Coochas

iTrader: (1)

I am checking the timing on my 79 12A. It's been a while since I used a timing gun and even longer since I used one on an Rx7.

I managed to find the red and yellow timing marks and touched them up with a little paint so that I could see them with a strobe.

I am checking L1 and setting the gun to 2-cycle and the RPM on my gun matches the dash.

I see the pin a few mm below the yellow mark (i.e. below yellow and even further below red). I then adjust the degrees on my timing gun until the pin is over the yellow mark. This is occurring at about 4 degrees. Does this mean that I am 4 degrees advanced?

Sorry for the basic question!

lduley

iTrader: (1)

No, if i am picturing what your talking about, that means your 4 degrees retarded because you had to make up the difference to get to the pin with your light. Now if you turned it and it was way past the pin, you'd be advanced

But, it could be I am COMPLETELY retarded and am very wrong about this, because its been a long time for me too

Joekaistoe

As I understand it, delay timing lights (ones with a dial) are only able to show degrees advanced. They do this by delaying the timing light flash after it detects the spark by a certain amount depending on the rpm and position of the dial. (i.e. it detects the spark, waits until the crankshaft will have rotated 4 degrees, then flashes at TDC, which means the spark was 4 degrees before top dead center.)

So your light should be showing 4 degrees advance.

Coochas

iTrader: (1)

Thanks guys. I think I got it.

t_g_farrell

iTrader: (1)

Put it on zero and just use it like a regular light and spin the dizzy to line up the marks.

j9fd3s

iTrader: (3)

+1 just set the timing light to zero, and line up the marks the old fashioned way. the rotary isn't a 2 stroke, so the number on the timing light is either half or double actual, and its too confusing to figure out when you're working on the car.

Joekaistoe

Each spark plug on a rotary fires once per revolution like a 2 stroke, so if you're using the advance feature on a timing light you will have to set it to 2 stroke mode. That said, a lot of people claim that the advance feature isn't as accurate as marking the flywheel if you're changing the timing from stock.

Coochas

iTrader: (1)

My timing light conveniently has a 2-stroke mode. As it turns out, the yellow and red marks are essentially what RB recommends for my Holley setup.
Thanks for all the help!

Coochas

iTrader: (1)

Resurrecting this thread!

Can I assume that the yellow leading mark is TDC and that if someone recs 10 degrees advance from TDC that it is from the yellow mark??????