Technical 235 Chevy distributor problem

So it seems that I got spoiled with my '54 that I had because it worked correctly (mostly) from the beginning. This '51 on the other hand is proving to be a learning car (not that I'm complaining, I just have to keep asking questions). OK so, I was trying to diagnose why it wants (still) to shut down when coming to a stop and I think I got it figured out. I noticed when I bumped the throttle the distributor doesn't move. The vacuum line IS hooked up to the carb. On the '54, it moved and ran fine so I'm thinking that's my problem. My questions are, should it rotate clockwise or counter clockwise when the throttle is applied (I can rotate it counter clockwise by hand and it raises the rpms substantially but I thought I remembered the '54 rotating clockwise), can the vacuum advance diaphragm /distributor be refurbished without being removed from the motor? If I have to pull it to rebuild it, I may just go with the langdon hei but money's tight so I'd rather not. Thanks to anyone who can assist

 

It will rotate opposite the rotation of the distributor rotor. Meaning on that one it should move counter clockwise to advance the timing.
There is a fair chance that the diaphragm in the advance mechanism is ruptured.

 

Unscrew the tube & check for vacuum signal - no vac. can be the wrong gasket under the carb (it doesn't use one) or cracked insulator.

 

I was actually just fooling with it. I pushed in on the connector that slides into the diaphragm and it rotated the distributor but I didn't hear and vaccum sucking or blowing sounds. I'm not sure if you're supposed to even but I'd figure it would make a sound one way or the other. I can feel the nut to remove the linkage from the diaphragm to the distributor but is there a way to remove the diaphragm from the bracket? I'd really rather not pull the distributor

 

It has a gasket between the carb and the insulator but if I took it out, the small hole in the bottom of the carb base would be closed off. Could the problem be that it's not closed off?

 

What sort of carb do you have? An old timer told me his Chevy truck would cut out like yours does, due to fuel surging in the float bowl. Switched from Carter W1 to Rochester B and fixed it. Rochester's have a concentric float bowl. I think Chevrolet went to Rochester's in about '49.

 

I have a carter yf 788 but the float bowl cover is from a different yf with a heat activated choke (the guy i got it from hooked up a manual choke but the heat stove and tube are still there). I actually took it apart today and I noticed the float bowl was only about a third of the way full.

 

That should be a better carb than both the W1 and Rochester B. Maybe it needs a kit and reset the float level. Make sure your distributor is OK first, be methodical rather than working on multiple areas at once.

 

The car runs fine if I give it even a tiny bit of gas coming to a stop. Once I'm stopped I can usually keep off the gas totally and it runs. Also, the second I start rolling it runs perfectly. Does that sound like the vaccum advance is shot or does it sound like something else? I tried the propane torch thing to find a vaccum leak but came up with nothing.

 

Disconnect the vacuum hose and put your thumb over the end to see if you have vacuum. Work the throttle a little to see if it increases, decreases, or stays the same. When let off the throttle you should feel a bit more suction.
If you have vacuum and the distributed does not rotate with the line reattached and the throttle advanced then you have a problem with the diaprhram.
If the distributed is advancing OK then you have a problem with the carb.
As already said, work on one problem at a time. Once you eliminate one possible source then you can move on to the next.

My guess at this point is that you need to rebuild the carb.

 

Yeah I guess I'll buy a kit to rebuild it. I just find it odd that it runs so well under power with the distributor not rotating at all. I would think it would idle good and run terribly under throttle

 

Have you adjusted your mixture? sounds like it leans off too much when de-accelerating.

 

I've tried. I screwed it all the way in and then out to the point that it seems like it's going to come out of the carb base and nothing changes.

 

I picked up a Rochester b from a '58 because they're easier to rebuild (and I rebuilt the one on the '54 so I'm more familiar with them) than the carter. I noticed a tiny bit of up/down movement in the throttle shaft. Is that acceptable or should it have zero play?

 

It should have zero play, but unless it is brand new, will always have a little. Stick it on, fire it up and see what happens. I ditched the Carter which was on my 235 and replaced it with a Stromberg, no more problems!

 

The notch in the base gasket must line up with the hole in the carb base for the vacuum metering system to work.

