83 z28, rebuilt 305 bored .30 over.holley 600 vacuum secondaries. msd streetfire distributor. edelbrock performer intake. Timing set to 36*. swapped medium springs in distributor. thumper 279H cam. only about 500 miles on rebuilt motor.

Motor won't idle in gear(idle mixture screws set to 1.5 turns out) won't accelerate hard down low. Changed accelerator pump nozzle to a 35, up from the stock 31. Power valve changed to a 2.5, also have tried 4.5 and 6.5 none seem to change anything. Surges throughout rpm range. Haven't touched the jets yet. Still has a lot of blowby. no smoke from exhaust just out of breather on valve cover. Any suggestions?

 

Is this a combo that once ran well and now does not or is this a issue that has existed since the motor was freshly assembled motor? Also are you sure you have a blow by issue? Ive seen smoke come out of the breather because of oil being burned on the bottom of the intake manifold due to the exhaust crossover I believe that manifold has the exhaust crossover how did you set up your restricter when you put on the manifold? Did you properly seat the rings after the rebuild?

 

the problem occured only after rebuild. I didn't put any restrictors on the exhaust crossover. and the rings were installed by the shop and i used moly rings. i ran the car from 30-60mph moderate throttle and then coasted back down to 30. Did this about 10-15 times.