Carb swap does the trick
So Iíve been running a 750 Holley 4150 on the 468 BB in my 67 SS for a while. Iíve always had issues with rich idle, fast idle when warm and dieseling on shutoff. I had the carb rebuilt and tuned by an old school local ďcarb guruĒ. Car ran better, but I still had those same three issues.
Recently a friend who has an engine shop handed me a lightly used Holley 650 HP 4150 (no choke) and said ďtry this, might work.Ē I slapped it on and wow, what a difference. It is just how it came out of the box, never been modified. I think 6.5pv, 69 primaries and 75 secondaries. Now Iíve got clean and stable idle, with no dieseling.
So whatís up here? Is the 750 bad? Is it too much for this motor? I donít have much info on the engine internals. I have dyno sheets from the builder showing 501 hp, but I donít have the build sheet. Previous owner ďstated 10.5:1 compression with mild camĒ. I know the 750 carb has a 4.5pv, 72 primaries and 80 secondaries. Obviously the POV and the primaries were changed at some point. Could this be the issue?
Iíll keep the 750 for now. Maybe it just needs a little tweaking. If I keep this 650 Iíll have to pay him something for it. I donít like that it has no choke, but I live in So Cal so itís a minor inconvenience.
Sent from my iPad using Tapatalk