I just swapped engines and dropped in the GM Performance 290 hp 350 available at summit and jegs. I put a bow tie 063 intake and an Edelbrock 1406 carb with a Street Fire dizzy and box.
I'm noticing a slight irregularity at cruise rpm. Whether I am in first, 2nd or cruising at 65 or70 in OD, I notice what I can only guess is a lean surge while cruising or holding steady at 2-3000 rpm. I backed out the adjustment screws on the front just a little and it did seem to help make it just a little better. But after adjusting the first couple "hours" on the screw there was no change. So they are pretty much back to my tuned idle settings and I will leave them there.

I am wondering if this is a lean surge that needs to be remedied with re-jetting? anyone know about this combo and if the stock jets are enough for this engine and setup? Do you know what jets I will need exactly for this setup to work correctly? Or is there another solution I am missing

Thanks for any help.

 

ok. here's the latest info.

I checked all the manifold and carb bolts. everything is tight. checked all vacuum ports, everything is snug and plugged, checked the choke operation and it seems good.

I spent a lot of time testing with the a/f screws. basically nothing besides the best vacuum at idle made it any better.

checked acceleration from all RPMs and there is no lag or bog off the line or with tip in from 2k to 3k rpm. (I'm not going much above 3 at all yet because it's still a fresh engine.)

So the problem I am having seems to be exclusively while cruising at part throttle above 1800 RPM or so all the way to 3k. It feels like a very faint miss, not completely SURGING, but not completely steady. The RPMs on the tach don't seem to really move but I can feel it.

After reading some Edelbrock tuning guide pages I think I need to change a rod to 1 step richer. Again, I'm just looking for any other input to help me out.

thanks