Right Cam does not want to rotate after being torqued (Stock 3.2)

[CBRacerX]

This is a first for me. I've got an 84 Carrara engine going back together after installing new Supertec Head Studs and the left cam installed perfectly and timed with no concerns.

The right cam is not cooperating. The cam rotates with no resistance in the cam tower on it's own. When the thrust washer and shims (4) and woodruff key and timing collar are installed, everything is fine. When the cam drive sprocket is installed finger tight, everything is fine and timing can be set on the Cylinder 4 intake valve without issue.

However - as soon the sprocket bolt is tightened down beyond finger tight, let alone 89 lb-ft, the cam will not rotate! I've taken it apart down to the thrust washer, made sure everything is clean and lubricated. I've tested without the chain in place, no change.

I don't see the sprocket touching the three bolt heads holding on the seal cover. The resistance seems to come from the stack of shims and the thrust washer but I don't see how.

Anyone run into this before? I'm perplexed....

[boyt911sc]

Chris,

How were you able to set the cam timing for #1-#2-#3 cam correctly without turning #4-#5-#6 cam? Did you set up both cam shafts @ 12 0’clock orientation initially? Did you have all the rockers installed or just for cylinders #1 and #4 only.

Tony

[CBRacerX]

Originally Posted by boyt911sc

Chris,

How were you able to set the cam timing for #1-#2-#3 cam correctly without turning #4-#5-#6 cam? Did you set up both cam shafts @ 12 0’clock orientation initially? Did you have all the rockers installed or just for cylinders #1 and #4 only.

Tony

The 4-5-6 cam turns fine until the sprocket bolt is more than hand tight. I've only got rockers on 1 and 4 intake at the moment, and I just removed the #4 rocker today as I'm ready to pull the cam out and inspect the whole thing again - I should have another gasket on the shelf to seal it back up with again.

[Flat6pac]

With no rockers, all problem has to be at the gear end.
A thick shim washer goes under the four stack.
Bruce

[CBRacerX]

Originally Posted by Flat6pac

With no rockers, all problem has to be at the gear end.
A thick shim washer goes under the four stack.
Bruce

Hi Bruce - yep I have the thrust washer in place and it's oriented correctly (beveled edge toward the cam tower). And the 4 shims are in place.

[CBRacerX]

Mystery solved! I removed the cam cover, replaced the gasket with a new one (mind you the one there is new and the same as the left cam) and put it all back together. It's fine now and torqued to spec after cam timed with no problems.

Did I really "solve" the mystery? I don't feel like it but I am taking the win and moving on.

[scootergt3]

did you have the cam gear on correctly? 123 the bevel faces out. on 456 side, the bevel faces in.

[CBRacerX]

Originally Posted by scootergt3

did you have the cam gear on correctly? 123 the bevel faces out. on 456 side, the bevel faces in.

Yes indeed! And parallelity was correct.

[mikedsilva]

curious about this:
was the camshaft different to the orignal> ie a regrind, new cam, coated, etc?
Was the cam thrust plate changed?

My understanding (and I have not looked into that closely) is that when tightened down, the thrust washer on the front, and the shoulder of the cam on the back (of the thrust plate) should result in a small amount of clearance that allows the camshaft to rotate. (i cannot remember the spec, it might be 0.1 or 0.2mm)
If there was something different or something like a bit of paper gasket material that got caught in that clearance, it might have caused the cam to not turn freely when torqued?

Did you try to rotate the cam with a socket or was it just not able to rotate using fingers?

[CBRacerX]

Originally Posted by mikedsilva

curious about this:
was the camshaft different to the orignal> ie a regrind, new cam, coated, etc?
Was the cam thrust plate changed?

My understanding (and I have not looked into that closely) is that when tightened down, the thrust washer on the front, and the shoulder of the cam on the back (of the thrust plate) should result in a small amount of clearance that allows the camshaft to rotate. (i cannot remember the spec, it might be 0.1 or 0.2mm)
If there was something different or something like a bit of paper gasket material that got caught in that clearance, it might have caused the cam to not turn freely when torqued?

Did you try to rotate the cam with a socket or was it just not able to rotate using fingers?

Everything is original to the engine which has not been touched since 1989. I do think this was a gasket issue that kept the "cover" that supports the o-ring from seating just a few thousands. The interference was enough to lock up the rotation completely - it was stuck very firmly (socket with pressure did not move it). A new gasket and it's perfect now.