Finally got new motor in and running half hour ago. Its a 355 with 11.2:1 compression, ported heads, gm846 cam and other various things. It'll run as long as you keep the gas to it. I kept the rpms 1500-2500 for first 20 minutes or so. As soon as you let off the gas the rpms drop to 400-500 rpms and it backfires and pops like crazy and this is with the throttle stop screw adjusted out. Its still on stock tune and stock throttlebody. Any way to get it to run until i can get a mailorder tune. Need help ASAP. TIA

 

Perhaps the rockers are too tight? Did you adjust them with the engine running?

 

no, engine off with 1/4 preload, same way i adjusted the rockers before new engine.

 

Was the "first time" with the comp RRs? I adjusted my RR's to 1/4 first with the engine off and my engine wouldn't idle.. I did it with the engine running and it stayed running. Might be worth a try.

 

yeah same rockers were on old engine, also have new lifters "summit" brand which I think are made by crane.