Engine stumbles

[mike mcdermott]

I have put on crane 1.6 rockers on my 87 vette after completing the installation I have encountered a problem @ 40 mph the engine seems to stumble this also happens when I acellerate @ higher speeds. I have also increase rpms to 800 @ idle and advanced timing to 9 degrees. Any recommendations to solve the problem would be greatly apreciated.

[fatherlarry]

Welcome aboard Mike. Sounds like your having some problems. Did you calibrate the rocker arms? Sounds like the valves are staying open as the rpms reach a higher point. I'm sure the mfg gave specs on how to install the rocker arms and how to load them. I would even give the mfg a call, or a local speed shop in your area and they may be able to walk you through. There might be something you missed. It's kind of hard to give you an answer without knowing step by step how you installed them? Did you use the factory pushrods or installed new ones? If you can give me more details on your installation, maybe I can help. If you want to wait, Corvette Kotze, our technician, will be back from vacation next week, and may have done a job like yours and can help you out. But, If I were you, I'd want to take care of it right away, so check with a local speed shop. You don't want to ride around if the valves are staying open at a higher rpm. You may end up hitting a piston if the rockers aren't adjusted right. Good luck and let me know how you make out.

[mike mcdermott]

I did in fact consult the manufacture and got great advice and I appreciate your advise. I went back and reviewed all work done and in retracing my steps I found a fouled plug and since the plugs I had were about three years old I replaced them all and it has solved the problem.This is not as easy a job as most people like to convey because you have to have a feel for TDC and and then a feel for the positioning of the intake and exhaust valves to set them properly and at the same time have a feel for movement of the push rod to insure that the rocker is not to loose or too tight. Thanks again for your quick responce and advice.

[fatherlarry]

I'm glad everything worked out for you. Sometimes it's right under our noses. But the challenge is fun and I'm sure you feel a sense of accomplishment. Job well done.;bt