Here is the problem: I am getting 6-8 degrees of timing retard from off idle to operating RPM range. The distributor is locked out (MSD pro-billet).

If I set the timing at Idle to 40 degrees, it will retard to 34 degrees at 2000RPM and above. It does not retard anymore throughout the upper rpm range, only from off-idle.

The igintion is a Crane Hi-6 with a Crane LX-92 coil.

I pulled the distributor tonight to check endplay thinking the force of the higher RPM would "walk" the cap up thus inducing retard if the endplay was excessive. The endplay was .013", hardly excessive, but is this enough to cause this problem?

It is frustrating, although not much of a problem, it has always been like this since I locked the distributor advance. Suprisingly I do not have any hard-start problems. Also, timing has been checked with two timing lights, just in case the erroneous reading was a faulty light.

Any Ideas?

Thanks in Advance!

 

I don't know why anybody would want a locked out Dist. But anyway timing shift can only be caused by a couple of things.

Loose cam drive either chain or gears or the dist. gear lifting on the cam gear teeth. You always need to shim above the dist. gear to the dist. body to set the installed height.

I have the Morroso tool for measuring that.

 

Well George, its pretty simple. You have mentioned your feelings about getting the Demon carb tuned well, and I found, and as they told me that they like a LOT of timing, EG a good vacuum signal (Kind of hard to come by with big cams and a lot of overlap).

The MSD advance setup would not allow more than 16-18 degrees intial advance due to the minium of 18 degrees manual advance available for adjustment.

I locked it out and it has never run better. I do not have hard-start problems, and it runs "best" this way.

That aside, I have been talking with Pete (79L82?) over IM and we have been diagnosing the problem. We thought it may be in the ignition, so I installed a locked out HEI and was getting the same amount of retard. He said it can be caused by excessive lash between the cam and distributor gear, and MSD makes oversized gears to correct that.

My distributor has a slip-colar and I set the installed height.

I don't "think" the timing chain is loose as it was nice and tight when I changed cams. It is the Comp Billet unit with a true double roller.

Hopefully I'll get it sorted out, it is annoyance more than anything and has run great for the last year despite it.

Thanks for the advice.