Took the Sunfire to a TMCC event this past weekend. Car ran great and consistent until the semis. Car fell off a 10th but it was a bye run. The finals car felt great on the launch and the opponent red lit and I just eased to the pits but sounded a little off. Got the car home Sunday night and found # 3 cylinder exhaust and intake rockers broken off at the shaft. That was the 12th pass on new engine, well all new except the shaft rockers. Wow what a bummer

How many runs are on the shaft rockers & are they aluminum?

2BKING

I bought this engine from a Super street racer before the car was ever completed. In 2018 it was fired up and found to be defective. We replaced everything new less the block,crank,and the Jesel rockers. Block was bored, crank was micro polished and rebalanced. The rockers looked new but were visually checked by me with no scratches, nicks,nothing. Long story long, didn't know how many passes were on them and they are aluminum. Were aluminum . Just stinks, but ultimately my fault.

Those will wear out after thousands of passes. From my experience if you have a failure like that it is due to coil bind, valve float, excessive lash or something like that. Other wise they should last for years and it is usually the bearing tip or shaft bearing wears out first not a failure like that. My opinion.

I did break a shaft one time when I thought the cam was on the base circle but was off just a little, tightened one bolt down and heard a slight "tink" and it was cracked. Relatively easy to do and could have been easy to miss had I not heard it. When they shaft is fully seated down in the stand they are stronger.

I would check for valve spring coil bind especially on that cylinder.

Aluminum has a cycle life as most have seen in aluminum rods. Doesn't have to be something mechanically beating it up.

The reality though is sometimes cr@p just happens on these things.

quote:

Aluminum has a cycle life as most have seen in aluminum rods. Doesn't have to be something mechanically beating it up.

Agreed. Jesel won’t service the sportsman aluminum rockers if over 10 yrs old and the dates (mo/yr) are marked on the side of the rockers. Jesel will sell replacement parts for them. I’m switching out my aluminum Jesel in my spare engine for either Jesel steel or going with the Crower steel that are in my present engine.

On my motors I have two sets of Crower steel, 3 sets of Jesel aluminum and one set of T&D aluminum. They are all good with my preference being the Crower steel.

I agree sometimes stuff does happen but I still think that kind of failure is usually from and parts binding / lash issue.

On Crower stainless steel shaft rockers on one motor it had hundreds of passes before it started having issues and it was the tip rollers first. One failed then another I knew it was time to have them rebuilt. That set was under a lot of spring pressure and RPM. Still got a lot of passes out of them.

All materials have a cycle life and some are better than others. That cycle life is reduced when it is ran near limit. Most by design should not be that close to limits.

The exhaust probably failed first and the intake followed.

Breaking exhaust rockers is no fun especially with boost. Broke one in the blower motor last year. The cam said I am NOT going to keep turning…it retarded the belt drive and bent all the other exhaust valves in about a half a second. Has steel rockers now.