I swapped my 305 quadrajet to a brand new 350 vortec (originally designed for marine use) with a 750 holley. She fired up first try. She runs but not good. It has vacum advance and I have an HEI dist. so I plugged the vacum line and set the timing but had to set it at about 30 degrees total to make it run ( I thought it needed to be 10 or 12)

The problem is it wont idle below 1500 rpm. It will just die out completely. It is responsive above 1500 with constant back fire or popping sounds (doesnt sound solid). I checked all my wires and for vacum leaks but I can not find anything wrong. I am running open headers right now so its hard to listen for any other abnormal sounds.

My Questions:

What should a vortec motor be timed at?
Could I have over tighted the valves?(might be bs but someone told me to loosen them up)(Hydro rollers, I took all the slack out then tightened 3/4 more turn)
Why wont it idle below 1500?
What could cause the popping noise?

 

Was the car originally carbed? If not, what have you done to convert it to a carbed setup? Have you thrown a vacuum guage on the engine?

 

Yes the car was originally carbbed. No I have not put a vacum gage on it. If I do what should I look for?

 

If that's all you did to adjust them, that's all wrong. Set them the correctly.

What front cover and harmonic damper did you use?

 

It has the plastic front cover with the two prong plug sensor in the bottom, that I dont use, and the harmonic balancer is the original one that came on the engine from GM Performance with one line ingraved into it. The plastic cover has a pointer made into it which appears to be in the same place as if I put an aftermarket one on.