Distributor advance info - SOLVED!

[KSpence]

Rebuilding my 351C distributor, and it's got numbers on the lower internal advance mechanism as well as the weights themselves. Just curious if anyone knows what they mean ... out of curiosity and if I wanted to tweak them later, to know what to look for. I have a few donor distributors, so would be neat to know what options I have.

Weights are stamped G3 and G4. I'm going to take these out an weigh them.
Bracket has 3L and (what looks like) 18L.
See the photo.

Anyone know have info on any of this? I love prying into this stuff

 

[Sheriff41]

Here ya go: https://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_page-2.html

 

[Hemikiller]

13L and 18L are the theoretical max advance degrees that the slot allows - in camshaft or distributor degrees. The cam & distributor rotate at half crankshaft speed, so you need to double the stamped number to arrive at crankshaft degrees - 26° or 36°.

The rubber sleeve on the stop is also part of the calibration, it is used to reduce total mechanical advance.

The weights are all the same through throughout the single point dual advance distributor line. The dual point distributors do not have a listing for the weights.

What's the stamped identification number on the distributor body?

 

[KSpence]

Thanks for the explanations guys! I've done some digging and what you're showing makes good sense!

Obviously that's a 13L, not a 3L. So that's 26 degrees at the crank, plus whatever I was using for base (8-ish?) and so my all-in would have been 34, which is why my 11:1 was pinging!!

Going to use my donor distributor and drop that all-in a bit ... see how it goes. Thanks again for all the help!!

For anyone wanting that deeper info, here's a guy who tears the entire distributor down and explains all the pieces and logic along the way

DIY Re-Curve'57-87 Ford V8 Distributors

 

[KSpence]

Swapped in a 10L, and lighter springs...so I should be around 28 all in (assuming 8 at idle).

The donor distributor had 10L and 15L, so I used that. It also had G1 and G2 stamps on the weights, but both came in at 12 grams, so I'm not sure what the 1 vs 2 is ... but I used that pair instead the G3/G4 pair that was with the 13L/18L bracket. Only remaining step is to dial in the adjustable vac advance once I start it back up.

We will see how it does on the next road test.