The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Sputter snap and can stall

Hey all, brand new here to Stovebolt! I'm working on a 65 GMC with a 230 and just recently had the rochester 1 barrel gone through by a carb shop. Trucks been sitting for a number of months, partially because when I try to drive it 2 issues; on snap throttle you can feel a major delay, like no accel pump function-but I know it is working well;2nd issue and the most annoying, after warmed up it stalls when coming to a stop sign or light. If I choke it a bit(pull choke mind you) seems like it isn't as bad. Intake was resurfaced with exhaust before carb was installed and I've retorqued all the mount bolts so they tight! I really feel this is a lean issue, but not familiar with these manifolds. Base timing at 4 BTDC and when I snap throttle timing doesn't even chage yet bc rpm hasn't but I'm already farting and popping from my sputter snap cause.

#1 possible vacuum advance issue.
#2 float not adjusted right

Just guesses but worth a look.

how are your vacuum lines?. that hose right in the front of the vacuum advance can be neglected quite easily. gas goes bad pretty quick if is left .
it is also not impossile to have a leak at the intake evne though the flanges have been resurfaced
ron

Sean:

I'm new to C10's as well. I recently bought a 63 short fleet with a 230 inline six. The description of your problems mirrors mine. I had a persistent stumble when I hit the gas and it was very unhappy when cold. My engine was pretty much stock, though the original Rochester Model B had been replaced by a Rochester Monojet. Here is how I attacked it:

1) I replaced the distributor with an HEI unit from 12bolt.com The reason I chose them is they actually put the distributor on a machine to check the advance curve. Replacing the distributor did little to solve the stumble. I made sure the timing was right (vacuum, centrifugal, and initial) including checking that the timing pointer was accurately indicating TDC. The new distributor did little to change the stumble and cold performance even with ideal timing.

2) I pulled the intake and exhaust manifolds. I knew my exhaust heat valve was frozen open and the gaskets were leaking. At the same time I purchased a "restored" Rochester Model B carburetor from Daytona Parts. (Their work and advice were fantastic.) After freeing the exhaust heat valve, cleaning, and putting everything back together, the truck runs really, really well.

In my case, the issue was most likely the carb, though several items were addressed during the carb install. Specifically, I believe my stumble was due to a bad accelerator pump. (It should squirt as soon as the throttle is moved.)

Regards, Cris