Cam Journals

[3p141592654]

The 7M cam journals are coated with a soft babbit like mystery material. My intake cam looks perfect, with no visible wear in the head and the babbit material is fully intact.

The exhaust is a different story. The first 2 journals from the front (where the cam oil feed is located) look perfect. The last 5 have the mystery material worn off of the cam journal and the head shows a faint ring in each bearing (about the width and location of the oil feed hole in the camshaft journal.

I will plastigage them once I pull the valves out, but I suspect they are over the limit with the mystery material gone. One obvious solution is to buy a new exhaust cam. Has anyone been able to workaround this problem and get their clearances back in spec?

 

[IJ.]

Not sure if it's babbit material more than likely it's the surface left by niteriding.

 

[aljordan]

I know that material will come off if you polish the journals. Its very much like babbit whatever it is.

 

[3p141592654]

Not sure if it's babbit material more than likely it's the surface left by niteriding.

Whatever it is, it is very soft. A fingernail will make a dent in it. I've never seen anything like it on other cars.

 

[Yellow 13]

You have any pics cause I just cleaned my cams today and have no clue what everyones talking about...

 

[3p141592654]

Okay here are a few pics.

 

[GrimJack]

From Reg's tech tips:

You should use good assembly oil or lubriplate grease on the bearings. Also note that the bearing journals on the 7M cams are coated with a soft bearing material that is easy to scratch and mark up. Most 7M's will have these scratch marks when you pull the engine apart. What you may see are scratch marks on the journal that look like a badly galled up bearing journal. This may look bad but is normal and will not hurt anything. Do not attempt to clean the surface of the cam journal. Just inspect it for bad cuts or grooves in the journal that is into the cam material not just marks in the soft journal coating material.

 

[3p141592654]

Thanks Grim. I have read that post from Reg. There has also been some discussion on the matter recently on the supras.com mailing list. I also saw mention of it on the toysport web site, their advice was to polish the stuff off.

The problem is that the soft coating has worn off of the cam journals, and that makes the journal clearances go out of spec on the rear most bearings (max per TSRM is .005" and with the mystery coating removed you typically see .006"). The only way to get back in spec is to either replate the coating (?), buy new cams, or lap the bearing caps.

 

[GrimJack]

No problem! I realize that the quote wasn't entirely on topic, as the material is gone, just figured that bit of info would be useful for future reference when people were searching.

 

[Yellow 13]

I just cleaned some cams from my supra that have 266,000 miles on it (original cams) and I see no trace of this mystery fluid stuff on them at all. The car ran fine before so I dont think its a big deal as long as you oil them.

 

[3p141592654]

Did you measure the clearances of the journals? Its pretty weird that the toyota spec is .005", half of the valve clearance spec and huge for such a small journal! I think Toyota knew from the start that they had a problem here.