Rich Running

[steve G]

Hi. I'm looking for a little help on a bowtie problem I have - I hope you guys can help.

I have a 383 chevy crane 284, Edelbrock RPM Setup, running 10:1
I'm using a 650 holley vac sec. mallory dual point vac adv. timimg 10deg

my problem is that I can't get the engine to run well at low throttle openings, it runs rich, sputtering until I get to 3000rpm, then eventually clears with acceleration, I can see a black deposit in the exhaust pipes, and whilst stationary, if I hold the throttle open at 2000 rpm I can feel lots of hesitation & stumbling

If pressing on hard, it runs well enough, until I drop revs.
I get a lot of popping in the sidepipes with any decelaration, and I also get high RPM at tickover perhaps 2000 if I get off the gas. this sometimes takes 10 - 20 seconds to get down again. this is not a stuck throttle. or a choke issue

It seems to do this at most RPM, with gentle throttle, but runs better with more throttle, it sems not to want to stay at part throttle

I've changed the power valve, jets etc, plugs, timing but to no avail.

It has ben sugggested that I look at the exhaust, which has a 13/4 primaries going into a 4 inch collector, then into a 2 inch side pipe. the suggestion being that I might be getting back pressuer at low rpm which is causing the block to run rich

I would be grateful for any help - I feel a little stuck

ps most cobra reps over here in the UK run bowties, and mostly SBC


steve