

DansYellow66

I think with the engine in the car I would just hit the individual holes ones lacking a counterbore with a file to knock any raised area off and then hit it with a countersink bit to slightly chamfer the hole. Save the counterboring for the next full dissassembly and rebuild.

scott1963vette

I think it is more important to take a 4" round india stone and rub over the entire deck to make all the holes flat and level. I wouldn't worry so much about the countersink.

Scott

jtranger

What type and size bit would I need and what is the process? The countersink bit will not burr the deck will it?

Which one of these would work?

http://www.google.com/#q=sears+count...w=1024&bih=605

midyearvette

go with the 3/4"
i have done this countless times but with an empty block on an engine stand
filings will go everywhere so be sure to cover things up
the process only takes seconds per hole, use a drill motor, light pressure......

jtranger

The countersink process will not burr or effect the deck surface of the block, will it?

midyearvette

no....nothing to be nervous about here....go for it...