Valve train sound from "dry" rocker foot

[JoeMag]

Heard an interesting "wonking" type sound coming from right side of motor after start and running for a while during idle tuning. Had just changed heads, intake and injectors.

Turning the motor over by hand there was a pinging type sound at certain points. Took off upper valve cover and discovered a rocker (#6) making the sound (touched it while turning and could feel the ping). Took off and rocker and found the foot/top of valve dry and dirty. Appears sound was coming from foot moving across top of valve and dragging. Cleaned up with 1200 grit and found foot worn.

Motor is 993 with solid rockers. Wondering if I should remove some of the baffling on the valve cover to allow more oil splatter up to top of rocker. I've ran this motor for a while (70 hrs) and have not seen this before (or at least noticed it). You can see from top of valve pic there is virtually no oil being splashed up there (granted I was only idling motor and maybe got up to 2k rpm max for probably 30-45 minutes)

foot as taken out of motor


after clean up with 1200 grit

[Classic 911]

Following


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[Black 993]

I can only share my experience, with 12K miles on a 993 motor with mechanical rocker conversion and stock plastic valve covers. No problem like this of any kind.

[JoeMag]

...well, after pondering this for a few days, below might be possible solution.

Since 993 rocker shafts are pressure fed for hydraulic rockers I think I can use that. When putting on solid rockers, you do not need oiling hole in rocker bushings due to oil feed. I think I can just drill a hole pointing toward valve end of rocker. No doubt will get oil in the foot / top of valve area. Hole in rocker shaft is 3mm, and drill bit I have that's long enough to drill relatively straight is 1.5mm.

Also, just noticed recent post about these elephant foots being wear items. Since had valve cover off inspected closely the other two. Both had some oil at foot/valve interface. Did notice one having small imperfection on surface (like cleaned up dry one above). Think I'm just going to replace them.

[stownsen914]

Do they all look like that? I'm more familiar with the oiling for pre-964 cam towers, but there should be pressurized oiling there, not just passive splash oiling. Is that not the case on the 964 and later type?

[JoeMag]

Originally Posted by stownsen914

Do they all look like that? I'm more familiar with the oiling for pre-964 cam towers, but there should be pressurized oiling there, not just passive splash oiling. Is that not the case on the 964 and later type?

If you mean the other rockers... No. Pic is #6 intake, checked 4 and 5 intake and they were fine, though there was really no oil on top of retainer, but oil at interface of foot and valve. Did not check exh or 1,2,3 intakes yet.

[JoeMag]

...well we have a foot and a half of snow now and it's 20F outside so figured I'd play a little more.

Have a few rockers setup for non-pressure fed rocker shafts, so tried two on the motor. These have the standard oil cup/hole through bushing (appx 2.5mm) on top and bottom of rocker.

Comparing before and after pics there is definitely oil getting up top (as expected). This was after about 3mins of idle little elevated at 1500 to 1750 rpm.

area before test. rocker was bone dry except for assembly lube on foot and cam follower pad.


rocker after test. covered with oil and foot clearly has oil on it. though there's no oil on top of valve. it must be dripping down rocker arm.


another foot that's getting worn (#1 intake). note some gouges in surface

[JoeMag]

after 3min idle with holed rocker.

[stownsen914]

Looks like that made a difference