Vibration at 4k RPM

[Spencan]

Alright, I found my mistake from a a year and a half ago. I did not clock the lower balance gear properly, I was off by about 15 degrees. It didn't help that there were no marks on the gear to show where the notch is, so I used my daughter's old red acrylic nail polish to do the job for future belt changes.

I also found that my cam gear 4* offset key failed and my cam gear is about 180* off now, yikes!!

[barnwerks]

I recommend posting a picture of the balance belt / pulley arrangement for help with identifying anything else that may not be correct.
Regarding the camshaft timing, it cannot be 180 degrees out of time, since the cam rotates at half the speed of the crankshaft.

[Tom]

I recommend posting a picture of the balance belt / pulley arrangement for help with identifying anything else that may not be correct.
Regarding the camshaft timing, it cannot be 180 degrees out of time, since the cam rotates at half the speed of the crankshaft.

Based on offline pics I saw, I think he means the gear spun/rotated 180° on the end of the cam (sheared key) but I'm unclear on what happened. I do agree more pictures would be helpful. I can't wrap my head around what exactly happened with the belt alignments... If the cam gear really spun on the cam when it was last running, you'd have noticed big problems...

[barnwerks]

Put another way: Every 180 degree (half) rotation of the camshaft coincides with the crankshaft TDC.

[Spencan]

Well it looks like I assumed incorrectly that I only had to find the "OT" mark to make sure that it is at TDC. Thanks "Barnwerks" for the reminder that the BOTH need to be aligned to be set at TDC.

I did remove the cam gear to confirm that the key is still there in the right spot.

So, can I now just put the cam gear back on and be good to go?

[Tom]

Look down into the window at the top of the bellhousing -- you need to lean over the drivers fender -- and set the engine so the OT line on the flywheel aligns with the pointer in the bellhousing window. With that mark lined up in the window, the cam gear then needs to be aligned with its mark (i.e., the two red marks in your picture). Since your motor ran when you took it apart, I suspect you had it at TDC #1 but on the exhaust stroke, explaining why you thought you had it at TDC despite the cam gear being off by 180° (i.e., one full crank rotation). Either that or I'm not tracking what's going on over there.

[Spencan]

It’s set and locked at OT right now, in its present state. That was the first thing I did prior to doing any work around the belts.

So I need to remove the lock, then rotate the engine until I see the OT again, and then put the cam gear back on. Is that correct?

[Tom]

It’s set and locked at OT right now, in its present state. That was the first thing I did prior to doing any work around the belts.

So I need to remove the lock, then rotate the engine until I see the OT again, and then put the cam gear back on. Is that correct?

Is the "OT" showing in the top bellhousing window when you lean over the driver-side fender?

[barnwerks]

A safe way to re-time the camshaft is:

Rotate the crankshaft backward (counterclockwise) a quarter turn (90 degrees).
Install the camshaft pulley and rotate camshaft to align timing mark on pulley with housing.
Rotate the crankshaft forward to almost (about 5 degrees before) TDC.
Install timing belt.
Rotate crankshaft clockwise to TDC and check alignment of camshaft timing marks.
Rotate crankshaft clockwise 720 degrees to TDC, check alignment of camshaft timing marks.

[Tom]

I spoke to Spencer and finally understood the pictures. I think barnwerks was trying to say this above too. The cam gear is aligned just fine. He just needed to turn the crank another 360 degrees -- once he does that, the cam marks will rotate 180 and line up and the OT will line up on the flywheel. I was just hopelessly confused as to what was going on until we talked - but in hindsight it was crystal clear.