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502 MPI valve keepers sliding

1345 Views 15 Replies 8 Participants Last post by  aquaforce
502 MPI valve spring keepers sliding

While doing some cosmetic upgrades on my Merc 502
MPI last week we found two valve spring keepers had moved out and hit the rockers. I decided to remove them all. I replaced with Crane Golds, conversion studs, and of course new keepers. Was this problem a symptom of impending doom (larger undiagnosed problem) or am I the luckiest MF'er this Spring? All other parts look good. Engine ran great all last year and has about 100 hours on it. What would make a keeper shift or come out?
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The keepers are the little wedjes that hold the retainers to the top of the valve stems. What came loose.
If you don't have screw in rocker arm studs that is the first thing you must do.
Did the press in rocker arm stud come loose?
I am going to the mechanics shop tomorrow. I will get
pictures and more info. Not sure of what exactly
I've never heard of keepers popping out. You had one keeper from 1 spring come out? and then one from another? Coming from the same valve you would have dropped the valve. Has anybody in the past messed with them? I've seen failures from people putting 10* retainers with 7* locks (keepers) and vise versa. What are conversion studs? I personally would have done new retainers too if you are unsure of what happen in the first place. Heck.. I'd probebly redo the entire valvetrain.
I have saw the keepers slid up the valves before, make sure the valves are sill good. If the retaining ring on the valve is wore then it will not hold new keepers either.
worst case senario is the valves are tuliped which makes them longer and the reduced spring pressure allowes the keepers to jump out.

Worn / weak springs can do it to. which your addressing.

Do a comperssion test after to se whats going on.
What is "valve tulipped" mean? I will look things over
and talk to the mechanic today.
The head of the valve ( the end that is in the cylinder ) is sapposed to be flat. When they tulip they start to sink in the center and look like a tulip.
I drove all the way out to the shop to look things
over but the mechanic had all the work completed and
engine ready to run on the stand. He said there was
no problem nor reason to think a problem was coming.
Two of the stock rockers had a wear pattern from the
wedge/keeper rubbing. I don't know what the valve
train looks like when assembled so I can't comment on
how the keeper rubbed the rocker. I guess we will run
it and hope all is well.
Finally remembered to get some pictures with the new
camera. These are of the "damage" that my mechanic
found when he put the Cranes on. Engine was run on
the stand but could only get 130 degrees of oil temp.
Sounded quieter than before. Eight of the rockers have
bluing from heat. I assume that they are the exhaust
rockers. Two oil bypass valves were removed. I sure
hope that was why I had black oil all the time. Is the
bluing on the rockers normal? Boat should get splashed
in a few days. I can't wait. I know the best thing to do
was remove the heads and inspect/fix problems if they
are evident, however there is no money for that. I just
hope this was an isolated problem.


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Some of the wrong/mismatched parts used there? Only thing I see in the pics, looks like the keepers may have been beyond the valve stem and rubbing on the bottom of the rocker...No idea how something like that would happen w/o flying apart. And somethings wrong when the rockers get that hot at their fulcrum. Rockers just cranked down WAY too tight or something odd. Hard to say from the pics and info. Somethings wrong and strange. Good Luck with the splash and new set up!
Just an update on my potential problem. Everything
seems O.K. We took it easy all year until mid October
just in case. Did some speed runs and we actually
gained 74 RPM's and .50 MPH. Running at 4999 RPM
and 71.2 MPH with the modifications. Thank God we
caught it before a disaster hit. Engine fund is gone
however so it will be at least a year or two before I
get the money together for a HP increase.
I've seen stuff like that from high milage cars. Not too uncommon. Good thing you caught it. Roller rockers are a lot better than those stamped pos.
The stock stuff can pull through like that with high spring pressures and high rpm. Kinda strang that it is so isolated though.

I bet the guides got some wear out of that. :unhappy1:
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