I just completed my 302 twin turbo setup. I rejetted the carb to where the air/fuel gauges said it was good. To make sure I checked the plugs and they are a little blacker than they should be. My problem is that when I get over 4000 rpm the engine dies. I thought I might be going lean, but that doesnt seem the case. Im running stock ignition with a holley 1850 carb. Any help would be appreciated. Thanks

 

We might need a little more info in order for us to help you out.

What is your definition of "good". . .11.5:1, 12.5:1, 14:1? Is this a narrowband or wideband O2 sensor?

Your subject line says it surges under boost. Does it surge, then die?

Both of those might be contributing to your problem. What exactly do you have for the ignition? What plug gap and heat range? How do you have that 1850 configured to open the secondaries under boost? The 1850 is really not a performance carb in the first place. Considering it's a vacuum secondary carb, it really does not belong on a blowthrough setup. There are members here that seem to have made a vacuum secondary carb work, but I just don't see any reason to go through all the trouble when it is so easy to convert a double pumper.

 

The stock ignition wont cut it. The vacuum secondary can be made to work but it is probally easier to do a double pumper give us some more info and we will see if we can help
Beanie

 

I'm with both of the above replies. That stock Duraspark ignition is just plain and simply not going to cut the mustard. Get a MSD or equivalent unit on there and also the 1850 is a no go. Those two things are a good start to solving your problem.

What bonnet are you using as well?

 

The engine just shuts off above that rpm. Its the narrow band air fuel gauge and it stays all the way in the green under boost. The carb hat is a superior airflow plastic hat. Would spark plug ap do this?

 

what's the carb setup?
modified secondaries?
blow-thru mods?
what fuel pump and reg?