The Stovebolt Site Forums The Shop Area Engine Shop 216 Camshaft Thrust Plate Not Even With Crankshaft Gear Shoulder

I checked the alignment of the camshaft thrust plate with the crankshaft gear shoulder as instructed in the shop manual.

It says to put two gaskets under the plate, put a straight edge across it, and bring it up to the crankshaft gear shoulder. If the straight edge hits the shoulder, you're supposed to add a gasket until the two surfaces are even.

On mine, it's the opposite. I tried it with only one gasket and, when I put the straight edge on the plate, there is space between the straight edge and the crankshaft shoulder. The manual doesn't say anything about this scenario.

Am I correct to assume this type of space is okay, being the manual doesn't address it, or does something need to be done to even them up? If yes, how would it be done?

Have you checked the end play of the crankshaft? It's not uncommon for the thrust surface of the #3 main bearing to wear, and let the crankshaft move forward, especially if the clutch isn't adjusted properly and the throwout bearing rides against the pressure plate fingers all the time. The crankshaft end play must be correct before doing the cam plate measurement.
Jerry

Thanks, Jerry. The bearings are all new so I assumed the endplay should be fine. Nothing seemed loose when the crank was installed.

You need to measure the end play, it is not possible to know what it is by feel during assembly.

Shawn, I will add one comment about the camshaft thrust plate: please check and be very careful to get the original spec for clearance (.001 to .003"). 001" is best if you can manage it.

This is important if you want a smooth idle. It has happened to me twice. Once 50 years ago and again within the last 10 years. At idle speed if you have too much clearance at the thrust plate your camshaft can walk in and out and if it does your ignition timing will be inconsistent and it will cause a loping idle. I understand the camshaft by design should be constantly forced toward the back of the engine but in these engines my experience has been if you have too much thrust plate clearance at idle rpm the camshaft will "walk" in and out enough to oddly advance/retard your spark timing...and it doesn't take much.

If your engine is all together and running and you know you don't have any distributor problems, bad plugs or plug wires you can check this with a timing light. Paint your needle and the bb with white paint and check in darkness. Watch at idle how your number one plug is firing. If you see things wandering around at all, you might want to remove the camshaft and see about the thrust plate.

Thanks for the additional insight, guys.

WICruiser, I'll be checking the endplay with a dial indicator to see what the endplay is in the crank.

Jon, I understand what you're saying with the clearance for the thrust plate between the bearing journal and gear when pressing the gear onto the camshaft.

My issue right now is the crankshaft shoulder where the crank gear presses against is deeper in the block than the cam plate when running a straight edge accross the two surfaces. With a feeler guage, it's about .015" with no gaskets between the cam thrust plate and the front engine mounting plate.

I applied a thin coat of gasket sealer to each side of the gasket between the front of the block and the front mounting plate. i can't believe that would "thicken" the gasket but, if everyting else checks out, I might pull it apart and put the gasket in dry.

I finally had a chance to check the crankshaft endplay. It's .006" - right in the middle of the spec range of .003" - .009".

I was able to find a NOS GM gasket for the front engine mounting plate so I pulled it back off, cleaned everything up and checked it with the gasket dry.

Same results. Even with no gaskets under the camshaft thrust plate, there was still a gap between the straight edge and the shoulder on the crankshaft with the straight edge flat on the thrust plate.

So I made two shims from a pop can. Now the shoulder is flush with the cam thrust plate with no gaskets under the thrust plate. I'm not sure if this was necessary but at least now everything should line up and I can put the crank gear back on.