Give us some more specifics on your combo.What are you running?Cam(give speck's),compression ratio,intake,gear,trans,stall speed?
The reason I ask this is to tight of a converter,or to high of a gear and the motor will not like a double pumper.
First off,make sure you don't have a vacuum leak!Reset your valves(1/4-1/2 turn down from zero lash for hydraulics).
You should work with your distributors advance curve first when tuning.You can not setup the carb properly if the timing is not right.YOU WILL NEED A DIAL BACK LIGHT FOR THIS TASK!!!
Set your timing at 36 degrees of full advance(when you observ it stop advancing)with the vacuum advance disconnected and plugged.If it stops advancing above 3000 RPM you need lighter advance springs.Put some springs in it to acheve full advance at around 2800-3000.
Are you running vacuum advance?If yes, than try hooking it up to manifold vacuum.If it starts pinging get a canister with less advance(8 degrees),or get an adjustable one.
You say you are not running vacuum advance,here's something to think about.
What is your initial timing?10 degrees?Many times an off idle stumble will magically disapear with slightly more initial advance,something like 14-18 degrees might just do the trick.This means you will have to install a larger advance stop bushing to reduce the advance.A BB usually likes around 36 total.Try to limit the distributors advance to about 22 degrees.If you have a very radicl cam and somewhat low compression(for the cam)you may want to run about 20 degrees.
I prefer to use MSD distributors because they limit the advance just like a factory unit.The Mallory unit requires you to bend a pin.This seems kinda hokey to me.I haven't seen the Pertronix unit so I don't know what to say about them.
Next work on your carb.Here's a list of things to do.If it looks grungey,give it a rebuild.Make shure the idle feed passages at the top of the carb are not plugged.Give them a shot of carb cleaner.Remoove the idle feed mixture screws and give the holes a shot of cleaner as well.Adjust the float level.Set your powervalves and jet it in.Make shure there is no play inbetween the acellerator pump cam and the lever that depreses the pump diaphram.Tune your accelerator pump squirters,now tune your accelerator pump cams.
If none of this works don't call me
[This message has been edited by mutant 68 (edited 11-12-2000).]