bad rocker?

slyguy · 08:34 AM

Just putting the motor back together, assembling the rockers shafts and doing the valves when I came across this... Can anyone tell me whats responsible for a wear pattern like this? Unfortunately I don't know which cylinder it came off of. Are other rockers at risk? Can it be salvaged or reconditioned or replaced altogether? Anything I need to look at? Thought i needed a valve adjust, this was a total suprise.... Thanks! Tom

slyguy · 08-10-2009, 02:07 PM

further inspection shows the lubricating holes in the bushing and rocker are no longer aligned... no oil to the rocker shaft. Time for new rockers or simply bad juju?

JFairman · 08-10-2009, 02:20 PM

Thats from lack of oil lubrication. You can see the heat discoloration on the metal. It must have been making noise for a while with that much damage and wear.

I've seen that before and it usually means the cam spray bar hole is clogged at that cylinder with burnt oil carbon particals from the turbo.

You have a big job ahead of you if thats the case because it means removing the cam spray bars from the cam towers to get them perfectly clean.

There's no way the cam lobe that was running that rocker is in good condtition, and the cam will need to be removed and repaired or replaced.
That rocker arm and shaft are trash.

You should also change the oil frequently for a couple few changes to try and rinse out all the metal dust thats in the oil system now.

slyguy · 08-10-2009, 02:39 PM

man.... I just got done timing the cams! the bushing was clearly starved of oil. Well the motor is closer to being apart than together...any suggestions on best way to check/clean the spray bars?

JFairman · 08-10-2009, 03:03 PM

It's been described before with pictures and everything so try a search.

There is an aluminum plug pressed into each end of the cam tower and a 17mm wrench size plug with a pin on the end that holds it in place.

The 17mm plug is in the same position as the oil line banjo fitting but at the other end of the cam tower.

The 10mm aluminum plugs are at the ends of the spray bar on the outer ends of the cam tower behind the chain cases and also at the other end. You drill a 1/8" hole in them, screw a self tapping screw into the hole and pry it out with needle nose pliers or dikes. Then use a pipe brush and carb cleaner or brake clean to get the junk out or buy new spray bars. They aren't much.

You can buy new aluminum plugs for the cam towers from Porsche and pound them in with a drift punch and a smear of aviation sealer on them or you can tap the holes with 10mm threads and screw in allen head plugs with thread sealant which is a nicer way of doing it.

I see you have a zork... maybe you couldn't hear all the rocker arm clatter over that.
I have the same modifications as you on my engine and the K27 HF turbos run alot hotter than standard factory K27 turbos and if you are not using synthetic oil they will coke the oil no matter what you do to prevent it.
I know that from experience because I have a 30 micron high flow oil filter in my turbo scavenge oil line after the pump and I've see it and there was a lot of it.
Then I put a K27 7006 on and with no changes in how I drive or idle the car afterwards... there were no carbon particals in my scavenge line oil filter.

The oil from the turbo goes back to the oil tank unfiltered in a 930 so all those carbon particals get pumped right into the oil galley in the engine and end up in the bearings and cam spray bars.... stupidest thing Porsche ever did.

DonE · 08-10-2009, 05:02 PM

Make sure you check the cam too. That is some REAL bad scoring. It is quite possible you have a bad rocker too. Some guys advertise they can reface these things, but they don't quite get them hardened well enough. Spend the extra money and get a new one for a replacement. If you are real annal about it, remove all of them, check their specs to make sure they all have identical distances from centerline to their faces. It makes a difference....

slyguy · 08-10-2009, 06:06 PM

New rockers on the way, gonna pull the cams and spray bars tomorrow, stay tuned folks!

slyguy · 07:52 AM

Quote:

Originally Posted by JFairman

There's no way the cam lobe that was running that rocker is in good condtition, and the cam will need to be removed and repaired or replaced.
That rocker arm and shaft are trash.

[QUOTE=DonE;4828479]Make sure you check the cam too. That is some REAL bad scoring. QUOTE]

Right you are...smoked the cam and another rocker as well. Looks like spray bar on number 6 is culprit... Can this be re-ground and can a single be done or should they be ground as a pair. Camgrinder suggestions? (these are stamped with elgin logo) It's dug into the lobe about .4 mm. Do the lobes in the last photo look suspect as well?

Miguel Antonett · 08-11-2009, 08:30 AM

Good catch!

JFairman · 08-11-2009, 08:48 AM

Those cams can be repaired. I'd call Elgin and ask them about it first since it's their grind.
They don't look like they were hard welded to get the higher lift and duration of 964 cams before they were ground. They may have been ground from new billets or the grinding may have been from the base circle of stock 930 cams to get the 964 grind if thats what they are. If so, I don't think a camgrinder would want to remove any more metal from the base circle so they would probably weld up the lobes and regrind them..

Webcam could do a good job of repairing them by hardwelding the damaged lobes and regrinding them.

You should probably at least remove your oil tank and clean it out and do some frequent oil changes to rinse out the stuff that was worn off your cams and rockers.
The valve guides were also starved of oil so they are probably worn too. Especially the exhaust valve guides.

mark houghton · 08-11-2009, 09:20 AM

Quote:

Originally Posted by JFairman

Thats from lack of oil lubrication. You can see the heat discoloration on the metal. It must have been making noise for a while with that much damage and wear.

