Hey all, i haven't had a post in quite a while but here i am, stumped again. I recently put a Holly 750 Double pumper on my Big block and are having a few problems. First off the carb is a manual secondary w/ no choke (doe not need it.fires up in the cold fine) The car idles fine but when i get on the gas, even slightly, the engine misses and boggs pretty bad. If i lay into the gas it will miss a little at the low rpms then pick right up and go screaming down the street. The problem also starts to go away, but is still there, after the car is warmed up really well (10-15 min of driving.)The timing seams to be pretty close but i did this by ear. My thoughts are that it could be too much carb (the carb has a lot of work done and flows well above 750 cfm, it came off of a 10 second gremlin w/ a 350 chevy.) which would mean i could try smaller jets but again it idles fine and runs well at high rpms. My other idea is that maybe so much gas is causing a loss of vacuum pressure that is not letting my distributer advance. either way i can smell a lot of gass and im pretty sure its running really rich. Would switching to a mechanical advance distributer help? (even though im not even sure how they work, lol.) Should i go with smaller jets? Both? Either way thanks for the help guys.

 

First step is to actually time it with a real timing light.

Does a lot of smoke come out of it when you mash on the throttle?

And you are running a 750 on a 302?...or what?

-Gun

 

ya. you write big block and the signature says 302.
what size engine, how high do you rev it and what modifications are done?

if it starts up straight on cold no problems without choke my thinking says "way to rich when warm".

as for the stump it could be either ignition retarded or the accellerator pump not adjusted. it could be as well that your're running rich warm and when you stop it it'll flood the engine (too much pump shot).

get the timing right first (what do you have it set to?), adjust points if you have them.
once that's done check for the accellerator pump linkage. there must no be any play in the linkage (the tiniest movement in throttle must push pump), and when fully open you have to have a bit of adjustment left (means at WOT you should be able to move the pump lever by another millimeter)

 

you probably want to make sure you have the pink cams for the accelerator pumps installed

 

Yeah those are for the sissy engines

-Gun

 

Ahem. Your detailed description absolutely screams "YOU NEED A CHOKE!"

All this crappy running when cold is conclusive. As mentioned, you probably have mix problems, too, but the above problems will go away when you get a choke.