timing distributor

Might help if you explained what problem you're having.

Seems like starting with stock springs would be best, then depending what it's doing, or what you want it to do, then you can try heavier or lighter spring until you get the outcome you want.

So I assume you don't have a re-curve kit, with instructions that tell you which color springs do what.

I'm not sure how you can tell by looking which spring is the stock spring, although I don't think it is colored, so depending what you have that might narrow it down.

I may have a box from a re-curve kit... and maybe the directions are inside. More than likely not, but I'll try to look for it.

Use the lightest springs, you want full advance by 2500 rpms

Agree, just suggesting thats where you start. Have an msd and went through the same issues. Lightest springs work perfect and thats basically what i find out 80+ % of the time to those ive talked to.

Had to do some poking around, but this is what I was looking to say.(copy/ paste below)
So I guess were both close, but I like my close more. Too much advance that soon (2500) could give silent detonation, I`d rather play it safe at the 3000 plus range. My 3500 might seem on the high side, but you have to let the olds torque loose.

Since the timing curve below your launch rpm is irrelevant to performance, you should be most concerned with your total mechanical advance and rate of advance. To determine optimum power at 2000 rpm, Dr. Chris Jacobs of Jacobs Electronics recommends finding the advance setting that makes the car accelerate quickest from 1000 rpm to 3000 rpm in First gear. Duplicate that procedure for each 500-rpm increment, then find the combination of advance weights and springs that most closely matches that curve.

A performance curve will usually call for 20 to 30 degrees of advance by 3000 rpm (with a total of between 30 and 40 degrees), so use a dial-back-to-zero timing light to set your total advance for best power, then alter the mechanical-advance curve so the initial timing allows for optimum idle quality. Finally, use an adjustable vacuum-advance canister to set up additional advance to keep the spark plugs clean

Nothing more be said, ported vacuum is an emission myth !!( were talking our vintage, basically stock to moderately modified) Ported vac. and manifold vac. require the use of totally different timing techniques, in base, vacuum, and mechanical calibrations. If you need to pass a emission test in your state go ported. Edelbrock even has a bulletin on this, it`s an old one, I`ll see if I can dig it out.

" Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts."

Nice job Mike,
that poor typing finger must be sore after all that.

So are you saying that I should go out into the garage and hook up a vacuum hose to my shiny new HEI distributor??? ;D

I'll give it a try... hell, I might even like it. And maybe it'll give me enough manifold vacuum to allow my power brake booster to work.

Uh huh!