924Board.org

[augidog]

We all know the TDC mark on the cam sprocket.
But did you know you could use your timing light here as well as the bell housing?
My flywheel was originally put on wrong so I never had timing marks.
With a little math I marked my initial timing mark and my full advance test mark.
The marks above are for a 78na but you can easily apply the spacing to your car. Each degree is .045 of an inch
I found it easier to strobe here and with the full advance mark I do not need to spend money on an advance timing light.
The full advance test has confirmed a leak in my vacuum system because I can only reach about half way to my full advance mark at 4500 rpm.
Oh well, onward and upward.
_________________
1978 924 95 mile daily driver.
Audi TB/POR174M/High Flow Cat/2.25" exhaust
I knew that positive thinking thing wouldn't work.

[Smoothie]

Hey Aug, I went through this a couple weeks ago and got different results - I figure each full tooth distance on the crank sprocket = 16.36° of crank travel and each tooth on the cam = 8.18° of cam travel. (Crank sprocket has 22 teeth and cam sprocket has 44.) To read crank travel from the cam you have to double the cam degrees, so while 1 tooth on the cam = 8.18° of cam travel, it equates to 16.36° of crank travel. 1/2 tooth of the cam sprocket is ≈4° of cam travel and equates to ≈8° of crank travel. Your "+3" mark should actually be marked "-8" and your "42 BTDC" is actually something like "+84" or "84BTDC". This should account for your thinking you're 50% off on the full advance - while actually, your not.

http://www.924board.org/viewtopic.php?t=14390&postdays=0&postorder=asc&start=12
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[augidog]

Sorry I missed that post. We must think alike here in Jersey.
And Wow, Thank you! I was hoping someone would double-check me in case I was off.
I only missed by 50%. At least I figured out the first half.
This is how I figured it;
dimension x 3.14
than divided by 360.
I forgot the gear ratio to the flywheel.

It did seem like I was running a little too far back on my timing because I was running low pressure at idle.
I'm going to set the full advance at half that mark and set timing to that and be done with it. It works out to be 1 inch
Thanks for calling me on it.
I'll feel a lot better knowing my full advance test mark is correct.
Thanks Smoothie.
I still feel the full advance test is underrated. With an older engine, it is the only way to maximize your timing.
Send me your book and I'll put a star in it or do you rather a president’s head or dinosaur? Nice work.
_________________
1978 924 95 mile daily driver.
Audi TB/POR174M/High Flow Cat/2.25" exhaust
I knew that positive thinking thing wouldn't work.

[Smoothie]

You got dinosaurs?! I'll take a carton of dino eggs. I wanna build a terrarium.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox