Ignition timing help request

[RETed]

I have to ask...

Do you understand the basics about ignition timing?

Since we're talking about an OLD vehicle, I would assume that emissions is not a concern.
If this assumption is correct, the timing marks - and what they represent - don't really mean anything; they are there as a guideline and make it easier to get the engine started.

Like everyone else said, you really need to verify TOP DEAD CENTER.
There is a quick and dirty method to do this by sticking something into the spark plug hole (after removing the spark plug) and seeing where the object would protrude into the engine the LEAST - shallowest.
Once you get an idea where TDC is...reference this with the pulley marks.

BTW, the later models usually have marks at 5-degrees *A*TDC and 20-degrees *A*TDC.
The *A* part is important, cause it means AFTER; if you confuse this with *BTDC* - we're talking a difference of 10-degrees total!

First step, adjust distributor until you feel the engine idles best...
Since we're not worried about emissions, use the pulley marks as a guide and go from there.
Typically, most engines will run a little better with a little more ignition timing advance than stock.
More advance at idle will cause the idle to bump up a bit, so there is a balance between idle quality and how much fuel it's going to drink - i.e. gas mileage.
Just adjust for what is best for you...

Now, as for absolute advance at full load - what you call pulling-the-vacuum-hose - start at 20-degrees and go up from there.
20-degrees is a good, safe starting point.
Most rotaries will make good power somewhere around 25 - 30 degrees of total advance.
I've seen some motors make power all the way up to 35-degrees, but EGT's tend to get mighty hot up there - you're sacrificing engine life for power.
If you don't know what you are doing at this point, I would HIGHLY RECOMMEND you find someone who does...


-Ted