Cast Iron Past Service Wear Limits and Oil

[CCI]

Shovelhead, unknown miles, over 20 years since last top end, with the heads off you can rattle the pistons around in the cylinder bore. No cylinder wall scoring, slight discernible cross-hatch remaining, rods are clearly not bent or twisted, motor looks and sounds great, it is just flat wore out.

Been running Rev-Tech 20w-60 which seemed to be an improvement over 20w-50, but the motor got really loud, by the end of last summer I thought it was rebuild time for sure.

Thought it couldn't hurt to try, drained out the black and nasty 20-w60 and put in 4 quarts of Kendal straight SAE 50 in. The difference is amazing. Ring seal is good, minimal smoking, valve train and piston slap quieted right down, I think I'll see if she can go another year.

Any ideas why?

Also, how come some aircraft oils but not others result in accelerated cam wear in old Harleys? AeroShell seemed to work pretty good, others, not so much. Lost the cam lobes in no time.

 

[Cujet]

Aircraft engine oil does not contain ZDDP. Some brands contain other forms of additives, that may or may not help.

For example, I am using Aeroshell 15W-50 in my small fleet of aircraft. It's working out well, with no abnormal wear. I also make sure to manage oil temperatures carefully and change oil often, about every 25 hours.

Heavy oil is often a good solution for old engines. Especially air cooled engines that can have 500 degree cylinder head temperatures and 300+ degree cylinder bore temperatures.

 

[CCI]

Thanks -- I had to Google ZDDP, makes sense. These motors have roller tappets and fairly high spring pressure.

True about the temperature -- the old gal gets good and hot in the summer after a couple of hours at 75 mph+ in 90F+ ambient.

I just built a stock shovelhead, intentionally just a little to the loose side on everything but the crank, broke it in on the 20w-60, changed the oil at 50 and am about to do the 500 mile oil change this weekend.

Thinking seriously about Mobil 1 20w-50 synthetic for Motorcycles -- their advertised "V-Twin" formula. Seemed to work real well in a stroker I built, but no chance to evaluate it over the long term.

Any thoughts on the Mobil 1 for old iron renewed? She doesn't leak a bit. Strange but true.

 

[440Magnum]

Aero engine oils are "ashless dispersant" additive packages. A lot of dispersant and anti-wear additives create combustion chamber deposits ("ash") that can foul spark plugs- and that's a BAD (potentially lethal, obviously) thing on an aero engine. So the engines are built to run with minimal additives- not nearly enough for most terrestrial-based engines.

 

[Ramblejam]

SAE 60 is appropriate here.

Amazon has VR1 for $35/six quarts.
http://amzn.com/B00DJ4FOEG

 

[ragtoplvr]

if you can still see the honing marks there is minimal bore wear.

The pistons may be forged, given the high temp, the may be supposed to be fitted so loose as too rattle.

Or they may have worn and collapsed. This was more common years ago newer alloys can be fitted tighter.

The 50 works because when engine is cold there is a lot of clearance, and the oil is much thicker than a 20W60. Then when hot, the piston expands, and less clearance, so the hot 50 is fine.

Rod

 

[BigCahuna]

Originally Posted By: Ramblejam
SAE 60 is appropriate here.

Amazon has VR1 for $35/six quarts.
http://amzn.com/B00DJ4FOEG
The $12.92 price of shipping kills the deal from Amazon.You can more then likely do better locally.,,

 

[Ramblejam]

Originally Posted By: BigCahuna
Originally Posted By: Ramblejam
SAE 60 is appropriate here.

Amazon has VR1 for $35/six quarts.
http://amzn.com/B00DJ4FOEG
The $12.92 price of shipping kills the deal from Amazon.You can more then likely do better locally.,,


It's a Prime item, so free two-day shipping for me. With everyone that has it nowadays, you're bound to know someone that'll get it, or a family member that'll put you on their account...

 

[BigCahuna]

Actually it's available at the local auto parts store for about the same price. Just pick it up and go.,,