High rpm, no load miss

[lostih]

Hi All-

First post here. I’ve been working on getting our family ‘27 touring ‘Hank’ running with my 13 yr old son. He’s the fourth generation to work on the car in my family…we’ve had it about 60 years…long before me .

Anyways, the car had a distributor put on it and was converted to 12v in the 60’s. We (dad and I) rebuilt motor in the 90’s. Dad is gone now and was the guru but we have the service manual and will carry on! We have it running relatively well at the moment. Drives fine. Lacks a little power sometimes but runs smoothly. However, at 30ish mph on flat ground there is an occasional miss…seems less frequent than a consistent dead cylinder. It accelerates smoothly without missing. Plugs are new, wires are new, cap/rotor are new. Any ideas? I’ve toyed with the mixture a bit but haven’t found a good spot. I’ve wondered if I can’t advance the timing far enough on the distributor conversion for low load, high rpm smooth operation?

I tried the search but most responses were about cars with buzz boxes so didn’t yield what I was after.

Thanks!

[TRDxB2]

First things first.
How did the engine run before you to replace the plugs, wires, points, cap & rotor?
-
What distributor is it? Need the model if its a 'VW'.

[erkbrn]

This sounds somewhat similar to an issue I just finally sorted after many months. Similar to you, I had low power in second gear (car struggled past 30 despite being a speedster), sometimes felt like it would "miss," but otherwise accelerated smoothly and ran fine. I also had the "cherry red" exhaust problem, which most people were convinced was a lean fuel issue. I went through and rebuilt the carb, new plugs/plug wires, cleaned fuel tank, more open exhaust, etc. and nothing seemed to make a notable difference. Then I had another club member over who helped me check the distributor timing (something that I was not sure how to do properly on my own) and it was about 10 degrees too retarded; it was probably set/wiggled itself over to be about 25 degrees after TDC at full retard since the engine was rebuilt (also rebuilt in the 90s). My car has a VW Bosch distributor. If you have no issues with fuel flow and tuning the carb doesn't seem to make too much difference, I would look there. It made an enormous difference once set properly.

[speedytinc]

Fuel mixture, points condition & gap, advance/retard.
A much overlooked item on VW distributors is shaft lubrication. Remove the rotor drop or 2 of motor oil on the felt button.
Check for wear/slop in the upper shaft/bushing from lack of oil & wear. A sloppy shaft meets your symptom VW or not.

[TXGOAT2]

An air leak might cause that.

[lostih]

Thanks for the tips. I’ll try and answer posts roughly in order:

1. It ran pretty terrible before spark plugs wires. We had to cut off the old aluminum power head as the steel head bolts corroded into the block and broke off. The car had been sitting for years due to a bad head gasket.

2. I don’t know the type of distributor…I don’t think it’s VW though. I’ll try and attach some pictures. When I was getting it running some of the linkage for adjusting timing on it was gone so I had to make new. I also set timing roughly by getting cylinder at TDC and then installing distributor. I suppose it could be a tooth off, but as I recall there aren’t very many teeth on the distributor gear so one tooth results in a giant jump in timing.

3. It doesn’t feel like there is much slip in distributor shaft…maybe 5 degrees of radial gear lash and no perceptible side to side movement.

4. An intake leak could be possible. We just swapped to the copper ring style manifold gaskets. Any suggestions for how to check?

Sorry…won’t let me attach pictures…is there a minimum post requirement before pictures are allowed?

[Jerry VanOoteghem]

Run a ground wire from the distributor head to ground. The distributor head can get worn & sloppy in the housing. At certain speeds, the head will vibrate and loose ground continuity, causing a misfire.

[Jim, Sr.]

Thanks for the tips. I’ll try and answer posts roughly in order:

1. It ran pretty terrible before spark plugs wires. We had to cut off the old aluminum power head as the steel head bolts corroded into the block and broke off. The car had been sitting for years due to a bad head gasket.

