I've got a new timing light with the advance feature.  From what I've read I'm thinking that if I dial in the advance such as 10 degrees, the pulley mark should line up on 0.  Is that right?  With the advance feature you don't use the 5 degree increments, just the 0 mark.  Right???

 

Thanks for any replies,

Cliff

I think that you just add the dial-back to whatever shows on the pointer or timing indicator.  If you only have a zero then you just move the dial until you get the light to zero and the dial reading is your timing.  But if you have the indicators then just move the dial until the light hits a mark, then add the two together.  Very useful for seeing timing at full advance, when the light is typically off the pointer or timing tab.  If you know that you have about 34 degrees full mechanical, for example, you would set the dial to 30, rev it up and should see around 4 on the engine's indicator (assuming no vacuum advance).

 

You can experiment to verify.  Set the dial to zero and see 10 on the normal indicators, set the dial to 10 and the indicators should show zero.

The main purpose of a dial-back timing light is to measure the total advance with the engine at speed. The timing marks don't go far enough to display total advance. As Zed Head stated, you add the dial back setting to the displayed value.

So 10 btdc would be 27 degrees at 2500rpm? Set the dial to 27 and it should hit on the third mark on the pulley. First mark is 0 2nd is 5 and third is 10 degrees? I'll try that.

I got the carbs perfect and then put the filter housing back on and dropped 200 rpms

damn it! I'm gonna through in the towel for today and watch some football.

Happy New Year everybody.

cliff

another way to look at it is set your engine at the desired speed and keep dialing back until the pointer hits 0, then the number displayed is the advance. so if you have 10 degrees advance at idle, you should be able to dial back your timing light until the flashing light shows the mark visually at exactly 0 and the meter on the timing light would read 10 - this is more theory than practice, as at idle it will jump around a bit, but you can get it pretty darn close. it's more consistent/stable at higher revs. if you want to see your total advance, including mechanical, just rev it up until you reach max advance (when the timing stops moving) and dial back until the pointer hits 0 and the meter will read total combined advance (initial + mechanical). you can also use the tach feature to see what rpms the mech advance kicks in at, and how it progresses - then plot the values to figure out your advance curve.

fun!

It amazes me that a pulley on front of a crank on a motor turning 2,500 RPMs is completely frozen to my eyes.  It's an eerie feeling for sure.

 

Thanks everybody for helping me realize how little I know.    

yeah, it's pretty cool - kinda brings me right back to the late 70's (when my car was young) and my buddy got a strobe light for his dance parties... we'd jump up and down at just the right speed and it would look like you were floating a few inches above the floor. and the weed helped...

Ahhhhhhh... the memories of floating...

Ahhhhhhh... the memories of floating...

Ahhhhh...last night...

I don't know what this means but I went for a few test drives this morning and after finding the sweet spot on the dizzy came home and hooked the light. Up button up up up until the pointer matched the zero notch on the pulley. 34 was where it matched up at 700 rpms with the vacuum plugged off and taped over.

34 degrees at idle would be a high number.  Many engines would be hard to start with that much advance.  Is this a stock engine or could it have a mix of damper pulleys and timing tabs?  Could be that TDC is not represented by the timing marks.

 

New toys = new problems.  Although, if you like the way it runs it's not really a problem.

Yeah I've been thinking the same.  I'm going to pull the valve cover off soon and see how far of the cam sprocket line up notches are off.  Probably needs to be put ahead a hole or two.  But it sure is nice walking into my garage now.