hi all,

in another post .bob says:
"To set the timing on an old or modified engine is with a vacuum gauge. Hooke the gauge up directly to manifold vacuum. Set the timing where the vacuum is highest.". I've heard it before and I'm curious about it.
I tried that with mine, but that left me at 15deg of advance at idle, which I believ is too much.
I have no ear for pinging, so I turned back to be on the safe side.
At the same time when my idle advance is over 10degrees the starter is complaining (whooop whoop whooop instead of whopwhopwhop).
So for me it doesn't seem to be a safe bet ... is there anything else you should consider?

Kalli

 

You are on the right track...
Advance as much as you can short of pinging under accelleration or hard to start when hot.

As the engine wears - that 'sweet spot' will move so one size (timing degreee) doesn't fit all!

No more magic than that.

 

Setting via vacuum timing can often get you too much advance at idle as well.

 

Yeah, you're not supposed to set the timing with a vacuum gauge. Under no load (and therefore high vacuum), the engine will run very well with a LOT of advance. But as soon as you put a load on the engine, BANG!, detonation.

Set the timing to about 12* at idle with the vacuum advance disconnected and plugged. If this changes your idle rpm, reset the idle speed and check the timing again. Fire it up and head up a steep hill at part-throttlein high gear. If you hear a sound like a bunch of marbles rattling around under the hood, drop the timing back to 10* and try again. Keep going until you get no pinging

 

This is the first time ive heard of setting timing with the vacume guage.. Sounds cool and easy but I guess it wouldnt be as accurate.. I still dont get it though.. It seems that all engines will require a little difference in timing, but all books and things usually point to one number (12*)

What does it help if you advance the timing? Ive never understood this.. Can someone explain? I hear that it can give you a little more pep, or throttle response. I guess I just need answers, and a better understanding.. I put my engine in after rebuild and timed by ear (too high 16*) and had all of the symptoms (pinging/ hard starting) Then timed it to 12*.. IF I go up to 14* will that pep it up or do I just have to try and find out? Not that Im going to,, but why not?

I know its kind of an open ended question.. Im sure someone will answer it though. Thats why I love this forum.

 

thanks all for clarifying. that's exactly what happened to me: adjusted via vacuum and ended up being too far advanced.
myth confirmed :-]
There's one great article I once read about ignition timing and why to advance and what the effects of load, idle,. higher rpms and everything is. all that in relation to mechanical and vacuum advance. It clarified a lot.
I'lll try to find it again.
But my original question is answered. you might end up advanced. in my case i did

 

Ok here's where an "old guy" steps in. We used to "power tune" cars back in the 60-early 70's (it was prevelant before then but I'm not that old) by advancing the speed to like 1500 rpm and then using a vacum gauge to get the highest vacumn reading we could we'd advance and retard the timing to come up with the sweet spot. We'd then reset the idle speed to normal. But remember, that was back in the day of leaded fuel and octanes like 97 and 100+. In today's world it doesn't make much sense cause like the fury says, it invites detonation.

 

hey, sorry I dont mean to hijack this thread, but what does pinging exactly sound like? Star said its like a bunch of marbles banging around under the hood? Not sure exactly what that would sound like....

 

It makes a metallic rattling sound if you can hear it. Like marbles in a tin can, or someone tapping on a metal object with a wrench or hammer. Often detonation begins and you get pinging before you can even hear it. Human ears can only hear across a relatively narrow frequency range.

 

Bring your children with you, if you have any. Likely they'll hear it before you will I'm only 25, but my high range hearing is pretty destroyed. What I get for all those concerts