rocker arm and cam lobe failure

[trond]

I just finished re-building 3.2SS with new cams and refurbished rockers. I ran engine 20 mins at 2000 rpm on mineral straight 30 and then changed to M1 5-50 (A40). Then took it for a drive an hour and removed valve covers to check. There I found #6 exhaust side rocker arm damaged and also corresponding cam lobe. All others were fine. As a part of the post mortem I checked flow pattern from oil splash tubes and all nozzles are spraying as they should. What may have caused this; 1) a problem with the cam or 2) a problem with the rocker arm ? Or can there be any other reasons ?

As a note the same happened on previous rebuild except it was #4 inlet. Same cam supplier but new OEM rockers

What to do on my next attempt ?

[r lane]

I would see this years ago when the chain ramps were a rubber type material. They would disintegrate and clog up the spray bars. Depressing. Bob

[trond]

yes depressing. Worse even. I tore down the previous fiasco inn November and the process of getting parts, getting machining done, the time and the money; it has been a long uphill struggle And now back to start and repeat. Same as two years ago. On spray bars; they are spraying as they should. I checked and rechecked both when assembling and when tearing down. And there is no plugging. never was. What is the problem here do you think ? I am thinking hardening of either rocker arm or cam. But hard to imagine it happening on both my two recent rebuilds. What else can be causing this ? This is no longer a hobby. It is a war


What happens to the debris. Will it end in oil filter or will it damage bearings/pump and other? I can not spot any anomalies in the cam housing bores for the cam and think debris pumped back by scavenge pump, to oil tank should be caught by oil filter. And hopefully not damage oil pump

[Richey]

I know that new rocker arms need to be resurfaced to be aligned with the cam . There was a time
when some new rocker arms were not any good . I think it is better to have good original used rockers resurfaced , but you need to find someone that does a proper job .

[targa72e]

do you have a picture of the adjuster end of the rocker. Wondering if its OE or aftermarket.

john

[snbush67]

Did you take pictures of, or do you recall, the position of the rocker shaft before you took it out. The wear on the rocker face looks like the rocker arm was not pivoting. Possibly the rocker shaft wasn't aligned correctly (shaft flush with the outside of the thinner boss) when torqued. A stuck rocker also may have resulted in the valve lash being out of adjustment.

[Magyar Kiwi]

Hi
I would suggest that the damage is consistent with a blocked hole in the spray bar.
Suggest firstly inspect all the holes using a small mirror for any blockage.
(In my case I was able to see a piece of debris plugging the hole that was meant to be lubricating the damaged rocker.)
Second, remove both spray bars for inspection from both ends and cleaning.
Cheers

[trond]

yes, I agree it looks like binding rocker could have been the issue, but I checked for free travel especially on assembly (have seen it happen before) and also when disassembling. No rockers were binding. I always adjust with feeler blade, then always wiggle by hand to check and yes I have caught issue on assembly caused by shaft not in correct posistion. I still agree with you based on the looks.,

Also on assembly the spray bar was replaced. And I checked spray pattern with spirits from a pressurized bottle. Perfect spray both on assembly and also on disassembly

Originally Posted by snbush67

Did you take pictures of, or do you recall, the position of the rocker shaft before you took it out. The wear on the rocker face looks like the rocker arm was not pivoting. Possibly the rocker shaft wasn't aligned correctly (shaft flush with the outside of the thinner boss) when torqued. A stuck rocker also may have resulted in the valve lash being out of adjustment.

[trond]

I used checked/resurfaced OE rockers straight from a well known machine shop. After re-surfacing; is it then the pad hardened ? to what hardness ? I plan to have mine checked to see if it is a hardness issue but need to know what rockwell c or maybe brinell it should be...?

Originally Posted by Richey

I know that new rocker arms need to be resurfaced to be aligned with the cam . There was a time
when some new rocker arms were not any good . I think it is better to have good original used rockers resurfaced , but you need to find someone that does a proper job .

