Redline 5w30, 1500 miles, 1985 Corvette track car

[A_Harman]

From Polaris Labs.
Wear Metals.
(Element: M1 blend 2013 sample, RL 5w30 2014 sample)
Fe: 34, 58
Al: 4, 9
Cu: 13, 17
Pb: 22, 107
Sn: 4, 11

Contaminant Metals.
Si: 49, 38
Na: 15, 12
K: 3, 3

Multi-source Metals:
Mo: 81, 480
B: 69, 77

Additive Metals.
Mg: 252, 44
Ca: 1862, 2528
P: 801, 1104
Zn: 935, 1216

Fuel Dilution: 2.5%, Soot: Water:
KV100 = 10.6, 10.3
TBN = 6.45, 5.67
Oxidation = 11, 97
Nitration = 10, 10

Polaris Comments: Suggest monitoring oil pressure closely between samples. Lube oxidation may be increasing. Bearing metal is at a significant level. Silicon is at a moderate level.

All wear metals are up in this oil sample, especially Lead. Tin is also up, so I guess that bearing overlay is wearing. Copper isn't up by a similar proportion, so maybe the bearing lining is not seriously worn. I get a kick out of Polaris' comment to monitor oil pressure. Lap average oil pressure hasn't changed on this engine in the 4 years I've been logging it.

It could be that I've found the limit of acceptable oil temperature in this engine. It was running a steady 315F at Daytona for about 15 minutes at a time. The previous maximum temperature the car had ever seen was 280F on shorter road courses.

The engine had a bad episode at Daytona last December when an exhaust rocker arm stud broke. I fixed it and ran two more days, and the engine performed flawlessly. But I suppose that some debris from the failure could be adding to the Iron reading.

Oil viscosity held up well. Virgin RL 5w30 is 10.6, and it only dropped to 10.3. The oxidation reading of 91 doesn't worry me; virgin for Redline is 108, according to a reading I had done a couple of years ago.

I thought the oil sample was going to have issues when I pulled the drain plug, and it looked like a little Brillo pad. Prudence would dictate that I drop the pan and pull some bearing caps to see how things look. But I haven't detected any change in oil pressure, and the engine still doesn't have any mechanical noises.

Any serious problems with this engine after so many years of thrashing will just prompt me to put an LS3 in the car. More power, less weight. What's not to like?

 

[racer12306]

Curious question, is this a 1985 SBC or something else?

 

[A_Harman]

Still the original L98 block, crank, oil pan, and oil pump.
Everything else has been changed. The long block has been in there since 1995, with the exception of the hydraulic roller cam installed in 2009.

 

[bigt61]

What class does this car race in? Is it street legal? Slicks or street tires?

 

[A_Harman]

It's for track days only. It's prepared past the rules for Corvette Challenge. Not street legal. It runs on Nitto NT01's.

 

[Geoff]

5w-40? Your temps will certainly thin it out.

 

[A_Harman]

I put RL 5w30 in it again, and may do something with the oil cooler to improve its cooling ability. I'm thinking of a dedicated duct sealed to the face of the cooler so air can't bypass around it. If that doesn't work, maybe I'll start increasing viscosity. Gradually.

 

[bigt61]

Stock Corvette radiator? What are your water temps? Obviously, 315F on the oil is too high. If you invest in a new LS3, consider a dry sump setup. Also a racing radiator.