View Full Version : timing mark

07-30-2008, 11:00 PM
so im used to timing vehicles with the harmonic balancer "labeled", mine seems to not have any numbers? So my question is...Is the gash in the harmonic balacer in the timing zone TDC or is that where it needs to be timed at 10 BTDC, because it seems to run the best right on it so i figured it was 10and they marked it so you could just set it to that...but if it is TDC how do i find 10 below??? Thanks in advance P.S. I also timed it without disconnecting the vacuum advance from the distributor. will this effect anything?

Big Jim M
07-31-2008, 12:47 AM
I have never yet found a dist that could be times with the vac connected!! So disconnect it and do it again..
Yes the mark on the balancer is TDC. I like to measure the outside circumference and divide that measurement by 360* and mark with a paint pen the advance I wish and also I make a maximum mark at 36* or therebouts.. Then when running the engine up I can see what the vac advance is and also the mechanical advance is and at what rpm these things happen..
One can purchase a TAPE with the timing marked on it to STICK on the damper also.
Big JIm
Big JIm

07-31-2008, 12:54 AM
wow you really get into this dont you??? they should really have the damn thing marked! i did a 40 foot 1 tire burnout with it the way it is now so when i get it timed right im goin for 80! So why the 36* mark and you say i should rev it when timing?

Big Jim M
07-31-2008, 10:05 AM
Because at maximum advance the TDC mark is out of sight and the mechanic cannot tell zackly what he is seeing.. With a 35* mark one can judge 40* or whatever he wants to be the maximum advance.. If one KNOWS what he wants the timing to be he can put a 39* or whatever mark on there and adjust the timing so THAT mark is the maximum timing. This method is used when the engine will spend most of it's time at WOT. But is helpful if the mechanic wants to know everything he can about his timing.
Big JIm

Big Jim M
07-31-2008, 10:33 AM
Ram the one thing that is to be considered when setting the timing is the LENGTH OF TIME THE PRESSURE IS AT IT'S HIGHEST! One times his engine to take full measure of that high pressure. The timing is adjustable because as the engine picks up speed the START of the burning of the fuel must be EARLIER so the pressure rise occurs while the piston is desending. If the spark occured at the same position of the piston at all times, as the engine speed increased the maximum pressure would occur later and later.. Finally occuring on the exhaust stroke in the exhaust manifold.. Which would be so retarded the thing couldn't pull a fat girl off a potty!
When an engine is ideling having the spark (with vac advance) occur at 20* or so BTDC works fine. However as the engine speed increases MORE advance is needed. And the faster the engine turns the more advance will be needed.
The reason to set the timing at 8/10* with the vac unplugged is that will always be the least advance the engine will EVER see. When one nails the throttle the vac goes away and the timing jumps back to that initial setting.. then when the vac increases the timing also increases and as the engine speed increases the mechanical timing starts making the timing even more advanced..
Go ahead and make a mark on there and watch with a light as you increase the throttle you can see all the timing features come into play.. It is an eye opening experience to see how gasoline is burnt in an engine..
Remember it all about TIME! The time it takes to burn the fuel to make the most pressure! We have nanno seconds to work with here. We want that maximum pressure to occur while the piston is decending..Not before or after.. And as the engine gets faster and faster the TIME it takes to desend is shorter and shorter.. So the initial spark must oblige the speed of the piston with more and more advance of the spark...
The reason for the vac advance is at the initial 20* or so if one NAILS the throttle the mixture will lean itself out and the advanced spark would cause a backfire out the intake from the mixture being lean and the timing being so advanced.. But because the timing jumps back from the 20* to 8/10* the fire tends to stay where it should..
I truley hope this will help both you and perhaps others to better understand spark timing.
Big Jim

07-31-2008, 11:05 AM
Timing lights are available with an advance dial on them. You aim at the TDC mark, and adjust a dial. When the flash hits the mark, you read the dial for your advance. These lights are getting cheaper all the time; see:
I don't necessarily recommend that particular light, but it will give you an idea of what's available.
And while we're here, not all lights agree with each other. That is to say one may read differently than another, but I don't think they are more than a degree or so off and it doesn't seem to make much difference.

07-31-2008, 11:16 AM
i belive mine is snap on...what degree is suggested for idle and what degree is suggested for whatever else...i read 10BTDC to time it period and the gash is definitaly TDC??? Because it really wont run well if its not on it

07-31-2008, 10:46 PM
ok so i didnt find a vacuum advance hose but i did disconnect the single wire black connector near the distributor, and now that timing gash in the balancer is nowhere to be found!!! What am i supposed to do?

08-01-2008, 01:58 AM
Get a manual. That wire is a SPOUT connector for the stock ignition.
In the meantime, experiment by rotating the distributor a little at a time. You will probably have to retard it to see the mark.

08-01-2008, 02:10 AM
i found it finally i had to go in at a diffrent angle and as soon as i did my inductive probe melted to my exhaust manifold :(

08-03-2008, 12:06 AM
ok so i am completely lost...for the life of me i cannot find the vacuum advance on this 2.8 nor do i know which single wire connector(black) the catalyst speaks of under the hood...can someone please tell me what the hell to unplug when im timing this beast??? Cause every time i set the timing it moves again

08-03-2008, 11:45 AM
There is a single wire with a connector that is near the distributor on the passenger side. The connector on mine is a light gray; the wire color doesn't matter because it is now probably black with dirt and oil.
After you set the base timing, it will change when you reconnect the connector.
One of the reasons that I suggest a manual is that it shows these things.

08-03-2008, 01:07 PM
i did that and when i plugged the wire up it reved up so high i had to cut it off and restart it

Eric Kropp
08-11-2008, 06:14 PM
I had the same question with my timing marks. What I did was draw a 6" circle on a sheet of paper(the size of pulley with the timing marks). Carefully draw on thin line from the out side of the six inch circle through the center with a very sharp pencil(this represents TDC). Line up a protractor in the center of the circle with the line and carefully mark 10*. Remove the protractor and take a ruler and line it up with the 10* mark and the center and carefully draw another line to the out side of the six in circle(This represents your 10* timing mark). Then measure the distance from the two marks on the out side of the circle and transfer that measurement to the pulley and see which mark is 10*. Seems to me like it was either 9/16" or 7/16". Can't remember. E-mail me if you like, erk4@pge.com.


08-11-2008, 10:30 PM
i got a timing light with advance and just set it to 10* i hope its right cause i damn sure aint messin with it anymore it runs fine now