Loose timing chains can be responsible for up to 8° of cam retard. If the camshaft was already on the retarded side when first installed, then the loose chain simply compounds this. I’ll suggest degreeing the camshaft before removing it just to verify both the camshaft specs and where it’s installed. This could answer the question about the low compression readings.

Lorena, Texas (South of Waco)

Thanks Ted. I have had a degree wheel, new in the package, that's been sitting in my toolbox for years. Guess I have an excuse to finally learn how to use it. Would you recommend putting a new timing chain on it before I do this? I haven't done an actual measurement yet, but it looks to have about 1/2" of slack, so I would like to replace it before it goes back together.

The degree wheels usually come with bushings to fit a variety of crankshafts which does not usually include the Y-Block. You will need to drill one of the smaller ones to fit or have a bushing made.


Lawrenceville, GA

I was helping my son with his car last night, so no updates other than I did check the timing chain and the play was 5/16".

I do plan on doing a leak-down test as part of my testing to decide how far to go while I have the motor out. That said, I'm on the slippery slope of "while the motor is out, why not do X". The time and expense of pulling it all the way down while it's on the engine stand is not great. If the cylinders are within spec, a simple hone and new set of rings is simple enough. Testing should tell me if I need to go that far, but my preference would be not to pull the heads and pistons if I don't need to. I will be installing a new timing set, and probably a new cam and lifters. We'll see what more testing tells me.

You' may well find it would be best inverting the block (literally) if you wish to change the lifters.

tim McMaster has a nice video on degreeing a yblock cam.google it.

Country squire:

I believe I would degree the cam as is, so you would have an idea whether or not cam position is the problem. Would be a shame to replace the timing set and find that you have exactly the same symptoms. Also, 5/16 doesn't seem to be excessive slack to me.

John - "The Hoosier Hurricane"

It's not really a slippery slope if if you don't give in to temptation and decide to do only what needs to be done.
What is more important than the cylinder spec is the piston clearance. The cylinder can be within spec but worn pistons bring the clearance out of spec so you need to be sure to check both.

You should go ahead and install the timing set to see if that brings your compression pressure back up. If it does, then things are probably good enough on the bottom end and you don't have to pull the engine from the car and the new cam and lifters will be going down that slope.


Lawrenceville, GA

Hopefully I will have time to do a leakdown test this evening. I'l have to do it cold, but that's my only option right now.

Well, hmmm. OK. Had a little time this evening to look at the motor a little more. The dots on the cam & crank gears were at 3:00 with twelve pins between them, just as in the picture from a couple days ago. Used a piston stop and found exact TDC, then installed the degree wheel. Popped of the valve cover and noticed that the valves on #1 weren't loose, so the engine was on the exhaust stroke. Turned it 360 degrees and the cam gear dot was at 9:00, as you would expect. When I popped the distributor cap, I see that it was 180 degrees from #1. Turned it again to get the rotor pointed at #1 and that leaves the cam gear dot back at 9:00.

Can you install the cam in a Y block 180 out, or is it only possible to install the distributor that way, like on other motors? Either way, how could it run this good with something 180 out?