64 Cj5 Running Issue Killin Me

Ok I'm in desperate need of help.

I have a bud with a 64 cj5 4cyl fhead.

It refuses to take more than 1/2 throttle.
You go past 1/2 it won't speed up it just bucks and stutters.
I've had 2 different carbs on it all new ignition good fuel pump , good fuel pressure, new exhaust system , new head gasket and valves adjusted all valves in good shape no holes in pistons and rings ok.



This things whipping me. I have no clue please if someone had an idea let me know.

Thanks

 

Hook up a vacuum gauge and see what it says.

Go through and methodically check that all your plugs wires are correct. Look for simple things you may have overlooked like timing or a kinked fuel line. Make a elementary check list and physically check them off. Circle/slash style even to ensure you have inspected the component.

Start simple and then move to more complex issues.

 

"all new ignition.."

Double check your point gap and definitely verify the timing.

Everything must be to factory specs before a diagnosis can be logical.

 

Maybe watch the throttle linkage in the engine bay when he is fully depressing on the pedal, make sure it's not binding somewhere

 

Interesting thought, although I don't see that causing 'bucking, stuttering" etc.

 

Check to make sure that you have 3-4 psi at your fuel pump outlet to your carburetor if using a YF; had this same issue. OldPappy helped me with this information, Thanks.

 

It does sound like a fuel mixture problem, and it would help to know for sure which carburetor is on it. I assume it is a Carter YF.

Before I started tearing into the carburetor I would first verify timing, point gap, and spark advance. Once that is confirmed, and corrected if needed, if the problem persists I would go into the carburetor. More information is needed, but it may be running off the idle circuit at low RPM and when the throttle is opened it could be dumping too much fuel (metering rod or accelerator pump), or not getting enough fuel (clogged passage, clogged jet stuck check valve, ect...,)

 

But the same problem with two different carbs???

I can picture the timing being retarded or the wrong point dwell.

 

I have a shelf full of bad carburetors that if I swapped them on an engine none would work right, but I agree that timing and points need to be verified first.

Many supposed carburetor problems end up being ignition problems, and given the quality of some of the parts out there "new" does not always mean "good".

 

I can picture a distributor that needs a total rebuild. Not just points, condensor, cap, and rotor. The shaft bushing may be worn. The advance weights may be sticking. The advance springs and/or their mountings may be worn. Any or all of these can and will cause your issue.

 

Verify you have the correct firing order. 1-3-4-2
Remember the distributor turns counter clockwise.

 

I’m with scout. Distributor issue maybe. Just a guess on my part.