When you are at WOT, there is very little vacuum to apply to the advance can on the distributor. Keeping it there on a street machine is a "no brainer". Vacuum advance for normal driving which is smoother idle, cooler running, and better mileage; at WOT the car operates without vacuum advance (no vacuum to activate it).

Quit listening to untrained mechanics....

 

I have the msd programmable 6530 box and an msd large cap distributor and a map sensor. Dist is locked at 42 initial. On start, the box is programmed to pull 25* between 100-600 rpm to get started. At 800 rpm idle, the vacuum pulls 8* from 42* initial. So, by way of programming the curve, idle is 24*, cruise is 42* and wot is 34*. Also, I programmed my curve to be a curve, not linear. Fun to play with with total control over the engines timing.

 

That's a pretty strong cam. It may like a little more total advance. Like 36 degrees. That would take your initial to 25 and it would probably still start OK with that cam. If it "kicks back" that's when you have too much initial.

It's the slow curve part that bothers me. And the fact that you didn't mention if you are running a vacuum can. Is your bog at light throttle or full throttle?

I would add a vacuum can, if not present, and restrict it to 10 degrees with a a limiter, on manifold vac. It will idle better and have 32 degrees at idle after starting. (No need for locked out timing or starter retard stuff, it's already there) And it may eliminate your off idle bog, which could be a result of insufficient timing at low rpm. This would help a light throttle low rpm bog.

That alone may cure your problem. But another member recently had a problem with the distributor "football" and it gave him very slow advance at 1800-2400 and he had a mild bog like you.

GM supplied many football shapes. but there are basically two available today. The std one and the hi-perf one. The hi-perf one (curve 1) gives about 7 more degrees at 75% of max rpm vs the retarded std one. Engines with better than mild factory cams really respond to it. Looking at it another way the high-perf football gives 11 degrees advance by 1250rpm vs 2 degrees for the slow std one. If you have a timing tape you could measure it and plot it. It sounds like it needs more advance, sooner. This fix would help a WOT low rpm bog.

 

Thanks Leigh, I have no vacuum advance on this its a summit/msd piece.
Has a very slight hesitation say if Im idling and give it a quick blip. Runs well otherwise I think it could be snappier theres more power in it.
Have to try this sometime....My timing light doesnt like this ign, the mark moves all over the place. Have to get a proper one then sneak up on the timing.
Ill have to look for the card and post it, was done by Bob Jennings (ran during the Muldowney/Prudhomme era)
I tried every bushing/spring combo I could in those msd kits, the car just wouldnt make power. Many including Bob said they are junk so he did his own thing to it.

 

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Agree, I run 36* timing at idle with a much lower overlap cam than what you have, for good off idle response.

Also agree that the stock GM curve for timing is kinda junk for higher performance applications. I ended up making my own curve, center piece, to get the timing advance I wanted.

 

Anyone know what curve looks like on l82..i discovered a ton of differences even from factory..
stock im all in 2000 mechanical and limited to 10 vacuum..i run 18 static dle toget 36 all in w/o vacuum with lars papers



79 l82 manual

 

You could read the timing every 200 rpm and make your own curve. Just use a dial back timing light, or a degree tape on the dampner.. With vac unplugged.

 

To the OP.
Debate it to death or just try it.
Put some garage door springs on there, and drill/tap and pin it. If you don't like it, take out the screw and reinstall the springs,.
Use a shitty spare weight.