Had my blown 354 running for a couple weeks. Fired right up on the button broke the cam in all ok. Been running like a clock. Fired it up yesterday to show a mate and after a minute it backfired and started running rough. Had a look at it today and found the tip of #4 exhaust rocker broken off???? Checked and double checked everything when we put it together. No funny noises when it was running. Just lucky I guess. Are 392 and 354 the same?
All the Chrysler Hemi rockers interchange between the 331, 354 and 392. The exhaust rockers weren't known for being strong.
I had the same thing happen in the '54 New Yorker engine in my dirt car. I have heard it is a common occurrence when running aftermarket cams and springs. They made Donovan forged rockers for a reason. I was lucky enough to put together a set. I found the first 7 at a swap meet for $35; the eighth was more than triple the price of the first seven.
Then you had the Surfers top fuel team in the 60s who built their car in their dad's garage, built the 392 basically stock and ran pretty much 100% nitro because they couldn't afford breaking hydrometers and ended up winning the March Meet beating all the big names in the process. didn't break anything. Now you have me worrying about the rockers in my hemi, although I have been driving it off and on for 40 years with no problems.
Take a close look at that break . The color of the metal is a100 % fresh break . Usually the metal will show signs of a crack first . But,,,,,,,the pushrod doesn’t look bent,,,,,,,you would think the rod would bend before the rocker failure. Probably just a bad rocker ,,,,,,,inspect it closely . Tommy
Not much clearance for push rod? No oil in the crack; ie no oil coming out the rocker? Maybe push rod binding in worn deep rocker arm socket?Just throwing stuff out. Never liked cast rockers in anything but enough things still had them.
The rocker gear was all stripped and thoroughly cleaned before being fitted. Before start up we primed the oil system while turning the engine over to check we were getting oil everywhere.
If you do some research on the Surfers, you will find that they did get a set of Donovan exhaust rockers after they broke an engine. I ran stock rockers on my old 392 but am well aware that I was really lucky.
I am going to suggest that you have an odd failure. There are plenty of documented failures, and I have experienced several myself, but yours appears to be a bit odd in my opinion. Do you have any history on these pieces? Were any modifications made? How much spring pressure? .
Have seen many a set with the ribs welded on top to strengthen. I would inspect close and replace. Was a known common source. Have had two sets of Donovan’s. The late style after market will probably be easier to come by but your gonna know you were there.
The rocker gear came from eBay and was unmodified. I gave it a thorough clean inside and out .I got my cam and springs etc from your good self. The engine was running really sweet before this no unusual noises .
Weird break for sure. If you can’t find a local replacement, pm me. If you’re looking for something better...
My good friend Gary Patrick at Rocker Arms Unlimited also has some nifty pieces that are investment cast stainless for folks with a good budget. .
Just helped out a guy in Texas,who also broke #4 exhaust rocker. Explained how to change that rocker without taking the head bolts out.
Actually it was one of the garages at the Red Apple Motel, which was managed by one of the team members mother. The engine LOOKED basically stock, but had countless improvements, most were not visible to the average racer (by choice). Mr Jobe said they DID break exhaust rockers. After breaking stock rockers, and having to replace all the damage caused by broken rockers ("sending the blower into low orbit"), then the Donovan rockers became more affordable. They could have afforded a hydrometer, they chose to not need one. There is an excellent video series posted by Bill Pitts on YouTube that has Mr Jobe's recollections. Well worth the time to watch the videos on that team that wrote the book on how to 'run the can'.