Odd hesitation

[73K20]

Ok I've got a 73 K20 that apparently has an 80s 350. Lately it drastically hesitates while going down the road. It started doing it a couple weeks ago but only did it maybe once in a week(when id get fuel) and I thought my carb just needed to be rebuilt but now it does it constantly.
Ill be driving down the road in say 2nd and i just lose all power like it died but it never actually dies, let off and coast a bit comes back like it never happened. I dont believe its done it in first does it in high rpm in 2nd and pretty much any rpm in 3rd. It did die once so I thought maybe the pump cuz there was no fuel I the filter and I couldn't get it to prime so I replaced that started up ran fine for maybe a half hour then started doing it again. Its been hot lately so i Went up the Mtn at night and ran the crap out of it, couldn't get it to do it at all so I thought perhaps vapor lock but today it was colder than the night up the Mtn and it was doing it still. I'm going to try blowing out the fuel line tonight see if that helps.
If anyone has any thoughts or advice I would greatly appreciate it. I just don't get what's going on and it's my work truck so I have to drive it daily. Sorry so long thanks for reading.


1993 F250 3k in the 460-my 1st truck
1973 K20 6" lift-bright future
1967 F250 2x4-diesel swap in its future

 

[MadOgre]

Power piston on the carb is sticking or the accelerator pump is worn

 

[73K20]

Really the accelerator pump would cause something like that? I didn't realize it would. I already expected a problem with it because when I'd open the rear jets it would hesitate then take off.
I was going to order a rebuild kit tomorrow from cliffs high performance, they claim the new pump seals are resistant to the new fuel types.


1993 F250 3k in the 460-my 1st truck
1973 K20 6" lift-bright future
1967 F250 2x4-diesel swap in its future

 

[350runner]

Cliffs parts are of high quality. Call him and talk to him out his wife. Very knowledgeable folks... last I heard there was a waiting list out the door for carb rebuilds. Yes the pump cups he sells are resistant to the gas we have these days.

Sent from the dust in front of you!

 

[73K20]

Cliffs parts are of high quality. Call him and talk to him out his wife. Very knowledgeable folks... last I heard there was a waiting list out the door for carb rebuilds. Yes the pump cups he sells are resistant to the gas we have these days.

Sent from the dust in front of you!

Cool I appreciate both your guys help. Hope there's not to long a wait. Might have to get a cheap one to hold it over til he can get me one.


1993 F250 3k in the 460-my 1st truck
1973 K20 6" lift-bright future
1967 F250 2x4-diesel swap in its future

 

[350runner]

No problem. Rebuilding a carb really isn't hard. I'd by the parts and do it yourself. Sense of accomplishment is awesome. Now if your wanting the carb to be missed out look like better than factory I'd say yea it's worth the wait.

Sent from the dust in front of you!

 

[73K20]

No problem. Rebuilding a carb really isn't hard. I'd by the parts and do it yourself. Sense of accomplishment is awesome. Now if your wanting the carb to be missed out look like better than factory I'd say yea it's worth the wait.

Sent from the dust in front of you!

I was planning to do it myself, carb rebuilds are cake. His website offers a rebuild kit I thought.


1993 F250 3k in the 460-my 1st truck
1973 K20 6" lift-bright future
1967 F250 2x4-diesel swap in its future

 

[350runner]

Yup they offer a couple kits. Way to go!

Sent from the dust in front of you!

 

[73K20]

Ok so driving today and the truck went all to hell, wouldnt get over 40 without the weird hesitation. did ok in first and alright for a min in 2nd but once i got to around 30 it would bog down bad and act like its going to die, never did though.
got it home rebuilt the carb nothing really looked all that old though; replaced plugs, wires, cap, and rotor along with the rebuild and now it seems to be eating gas, it didn't really do the same thing but something is def wrong. Would the secondaries opening to much or too soon or maybe not enough or something cause any of this?


1993 F250 3k in the 460-my 1st truck
1973 K20 6" lift-bright future
1967 F250 2x4-diesel swap in its future

 

[350runner]

Yea it would cause the engine to bog. Have you checked the trans fluid?

Sent from the dust in front of you!

 

[Boone83K10]

if you have a cat then it is clogged. classic symptom of a clogged cat, idles good but won't get out of it's own way at around 20-30 mph.

 

[MadOgre]

WTF is a cat?

 

[350runner]

You must be registered for see images attach

Sent from the dust in front of you!

 

[MadOgre]

What do you mean by eating gas? If the power piston was sticking before you would have been getting amazing fuel economy. So not sure if its just actually normal economy that now seems harsh?

the secondaries are vacuum actuated so unless you bent some linkages while rebuilding that should all have stayed the same

 

[MadOgre]

lol