M117 rounded cam lobe, what are my options?
 

Well, finished the guides in the 380 that has w/ the M117 swap and noticed one of the intake lobes on the drivers bank is wiped. :(

Can the cam and the rocker be replaced alone?

i would think yes. probably replacing all the rockers would be recommended in case some are worn, but i would think you would be ok to just change the cam and one rocker.

tom w

Cool. I have a complete spare Euro 500 motor that needs to be rebuilt, so I may steal the cams from it. :)

Figure I'd replace them in pairs. I could also do the rockers too.

get new rockers while you are doing it..

Or, we can send you a set of AMG spec cams;-)

Setting the lash can be a bit of a PITA w/o a large selection of spacers/shims.

Jonathan

I should use new rockers as opposed to the used ones on my spare motor? :confused:

Another thing I noticed, which I believe attributed to the lobe issue, this locknut at the base of the head was FINGER tight! :eek:

Yes, I would use new rockers. You can get away w/ the old ones as long as you keep them w/ their respective lobe.

They do loosen w/ age/time..not uncommon.

Jonathan

I assume there are torque specs for that lower bolt?

Can you elaborate on the shims required?

I'll need to dig to fine the torque #'s but I remeber it not being terribly tight..

There are a large selection of shims that go b/w the rocker and the lifter. It's critical that you get said spacing correct. There is a special tool used, or you can get by w/ a set of feeler gauges.

Typing out the procedure is a bit long winded..

Jonathan

Is the procedure in the FSM?

might be... it's in my printed manual..

Jonathan

Okay, I'll have to go through the disc and have a peek.

i thought that motor has hydraulic lash adjusters.

what are shims for?

tom w

Swap the cams from your spare engine. Swap the rockers, too. Make SURE to match the rockers (exhaust on cyl #1 goes back on exhaust on cyl #2, etc). Otherwise, you'll need all new rockers.

And the m117's older than 4.5's do have hydraulic adjusters, so I'm curious just like Tom W as to what you'd need shims for...

i think tomguy meant newer than 4.5s right?

tom w

I believe he did..however, they Still have shims even w/ the hydraulic lifters. I'll post a pic or two from the EPC if need be later on.


Jonathan

really?

where do they go? and what purpose do they serve?

tom w

They go here b/w the spring retainer and the rocker arm as can be seen in the attached images (#44)

You need to set the static spacing when assembling these cams, the hyd. compensator can only do but so much.

Jonathan

Speaking of wiped cams.....

At lleast three years ago, ZDDP, a zinc compound, was greatly reduced in on-road engine oils. The reason was aledgedly, the ZDDP was causing CatCons to fail.

ZDDP, Zinc, is a major wear inhibitor in cams/lifters.

On the racing scene, just about everybody has switched to roller cams now that all of their flat tappet cams have been destroyed because of this removal of a critical wear reducer. Those that can't afford to buy roller kits are using off-road only racing oil. Regular Racing Oil has had its ZDDP removed as well. "OFF ROAD ONLY" racing oil is the only gas engine oil that still contains the normal compliment of ZDDP. An alternative is Diesel engine oil, such as Delvac, Rotella, Dello. etc. I now run Rotella T in my engines, other than the 97 C280 and the 2001 E430, which get Mobile1.

FYI, the new diesel oils have had their ZDDP Greatly reduced as of 2007 with the advent of the new diesels. You can still get the old style but you have to buy it in a drum.

I'm using GM's cam/lifter additive that brings the levels of ZDDP etc back to as they used to be.

Jonathan

Now that I did not hear.

What is the additive called / part number, and how much is needed per gallon of oil?

But with all the oil I use, I may as well buy a drum. The problem is moving it! fwiw - 3 14 quart pans, plus oil coolers, and lines. About 17 quarts an engine, times 3.

GM Part # 12345501. Only available in 4oz containers. I use 1 & 1/2 containers per change (given we run a good bit more oil then domestic cars).

Jonathan