I'm losing somewhere around 15-20 degrees of ignition timing once I get above 2000ish RPM on my 383.

The ignition is a MSD 85551 distributor and a MSD 6AL-2 box, part number 6421.

I changed the magnetic pickup in the distributor and it didn't do anything to improve it. After that, I found the vertical play in the distributor shaft to be well over .050", so I shimmed it to be around .015", but I haven't tested that yet.

Also, the camshaft thrust is right. This engine was in my car for over a year without this issue and I didn't change anything internally when I put it in my truck.

If shimming the distributor shaft doesn't fix the issue, where else should I look? Borrow another timing light? Try another ignition box?

Flip the pickup wires.

quote:

Originally posted by Jason Haley: This engine was in my car for over a year without this issue and I didn't change anything internally when I put it in my truck.

Engine timing worked correctly in vehicle A, then swapped engine to vehicle B (recently?) and now timing retards when over 2000 rpm?? Did engine timing ever work properly in vehicle B it is now in?

Melonized, bronze or EverWear distributor gear??

8620 carbonized Billet Steel cam core??

quote:

Originally posted by BJs Wild Ride:
Flip the pickup wires.

This

quote:

quote:
Originally posted by BJs Wild Ride:
Flip the pickup wires.


This

this first , then change the ign.

Agreed^^^

Do you have ANY retard chips in the system anywhere. We had a 2 degree chip that was doing eactly the same thing in our dragster with a 7al3 a few years ago. Might want to swap any you have with a new one.

quote:

Originally posted by BJs Wild Ride:
Flip the pickup wires.

This first!

Some timing lights don't work with an MSD. The switch from multi-spark to single spark happens around 3000 RPM so your light may be reacting to the switch.
New vehicle, same timing light, I'd say the distributor pickup wires need to have the polarity swapped. The wire colors don't always match up.

First things first, thank you for all of the suggestions. I'll be sure to remember them if I have this issue again in the future.

Second, I flipped the pickup wires to the most retarded position last night (what MSD told me to do) and there was no difference.

Finally, shimming the distributor shaft last night solved the problem. I put the distributor back in today and I now have a solid 36° like I'm supposed to.

Thanks everyone!

Great you fixed it. Check the center terminal inside the cap and the spring on the rotor.