OK, I know I should be doing a leak down test.. and I will first thing tomorrow.... but in the meantime....

Bought a used LT1 to use for a smog motor/LT1 build. Before slapping the motor in, was checking out the bottom end and decided to turn the motor over by hand and run a compression check.

Most cylendars tested at around 30-40max, several at 60 and 1 at 120. The 120 surprised me greatly considering that was by hand but checked it again and it was consistant.

I am assuming this means the motor is essentially junk? Even at hand turning speeds, I am assuming there should never be that much of a discrepency in compression at any speed correct?

 

Not only does it have to turn consistantly at about the same speed, it must be faster than you could possibly do it by hand. Your wasting your time. The throttle plate should be wide open as well.

Even if you got bad results, it doesn't mean anything until you get in and look at the block. Even bad results of a leak down test won't mean anything.

Just pull the heads off. Then pull the main bearings off.

 

Bolt a starter and flywheel to the block, hook the starter up to a battery and then use a remote start trigger (the kind for diagnosing not the kind for starting your car from in the house) to turn the engine over. No reason it shouldn't work it just won't fit on an engine stand youl'l need to use something else.

 

Thaks for the feedback. I was thinking of turning it over with the starter on the stand to do a real check. Will maybe try that tonight.

If I pull the mains, I would need to put in new bolts right? Not that it's a big deal, probably a good idea anyhow, just seems like that might snow-ball as I may as well do bearnings too at that point etc. It definitely has some noise when turning it by hand but thay may be expected with the pan off and no oil pressure.....

 

So what if the tests come out ok. Wouldn't you still want to put new head gaskets in it anyway. When you do pull the heads, you can do the following:

Check the valves
check the heads for cracks
check the cylinder walls for ANY type of defect.
check the pistons for cracks
clean carbon build up from the top of the pistons and in the combustion chamber.