I have my 340 apart right now for problem with #5 exhaust
Bent the push rod.
Comp cam tech said the cam looks like it has 100,000 miles, actually has 3,000.
Pulling it down, putting in solid lifters & cam
The new oils have been found to damage flat tappet cams. I contacted a buddy that works for Valvoline for his recomendation and he contacted the engineers and they said to run VR1 oil.
Before changing much in the engine it might be helpful to measure the travel on the cam to see if it is worn out
I talked to a guy this week who has a very cool 61 Ranch wagon he has been working on for the past few years. Rebuilt 390 with 30 miles on it. Had to change the cam in it, LOBES WORN OFF
WE NEED THE ADDITIVES BACK IN THE OILS FOR OUR OLDER ENGINES
It has something to do with the time the engine sits also. I have been told it is a dry start if the engine sits alot without the additives.
Hope you find your problem
Send me an email if you want any info on my 340
lmayes8@insightbb.com
I should have bought a crate motor, less money, warranty and would not have had it out of the car twice in 3,000 miles since built