Are you running ported or direct vacuum advance? On my 2 60's iron headed, high compression V8s I limited the total mechanical. They don't see many miles, and are certainly not beat on so I get by with wannabe 91* Premium.
Buick 401 Nailhead Oil
- Thread starter 65riv
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I was running ported but I remember I monkeyed with the vacuum advance canister chasing fuel economy.
That car was not configured optimumly as the previous owner had put a low rise Weiand single plane manifold and a Holley 600cfm on a stock 289. It took a lot of tinkering to get it to make 16 to 18 on the freeway.
That car was not configured optimumly as the previous owner had put a low rise Weiand single plane manifold and a Holley 600cfm on a stock 289. It took a lot of tinkering to get it to make 16 to 18 on the freeway.
Ported is for smoggers. I would run full manifold vacuum with a cannister that limits the lead to 10*. Put the stock springs back in. Set base to stock setting (vacuum advance plugged). See how she runs. Adjust from there. If you want the curve to come in faster, try 1 weaker spring. Small changes so you know what is working. Good luck and have fun with it.
It also depends on what you want from this engine. Are you still running the single plane? If so, get rid of it unless you are building a dragster.
This was years ago, but I did all that. It was quite the process. I welded up the slot and gradually opened it up until I had about 4 degrees less than stock overall mechanical timing. This let me bump up the initial timing without pinging. My goal was fuel economy on 87 octane and the leanest mixture I could safely run with good drivability.
It was a lot of fun and eventually I locked out the mechanical advance and bought an MSD timing controller so I could fiddle with it even more easily.
Ported vacuum advance, on that application at least, minimized a slight bog at partial throttle I was having.
Yeah, you have to limit the vacuum advance to about 10*.
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