rcdynamic88

How many degrees of mechanical advance should a stock points type distributor be adding when checking the total advance? I set my initial timing to 10 degrees BTDC (with the vacuum advance disconnected and capped off). When I take the RPM's up to 2800-3000 RPM the total timing stops at 22 degrees BTDC. Doesn't that indicate only 12 degrees of mechanical advance? If I hook up the vacuum advance (to manifold vacuum) the total goes go 34 degrees BTDC. I was under the impression I would see 32-34 degrees total with just the mechanical advance, and that the vacuum advance would take it up to 46-48 degrees.
What limits the mechanical advance in these older point style distributors? Is there a bushing that can be changed or modified to allow more mechanical advance? Is there something in particular I should look at that could be limiting the amount of advance?
This distributor just came back form Dave's Small Body HEI's. He takes your point type distributor and converts it to use HEI components. The 4 pin module is mounted underneath the distributor body and he adds the reluctor and pick up under the cap. I have also sent an email to them concerning this issue, but I wanted to check here on ClassicOldsmobile to see what you folks can tell me.

Nilsson

A stock V8 distributor with stock weights will be 20 degrees BTDC.

MDchanic

Maybe he also changed the advance to HEI specs.

- Eric

oldcutlass

There may be more advance coming in at higher rpm's. You need to call Dave's and pose this question to them. Ideally you should be getting 36 total (initial and mechanical) at some point. He may have set your distributor to run a higher initial but I highly doubt it was setup to run 24 degrees.

DoubleV

I'll bet Dave flips out and accuses rcdynamic88 of questioning him or something....

oldcutlass

Hopefully not, it should be an intelligent and informative conversation.

Fun71

That depends upon the year and application of the distributor. I'm familiar with the '70 and '71 350-4bbl engines that have 24º of mechanical advance in the points style distributors. The RPM at which the advance is all in is dictated by the springs: lighter springs allow the advance to come in earlier, stiffer springs make it come in later. Not all combinations will have the advance all-in by 3000-3500 RPM but may be higher than that.

Since your distributor is no longer "stock" your question may not be valid. I agree with the others that you should ask Dave, or check again but rev the engine up to a higher RPM.