High Compression and Valvetrain...

I've been trying to figure out what could've broken a valve and a roller rocker on my 383 LT1 Stroker. It has a 11.5:1 CR w/6" rods, JE Pistons, and AFR 190cc Heads. For more details...see sig below.

A little info to help me out. The car started to make a high pitch ticking sound, and started to miss. I towed the car home, and while fishing for origin of the sound, I rev the car a little, and that's when everything broke, and a nasty rattle sound emerged, I shut the engine off, removed the head, and found the damage.

The valve broke at the base, and made a hole on the piston. Cylinder wall is fine. Thanks God.

Out of the 16 roller rockers, one broke and 4 on the same side -including the broken one- had the retainer form etched on the bottom, as if the rockers were pushing down on the retainer flush.
My car never knocked, and the most I ever saw was like 2 degree knock.
After talking to some people they say stainless steel valve don't break that easily, and some have commented on my 11.5:1 compression as perhaps a cause, since it may generate more heat in that area. The rr's were the Crane Aluminum, similar to the LT4 Hotcam kit ones.

Anybody here has had any valves issues with high compression strokers?

I can't report any valvetrain problems on any motor I've built related to high compression (unless the high compression pistons were contacting the valves, obviously.) Too-high compression can cause plenty of problems but busted valvetrains isn't one of them.

Now once the piston got blown into chunks THOSE can do some vavletrain damage, that's for sure.

How many miles or hours and drag runs on the engine before if messed the bed?

What's the higherst you've ever revved it?

Any damage on the other side?

What gas with 11.5:1 ? Street car?

How much cam? (looking for DCR here)

Data, we need more data! :)

Originally posted by OldSStroker
How many miles or hours and drag runs on the engine before if messed the bed?

What's the higherst you've ever revved it?

Any damage on the other side?

What gas with 11.5:1 ? Street car?

How much cam? (looking for DCR here)

Data, we need more data! :) It had 10k miles on the motor when it happened. It was during the off-season, few runs at the track. Never revved it past 6200rpm. The cam that is in it right now is the Crane 222-230 .541-.558 lift with 1.6 rr's.
I was just cruising when it happened, wasn't even hot rodding it. The A/F based on a dyno I did 3 weeks before was at 13.1 and the numbers were 363rwhp and 387rwtq. Kinda low dyno numbers, which I think may have been the telling signs of something being wrong.

"Out of the 16 roller rockers, one broke and 4 on the same side -including the broken one- had the retainer form etched on the bottom, as if the rockers were pushing down on the retainer flush."


Running a Cloyes double roller or equivilant? Wondering if you got slack in your tc and slapped a piston b/c of timing issue...
RR in full down position...engine slightly out of static time...piston slaps valve...retainers under bind and pressure etched impression via retainer locks...breaks valve and rr...
Sounds about right?...

Yeah, I DO have the Cloyes double roll TC. Did I miss something here? I did hear a few piston slaps on and off on some days. Can you explain some more? If that's the case, I'm going back to the LT4 Extreme Duty TC.
Thanks.