General question. I had a rocker lock nut break on HP500 on the exhaust valve hole #7. Tech replaced lock, checked push rod and all was ok. Fired it up and no noise and seemed to be hitting on all 8. Started it this week and it is miss firing and is not accelerating on the muffs smoothly. What are the potential issues? Was going to pull plug to see if it is fouled, do a compression check, maybe the rocker is adjusted too tight or loose. Any suggestions appreciated.

Loose would probably tick, tight would probably miss. How and why did the lock nut break, are there more ready to go.

Maybe another nut broke?

This thread has some info on a BBC rocker nut breaking. It'l doesn't appear to be a common event compared to rocker studs breaking.

https://www.hotrodders.com/threads/r...agnose.148710/

I don't think there is any others broken, no weird noises just missfiring. I am considering replaceing all of them on both engines. Question is, who makes the best ones out there? ARP?

It's hard to beat the availability, quality, and price point of ARP hardware.

Need to be careful buying aftermarket, the Merc ones are shorter to clear the stock valve covers, all my years Ive never seen one break

I'm not familiar with that exact motor, what brand rockers are they and are they aluminum ?

If they're stock it should have Crane gold aluminum rockers, but so many have been changed out over the years

I was just curious, aluminum rockers have a cycle life.

the poly lock nut broke not the rocker