35fountain

Not a good weekend for me, First a power steering pump and now a broken pushrod ball...I heard a loud tapping noise while just getting off of plane. Remove cover and noticed # 3 exhaust valve rocker very loose. Remove rocker and the little ball fell out in my hand. WOW lucky it didn't fall into the motor. I just installed these rockers 3 weeks ago because they got hot and changed to a burnt color from using the wrong chrome valve cover last summer. I put on covers without drip rails and the rockers were starving for oil at high rpm's. The rockers are comp cams steel with roller tips. I set lash @ 0 and the 1/2 turn more with the Mercruiser adjustment sequence. example : TDC firing #1 you can adjust rockers 1 int 1 ex etc.. then turn 180 degrees firing at # 6 and adjust rockers on another bunch of cylinders. Installed a new pushrod today.. set lash @ 0 and 1/2 turn more.. replace valve cover.. sounded quiet. Cruising at 3200 rpms and when I got back to my home port A rocker tap again. Not sure yet if it was the same one.
I decided to replace all pushrods, arp studs and locking nuts.. What is causing these rockers to loosen @ 3000-3500 rpms.. rockers, balls, nuts are new except for the pushrods that may have gotten hot from the no oiling issue. Engines are twin 509 490 HP Dyno mild crane cam 531 lift 236 duration, emi exhaust msd ignition locked out at 34 degrees. I have this boat 5 years. It originally came with regular stamped steel rockers. I upgraded to the roller tipped when I did a valve job last year.
Any help would be appreciated

MESABALANCING

You may want to check your exhaust and make sure you have no leaks. Up north many times the boats sit for long periods without use and when you start to use them any moisture in the exhaust ports can cause this type of problem because the valves can stick in the guides from lack of lubrication or corrosion. If you had one push rod break Id say ok it failed but with the troubles youre having I feel its a bit deeper of an issue. I personally dont build engines with three piece push rods but I know they have been used for years by manufactures and as long as everything is text book they work fine. Check it out and let us know what you find. Sincerely Laz Mesa www.mesabalancing.com

vintage chromoly

iTrader: (3)

Get a good set of pushrods. A quality set can be had for less than 200 bucks.

Also, I agree that something else may be happening to cause these failures.

How many hours are on the engine?

35fountain

I just ordered comp cams magnum pushrods one piece with no welded ball at the ends and 2 new sets of Arp studs. The rockers are 3 weeks old. The original problem with the nut backing off I believe was caused by no lubrication and the rocker, stud, nut and possibly the pushrod got hot. That issue was resolved by putting back the valve covers with drip rails so it catches the oil and sends it to the pivot ball. This was happening at high rpms, the oil was over shooting the rocker. This latest issue with the pushrod ball may have been related to the last overheating problem. A friend of mine said that the heat that was generated from the no oiling situation could have caused the ball to become loose and move stopping oil from getting to the rocker. Like I said it was very loose and when I lifted it off the stud the ball fell out. The first failure (valve cover issue) MY Fault...I should have replaced them with drip rails. No water in exhaust. New heads last year. garage kept never goes below 38 degrees, Plugs show no signs of rust and we already ran several days before the pushrod problem. Could the adjustment cause it, too tight or too loose? Thanks for you replies

35fountain

I also found out something very interesting today...The OEM lock nuts are not compatible with ARP rocker studs. This is why they are loosening. Confirmed with ARP themselves.. They said they can make locking nuts for me that are compatible for around $ 700.00
I'm going to order GM studs

Look at the attached pic and read what it says in the center (bold letters above the stud)