 

It has one of those gaskets with the 4 slots on it so it lines up with the hole. If I bring the rpms up by 50 to 100 coming to a stop it's fine but, if I just use the brakes it dies on me. The vaccum port for the advance looks to be above the throttle butterfly (looking from the outside). Is that the correct orientation or should it be below it?

 

Above the throttle blades is ported vacuum and will have no vacuum at idle, but will pick up with rpms and more throttle opening. Below the throttle blades is considered manifold vacuum, and will have a strong vacuum signal at idle, and decrease temporarily when you open the throttle.

On my 37 Chevy, with 216, distributor is hooked up to ported vacuum at the carb.

 

OK so mine is good. I couldn't remember which was which

 

Check the carb base with the gasket; not all bases / gaskets match

 

So the right side upper slot on the right gasket doesn't line up with the hole in the carb base? In that case I have the wrong gasket on mine. Can't I just cut the slot that I need or do you happen to have a part # for the correct one? Does the vaccum from the base directly affect the vaccum advance vaccum?

 

Check the base and the gasket. Yes, you can cut a slot in the gasket you have. That passage allows vacuum to a piston that pulls to power valve to the lean position; when the vacuum drops under acceleration the piston moves a tapered rod to the rich position. No vacuum through the slot to the passage means a rich condition under all conditions especially at idle.

 

And that would then explain the rough running. I guess when I give the throttle a tiny push, the extra air balances the mixture out? Would that also prevent the air/fuel mixture screw from doing anything?

 

If that vacuum port is partially blocked it can also cause it to run rich(and bad) along with no advance. If theres not enough vacuum signal the carb thinks its under load and adjusts with more fuel.
I went through this wrong gasket thing before. Pic below.

I had to cut the gasket to match the notches in the spacer. On the top left of the gasket you can see the indentation of the blocked port on the carb.

 

Alright guys, new info pertaining to the situation. The small hole on the bottom of the carb does in fact line up with the left side gaskets upper right slot. However, the gasket was overlapping the hole a tiny bit and my insulators indented grooves didn't line up with the gasket notch/carb hole. I took my Dremel and I notched the insulator and I took a razor knife and enlarged the gasket notch. Now I notice the distributor slightly moving (thanks to everyone who responded by the way...I love this site because you are all amazing) but it's moving clockwise.?. WTF...I can drive and stop in gear without stalling but the idle rpm in gear is close to 800. I adjusted it down to just about 600 and it aaaalmost wanted to die on me so I bumped it back up. The air/fuel mixture screw still does absolutely nothing though. I screwed it completely in and out to the point that another half turn would have made it come out. Any ideas?

 

Sounds like the orfice the air/fuel mixture screw seats into might be clogged. I would disassemble the throttle plate from the main body and thoroughly clean it.

 

Well...not wanting to take the carb off again today (figured I'd try this first), I took the mixture screw out and used a piece of wire to poke through the hole. I kinda scraped it all around in circles so we'll see if that did anything. I'm rebuilding the carb next week, I just didn't have time to soak it and throughly clean it today since i have to work. I'm almost tempted to rebuild the rochester instead but it came from a manual truck engine and I'm pretty sure manuals and autos use different jets.

 

With the engine idling, the air cleaner removed and the the choke blade fully open, look down the throat of the carburetor. If the throttle blade is near fully closed, as it should be at idle, you shouldn't see any fuel entering the carb from the main nozzle. If you see fuel dripping from the main nozzle and puddling on the throttle plate, then it's too rich at idle. Or the throttle plate is open farther than it should be at idle to offset the rich condition. It could have an inoperative power valve, sunk float, dirt in the needle and seat, too much fuel pressure or the float level set too high.

 

I pulled the carter apart and realized the float height was over a half inch off so I adjusted that, put a new needle/seat in, new float bowl gasket and cleaned some crud out. It's running pretty well now but it still wants to stall if I hit the brakes too fast. I pulled the rochester apart but the plunger (I can't remember the official name of it, it's the one that has the rod on it next to the jet) is super stuck and all I'm doing with pliers is tearing it up. I'd like to buy a bc but everything I've read says it's for side motor mounts only. What could the difference possibly be? I already have the choke heat stove attached to my manifold so that's taken care of

 

Shouldn't an automatic transmission car have a dashpot on the carburetor?