"A vacuum leak would make you have to set the carbs too rich and would have
the greatest effect at idle."

There is a 1/4 diameter nipple at the top, rear of the airbox which is unused and open. I really don't feel any suction there, even with high idle. I tried hooking up vac line from the dizzy diaphram to this, but it made no difference.

Does the vac advance still function/need to function with this Crane electronic
ignition?

"n addition to checking the booster and PCV system you should probably also
check the manifold gasket and secondary butterflies (if you have them)."

What's to check in the PCV system? All this is is a hose from the oil separator and flame guard to the airbox, right?

Have sprayed carb cleaner all around the gaskets. No effect.


"I've found the Uni-Syn to be pretty much worthless because the engine is not
big enough to activate them unless you choke it way down. Probably better
to do it mechanically. Loosen one of the throttle actuating arms, loosen
the idle screw till you can completely close both butterflies, then take the
slack out of the linkage and tighten the arm. The manifold has a BIG balance
tube so more accurate synchronization is really unnecessary"

Well, I bought mine at an recent auction of shop equipment, so, I HAD to try it. Got it to work, but, yes, as you say, you need to close down the orifice, or start with the idle high and throttle stops turned in about 1-1/2 turns to set the idle there.

Now I understand how the throttle stops control the butterflies...indeed, it is almost as if the engine needs these open a bit in order to stay running at idle.

I'll try your suggestion here.


"Try setting the advance by ear (till it idles fastest) and see what you have.
I'll bet it will be about 20°"

Umm....when I do this, I can go only so far, increasing the idle, then the engine speeds up way far. But, this is just beyond the 20 degrees mark you mention. Now the idle will be about 1500 -- but the throttle stops will be backed all the way off. So how do I get the idle down to the 800 called for?

I have only been able to achieve idles between 800-950 be retarding the ignition to about 10 advanced, stops backed off.


"Some carbs have a place to hook up the vacuum advance. If yours has such a
fitting it should be used or plugged, NOT left open"

OK, so even with the Crane, I need to get the vac advance working? It's currently plugged at the diaphram.

Thanks for all your suggestions.