Can anyone tell me the minimum acceptable cylinder compression? About two weeks ago my y block blew a head gasket ,between cylinders #2 and 3. I replaced the gasket this week ,had the head surfaced .0035 (3 and a half thousandths). a good mechanic friend helped me re-assemble the engine and adjusted the rockers. After all the other stuff was completed I drove it a few miles (gently) when I returned to the garage it was smoking a little out of the same engine side as the repair. After cooling down I pulled the plugs again ,they looked ok. I then checked compression again, they all had from 150 to 160 lb. each except #2 which had 140 lb. (dry) when I added oil to the cylinder it went up 15lb. (155lb) are these compressions acceptable or am I going to need a rebuild. I don't know how many miles are on the engine since it was re-built.
Thanks
Barry
Here's a chart to go by. I don't think it matters if it's a gm based chart.
140 should be OK, Double check the valve adjustment on that cylinder.
Did you set them hot?
Was the carb wide open when you did the test?
Also, oil or antifreeze in the exhaust can sometimes take quite a while to completely burn out of the exhaust. I would pile up some freeway running miles on it before I was too concerned. Also, assuming they are steel shim head gaskets, be a good idea to retorque the head bolts after a while too.
The valves were initially set cold but then re-set hot. We have thought about a contaminated exhaust system. That would be great! The carb was wide open for the comp. test and the new head gasket is compozit.
If it was me I would take it for a good run and let it burn off anything in the exhaust, If you only changed the head gasket there is no reason not to. Depending on the type of gasket you used it may need to be re-torqued.
I had a pretty bad valve cover leak and put on a new gasket yesterday. I took the 57 for about a ten mile drive this morning and did not see any smoke from the exhaust or the valve cover. It looks like the smoke I was seeing was from oil etc that was left in the exhaust system from the blown head gasket. I think I have everything fixed now. Keeping my fingers crossed. I need to change the oil and I want to drain all the coolant and re-fill. I hope to take it to the Dawsonville Moonshine Festival next month its about 210 miles round trip.