I currently swapped out my LG4 for the engine in my signature. I was running a holley 600 with vacuum secondaries on the LG4, and I was hoping to run this on the new engine until I can get a 750. The problem I am having is I can't get the car to start with the 600 on there. I had to borrow my buddies 650 double pumper. What can be wrong with my carb, and what can I do to get it running. I hate the gas milage of the double pumper. Also I am running melling's 22401 cam in my engine. What power valve do you suggest running in the 600 and 750 when I get it. I don't have access to a vacuum guage right now.

 

Can you describe what happens other than "doesn't start"? Does it flood, not get any fuel - what?

Which ever it is, very likely something happened to your needle and seat while off the engine, if it starts with another carb on it. That's a good place to start looking.

As for the power valve, you can either do the trial-and-error method by putting a number higher or lower in and seeing if it runs better with one of those. Or, you can get a vacuum gage for about the same price as a couple of power valves and do it the way Holley suggests. No tool box is complete without a vacuum gage.

 

I actually played around with it today and got it running. I think my power valve is blown because of the numerous backfires that happened with the old engine. The idle is sparatic at times, going up and down like it has a vacuum leak. The 600 has much better throttle response though.