Attached is a close up photo of the cylinder wall of my 944. The score mark is about 1mm wide at the top and gets narrower as it goes down the cylinder. I can catch a fingernail on it. How bad is this? How much can it effect performance and what should I do about it?

Well, I measured the scratch. I used a piece of electrical solder taped onto the scratch, then I used a small C-clamp to squeeze the solder into the scratch thus making an impression. I can then attach it to the jaws of my vernier an look at it with a 10x loop. Comparing the impression with the gap in the jaws I measure the scratch to be .010" wide and at the most .002" deep.

When I get the head back I'll put it back on and do a compression test. That should tell the tale.

A score that size will not be good for performance, consumption or reliability... but your choices are sort of limited.

1. run it....

2. overbore the block to the next piston size and get ready to spend some big bucks on those.

3. Sleeve the block with cast iron sleeves and buy yourself some J&E 88 spec pistons. ( opportuniity for an upgrade!)

4. change the block for a known good unit.


Greg f

I got the head back from the machine shop, 3 angle valve job and decked for only $125!
So I did a wet compression test with spark plugs removed.

1 - 210 psi 2 - 200 psi 3 - (scored) 190 psi 4 - 210 psi

So the scored cylinder is 10% lower than the highest reading.
I'm going to run it this way. Hey, I'm sure I'll find someone out there I can race.

You can absolutely run it as it is. If you want to fix it, you can have someone hone out the bore and use oversize rings on the stock pistons. If necessary, you can re-coat the pistons to take up some of the slack. I got a quote of $200 for the honing, using the proper hones for the 944 block.