65 gs stumbles

[Jim]

Hi, car runs fine  normal driving ,but taking off  low gear to 5,000rpm no problem  shift to drive sometimes hesitation over 4,000 then letting off car surges for 10-15 seconds  then runs fine again  motor  was rebuilt 20yrs but only 3,000 miles ago  maybe fuel pump,filter ?  Jim

[jmos4]

Hi,

Auto or stick?

How long ago was the carb last rebuilt?

Sounds a little like accelerator valve gone bad or something not adjusted for the kick down/stall converter linkage if automatic

Regards,
Jim

[Jim]

Auto wasthinking I was running out of gas or advance sticking ?Jim

[jmos4]

Hi again,

Try and lube th weights and check everything moves freely and go from there

Regards,
Jim

[GS66]

Replace the fuel filter too.

[Rollaround]

A couple suggestions.
I would check timing then make sure the harmonic balancer has not or is not slipping as a starting point. Then check the carburetor float adjustment.

[schlepcar]

All of the above and a quick look into the carb without it running. Look closely at the two streams of fuel as you pump the throttle. They should be same size,length and steady as you move throttle. If car pulls normal up to 5,000 rpm and fuel streams look normal I would question the quality of the fuel in tank and check the dwell if fuel seems OK. It may rev to 5000 under little to no load on kerosene,but may be misfiring after it shifts into second and loading crankshaft. I would pull off fuel line and run some on a paper towel. It will either flash or light like diesel fuel.

[Jim]

Going to pull the carb and check it and pump,filter  ,also check distributor, how long do you trust a 20 yr old  no real mileage fuel pump?  .Jim

[schlepcar]

 The fuel pump is generally good if your oil is not gaining on the stick,but it never hurts to check the pressure. I think anywhere around six pounds while cranking is plenty. If you are fortunate enough to have an AC pump still on it I would not fix it if it aint broke. If it is starting,idling,and revving like it should sitting still....I would lean towards fuel or fuel supply. The carter or 4GC rochester can be pretty moody with old gas in them. The 4GC used a stone filter that can be an issue and I believe the carter only had the inline filter. Before I get too stupid....it is always an overlook to find a dry rotted hose by the tank sending unit  or pump just pulling enough air to empty your wallet replacing unnecessary items.