The Stovebolt Site Forums The Shop Area Engine Shop 235 Runs Only With Full Choke

I am trying to fire up my 58' 235 and am having issues. I can only get it to run with the choke fully closed. As soon as I back off of the choke, the engine stalls. Since the engine had been sitting for 3 years, I rebuilt the Rochester B that it had, to no effect.

Before even attempting to fire the engine, I pulled and cleaned the head and valves, so I know none of the valves are sticking. I replaced the intake & exhaust manifold gaskets, again to no effect. I also made sure to plug the vac advance port on the carb itself.

I know I am getting fuel because I can see a jet of fuel when I work the throttle with the engine off. I verified that the firing order was correct and that each plug was sparking.

When the engine is running, there is a backfire through the exhaust. (Orange glow and all). There is no exhaust setup on the engine.

What am I missing?

I would double check my carb settings for the idle mixture and idle set screws. Might want to check your ignition as well. Check Dist. cap for cracks, check the rotor, wires an plugs are set right. Good luck!

Vacuum leak at carburetor to manifold or manifold to block?

maybe a valve is adjusted to tight? spark plug wires off one position?

I set the idle mixture as listed in the rebuild instructions, bottom out than turn back 1 1/2 turns.

I just went out and looked at the idle set screw and it was screwed in all the way. Roughly how far should it be screwed in? I know it should be set with the engine idling, but I'd like someplace to start.

Is using propane or starter fluid the easiest way to test for a leak around the manifold?

You wanna set the idle mix screw by screwing it in all the way, bottoming out gently, then unscrewing it 1 1/2 turns. That is a good place to start before tuning it.

I would say you found your culprit as to why your truck isn't idling.

My experience with a large vacuum leak is that it wouldn't idle and it pinged like crazy. I would be looking for something to do with the carburetor. Also the gasket under the carb needs to be installed to let vacuum feed the port on the bottom.

The idle mix screw was setup like that when I rebuilt the carb, so it was set like that when I tried to run the engine.

It was the idle screw that was in all the way, and as far as I know(which ain't a whole lot) it would only bring my idle up, not cause the engine to backfire / stall.

i would suspect the position of the cut out in the insulator under carb.

Are you sure the float level is right? If you are sure there are no serious vacuum leaks make sure all the air bleed holes in the carb are open. Run a tag wire through them. Take the idle mixture screw out & blow air in it. I would start with the idle mixture jet about 3 turns out. After you get it running correctly you can turn it in to fine tune it.

I had a problem somthing to that affect with my first 52 chevy half ton back in the early 80's . The guy at the shop told me my head gasket was on up side down. turned it right side up and that took care of the problem, Go figure ? Hope this helps,good luck

Boy! I wish I had thought of that one back when I was in business.

have you checked the timing, sounds like might be retarded too much.

had same problem with the 52, had to replace fuel filter, just not enough gas to keep it running, have you tried spraying carb cleaner around the base of the carb and side,could be a vac leak like stated above, hope you get it figured out. just my 2 cents.

If you suspect that you have a vacuum leak you can use either a unlit propane or acetylene torch. After you start the engine take the unlit torch and move it along the head to manifold areas, carb base and see if the engine smooths out or speeds up. If it does, you have found a vacuum leak. I remember years ago that we had a work truck that was outside and the weather got really cold, carb was a mess and Dads mechanic showed me that using some acetylene down the throat of the carb did the trick to get it started. This might narrow down your source of trouble.

By now the plugs will be fouled by running on full choke and the plugs will have to be cleaned/replaced or it will never run with the choke off, and soon cease to run at all.

Alright, I went through and replaced a few gaskets (manifold, carb) and adjusted the idle and fuel/air screws. The timing is set at 0. I was finally able to get it to run without needing the choke. Here is a clip of it running:



I am new to all this so I can't know if how it sounds is telling me anything. Does it sound like it is running alright? Note there is no exhaust setup beyond the exhaust manifold.

I didn't listen to it but 0 timing is too slow. Set it about 5 degrees BTDC.

That is a very cool video! It should be timed by the light so that the steel ball aligns with the pointer.

Cant do a proper set up with out a pipe. Every change to the exhaust or intake will completely chafe how it idles and runs.

Sounds lean. Low restriction air cleaner and no exhaust for back-pressure makes it lean. Add the pipe and muffler and it will help alot.

It also looked like you have nothing connected to the wiper connection on the side of the manifold. Do you have it plugged?
If not, it'll leak enough to screw up the idle.

regards,
Leon