Hey, I just bought a Chevelle with a 350 - Have some carb (I think) issues. It has a 750 dual feed with a Victor JR intake. (way too much for this motor) so I bought a 600 Holley (very new, Ran for 2 hours on a dyno) snd a Weiand Stealth intake. I decided while I wait for the intake to try the carb. I can get it to fire by pumping it but it will not keep running unless you keep pumpung the gas. (to keep the squiters going)
It also "pops" out the exhaust. I have adjusted the timing all over the place and nothing helps. It would idle with the 750 but still popped through the exhaust at cruise. It also will rev up but if you hold the gas in one spot it will die shortly.
I am beginning to think that the cam might be going flat, I have not pulled the valve cover yet. The kid said he replaced the lifters but no mention about the cam. Or maybe the cam sprocket is off 1 tooth or something. I have a 406 to put in but I guess I would like this to run because I will be swapping everything from this motor to the 406 long block.
I guess I am curious why the car won't idle with the 600 but it did with the 750. I might swap them back to see if I can get it running again with the 750.
Any suggestions? Comments?

LK

Check your float levels first, might be set too low.

Carb might also need some cleaning - how long did it sit before you got it?

OK, I tore the carb apart and it was spotless inside, like new. I blew everything out and adjusted the floats with it apart. I got it running. I swapped the distributer for a normal HEI (the other one had a MSD) I set the timing 4 degrees advance but it really turns over hard so set it by ear. It runs and idled OK, I can rev it up and it sounds OK. I go down the road and it pops through the exhaust. I moved the timing all around and no better.
I then took the valve covers off and they had the rockers very tight so I adjusted them and it idles better and revs up great, no popping. Still runs like $hi+ when I accelerate on the road.
I guess my next step is to pull the timing cover to make sure the gears are installed correctly. The guy I bought it from was only about 21 and it looks like he just kept throwing money at it to try to get it to run better but it doesn't.
Any other ideas? I put new plugs in it and all for the cylinders are firing. (headers are hot) Could plug wires do this? I have not swapped the intake, still running the Victor JR - It still seems like it would run fine with this intake, just no bottom end. Oh yea, When I put it in gear it want's to stall the car unless the idle is extremely high.

Any ideas welcome.

Thx.

LK

vacuum advance working? 4° advanced sounds low - I would think up to about 10° would be better but may be pushing it. Should re-time anyway after adjusting the rockers.

Check for an exhaust leak also on that popping. Bad header gasket is a possibility.

Do you have 12 volts at the HEI dist?

Sounds like vaccum leak. Did you look at the base plate to make sure ALL plugs are in place? I think there is one at the rear (1/8" pipe thread) that a lot of people miss.

You don't have to pull the timing cover to check the cam timing. All you will need to do is verify your timing mark at TDC on the balancer with the timing tab. Then check your cam lift at TDC at the pushrod side (assumption here is you know exactly what cam is in there). You can get the cam data from the cam manufacturer. They will give you lobe lift at TDC for a given cam. Also, you can check your timing at .050 using nothing but a marked/degreed balancer.

I'm guessing vacuum leak too. At one time I pulled my carb and when I replaced it I failed to clean a little stuck on carb gasket material so the new gasket couldn't make a good seal all the way around. It exactly like you describe. Make sure the gasket is sealing all the way around and that you don't have any open vacuum lines coming off the carb.