carb jetting

[Boog]

Who has run an RV cammed 350 in their truck? Stock qjet with performer manifold. Did it run much richer than before the cam install?

[jmorri34]

Im not sure what Cam is in my 350 I think it might be the RV cam but I have the edelbrock carb and performer intake and Im catchin 9 kindsa hell leaning this thing out.

[geezer#99]

Nothing wrong with either one of your carbs.
Lack of initial timing is the problem.
If you bump the timing up, the engine rpm increases, and then turn your idle speed down with the curb idle screw on your carb.
At present you're idling rich because with the increased carb idle setting your carb is idling on the power circuit.
Closing the throttle gets you back on the idle circuit and your mixture screws will become active again.
Easiest way to tell if you're idling on the power circuit is to screw one or both mix screws in. If it keeps running, it's idling on the power circuit.

[jmorri34]

Hmm interesting, Thanks for the information that might help me alot!! Thanks geezer

[geezer#99]

I forgot to mention that you want to cover the transition slot in the carb to get back on the idle circuit.
Here's a link with some info. It's a holley but they're all the same.
http://www.crankshaftcoalition.com/w...ve_carburetors
Also another trick is to hook your vac advance to manifold vacuum which also speeds up the rpm allowing closing the throttle more.
There's no reason you can't get any motor to idle under 750 rpm cleanly.

[GASoline71]

Yep... once you change that cam... the stock timing goes out the window. Even a mild RV cam requires more initial advance. You can still shoot for 33 to 38 degrees total, but your initial will always increase a little after a bigger cam swap.

Gary

[Boog]

I believe it's on the idle circuit ok since I can shut the engine down by turning in both mixture screws. They are presently 3 1/2 to 4 turns out and it's maintaining 17" of steady vacumn. It will idle real steady until I give it a quick rev or two and then the idle drops and it will take a while to recover. It starts easily with no pumping of the pedal and the choke is wide open.
Did I mention this is a fresh built engine that only has a few hours of run time on it? I had it built a few years ago and the truck hasn't been on the road yet. It is a 9 to 1, 40 over 350 with Performer intake and stock ram horns and rv cam. Just a neat little small block. The qjet is a 75-77 model with the 76 jets and 52 rods. It's been thoroughly cleaned and new Napa kit used. It has an all new HEI distributor also.
I have played with the timing a bit but having not driven it I cannot say how it will run out. I may dial in more and see how it responds. The plugs are not just sooty black but aren't gray or tan either.
I appreciate you fellas input.