Stuttering or missing in high rpms in every gear.

[Captin840]

So in every gear and usually at high rpms the engine will stutter or miss like it's cutting out. Messed with all the timing except the timing chain. Does a worn chain or tenchiners let the engine do that? It's the L16 1973 620, with about 100,000 original miles on it. It does have a Weber carborator on it with some vacuum lines not being used anymore, they have bolts in the ends of them, and that's how I bought it, haven't messed with them at all. The truck sat for awhile and when I first started driving it,it was fine, and now that I'm driving it alot more it's starting to act up on me. 

[datzenmike]

Check the valve lash (hot) and the timing. Shouldn't cost much to do this and it eliminates them as a cause. 

 

As it is cheap and I doubt that you have ever checked, replace the fuel filter. If getting plugged it reduces fuel flow. Under full throttle high demand the carburetor may be emptying faster than the gas can get in to keep it full. If it doesn't help it probably needed doing anyway.

 

Inspect the plugs, cap rotor and wires. NGK plugs only, B6ES 0.030 gap. High voltage ALWAYS looks for the shortest path to ground, ALWAYS. So you have to make the spark plug the only path by assuring that the wires cap and rotor are in good shape and highly insulated. Check the black plastic tower on the coil under the high tension nipple for any cracks or 'carbon tracking' which will present as looking like a crack. This is a spot where a spark has burned a path and will continue to leak voltage and jump onto the negative terminal nearby.

 

 

This little crack caused me random just off idle sputtering for years till I accidentally discovered it.

[G-Duax]

I'd start with house keeping...

Clean everything.

Remove unused hoses, and use proper caps to plug off caps.

While your at it, address any other issues, and look for signs of an ignition malfunction, and that includes all wires going to the coil.

Mike is spot on inspecting the coil, I had Crane CDI coil on my Toyota, that decided to ark out through the side.

Would have never found it if I didn't keep my engine bay spotless. It showed up as a faint white haze spot on the coil, and I instantly recognized it as an ark trace.

 

The other thing to look at is fuel supply.

A loss of volume, or pressure will cause high RPM cut out. So check your filter(s), and fuel pump.

I experienced this after installing a cam, big valves, and port work, the Carter in-line pump just couldn't keep up, and the float bowl of my Weber would run dry, and the engine would start to sputter, and die out at the top of each gear.

The way around that is to go to a larger inlet needle & seat.

Both of my Webers came with 2.0 seats (the brass part that holds the needle).

I reamed mine to 2.5mm, and the issue went away.

Redline sells the larger sets. I don't recommend doing it yourself, if you don't have a machine shop, as you can easily screw it up.

 

 

[banzai510(hainz)]

I swapped out the worn distributor and it fixed it. Distributor shaft wiggle. Worn out bushing

 

adjust the points, new condensor

Edited May 21, 2019 by banzai510(hainz)