Compression

[SuperRedMR2]

I tested my compression on Saturday.

I removed the AM2 fuse but my engine wouldn't crank so I put it back in again.

Battery life was poor.

Cylinders 1, 2 & 4 put out 160 with no 3 on 155

I have had a head skim and running longer duration cams...

Would a rebuilt engine be down on compression?

[LimeyMk1]

Most likely due to the battery not having the juice to spin the engine up, I'd eliminate that variable before considering other causes.

If not the battery it could be poorly seated valves or piston rings not sealing, however for it to be universally low across the cylinders they'd all have to be equally badly sealed if you see what I mean.

Oh and seeing as you haven't run the engine in yet the rings won't be fully bedded in so that may also be a contributing factor.

[scomr2]

Test should be done at WOT else the readings will be low.

[charlie]

as limey said it could be the rings but acording to the book 178psi is std 128 psi limit.also with bigger cams you loose compression due to the longer valve overlap.