Hi What should I expect from a compression test? I've got a 1600cc 74 Camper. Tested all 4 cylinders and got the following readings: Head 1: 122 134 Head 2: 118 138 Concerned that there is such a large variation so now I need to work out what to do next. The engine is already out.
I wouldn't say the results were bad - there is only 14% difference between the highest and lowest. Did you test because you had issues or just to see if anything was up?
It lacked umph in 3rd and 4th gear. Seemed to have a flat spot. I needed to changed fuel lines anyway so out came engine.
I think they say all results need to be within 75% of the highest to be ok. So in theory they could go down to 104. Plus all readings are reasonably similar. I.e there isn't one that stands out particularly.
You could try the test with addition of oil to the chambers (as in link above) but based on your results I would be looking elsewhere for issues.
Timing would be my favourite unless the van trailed blue smoke and had very oily spark plugs. In which case it would be a Head / Piston rings issue.
You need to do the compression test twice. Once dry, and once with a squirt of oil down the cylinder. This is to check if it's the cylinder bore that's passing pressure (back into the block) or the valves (pressure passing into the head)
