Locking Out Advance

[FSA1673]

When you lock out the mechanical advance on a GM HEI Pontiac distributor do you tack weld it at full advance or at the initial setting?

I assume after it has been locked out you use your damper to set the timing and drop the distributor in making sure the rotor is pointed at #1. Then check the timing with a light to make sure it is ok, and make small changes with the distributor to get the exact desired timing.

[Sean Marconette]

Mine is locked at full advance. FYI make sure it is welded or bolted, as my tack welds came loose at a recent divisional, and I was lucky enough to find it in the thrash. It really should not matter where you lock the advance, as when you set the timing it will be total timing anyway since the mechanical is fixed. Set the timing off the balancer with the timing light and your done.

Sean

[Ed Wright]

I would TIG weld it with the shaft removed, as the heat from welding won't do your lube any favors.

[Phillip marvetz]

You might want to find a ignition box that will retard the timing when cranking to start also.

[Mark Yacavone]

In my way of thinking , you would want to fix it in the middle of travel, seeing the vacuum advance would swing the arc across the lug in the cap, depending on degrees of advance.

There is actually a GM factory fixed advance tab made for big block, governor equipped trucks..I don't know if you can buy it separate.

Sean, turn up the heat!

[Ed Wright]

Originally Posted by Mark Yacavone

In my way of thinking , you would want to fix it in the middle of travel, seeing the vacuum advance would swing the arc across the lug in the cap, depending on degrees of advance.

There is actually a GM factory fixed advance tab made for big block, governor equipped trucks..I don't know if you can buy it separate.

Sean, turn up the heat!

I always made them if I needed one. Just welded the rod to the bracket, then cut the canister off flush with the edge of the dist housing.

[BlueOval Ralph]

Lazy mans way just start cranking the engine then turn ign on.

Originally Posted by Phillip marvetz

You might want to find a ignition box that will retard the timing when cranking to start also.

[FSA1673]

I have a MSD digital 6 plus box with a 20 degree start retard option. That should help with the starting. I want to run 36 degrees timing. I welded it in the full advance position but I now think my distributor may be out of phase causing some ignition issues.

Can you check the phase of the distributor by turning the motor over by hand? I have an old MSD HEI cap with the center cut out and a fully degreed ATI balancer. With the engine running it is showing I have 36 degrees with the light. But when I turn the engine to 36 degrees by hand the rotor and the cap do not line up perfectly. They are rougly 15 degrees off.

Any thoughts?

[R. Thorne]

MSD makes an adjustable rotor you might consider. Don't know if it will fit an oem distributor, though.

[Ed Wright]

Might try turning the distributor until the rotor is aligned with the cap correctly, then useing a hand held vacuum pump on the vacuum advance until the timing light shows 36 degrees. Make a note of the vacuum required to get 36 degrees. Shut it down, pull the vacuum advance, pull that much vacuum on it, and tack weld it in that position. Put it back on the distributor and recheck the timing and rotor/cap indexing. If it checks out, pull the vacuum advance back off, finish weld it, and cut the vacuum chamber off if you want. Might be worth a try.