Dizzy advance / retard highway backfire

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Gents,

I have had the symptoms return. They are:

Will not go over 50 on the highway,
bogs down and eventually coughs,
it does hesitate / stumble when trying to accelerate hard.

I checked all the usual suspects. Figuring FUEL STARVATION, (possibly more debris in the tank) since that was the issue last time (piece of gasket). But first performed the following:

  1. Reset / confirmed timing on BB (It is not steady, I can see it jumping 2 - 3 degrees) Dwell out is of spec. but not worried about that.
  2. Vacuum is just in the good by a few degrees (19)
  3. Tightened all the clamps on the new fuel lines and new fuel pump, wondering about a leak
  4. Ran can of Sea Foam before draining and washing out tank
  5. Blew the lines Old school (I don't have a compressor where I am) manually.
The weird thing is it was fine last week and now just crapped again. Open for other suggestions.

Thanks in advance.

Boaf
 
Fuel starvation often feels like bucking as it takes off every now and then when it gets fuel and then cut back out.

It could also be a problem with a stuck centrifugal advance, but that will run fine up to a point and then power falls off. It is more uniform than fuel starvation. Pop the distributor cap and check the rotation of the rotor. It should rotate back and forth smoothly about 30 degrees without sticking.
 
Thanks @Pin_Head, knew you would add in.

It does move roughly 25 degrees, but a bit sticky (took it apart and cleaned it 4 months ago). As maybe you and others have read, I long suspected the distributor as an issue. It does move but a bit sticky. The fact that the timing moves + / - a few degrees makes me believe there is a wobble in the shaft and still sticky weights. Will bite the bullet and will replace it. I like to keep original, but the PO has altered that.

Boaf
Pin_Head said:
Fuel starvation often feels like bucking as it takes off every now and then when it gets fuel and then cut back out.

It could also be a problem with a stuck centrifugal advance, but that will run fine up to a point and then power falls off. It is more uniform than fuel starvation. Pop the distributor cap and check the rotation of the rotor. It should rotate back and forth smoothly about 30 degrees without sticking.
Click to expand...

Interesting, this distributor pictured below is a Non-US performance distributor Manufactured by Toyota. The US has no fine-tuning advance / retard dial. Just FYI.

Boaf

Distributor 2.jpg
 
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Dizzy said:

?
Better way to Weber?
Click to expand...

I have Weber 38 / 38 DGEV manual choke. I like that @Dizzy !!! Have you used it? What were the results?
@Weber Sarge, have you seen this? In one of my threads, someone (thought it was you) indicated they milled there own Weber adapter out of aluminum, because the 3 piece set up was garbage.

Thanks Dizzy.
 
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I had the same distributor, looks like yours is an old used one judging by the patina and original copper vacuum line. Those were used on F engines prior to 1969, so miles and wear is a big variable. Mine was also worn, and although it gave good running and performance most the time, the wobble in the shaft kept kicking the timing and point gap out. It would start to misfire, especially after a long highway trips. Oddly, I pulled a tent trailer 200 miles back from Moab with a bad miss and still managed 70MPH down I70 before I fully grasped why I had such a weird sound from the engine. So sticking weights could be the issue. A 1F distributor is preferable on a 1F, they have more advance and a more aggressive curve than any 2F ditributor which pairs well with the low compression of the F engines. I had similar loss of performance with distributors that were not advancing enough at highway speeds, primarily 2F tuned distibutors. I'm running a custom hybrid now.

I would still question fuel though, the bucking PinHead mentions is key to that. That was my first idea when looking through this thread, plugged something or not big enough jets. I don't know much about a Weber though, but other guys do, sounds like you are on the right track, but coughs out the carb are usually a lean condition, as in not enough fuel.
 
MoCoNative said:
.
Click to expand...
MoCoNative said:
I had the same distributor, looks like yours is an old used one judging by the patina and original copper vacuum line. Those were used on F engines prior to 1969, so miles and wear is a big variable. Mine was also worn, and although it gave good running and performance most the time, the wobble in the shaft kept kicking the timing and point gap out. It would start to misfire, especially after a long highway trips. Oddly, I pulled a tent trailer 200 miles back from Moab with a bad miss and still managed 70MPH down I70 before I fully grasped why I had such a weird sound from the engine. So sticking weights could be the issue. A 1F distributor is preferable on a 1F, they have more advance and a more aggressive curve than any 2F ditributor which pairs well with the low compression of the F engines. I had similar loss of performance with distributors that were not advancing enough at highway speeds, primarily 2F tuned distibutors. I'm running a custom hybrid now.

I would still question fuel though, the bucking PinHead mentions is key to that. That was my first idea when looking through this thread, plugged something or not big enough jets. I don't know much about a Weber though, but other guys do, sounds like you are on the right track, but coughs out the carb are usually a lean condition, as in not enough fuel.
Click to expand...

Yep, I've learned that out the carb is not always timing. But I cleaned the tank, blew the lines and cleaned the carb and fuel filters. We'll get there. If it ran fine one week, and not the next, that inconsistency reminds me of sticky weights.

The truck also struggles at low Speed when I stand hard on the gas. It is almost like a Rev Limiter sensation. Like @Pin_Head said, it's not just fuel, timing and ignition. It's a combination.

Thanks

Boaf
 
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Update all. New distributor and calmp installed. It feels good, no hesitation and the timing was steady, not jumping around inthe window. Will go on the highway but have good expectations. Thanks to all for suggestions and good advice. Able to close this thread!
 
Lessons learned on lack of highway speed, and sputtering:
  1. Check timing
  2. check fuel filter
  3. check fuel mixture
  4. If timing fluctuates, distributor is very suspect.
Hope this helps. Always check with the experts here!

Boaf
 
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