Broken rocker arm need advice

[LCOX]

My 911 developed an engine rattle yesterday. Today I checked the valve adjustment and found a broken intake rocker arm assembly on #5 cylinder.

Can this rocker arm be replaced with out removing the engine and taking off the cam box, timing chain etc?

[proporsche]

well? it can be replaced in about 30 minutes..but..there must be a reason why did it brake..can we see the picture...personally i have never seen broken rocker arm unless the valve hit the piston....
Is there a story to this before it broke?

Ivan

[boyt911sc]

Originally Posted by LCOX

My 911 developed an engine rattle yesterday. Today I checked the valve adjustment and found a broken intake rocker arm assembly on #5 cylinder.

Can this rocker arm be replaced with out removing the engine and taking off the cam box, timing chain etc?

LCOX,

The answer is YES. You can replace the rocker arm/s in situ.

Tony

[john walker's workshop]

Over-rev usually does it. Did one on my 930 when the clutch slipped under boost. 30 minutes later and a good leakdown, back on the road.

[LCOX]

Ivan l. Not aware of any issues that would cause this. I don't push the car at all or over rev it. Would a compression test show me any other issues in this #5 cylinder. I don't have a leak down tester.

[Trackrash]

As mentioned, I would be concerned about a bent valve. It might be a good idea to check your cam timing just to make sure you don't have some underlying issue.

There used to be spark plug adapters available that would hook to a compressor. With around 80 psi going into the cylinder at TDC, with the crank locked, a bad valve would be obvious.

[Jeff Burger]

how does the bushing look, was it getting oil from the drip bar? is the adjuster in tact or show signs of coming loose.

leak down test the cylinder and make sure you account for all the pieces before you replace it. I have seen them break on track/race cars with no other apparent damage . My buddies and I always carried a spare rocker arm and shaft when we went to the track.

[Jeff Higgins]

Porsche engineers designed the rocker arms in these motors, intentionally, to be the "weak link" and therefore the point of failure should the motor ever be over revved. They are meant to break before a valve gets bent. In light of that, it is extremely unlikely there is any other damage.

How many miles are on this motor? Could you have missed a gear at some point and unintentionally over revved it? What motor is it?

[3rd_gear_Ted]

FWIW@ the racetrack; a new rocker arm being put in is the usual course of action I've seen many times.

[boyt911sc]

Originally Posted by 3rd_gear_Ted

FWIW@ the racetrack; a new rocker arm being put in is the usual course of action I've seen many times.

Replacement of broken valve springs in situ at the cockpit during a track event is a common a course of action too. Replacing a rocker in situ is easy and more convenient than valve springs removal.

Tony

[Flojo]

Originally Posted by proporsche

well? it can be replaced in about 30 minutes..but..there must be a reason why did it brake..can we see the picture...personally i have never seen broken rocker arm unless the valve hit the piston....
Is there a story to this before it broke?

Ivan

A friends rockers... 8k+

[proporsche]

there you have it ..........reason ....8K

how was the rest of the engine ;-) ??
Ivan

[nene]

Damnnnnnn!!!!!

[Flojo]

Originally Posted by proporsche

how was the rest of the engine?

ist was oK, got rebuilt, runs beasty

[proporsche]

that is what i thought-got rebuild;-) somehow the 911 is not meant to be at 8k unless is specially made and set up...............

[3rd_gear_Ted]

Originally Posted by Flojo

A friends rockers... 8k+

Flo,
How do you say "moneyshift" in German or the equivalent???

[LCOX]

Here are a couple pictures. Sorry for the poor quality.
- The rocker arm broke in half. The other half of the arm is still stuck on the shaft.
- I lightly tapped on the part of the rocker arm that is still on the shaft but it wouldn't come off. The shaft will turn freely.
-Any idea on how to get the seized half off?. I guess you have to take the engine out to take off the cam box right?

[Trackrash]

Are you saying the shaft is stuck? You should be able to push it out with out removing or lowering the motor.

[pampadori]

You might need to use a socket that is slightly smaller in diameter than the rocker shaft and use it like piston and a large screwdriver to push against the socket. Apply leverage against the socket to push out the shaft.
Hopefully that makes sense.