[Henry Schmidt]

Given the large number of failures associated with "new" rockers we've chosen to avoid their use.
At the present we are testing some new forged rockers and so far they look pretty good.
In our rocker rebuild process, we've chosen to resurface the face (to insure bushing to pad parallelity ), dry film the pad and Cryo treat the entire rocker. Over the years, we've found great benefits associated with Cryo and cast materials.

[trond]

what would you say then is a safe way with rockers ? On previous lobe wipeout I had 12 new OEM on new cam. On this lobe wipeout I had 12 rockers checked for alignment and resurfaced. Eliminating oil supply as a cause I see two common factors; same cam supplier and I as mechanic

Originally Posted by Henry Schmidt

Given the large number of failures associated with "new" rockers we've chosen to avoid their use.
At the present we are testing some new forged rockers and so far they look pretty good.
In our rocker rebuild process, we've chosen to resurface the face (to insure bushing to pad parallelity ), dry film the pad and Cryo treat the entire rocker. Over the years, we've found great benefits associated with Cryo and cast materials.

[Henry Schmidt]

Originally Posted by trond

what would you say then is a safe way with rockers ? On previous lobe wipeout I had 12 new OEM on new cam. On this lobe wipeout I had 12 rockers checked for alignment and resurfaced. Eliminating oil supply as a cause I see two common factors; same cam supplier and I as mechanic

I can't speak intelligently about what caused your issue.
My guess is rockers are at fault. Compatible materials and properly ground faces are critical.

[trond]

I checked contact patch and they were all perfect. I was thinking cam issue as the same happened on previous rebuild with same cam supplier & new OE rockers. But hard to imagine such damage in just 1 hour caused by hardness anomalies so need to investigate oiling further... maybe crank engine without valve covers and check how much of a mess I get.

Meanwhile I need to start sourcing new parts. Cams from another vendor to eliminate that question, and rockers from I don't know where. I would be happy with any advice on rockers... can not take any risk of a 3rd disaster

Originally Posted by Henry Schmidt

I can't speak intelligently about what caused your issue.
My guess is rockers are at fault. Compatible materials and properly ground faces are critical.

[Magyar Kiwi]

Hi
I would suggest that if it was a cams or rockers manufacturing issue you would have had 12 rocker failures or 11 rockers with signs of impending failure.
Limited or no oil supply from one spray hole is sure to cause a single rocker/lobe failure.

In my engine I identified the problem when adjusting the valve clearances and was able to repair by removing and cleaning the spray tube and fitting a replacement rocker.

Porsches later removal of the engine mounted oil cooler and fitting of a (pressure side ) oil filter has some merit.

Cheers

[trond]

agree. But HOW can there be an oiling issue when I have good oil pressure and no plugging in the spray tube ? (new tube and bench tested they all spray). No lack of oil when I took off the valve covers (after draining engine). But there was one more rocker/lobe that had scuff marks on same cyl bank... All others and opposite bank looked good as new

Originally Posted by Magyar Kiwi

Hi
I would suggest that if it was a cams or rockers manufacturing issue you would have had 12 rocker failures or 11 rockers with signs of impending failure.
Limited or no oil supply from one spray hole is sure to cause a single rocker/lobe failure.

In my engine I identified the problem when adjusting the valve clearances and was able to repair by removing and cleaning the spray tube and fitting a replacement rocker.

Porsches later removal of the engine mounted oil cooler and fitting of a (pressure side ) oil filter has some merit.

Cheers

[trond]

looking at oil circulation diagram it appears all returns from engine go through the oil filter. What are chances for metal debris from cam lobe goes back into engine ? I have not seen any damage in cam bearing surfaces. Should I still split the engine ? Enough to inspect rod end bearings and if good then rebuild. Or split engine. After this repeat fiasco I don't feel certain about anything

[Classic 911]

Start the engine for a few seconds without the upper cam cover to check spray pattern and amount, not just crank it. Then you will see what actually happens.

