Ignition Timing Dauntless

I have a 67 CJ5 with a Dauntless and HEI distributor, and I'm wondering if I'm doing something wrong setting the timing. The engine idles great with about 20 showing on the vacuum gauge. When you disconnect the vacuum from the distributor and adjust the timing to about 5* BTDC, when you rev the motor the timing advances to about 12*. When you hook the vacuum back up and rev the motor it goes off the scale advance. Is this correct? The timing marks are the kind cast into the timing gear cover. Is this correct?

Another issue is the accelerator booster pump in the Rochester carb. The motor was responding great to the throttle, but now it stumbles or has a dead spot just off idle. Is there something that could cause a booster pump to get out of kilter overnight? The carb has been freshly rebuilt.

Thanks for all the help.

 

FWIW my accel/ pump rubber cup turned out and up and did not provide that initial jet of gas just off idle. Once I was past off idele it runs like a champ. I put it back together with the cup turned down and it worked for a while but it is doing it again so i think I will need a new cup. I was told in another post that i should have lubed the cup during my rebuild. Live and learn.

Todd

 

The fuel we have to use these days ruins the accelerator pump "cup" in older carbs due to the alcohol content. If you lubed the cup, I'd think the fuel would wash it off in a pump or two and then you'd be back to where you started. What intrigues me is that if you have a std. 2G two barrel carb, how you are reading any vacuum at idle at all. The 2G wont allow vacuum until a ways after idle, at part throttle.

 

The 2G has ported vacuum and not manifold vacuum. The butterflies don't expose the vacuum ports for the distributor in the throat of the carb until they are opened up some. We've had this discussion before. Where is your distributor vac. hose connected to?

 

Ok, well now I'm confused too then. Do yo mean that to tune I would connect the distributor hose to manifold vacuum somewhere and then move it back to the ported vacuum on the carb to drive?

 

The motor was running fine here in Austin, but when I trailered it to the coast, the carb started acting up. It's only a 600' change in elevation so I don't think that has anything to do with it. I guess it was a coincidence about the carb trouble starting at the time of the trip. I did use manifold vacuum to set the carb idle mixture. Do I read correctly that you plug the vacuum to the distributor while setting the idle mix with manifold vacuum?

When I said the timing moved off the scale I did mean that the mark on the crank moved off the numbers on the timing cover once the carb vacuum line was reattached to the distributor.

I'll check the condition of the booster pump cup. Will Marvel Mystery Oil in the gas help any with the alcohol content playing havoc with the rubber parts?

Thanks for the help.

EUREKA The accelerator plunger/spring/rod assembly had become disassembled when a clip came loose. Motor runs fine now