I've seen that before and it usually means the cam spray bar hole is clogged at that cylinder with burnt oil carbon particals from the turbo.

You have a big job ahead of you if thats the case because it means removing the cam spray bars from the cam towers to get them perfectly clean.

There's no way the cam lobe that was running that rocker is in good condtition, and the cam will need to be removed and repaired or replaced.
That rocker arm and shaft are trash.

You should also change the oil frequently for a couple few changes to try and rinse out all the metal dust thats in the oil system now.

They make this engine flush crap where you add a quart of what's basically a petroleum solvent to your crankcase and run it at idle for 10 minutes prior to draining the oil for an oil change. Supposed to dissolve gum and goo, clean out oil pathways, etc. I used to use it many moons ago on V8 engines but have never considered it for my 930. Might just be snake oil, but also might not hurt doing this at oil changes...or may be dangerous for air cooled engines.

JFairman · 08-11-2009, 10:49 AM

Quote:

Originally Posted by mark houghton

They make this engine flush crap where you add a quart of what's basically a petroleum solvent to your crankcase and run it at idle for 10 minutes prior to draining the oil for an oil change. Supposed to dissolve gum and goo, clean out oil pathways, etc. I used to use it many moons ago on V8 engines but have never considered it for my 930. Might just be snake oil, but also might not hurt doing this at oil changes...or may be dangerous for air cooled engines.

That stuff is OK for cleaning sludge and varnish out of the check valves in the hydraulic lifters in American V8s that havn't had regular oil changes but I wouldn't put it in a 911 motor.

It might loosen up more crap and clog the cam spray bar holes and piston squirters even worse, and it's alot of extra work to get all the solvent contaminated oil out of all the hoses, external thermostat, and oil coolers.

So some of it would be left behind to mix with the fresh oil going in and that can't be good.

slyguy · 08-11-2009, 03:30 PM

from the right side spray bar, lodged in the spray openings.

David · David's Garage

Damn!!! Now I'm nervous!

slyguy · 08-11-2009, 04:43 PM

Yeah, me too. Especially since I just pulled the left side and just as much came out. could be a battle cry for the synthetic oils. threaded plugs are on the way and should make checking and cleaning of the spray bars fairly simple maintinence. Only going to tap the backs as the fronts would require chain housing/cam removal

DonE · 08-11-2009, 04:54 PM

Based on my experience in having cams re-ground - DON'T. Spend a couple extra bucks and get a set made from blanks (billet). Also, be VERY picky on who you choose as a supplier. We will spend hours debating which is the best method for setting valve lash, but the vast majority of us don't even know if our cams are even in spec. I've lost 2 sets of valves and valve guides because of a poor regrinding job. Don't short-change yourself on the heart of the motor.

PS - consider a custom grind too.

slyguy · 08-12-2009, 01:25 PM

Quote:

Originally Posted by DonE

Based on my experience in having cams re-ground - DON'T. Spend a couple extra bucks and get a set made from blanks (billet). Also, be VERY picky on who you choose as a supplier. We will spend hours debating which is the best method for setting valve lash, but the vast majority of us don't even know if our cams are even in spec. I've lost 2 sets of valves and valve guides because of a poor regrinding job. Don't short-change yourself on the heart of the motor.

PS - consider a custom grind too.

Thanks for the heads up here Don. I know you've spent tons of time researching these finer points and your experience and insights are not lost on me at all. I'll be brushing up against the limits of the induction when I'm through, what could I expect to gain here? Would it be worth getting into a custom grind given the limitations of the CIS? I have a sneaking suspicion I know where this is going (really not planning an EFI conversion, really I'm not...) Who do you like as a supplier and grinder? Cheers!
Tom

JFairman · 08-12-2009, 01:40 PM

There are alot of plus or minus opinions on Webcam hardwelded cams.
The plus sides are they can repair or regrind another profile on just about any cam, including rare no longer available cams as long as they are still straight.
The other plus is the welding process also really hardens the steel.

The down side is there can be air pockets in the steel after welding and there have been time the welds have come apart or little chunks have come off.

Maybe it all depends on who actually does the welding and if it was done on a monday morning or a friday...

Anyway, It looks like the only way you can repair your cam is hard welding to build up the nose of the cam and regrinding it.
Repairng your cams will probably be about $250 less than buying new cams.

There... some more worthless hearsay for you digest.
Call Laurie at Webcam, she runs the place.

I have Webcam 964 hardwelded cams in my 930 and so far they are working great. They are grind #40 at Webcam.

Email her the pics you have, and listen to her opinion.

DonE · 08-12-2009, 06:04 PM

Quote:

Originally Posted by slyguy

Thanks for the heads up here Don. I know you've spent tons of time researching these finer points and your experience and insights are not lost on me at all. I'll be brushing up against the limits of the induction when I'm through, what could I expect to gain here? Would it be worth getting into a custom grind given the limitations of the CIS? I have a sneaking suspicion I know where this is going (really not planning an EFI conversion, really I'm not...) Who do you like as a supplier and grinder? Cheers!
Tom

Performance Developments and Jerry Woods can give you an idea on what grind they recommend for CIS for custom (if they even recommend custom). It is worth the phone calls. If you want to buy off the shelf, call Webb or Elgin - no others.