I have been working on a 74 chevy g20 van with a 250 inline 6 motor and it has a rochester monojet carb on it, I have put the timing mark at 0 degrees and the mark jumps back and forth a little bit, the other day I had it perfect and now i cant figure out why its jumping again, i read on another site tonight that its suppose to be timed at -4 degrees so i set it to that, but the mark is still jumping around, it has new points in it not even a week old, and a new vacuum advance, when sitting idle or starting to accelerate it sputters a little bit, can anyone tell me what I can do to fix this? Also I believe I gaped the points to .018. Any help is appreciated.

 

Make sure you have the firing order set correctly. 153624. Did you set the timing with the vacuum advance disconnected? More than likely there is a vacuum leak. You may also want to rebuild the carb.

 

Yes the firing order is correct, and yes i disconnected the vacuum advance, I have taken the carb apart to clean all the crap out of it I'm pretty sure i got it back together tight but i can check tomorrow, some vacuum lines are not clamped down but are tight enough so they should not be leaking but i can look farther into it when i check the carb. Thank you for the reply I will post back what I find out.

 

Ok so this thing is extremely weird, I went out today and pulled the distributor cap as I think I set the points wrong I think I had it 0.018 and the book calls for 0.019, so I put the harmonic balancer timing mark to -4 btdc put the distributor at a rise in the cam and recapped the points and now the timing mark is all over the place from what I seen its hitting 3 to 4 different spots, I checked for leaks around the manifold and carb and I have that all tight all vac lines are clamped, and I even tested to see if the old charcoal box was leaking and it's not. Anyone have any more ideas because I'm lost?

 

Do you access to a dwell meter? That is what we used in the old days before electronic ignitions to check the points. If it started after you regapped the points, do it again to make sure they are correct. Changing from .018 to .019 should not make that big of a difference. It still could be in the carb.

 

I have access to a digital multi meter with a dwell setting on it, will that work?

 

Not sure. I hook my dwell meter to both small terminals on the coil.

 

I assume you are looking at the timing with a timing light. That being said, it sounds like you are not on #1 plug wire.

 

I'm sure it is plug one, on that motor it's really hard to not find plug one, also on another note I have rebuilt the carb and now the mark is now bouncing between -4 btdc and 0 so it's better, going to try to regap the points today also I have this pic under the hood.

It is a manual but I don't have anything that will read in degrees for the dwell, I did a dwell test with the multi meter and for once it's steady started out at 088 rpm and one it warmed up it went to 101 rpm the meter is X10 rpm, so I'm stumped as to the degrees of dwell it should be at.

 

Disconnect the vacuum line to the advance on the distributor and plug the vacuum so there is no leak. Does the timing still jump around?