Hey guys what would cause the initial timing to change on my car? I need to check into it but I'm not quite sure where to start.

The car is a 71 with a 454. Running a billet Isky roller cam with a cast dist gear pressed on, an MSD 6AL box and a Pro-Billet MSD distributor (PN# 85551) and the cast gear that came on it.

Had the cam out last winter and the timing chain seemed in good shape. (not much slack in chain)


Last year I had the timing set at 20-22 initial (38-40 total).

Was doing some tuning about a week ago. Checked timing and it was about 14-16 initial. Distributor was tight. Readjusted to about 20-22 initial.

Started and idled the car last night for about 1/2 hour. Rechecked timing; initial is now at 30 degrees. Distributor was tight.

Any suggestions on where to look?

Thanks in advance. smile.gif

Did you set your camshaft end play with a button when you installed your roller? You should have between .005 and .010 end play. A roller has flat lobes that allow the cam to walk in the block. Excessive clearance can cause timing variations.

Could you have a counter weight in the distributer that is hanging up?

I was thinking about the advance weights, that is one of the things that I was going to try.

As far as the cam end play, the engine builder set that up originally and I did not recheck it when I reinstalled the cam. (not even sure how to check it graemlins/clonk.gif ) I wouldn't think that would be an issue because I have not had any problems with the timing since the engine was put together (about 5 years).

It does sound like the advance weights are sticking or the springs are getting worn. Just my.02 worth.

Maybe the outer ring of the harmonic balancer slipped. If you have an adjustable pointer, could that have slipped? I'd check TDC in relation to the zero timing with a piston stop in the spark plug hole.

Would sticking weights cause the "total" timing to change?

Didn't check total last night but a week ago when I noticed the problem the total timing seemed to be effected about the same amount as the initial.
I think the entire advance is shifting. :confused:

Von,

Using a Fluidampr, nothing to slip.

I'll check the adjustable pointer to see if it's moved.

Any issues with your timing light?

I'll vote for the sticking advance.

Did your idle speed drop also?
Double check your TDC marker,timing light,also try a different light.
Try installing stiffer advance springs for checking purposes and set your total timing.
Then check to see if its moving.