Simple question, is it safe to crank the engine with the starter without the rocker arms installed? The idea is to hopefully eliminate stuck valvetrain components when I preform another compression test on my truck. Im thinking stuck or broken rings.

Long story short, I have a 1974+ 360/390 truck engine that has basicly sat for 20 years, been ran here and their every 5 years or so and driven about 10 miles during that time.

After working on the truck for the last week or two and not being able to get it to run quite right I preformed a compression test yesterday and my results were terrible. All cylinders under 110, #2 and #5 were both at 50, #3 was 90, # 8 was 35. The test was done cold and without oil.

So I parked the truck amd removed the valve covers, rockers, and plugs and slathered the poor thing in Mystery Oil in hopes everything is just sticky; but im suspecting a overhaul is needed.

I will note the truck has good oil pressure according to the original gauge, I cant judge the sound of the engine at idle because the exhaust manifolds are shot and leak bad. At about 2000 RPM the truck sounds good to me without any clashing or metallic sounds.

Feel free to ask more specific questions I just wanted to keep it simple until I let the snake oil do its thing.

 

Welcome to FTE!

As long as there are no other parts in the way--lifters and push rods and any thing else, you can turn the motor over with the rockers removed. All valves will be closed. A compression test is not possible under these conditions. Since the valves are closed, there is no air in, no air out and the "compression" figures will be of no value. You should have oiled the cylinders and retested with the valve train intact.

Did you keep the push rods in order?

 

I realized a compression test would not work without the rockers shortly after asking the question.

I left the push rods in place when I removed the rockers. Confirmed engine stroke of 3.5"

I went to remove the rods to check for flatness amd wipe them down, and pulled a little too fast and pulled the lifter out of the bore. So the intakes coming off.

I took a peak inside my cylinder bores the best I could and I have some deep scratches definitely in a few cylinders; thinking rings were rusted to the pistons and broke the at some point. I have never done any bottom end work before but im going to guess I would need to take the block to a machine shop to be bored; if it is even still possible.

I am ripping the intake off tonight to examine things closer, put the lifter back, and reassemble to preform another compression test.

Regardless of these results I'm damn sure im tearing it down for a peak.

I did not have the throttle open during my first test. I heard that can read low numbers.

 

When I rebuilt my 428cj, the machine shop that I used assembled the lower end for $200 and then gave me a warranty on it. Might be worth checking into.