[Cliff R]

You are most welcome Steve.

You may noticed that I somewhat avoided two things.

Ported vs Manifold vacuum and how "quick" the timing curve needs to be.

Here I use what works best for the job at hand when it comes to ported vs manifold vacuum. Engine fall into three categories tuning them with vacuum advance. They don't like, want, need or respond well to a lot of timing at idle, they are OK with a lot of timing at idle, or they buck, skip, and sound funny in the exhaust note with a lot of timing on them at idle. There is actually a 4th category, when you add so much timing at idle that they are so smooth and so much vacuum you can't get the idle speed below 900-1000 rpms or so no matter how hard you pull back on the throttle arm with the speed screw backed all the way out.

Here, a simple and quick method to determine or get close to the ideal timing the engine is going to want at idle is to make sure it has adequate idle fuel/bypass air FIRST. Then simply loosen up the distributor and advance the timing till it smooths out and makes highest vacuum (going further it starts to "buck and kick" in protest}. Then slowly retard the timing until the engine just starts to slow down a tad and develop a nice exhaust note (deep/heavy sound), stop, and take a gander at it with a timing light. Of course at this point if it's up near 25-30 degrees you are screwed for setting the initial that high because you will WAY too much total timing plus it will knock a tooth off the flywheel on a hot restart. This is where dropping the initial timing back to a more optimum number and adding timing via the VA hooked to manifold vacuum comes in. I do that but not often as NONE of my engines need that much timing and with many combo's we're more times than not just applying a "crutch" fix for too much cam, LSA too tight, and not enough static compression for what they were trying to do with this "street" engine.

When I do the distributor advance/retard thing to engines I've built here they almost always "settle down" nicely around 8-14 degrees initial timing. This really makes things easy for distributor tuning because most are already adding close to the right amount to get the total where I want it. So about all I have to do at this point is to make sure the curve is starting right off idle and advancing smooth and steady all in where I want it, and shortening up the slot in the VA to reduce it to about 10-14 degrees to get timing at light engine load/cruise where it needs to be.

Here, for street and street/strip engines I actually avoid a super-quick timing curve. The ones I've done for sure with higher compression, tight squish/quench and well chosen cams will not be wanting a lot of timing/fuel anyplace right to start with.

This distributor "re-curve" thing with heavy weights, modified center cams and cheap light springs is a fad that should have been forgotten decades ago. It never worked well back in the day but folks still do this to every engine they get within arms reach of. ALL of them believe that this negates the need for a VA and don't hook it up or disable it. It seems that the Olds and Buick crowd are by far and above the worst with the "all-in" by 1500rpm thing. I lost count at least a decade ago of how many pristine fully restored Olds 442's and Stage I Buick 455's (poor running BTW) I've yanked all that crap out of, re-installed original weights/springs and hooked the VA back up for a perfect end result.

Anyhow, I'll take a break here. Had a little extra time the past couple of days and hopefully some of the info helps a bit........Cliff