360 timing issue, retards before advancing?

[mguner]

i can't wrap my head around losing 10 degrees???

Me either. Almost sounds like a supply voltage issue and a control box trying to keep up. What voltage readings going into the box and at the coil positive terminals?

 

[Lonewolf3165]

Gotta think a little beyond the distributor here if all checks out with the bushings & advance mechanism. Make certain the drive gear is fully engaged with the cam gear & there is no excessive play (Lash) between the gears. Also look at the end of the distributor shaft where it fits into the slotted part of the drive gear as well as the slot itself for wear.
Be certain the pump drive part of the shaft is full engaged in the oil pump or it will try to climb the cam gear as it is revved & eventually break the distributor shaft. I've seen it happen.
Verify that you don't have any excess slop in the timing chain or gears. Remember that even "New Parts" are new in name only & can still be defective.
Good luck & keep us posted.

 

[ir3333]

if the engine is running the play in the shaft should be taken up,revving it should keep it pinned....or do i have that backwards?

 

[dusterglenn]

I haven't had the chance to borrow a dial indicator to test distributor shaft wear yet. So instead I tried a different distributor, with different springs, and no difference. The timing retards about 8* only if I quickly rev it up. If I bring the rpms up slowly, it advances fairly steadily.

 

[Inertia]

Hey Glenn,, have you got time to bring it over,, see if we can figure it out..??

Maybe this weekend?

 

[ir3333]

how might a badly worn timing chain affect timing

 

[dusterglenn]

I hope it's not the chain, it was brand new. I'm leaning towards the Crane ignition box, apparently they had a high failure rate...

 

[67Dart273]

Do you have ANY other distributor you can plunk in there that might eliminate cam drive / intermediate shaft problems?

Tell ya' whut might be ideal, is an old "lean burn" with NO advance.

 

[dusterglenn]

Actually, I do have a distributor with the advance plate welded, part of an old throttle body injection experiment...

 

[mguner]

Actually, I do have a distributor with the advance plate welded, part of an old throttle body injection experiment...

Lean burn distributors are live shaft also... No advance.

 

[dusterglenn]

I finally got the chance to use my friend's old analog timing light, and the advance works as expected. No retard, before advancing. It looks like it was a timing LIGHT problem all along. I also found some Mr Gasket 925D springs, used one with one stock light spring, and have all my mech advance int by 2400 rpm.

 

[67Dart273]

This is a well know problem with the likes of MSD, I should have mentioned it

 

[Lonewolf3165]

how might a badly worn timing chain affect timing

Think about it. If there is slack in the chain the cam will speed up & slow down inconsistently of the crank speed. The camshaft drives the distributor, therefore affecting the ignition timing as well.