Hi all.. sorry for the long post, ill try keep it short as possible - without cheaping out on the details ~

so i seemed to finally have got my head wrapped around the basic timing concepts, but im having some issues. Just got back from the car for the 2nd time- each time with new findings -

Ive been poking arund with springs and things - and puckering around with timing etc.. a few things are on the chalk board so far -

I set initial with vac plugged - soon as i plug the vac in the timing goes up by 10 degrees almost to the t. I looked up the specs of my can (AR22), and its a 5 degree (dizzy, 10 crank) 12-14Hg, model which is kinda cool since most are double that (the max advance at least).. which seems close to a few hei recipes ive read about where folks want 14 inn / 22 mech / 10 adv.. Now my cam is a lunati barebones which pulls a fair amount of vac (i havent measured yet), but its a 112 lsa and chosen for mileage and mid range torque.. its similar to the GM HO 350 motor actually..

Now with the vac plugged, and initial at 12, the most COMBINED adv i can get is about 30, 25 with lighter springs.. Im using the stock GM weights, and below are some pics.. do these look worn or is it something else? (I cleaned them with brake cleaner and used a tiny bit of oil on the parts. They snap back nicely when released)

Weight:


MAx and min movement:




more pics: is the assembley looking correct? this is how it came:






Before i pop down again 2moro - im wondering:

can the vac can be limiting the centrifugal advance? Most ppl i know try and RETARD mech adv?

Why is my vac can applying advance at idle - is it because my idle vac is within the cans range? Do i need a lower Hg rating can? like say an 8Hg? so it only starts applying advance light/mid throttle?

Are vac cans supposed to add some adv @ idle? if so my initial is then obviously much lower (2 if the can adds ten immediately when plugged in)?

Ive tried all combinations of springs, and getting VERY similar results, only the 2 light springs (mr gasket pieces of junk) showed a drop of about 5 degrees less @ max..

* I guess before anything i have to get mechanical up to about 25? (37 total incl initial)
* Get correct vac can for my idle vac (about 2Hg lower ive read)


What i have found out is this gr8 post with GM base platres, weight part numbers and the amount of crank advance:
Hei dizzy part #'s & crank degrees, so ill prob have to see what I have.. there are some that look like they give very little advance. I will also pull the dizzy to see if theres a limiter bush on the bottom pin - but i doubt it..

"The center plate installation, as designed by GM was with its numbers facing down. So many of them didn’t yield enough advance for performance applications ..." - mine face down too i think.

Also - my can is only 2 degrees off the highly recommend AR12 in this link/article here:
http://www.corvette-restoration.com/...c_Adv_Spec.pdf - so i was hoping id be close, however vac 2 idle is prob not a good thing..


Engine specs: Start/ runs well.. idle not bad

350 40 over
Air gap intake
Quadrajet (up 2 sizes in pri jets)
vortec heads
200-4r OD
lunati 10120101 cam
2 1/4 inch true duals
Long tube headers (1 5/8)

Lastly: since i installed my cam, if i have my head over my motor while its idling, i hear this pssst kind of sound coming out from the valve covers - should i re check lash? almost sounds like the way u call a kitty cat.. like a soft kiss almost lol!!

tx in advance (pun intended!)

 

Because most likely you probably have the dist vac line connected to a full time ( manifold ) vac port on the carb , not the ported vac port
Read
http://www.gofastforless.com/ignition/advance.htm
http://www.bangshift.com/forum/showt...l=1#post622365
http://www.msdignition.com/forum/sho...03&postcount=7
http://www.chevyhiperformance.com/ho...8/viewall.html
http://www.hotrodders.com/forum/port...ml#post1576730
http://www.hotrodders.com/forum/port...tml#post150858

 

i know i switched to both on the qjet, the one on the base plate and another above where most are connected. Ill double check but im sure both went up.. I am noticing my idle setting is higher than before, so i might be on the main circuit and not on the idle meaning there will be vac on both.. perhaps i need to drill the idle passages.. the air screws make a difference in how it runs, so that indicates im in the right ball park.. how do i know if im on main circuits or idle? car drives nice, no bog or anything..

 

Are we talking about the carb now?

 

vette thanks for posting those links!

 

yeah - some more good reading. Ive read some ppl do inn., then vac, then adjust idle back. I was getting so much advane only cos my revs went up, and i mistakenly adjusted the inn adv back to compensate.

As i see it: set inn with vaac un hooked. plug in vac, adjust idle back down.

Ill do a test and see what happens

tx guys - vette, nice links yeah

 

The maximum centrifugal advance amount is limited by the CENTERPLATE on a stock HEI- the thing the "tails" of the centrifugal weights push against. I can't read the number stamped into yours but ~20* of centrifugal advance is common with MOST HEI centerplates. Yours might be on the lower end of that range. It might also be lower because the plastic bushings in your advance weights are a little worn.

Still, most HEIs the advance mecanisms work amazingly well until they are so worn they're practically falling apart. Yours still look BETTER than some of the ones I've run myself!

Your 10* vacuum advance canister is a major advantage. Most stock canisters supply about 20* of vacuum advance which is way too much for a performance application. You're good to go on the vacuum advance side of things!

"As i see it: set inn with vaac un hooked. plug in vac, adjust idle back down."

Exactly correct.

 

Awesome damon - thanks for confirming on the plates and all. Yes i was quite lucky to - seems the guy that put this together was on the right track. 2 med springs as well, and they werent like the junk from the mr gasket set, better quality.

Glad i have good enough hardware @ least. is motor oil on the metal contacts ok? (i dont think so!) - i have reel grease that i think wd work better? sure the oil will just go everywhere?

 

No grease. Only attracts dirt. Run it dry (but clean).