I need help. I have a 92 Silverado with a 454bb,bored out to a 468 . It is popping and cutting out between 3-4000 rma. It has had this problem for about 3 months now. It has a rv cam also with 125 shot nitrous. It ran perfect up until this problem. We have changed the distributer, fuel filter,. New push rods, rocker arms. Not we only changed these parts because we thought we had it fixed and then I took it for test drive and nbroke a push rod. After we changed that itwe still had the problem. Also new vacuum lines. We recently thought we had it figured out because the valve springs were kinda loose. So as of today we changed the valve springs thinking this could be the fix but it is still cutting out between 3-4000 but not really after 4000. I apologize in advance for spelling punctuation and grammar. Any help would be appreciated. I have some good mechanics working on it but they are kinda stumped.

 

No such GM engine, a 468 Big Block was ever made. You might want to correct this.

 

It's a 454 bored over to a 468

 

Kinda what I figured. I've been around Chevy's since before the 454 was even manufactured. Want a good truck motor, stuff a big block 366 cubic inch motor in your pickup. That motor is as solid as they come and with a torque curve the likes of which will blow away any 454..