The Stovebolt Site Forums The Shop Area Engine Shop 1966 Chev C30 Panel 292

Good evening , this is my 1st post, so hope it is i the correct spot . I am starting on a 66 C30 panel with a 292 in it . I am going to pull the motor and trans to do the engine compartment , so I want to check out the engine. It runs and drives but blows a bit of oil, I dont know if its just valve seals or what yet. I read the cylinder diameter is 3.88 inches or 98.55 mm . if I dont have to have the motor bored , I won't . I dont see the point . I can hone the cylinders and do a re ring and bearings etc . My questions are , does anyone know what a reasonable compression check should show? and also what tolerances do I have for that cylinder diameter before it needs a re bore ? Thanks Very much, Bob

You should have at least 100 PSI of compression on each cylinder with no more than a 10% variance between cylinders. As far as cylinder wear you will find that the amount of taper and out of roundness will be the problem. Any cylinder with more than 5 thousands of out round will need to be bored. I am not sure what the spec is for taper.

Taper wear in a cylinder is not linear- - - -most of it happens at the top, in the first 1-2 inches of piston travel. At 2000 RPM, a ring is expanding and contracting 60 times a second, trying to stay in contact with the cylinder wall. That makes for very short ring life if the taper wear is more than .005". Boring a worn cylinder eliminates the taper and takes a lot of stress off the rings. Out-of-round isn't nearly as critical as taper, but neither one is a good thing.
Jerry