2. I don’t know the type of distributor…I don’t think it’s VW though. I’ll try and attach some pictures. When I was getting it running some of the linkage for adjusting timing on it was gone so I had to make new. I also set timing roughly by getting cylinder at TDC and then installing distributor. I suppose it could be a tooth off, but as I recall there aren’t very many teeth on the distributor gear so one tooth results in a giant jump in timing.

3. It doesn’t feel like there is much slip in distributor shaft…maybe 5 degrees of radial gear lash and no perceptible side to side movement.

4. An intake leak could be possible. We just swapped to the copper ring style manifold gaskets. Any suggestions for how to check?

Sorry…won’t let me attach pictures…is there a minimum post requirement before pictures are allowed?

Andrew,
To check if you have a leak after replacing your manifold gaskets, or rings and glands,--- Remove the heat pipe that goes to the carburetor.
With the engine running at a fast idle, carefully spray carburetor cleaner around the intake manifold connections. If there are leaks, the engine will speed up.

[Jerry VanOoteghem]

I also set timing roughly by getting cylinder at TDC and then installing distributor. I suppose it could be a tooth off, but as I recall there aren’t very many teeth on the distributor gear so one tooth results in a giant jump in timing.

You don't adjust timing by how the gears are meshed. That basically does not matter.
- Set your spark lever about 3/4" down from fully retarded.
- Determine which direction your distributor rotates, either CW or CCW.
- Loosen the timing arm on your distrubutor head so that you can rotate the head freely by hand.
- With the engine sitting with #1 at TDC, identify which distributor cap terminal the rotor is closest aligned with. That will be your #1 terminal.
- Keeping in mind what direction the rotor turns, (CW/CCW), by hand, rotate the distributor head so that the rotor is just about to approach the #1 terminal. Be sure that the points have not yet opened up.
- Install your dist cap and the #1 plug wire. Attach the plug wire to a spark plug and lay the plug on the engine, so that you can see the plug gap. (Don't let the plug wire touch the engine.)
- Turn on your ignition.
- By hand, slowly rotate the distributor head until you see the sparkplug fire. The head must be rotated in the direction opposite the direction of the distributor shaft. If your rotor turns CW, the head must be rotated CCW, or visa versa.
- Being cautious to not move the distributor head, tighten the timing arm clamp on your distributor head.
- Double check the setting by moving the spark lever all the way up and then slowly moving it down. You should get the plug to fire at approximately the same lever position as when you set the distributor head by hand. (It doesn't need to be exact.) Make minor adjustments as needed.

Your timing will now be at TDC with the lever 3/4" advanced. Moving the lever all the way up will make it retarded for starting. Attach the remaining plug wires according to the firing order, begining with #1 and progressing in the direction of the rotor rotation.

[lostih]

Thank you both for these answers…most helpful. I will try them and report back!

[lostih]

Tried these suggestions and didn’t make progress. Last remaining one is to clean the carb. I just can’t wrap my head around why it’d cause a miss at low load, but not while climbing a hill or heavy loads…but we’ll give it a shot.

[Norman Kling]

There are idle passages for idling and very low speeds with the throttle closed. When you open the throttle, it uses the high speed jet which is controlled by the needle valve adjustment.
Norm

[speedytinc]

Did you adjust the mixture needle during the time it is missing?
Rich/lean looking for improvement in either setting.
NH's float setting has a starting setting per the T1 manual.
How well it runs @ hi speed & idle Is dependent on its needs adjusted by changing the fuel level.(per service bulletin)
You tweek the float a little until the mixture needle is perfectly set for both idle & hi speed operation.

Aside from carb setting, If the carb cant get enough fuel @ hi speed, it will lean out more & more as fuel flow doesnt keep up with demand.
This is caused by fuel system obstructions. A big culprit is the viaton needle/seat as it comes from the parts vendors.
A hi flow unit is available from Scott Conger on this forum.

Anyway this is where I would be looking after perfecting your timer.