Cylinder compression specs

Posted by 54ocmac On 2022/6/3 8:04:20

Good morning,

Are there any factory spec callouts for what the cylinder compression should be on the 359 CID engine? I’ve viewed various threads regarding this in the forum, but I don’t seem to find anything that nails down what it should be.

Here is my situation:
1. All the work on the block was completed, e.g., cleaned, checked for cracks, sleeves in 3 cylinders, valve job, etc.
2. Pistons deemed to be good, so new rings installed, new bearings installed, etc.
3. Aluminum head cleaned/inspected. It was not milled.

With all the above completed, the engine is ‘buttoned up’, but not installed back into the car. Installed an Autolite starter and the engine cranked Cylinder compression measured and is consistent in each cylinder at about 75 psi. I think we were expecting it to be higher, but pleased it was consistent.

I’ve seen threads that indicate compression in running engines to be in the 130’s and 140’s and one that indicated even lower compression in the 90’s, but these were not for the 359 engine. One responder even stated that as long as the engine is running good, no smoke, etc., then the lower compression should be “fine for now”.

Whereas I’m encouraged that the consistent compression from cylinder to cylinder is a good indicator, is it enough? My thinking is that it will increase with lubrication once it’s running and rings settle in, etc.

So . . . .

1. Is there a factory callout for cylinder compression?

2. If not, it there a consensus among ‘the Packard community’ what a reasonable number would be for an engine at the stage mine is?

Thanks again for any input/guidance!