Cylinder block surfacing

[DougT]

I have a J series block that has been left in the weather and as a result rust has formed on the top deck, luckily it was stored upside down with the sump in place. My question is, how many thou can be shaved off before it becomes untenable to use?  Doug

[ardiesse]

Up to a head gasket thickness (at a first guess).  Most aftermarket grey motor pistons have a lower crown height than the originals, so you have very little risk of the piston crowns bashing into the head.

If you have an oilstone, work up the block deck gently with the coarse side first, then use Scotchbrite and rust converter.  You'd be surprised how well it will clean up.  As long as you don't have extensive pitting, the block deck will only need a light skim.

Over time, low spots develop between cylinders 2 and 3; and between cylinders 4 and 5.  It's a good idea to get the block decked to cure this condition, regardless of rust on the deck.

Rob