The Stovebolt Site Forums The Shop Area Engine Shop Hesitation/stumbling while accelerating

Hello all, I’ve been a long time fan and have a 51 3100 with a 216. I believe the 216 is a 1948, since it has a 48 stamped on the block. It is converted to 12v. I replaced the carb with a remanufactured Rochester b since the old one had seized check balls. I replaced plugs, wires, cap, rotor, coil, and reset points gap. Fuel filter has been changed at carb. Adjusted valves. Set the timing to the bb and probably more that I cannot remember.

Now my issue: I can get her idling decently with the exception of the slight miss heard through the exhaust, which is dual straight piped. Under acceleration it stumbles and hesistates under load. Also, when setting my timing I can visually see the bb jump/bounce with the misses. I cannot think of anything else to do. I was hoping you all can help!

Also, I pulled the distributor out and Inspected it there seems to be too much up and down play in the gear on the shaft. Lastly when watching the timing with my light, I can apply pressure to the dizzy in any direction and it will cause the timing to react depending on which direction will cause a different symptom.

Sounds like the distributor bushings are worn out along with shims that hold the up and down to a minimum. That would explain the BB not holding steady. Start with rebuilding the distributor then move to the accelerator pump in the carburetor.

Do as Joe says with the distributor.

In addition - you can't assume the carb is good just because it's shiny. "Refurbished" can vary greatly depending on the rebuilder's experience with these old carbs so keep in the back of your mind it might still need some tweaking for your application.

You also should be cleaning the fuel system completely out. Remove and clean the tank, clean/replace lines and clean/check fuel pump. It's very common to install a fresh carb and then fill the passages and lines full of crap that is sloshing around in the tank. While going through this, also eliminate any rubber fuel hoses or plastic inline fuel filters in the engine compartment and try to use hard line as the previous can start fires.

Does it hesitate like that regardless of the choke position? I've seen hesitation like that when it needed more choke on a cold morning.

Thank you all for the speedy responses, I ordered a refurbished distributor lower end. Hopefully this will Be the fix. I’ll rebuild the one I currently have and keep it as a backup. Does anyone know where I can find the shims or is there a specific part number? My distributor number is: 1112362-1l01.

Also I noticed there are two grooves near the top of the shaft... is there supposed to be packings or o-to gs on these distributors?

I’m leaning towards the distributor... I put one on order since I don’t have time to tinker with it right now. If it’s a fix I’ll rebuild mine later and have a spare.

I’ve checked to see if the accelerator pump is working and it appears to be. It’s spraying as advertised. If the dizzy do isn’t fix it I’ll tear her open and ensure it’s all in good order.

As for the fuel, I have been keeping an eye on my filter and it’s clean as a whistle.


Last drive I took I pulled the choke out to see if it would help and it didn’t...I tried different positions to see if it would help and no go.

Does your distributor have the grease cup and the spring and disc in place and packed with cup grease? That assembly removes wobble in the distributor shaft.Without that, you will have an issue with the timing jumping around.

It does have the grease cup, but I am not sure about the spring. I will have to pull it apart and check.

Wound up ordering a HEI kit from Langdon, hopefully this cures my issues! Unfortunately I had shoulder surgery today, so it’ll be a while unless my buddies will come help me.

Random question, what is everyone’s preference for valve lash clearance? Does anyone use the “heavy duty” clearances? I keep reading that looser is better on these engines.