cwmore1169

I have a 1970 olds cutlass and I switched from the 350 to 455 out of a 71 442. wondering what kind of specs should I expect the engine to have? I haven't run the engine but I did a compression check and one cylinder was kind of low, around 90. I dropped a little oil in the cylinder because the engine had been sitting for a while and most of the cylinders came up to around 130 but one has lingered around 120, is this good and any input is greatly appreciated.

Charlie Jones

A common rule of thumb says that a 10 percent or more variation between the highest and lowest cylinder is an indication of a worn engine.
The fact that the compression came up when putting oil in the cylinder is usually an indication that the compression loss is due to bad rings rather than leaking valves.

cwmore1169

cylinder stats Before Oil and after oil
7-120 after oil 140
5-95 after 140
3-90 after 140
1-120 after 145
2-110 after 130
4-110 after 135
6-110 after 135
8-100, 60 after 130

Charlie Jones

With the figures you posted I'd say the rings are bad. There is more than a 20 percent variation "dry". The fact that the compression comes up to normal "wet " means that the valves are still sealing.
Unless you are just going to take the kids out for ice cream once in a while, I would suggest a complete overhaul. Including grinding and seating the valves.