Do you have original cam covers?
Some aftermarket ones can alter / change the direction of the upwards spray pattern because the oil hits not a flat surface as on the original ones but hits an angle.


Sent from my iPhone using Tapatalk

[Henry Schmidt]

There are a number of rockers on the market including some you would get from the dealer (OE) that are just low quality.
We are also seeing "re-manufactured" rockers with less than stellar technique in the grinding process.
At this point, I'm still thinking rockers not cams or oil delivery.
All of the images below were offered by John @ DRC

[MoreGAS]

You might weigh all the rockers, and if all the same type, get an average and see how much cast iron material is missing by noting the weight differences. You didn't share which rockers you are starting with. That debris is floating in your engine as well as what is missing off the camshaft lobe, it is very abrasive, like cast iron lapping paste.
We very recently pulled apart a clients extremely costly engine, where someone chose aftermarket "trick"rockers(Brand remaining nameless) , DLC coatedpads ... well all the DLC coating wore off in no time at all, and the rockers began eating the cams, one rocker was missing 7 grams of material and the cam a whole bunch more not determined but it had to be welded-up to repair. Long story short , I had to advise we pull the engine apart with all that debris circulating in the oil . ALL rod bearing looked critically wounded and one was flopping in the rod cap with zero press or retention as all crush was gone and I don't know how it didn't over lap the other 1/2. If car was not towed to our shop, it would have tossed a rod straight out the top of the new case I am convinced. It also damaged the Nitriding on the crank on a couple journals.

Realize also that changing cam brands may do nothing for you as I believe from talking to the Porsche cam providers, all the billet blanks come from the same source. Billets are less prone to these issues vs. the hardwelds and regrinds, we never take that path any longer.

Who resurfaced you rockers and rebushed them? We have seen the new OEM rockers recently, not run parallel to the bushing bores, and not touch flat on the pads to lobes, Brand new. They also are senselessly heavy. Pass on those.

BeST

Kevin
GAS Motorsport

[trond]

thanks a lot. Much appreciated. I am now in the process of splitting the block. From oil flow diagram all debris is pumped back to oil tank, via oil filter. Yet I found no magnetic debris in oil filter. The failed cams (same brand as previous failed cams) were both welded up cams. My rockers were all rebushed and reground by a reputed machine shop, and they all had perfect contact with the cam. I checked this especially. The failed rocker is marked DP1120.

Question on rocker arms; is the pad surface hardened or not ?

Originally Posted by MoreGAS

You might weigh all the rockers, and if all the same type, get an average and see how much cast iron material is missing by noting the weight differences. You didn't share which rockers you are starting with. That debris is floating in your engine as well as what is missing off the camshaft lobe, it is very abrasive, like cast iron lapping paste.
We very recently pulled apart a clients extremely costly engine, where someone chose aftermarket "trick"rockers(Brand remaining nameless) , DLC coatedpads ... well all the DLC coating wore off in no time at all, and the rockers began eating the cams, one rocker was missing 7 grams of material and the cam a whole bunch more not determined but it had to be welded-up to repair. Long story short , I had to advise we pull the engine apart with all that debris circulating in the oil . ALL rod bearing looked critically wounded and one was flopping in the rod cap with zero press or retention as all crush was gone and I don't know how it didn't over lap the other 1/2. If car was not towed to our shop, it would have tossed a rod straight out the top of the new case I am convinced. It also damaged the Nitriding on the crank on a couple journals.

Realize also that changing cam brands may do nothing for you as I believe from talking to the Porsche cam providers, all the billet blanks come from the same source. Billets are less prone to these issues vs. the hardwelds and regrinds, we never take that path any longer.

Who resurfaced you rockers and rebushed them? We have seen the new OEM rockers recently, not run parallel to the bushing bores, and not touch flat on the pads to lobes, Brand new. They also are senselessly heavy. Pass on those.

BeST

Kevin
GAS Motorsport