I have a 259 cu in engine in a 60 Lark that I purchased about a year ago. The previous owner had absolutely no knowledge of what, if any, mechanical work may or may not have been done. When I test drove the vehicle it started, idled and drove around the block. However after going around the block and trying to accelerate in traffic it stalled, restarted, idled and stalled again. We chalked it up to either vapor lock (the car was in Nevada) or the fuel pump. The fuel pump was replaced and I purchased the car without test driving it again. Fast forward a year and I'm still having the same issues. I've drained the tank, blown the fuel line, replaced the pump (measuring vacuum and pressure before installing) replaced all hoses and made sure when the tank was drained it was clean inside. There is no screen on the inlet to the carb and I've replaced/removed the clear fuel filter the previous owner put on. I've borrowed a pump from a friend (1 new pump, one that came off the car (nearly new) and one from a friend who says it came off a running driving 259 and assures me it works. All three pumps provide a little fuel into the carb so the car starts and drives around the block but not enough for hard acceleration or higher speeds without stalling.

I've decided to hold off removing the radiator, fan, water pump, etc. to measure the eccentric, which I read is supposed to have 0.485" of lift. I can see the eccentric with a mirror and well it looks like an eccentric but I haven't tried to measure it with the pump off. Any suggestions for how to measure the lift of the eccentric through the fuel pump arm inlet hole?

I've fashioned another solution using the cover bracket on the end of the pump arm (see pics) and with two spacers the pump is bottoming out, one spacer improves flow but pressure is still below specification.

My theory is that pump arm travel is reduced due to wear on the eccentric causing fuel starvation under load. With the two spacers added the pump is bottoming out, the question is what is the right thickness for the spacers to achieve correct vacuum and pressure?

I'm guessing but I think the eccentric lift has been reduced to somewhere between 0.36" and 0.235" from 0.485" if each spacer is 0.125" thick. This seems like a lot of wear to me but I don't know if it is.

The other two solutions as I see them are to pull off the radiator, fan, water pump, timing cover and valve covers and attempt to replace the eccentric. Or move to an electric fuel pump.

With the spacers I'm concerned about additional wear to the eccentric or potential breakage. I don't know how long the spacers/pump would last and if they wouldn't accelerate the eccentric wear further. I don't relish the thought of tearing apart the the engine and I'm not sure if the cam would not have to be pulled in order to replace the eccentric.

Questions: does anyone see any downside to temporarily using the spacer solution? How much work is it to replace the eccentric and does it require a part that is hard to source? Or does it require a new cam?

Thanks for the advice!!

Mike Spacer1.jpgspacer2.jpg