We have the 455 running after the 1977 260 swap. The vacuum advance is shot. What brands are you using? Looking for something that works well and is easily adjustable. We are running the 260 OE distributor, would it be better to replace the distributor? We don't need a high tech distributor or something new from China. I am not sure I trust off the shelf rebuilt. TIA

 

I'd say keep the original GM distributor and install an adjustable vacuum advance canister. My car has the vacuum canister that came with the GM HEI that's from a 77-79 403 engine - originally 24º vacuum advance, but I made a stop and set it to 10º vacuum advance.

 

If the 260 distributor is in good condition, it will work just fine once calibrated for the 455.

This is the adjustable valve advance with the limiting cam. Get the initial, centrifugal advance, and ignition curve dialed in before messing with the vacuum advance. Once you have the initial/total/etc is set up to where the engine is happy, don’t mess with it, adjust the vacuum advance to work with the setup you have.

For example, once you have the advance rate perfected, and the engine is happy WITHOUT the vacuum advance, and you find it pings and rattles once it’s connected, you need to reduce the amount of advance the canister provides. If it rattles and pings as you crowd the throttle, then stops, you need to play around with the setscrew in the canister vacuum hose neck. The setscrew adjusts the spring tension and the amount of vacuum needed to get the advance to move.

Modt engines like 10-15 degrees initial timing, another 20-25ish centrifugal advance, and another 10-15 vacuum advance.

 

Or… if you are serious of getting this thing dialed in. Get one of these. Old school isn’t always better.

https://progressionignition.com/

 

If that distributor works as well as it says, it’s probably worth the money!

 

cant argue, that looks pretty slick!!

 

Give this a read. After doing so, I added a non-Olds fixed advanced can to my ‘66’s with big blocks. I believe it was a Buick for HEI.

https://www.460ford.com/threads/timi...gineer.117504/

I didn’t have good luck with adjustable, I fiddled with various home fixes to limit the travel and so on, but ultimately concluded I wanted less advance and got there with factory (non-Olds) parts.

Chris

 

Yeah, a few have had issue with the aftermarket vacuum advance failing. Mine have held up fine, years old. The aftermarket ones put out 20 degrees and easily adjust with an Allen key. All the factory ones I have are 30 degree units, the 24 would have worked great with my 9 to 1 350.

 

That is very cool.

 

Thank you.

 

I like the adjustable vac advance unit too. I found the original (HEI) had too much advance. I agree, ten degrees is about all I wanted from my vac advance. After I had mine adjusted to a total of about 38 degrees (12 base, 16 mechanical, 10 vacuume) I found that I had spark knock at mild throttle positions under light exeleration. Turned out the mechanical advance springs were too light and I was getting too much advance too early. The kit matt69olds posted looks like it has everything I needed in one kit.