I followed the haynes procedure to set the timing on my GSL-SE, but they say to set the timing at idle.
I guess the marks on the pulley are 5deg. leading and 20 deg. trailing, so;
If I rev the engine up so that i'm at full mechanical advance, how do I know how many degrees i'm at???

Thanks

 

first off you will have vacum advance not sure about mechanical on our cars. so go full open throttle, the vacum drops off, and your timing "advances". the vacum advace doesn't realy advace the timing. it retards the timing at idle and as the vacum drops off the timing approches what the most advanced timing posistion. so when you set the timing your acctually seting how far it's going to be retarded and how it will get advanced when you open your throttle. if you have some insane urge to see how much the timing changes then this is what you do. make a mark about 10 degrees advanced on the main pully. start the car. unplug the vacum lines for the vacum advance. see how close you are. you could get real precise by figuring the circumfrance of the pully and then dividing it by 360. and the number you get is how far apart each degree is on the pullys edge. make a mark for every degree. make sure they are different colors. and then unplug the vacum advance. make sure that you hold you fingers over the 2 vacum lines so you don't end up with a vacum leak. also don't confuse open throttle with engine revs. vacum advace and mechanical advance are different. you can go 25 mph and put it in 5th, stomp on the gas and you'll be at open throttle with no vacum. meaning that the vacum advance has advanced the timing all the way. where as mechanical advance depends on engine revs. as the rev rise the timing advances. vacum advance moves the trailing mag pick up. mechanical would move both pick ups. all it does is cause the coils to fire sooner.

jerad

 

Thanks for the reply, I don't quite follow what you are saying though..

Does this mean that if I unplug my vacuum advance and block off the hoses, I can set my timing at idle?

I was under the impression that the change in mechanical advance varies too much to be accurate when doing the timing at idle. (ie. if I set my timing to stock, by the time it reaches full mechanical advance it will have advanced too far or not far enough)
can someone verify this plz?

 

Timing is supposed to be set at idle, and then the vacuum advance advances/retards the timing depending on the load on your vehicle. If you set your timing when the distributor is at full advance, then once you take the vacuum off of the dashpot, the timing will drop down to a way-too-retarded position, causing your car to run like **** at idle.

 

The part about the vacuum advance is pretty much just wrong. Vacuum advance does exactly that. It advances the timing at idle and whenever there's vacuum present, it doesn't retard it. At wide open throttle there's no vacuum so there is no vacuum advance.

Mechanical advance as you say goes up with rpm. Mechanical advance on these dizzy's is 20* and is fully dialled in before 4000rpm.

 

To set the timing for full mechanical advance you either need to mark the degrees on the pulley or use a timing light with an advance dial. You should always disconnect the vacuum advance when setting the timing. Most people just leave it off anyway as it's mainly for emissions.

 

Thanks, exactly what I needed to know..

Advance on the dial is 2x above normal right?
ex. 40* on the advance dial = 20* on our cars

 

Nevermind, saw that other thread

Thanks !