Limit total advance???

[Wbulk]

I read the article in the link that Tom Cimino posted. I have been adjusting centrifical and vacuum advances since the late 60s and have read lots of articles on the subject over the years. That article is the very best on the subject I have ever read, and covers additional issues such as compression ratio, and cam timing and how they effect ignition timing. If you are not an expert on the subject it is a great learning tool and it explains it all in detail. I would suggest everyone print all 12 pages of that article and keep it for reference. Thanks Tom.

Wayne

[Excaliber]

Infletcher, good points! I to prefer my vacuum signal directly from the intake for a smoother idle AND it helps to stop a "run on" condition when the motor is hot and shut down. If for no other reason, I would vac advance for those features alone. Any increase in mpg while cruising is just icing on the cake.

Secondarily, the fuel/air mixture cannot be over looked! A "lean" condition will accentuate a "ping" problem. When I prep my car for some serious track work, I purposely change the jets to a "rich" condition, which would not be acceptable on the street. For ping control, rich is better than lean, especially if your running a LOT of advance, like I am.

Perhaps Azfordman's vac unit is not returning smoothly and quickly enough? Therefore, the added timing (vac timing) remains in play in spite of the loss of vacuum signal. That additional timing results in a ping condition when WOT is suddenly achieved.

After market vacuum dist's have a pretty strong return spring that responds quicker than a stock OEM unit. Plus, after market vac dist's typically have to get a fairly high signal before they even start to move, whereas a stock vac dist may move at a lower signal and return more slowly.

You will find very few, if any, professional engine builder that even recommend a vacuum advance. There just to risky (if they hang up, don't return quickly enough or add to much timing). Plus, there a pain in the butt to field questions about "how it works", how to tune it, etc. Example: THIS THREAD!!! I certainly won't recommend one, but some of us understand them, like them and are willing to deal with the RISK for the benefits. Choose wisely your distributor and tune carefully it's "curve".

That is an excellent article, Tom gave us the link too. While we are dealing with a small block here, it should be noted that FE's like a LOT of timing advance compared to many other engines. I specifically added "quench" (a whole 'nother can of worms there) to my FE to enhance the stock combustion chamber design and promote a faster and better burn. One BIG result of "quench" is that it suppreses "ping" so you can either run more advance or lower octane fuel. Quench is a favored "trick" that the Engine Master's competition builders use to gain horse power with pump gas. It is also one of the reasons I don't have a problem running a vacuum advance on MY engine.

[azfordman]

I got around to pulling the distributor on the car apart yesterday....what a pain! Between trying to get that tiny clip out and trying to get it reinstalled...I am not sure which was more difficult! Also, when trying to reinstall the clip, it shot out and disappeared into oblivion...luckily I had the one from the old distributor.... Everything on the bottom end of the cars distributor seemed to be in tact an operational, albeit a bit dry, so I greased it all up. I went ahead and used the 16 slot to try to reduce the amount of overall timing...seemed easier and smarter than trying to weld the larger slot. Finally got it all back together and.......the car would not start!!! Was out there until midnight or so messing with it. Everything seemed fine, fuel, spark, timing marks lined up, etc...but no life to the engine. Sitting in my room this morning the problem hit my like a ton of bricks........



Do you see what I saw?????

Went out this morning pulled the distributor out and rotated the shaft 180 degrees.... Voila!!! She fires to life! Flipping the advance plate around to change the mechanical advance was mentioned in several of the articles, but no one ever mentioned it throwing off the position of the rotor, very frustrating indeed! Also, the vacuum advance that came off the old distributor had around half the movement of the one on the car, so I put that on as well. I cannot say the car is running "better"...but it is running different. Seems to have lost a little pick up off the bottom end, but it does come to life now in the top end.....the one time I really got on it the rear end broke loose shifting into 3rd and 4th gear....had never done that before. I think it will take some more carb adjusting to get a little more pick up on the bottom end. Sorry about the long winded post, just wanted to share my experience. Mark

[Excaliber]

Sounds like your making good progress.

Long winded post? Pfffft, you aint got nothing on me, I'm the king of those around here.

[azfordman]

Yes, making progress... I think that is one of the best parts about these cars...they're not just "drivers".... The cool thing is I am learning a lot as I go, with mucho help form all the owners here on the forum. I feel like such an idiot for not realizing that turning that adjustment plate would throw of the alignment of my rotor....but the good thing is that I can laugh at myself and not stress about it. As I get her more dialed in I am realizing the worst part about these cars is they cannot really be "driven" on the street...100+ mph is just so easy and it happens sooooo quickly!!!

[Rick Parker]

AZFORDMAN:

You should do this sort of stuff on the workbench with the distributor in front of you. Working on it while still in the car is asking for trouble, besides being difficult to access, if that little spring went down an open carb throat....yikes!!!