What could have caused these......

[boyt911sc]

I was doing an engine teardown due to broken head studs for a 3.0 liter SC engine. During the process, I was caught by surprise to see unexpectedly these cylinders and pistons in this condition. What could have caused these on a running engine. Why are the abrasions so severe in these areas exposed to the engine oil? Any feedback, comment, remarks, etc. are appreciated. Thanks.



What should I check to prevent this from happening to the new set of P & C I'll be installing during the rebuild?

Tony

[HawgRyder]

My guess....Piston squirters not working....too much heat (engine overheated)....foreign material got in (bad air filter or no air filter).
All of above?
Bob

[nocarrier]

You might want to split the case..................

Pull number 5 rod and check the bearing.

[Steve@Rennsport]

Thats a lubrication failure. The engine might not had had sufficient oil in the system.

[tom1394racing]

Tony

After you remove the pistons, check the resistance of the connecting rods on the crank journals. They should all rotate freely under their own weight (as demonstrated in Wayne's book). They also should all have the same resistance.

If one or more do not move freely, it is an indication of a spun rod bearing which also is a consequence of poor lubrication.

You should probably split the case anyway and have the crank checked.

[boyt911sc]

Originally Posted by nocarrier

You might want to split the case..................

Pull number 5 rod and check the bearing.

This is how the engine looks like at the moment. Also awaiting the courage to order all the parts needed to complete the project from Pelicanparts (our gracious host). Thanks for your comments and suggestions.



Will perform the different suggestions. And thanks to all.

Tony

[lucittm]

Tony,
What kind of oil were you using and what was the change interval?

Mark

[docrodg]

Looks like a lubrication failure at least.

Pic looks like pistons only scored on thrust sides too. Possibly it was made worse by loose pistons? If the clearance is not right they will rock and score to heck. Hard to tell by pictures.

[Eagledriver]

Looks like some kind of contamination in the oil. Look at the grey stains on the crankshaft and inside the case. Maybe someone tried to use some teflon additive? Maybe some kind of lead contaminate from Aviation gas?

-Andy

[docrodg]

Originally Posted by Eagledriver

Looks like some kind of contamination in the oil. Look at the grey stains on the crankshaft and inside the case. Maybe someone tried to use some teflon additive? Maybe some kind of lead contaminate from Aviation gas?

-Andy

The case looks awfully clean... thought the gray there was from cleaner.

old age? your crank turns gray?

[WERK I]

Originally Posted by docrodg

.......................
old age? your crank turns gray?

LOL!!! That's choice!

If you look at the first post/pic, you'll see white carbon on one of the piston tops. I'm wondering if it is a fuel additive as well or one of those do-it-yourself fuel system cleaning kits? SeaFoam? or............Are you cleaning, spraying parts with some solvent (carb cleaner, brake cleaner) as you progress with the teardown? I agree with docrodg, the case looks too clean not to have been touched up with something. The white color of the pistons might be a result of a chemical reaction with the cleaner.

[Wayne 962]

Looks pretty suspect - I would do a *complete* overhaul on everything to ensure that the problem is fixed. I haven't seen the grey junk like this before, I agree it may be some type of oil contaminant. The bad news is that the grey crap is now in your oil pump, oil cooler, and oil lines. You need to do a full cleaning and/or replacement. I would think take apart the oil pump (make sure the gears go back *exactly* the same), and flush it. I would probably replace the cooler(s) at this point too, as they are near impossible to clean stuff like this out of (especially if you don't know what it is).

-Wayne

[boyt911sc]

Originally Posted by Wayne at Pelican Parts

Looks pretty suspect - I would do a *complete* overhaul on everything to ensure that the problem is fixed. I haven't seen the grey junk like this before, I agree it may be some type of oil contaminant. The bad news is that the grey crap is now in your oil pump, oil cooler, and oil lines. You need to do a full cleaning and/or replacement. I would think take apart the oil pump (make sure the gears go back *exactly* the same), and flush it. I would probably replace the cooler(s) at this point too, as they are near impossible to clean stuff like this out of (especially if you don't know what it is).

-Wayne

I bought the engine from a Pelican member 2 years ago. And he purchased the complete car from another member. All I knew about the motor was it had a broken head stud. So instead of buying an engine sitting on a pallet, it seemed wise at that time to buy a running motor like this one from someone you personally know. BTW, the motor is a '78 ROW.

Not only did it have two (2) broken head studs, it has two (2) different cams. Please see pictures.

Two (2) broken Dilavar cylinder head studs:



Left cam shaft:


Right cam shaft:


Notice the difference between the left and right cams? The right cam is from a later SC which has the same profile as with the other SC cams. I had better luck with my other engine that needed only cylinder head studs and a set of new rings. So even a PPI could not detect these kind of problems when buying an engine with unknown history and background.

Tony

[BURN-BROS]

Cams...

Not necessarily, the end of the cam can break off when torqing it. The fix is to machine it for the later bolt and washer setup. However, You typically modify both cams when this happens for symmetry.

Another cause for the piston scouring could be a overheat condition like a slung belt.

[patkeefe]

Tony:
Are there other broken rings on the pistons besides the one in the top picture on the left? (edit: Wait, maybe the top ring is still intact? Hard to tell without my glasses!) And, are those Alusil cylinders?
Pat

[boyt911sc]

Originally Posted by patkeefe

Tony:
Are there other broken rings on the pistons besides the one in the top picture on the left? (edit: Wait, maybe the top ring is still intact? Hard to tell without my glasses!) And, are those Alusil cylinders?
Pat

Pat,

All the rings in the engine were all intact. No missing pieces or broken rings found during the teardown. As a matter of fact, the engine was running OK before the teardown and no sign of smoke at all during the test (see attached picture).

Picture of the running motor with CIS gauge hooked up:


These are Alusil cylinders and will be disposed. Replacement Nikasil cylinders with pistons obtained from Tom Butler. Mismatched SC cams will be replaced too with 964 cams. New engine cooler and crankshaft bearing/journals need replacement too.

Any comment, suggestions, or recommendation to prevent such catastrophe from happening again is much appreciated. Thanks.

Tony

[patkeefe]

Tony:
Were the pistons the type which match with the Alusil cylinders (I think they are ferrocoated KS)? I would tend to agree regarding some sort of lubrication failure, but I would think there would be other evidence of lubrication failure somewhere else in the engine.
Pat

[smokintr6]

To offer my pure speculation on the gray material... my guess is that it is the oily metallic paste that is scuffing off the pistons and cylinders. Like I said, just a guess. It seems to be predominantly on the crank journals, rather than the whole case. It makes sense to me that as the crank throws reach up toward the cylinder base they would pick up some of the damaged cylinder material.

[nocarrier]

These pistons really look like they were seizing in the bore.

Were they the correct sizes for your cylinder?

Did the car overheat at one time or another?

[Rich76_911s]

Tony,

Any update on how the rebuild is going?

I feel downright awful about being the one who sold you this engine.

Rich