‘65 sporty vert running poorly….need help

[Yooperdan]

She just started running very poorly after warming up seems like around 40ish just surging then nothing…go, no go
all the while losing speed. A couple of times slowed and stalled, stopped started right up ran good for a while then started with the “bucking” surge then nothing then on then off, then will run fine for a little bit then the same.
I don’t want tempt fate and get stranded with the old girl. New plugs, wires, coil newer fuel filter just put 15 gal. of
Premium in to fill her up. She did start doing this before the fill-up just before filling up.
Was running great and strong before. Short top down season here…gotta get her going right!!

Thanks for any thoughts,
Yooperdan

 

[CBODY67]

Several possibilities. One is the fuel pump push rod IF it is a B/RB motor.

Otherwise, when was the last time the rubber fuel lines were updated? Updated? All rubber fuel lines made since 1992 have had to be "resistant" to the oxygenated fuels which came to be used back then, which evolved into the current ethanol'd fuels. Ethanol is a solvent and "grease remover", which means it will dry out the rubber fuel lines from the inside out. They might LOOK fine, but be getting ready to flake off the outer layer of rubber (on top of the internal cloth braiding reinforcement) at any time and "leaks" happen suddenly. So, reasonably fresh rubber is important.

Three sections. One at the fuel tank (with the special clamp that has the fuel sender ground in it). One is at the rh rr corner of the front stub frame. The others are at/near the fuel pump, intake and outlet, plus at the inline fuel filter.

AND, it might even be the fuel pump having internal valving issues.

Keep us posted on what you find,
CBODY67

 

[Yooperdan]

Several possibilities. One is the fuel pump push rod IF it is a B/RB motor.

Otherwise, when was the last time the rubber fuel lines were updated? Updated? All rubber fuel lines made since 1992 have had to be "resistant" to the oxygenated fuels which came to be used back then, which evolved into the current ethanol'd fuels. Ethanol is a solvent and "grease remover", which means it will dry out the rubber fuel lines from the inside out. They might LOOK fine, but be getting ready to flake off the outer layer of rubber (on top of the internal cloth braiding reinforcement) at any time and "leaks" happen suddenly. So, reasonably fresh rubber is important.

Three sections. One at the fuel tank (with the special clamp that has the fuel sender ground in it). One is at the rh rr corner of the front stub frame. The others are at/near the fuel pump, intake and outlet, plus at the inline fuel filter.

AND, it might even be the fuel pump having internal valving issues.

Keep us posted on what you find,
CBODY67

I’m not sure what B/RB motor is? I’m wondering about the fuel pump as it has two or three fairly strong surges
then nothing then on off like not getting fuel. Any thoughts on where to get a quality fuel pump might be a good place to start. Thanks for the tip on the fuel lines and your response appreciate it CB67.

 

[Blusmbl]

Big blocks are the B/RB motors. 361, 383, 400, 413, 426, 440. They have a fuel pump pushrod that is between the pump and the camshaft.