Don Terrill’s Speed-Talk

Nut124 wrote: ↑Mon Jul 27, 2020 10:03 am I'm looking for recommendations for motor oil for break in and use afterwards. This is a -78 Fiat twin cam 1800 for street and track.

My build has newly honed cast iron bores, new rings, Total Seal steel top ring. Big overhead cams and flat tappet followers/cups.

I had been using 15w-40 synthetic. There was some cam lobe damage after 20 years, but still in spec. Bigger cams now.

High zinc?

pdq67 wrote: ↑Wed Jul 29, 2020 11:00 am Where is 540Rat at??

He can tell you in a NYM!!

pdq67

RDY4WAR wrote: ↑Wed Jul 29, 2020 10:42 am I'd recommend Driven BR40 for the break-in. Valvoline VR1 will be fine if you want an oil with more ZDDP. It's ~1400 ppm Zn.

I do not recommend Lucas Hot Rod oil with it's 2100 ppm Zn for regular use. There's no application on Earth that needs more than ~1500 ppm for regular use. More ZDDP than necessary doesn't give you any additional wear protection. ZDDP is a tri-molecular ester that is acidic in nature so as the concentration increases, so does the oil's acidity which promotes corrosion and shortens oil life. This starts to become a problem above ~3%wt (~1920 ppm Zn). Increase iron, lead, and copper wear metals in used oil analysis is common in oils with too much ZDDP due to corrosive wear. Lucas knows this but they also know a lot of people buy into the "more must be better" theory. That much ZDDP is added purely for marketing.

Another downside of ZDDP is it increases hydrodynamic friction proportional to concentration. This is because as the concentration increases, so does the thickness and roughness of the tribofilm which induces higher shear stress on the oil film. Higher ZDDP without higher amounts of friction modifiers to counter means the oil's friction coefficient increases, creating higher oil temps and robbing power. Now this effect is slight, would take repeated runs on a dyno with averages to see a difference, but it is there.

Also note that ZDDP isn't a single additive but is a family of additives. There's ~200 different ZDDPs out there, and they all behave a little differently. Some are highly reactive with excellent wear protection properties while others serve more as anti-oxidants with little effect on wear. Common API oils on the shelf at Autozone use a cheap, blended alkyl ZDDP while your break-in oils and true racing oils contain the more reactive secondary alkyl ZDDPs. Valvoline VR1 uses the same blended ZDDP as API oils just at a higher concentration. The same with a lot of low buck "racing" oils. Your boutique oils such as Red Line, HPL, Driven, etc... tend to not spare any expense in this department.

Any oil with 1000-1200 ppm Zn is more than sufficient for 99% of applications out there.

Powertrip wrote: ↑Wed Jul 29, 2020 11:54 am RDY4WAR, you seem to know what your talking about.

Any input on Amsoil Break-In and Hot Rod oils?

Bob Hollinshead wrote: ↑Wed Jul 29, 2020 12:44 pm Good stuff, why is the BR40 break-in oil only good for 400 street miles? The Brad Penn break-in oil they say you can run longer? Whats the differences?

RDY4WAR wrote: ↑Wed Jul 29, 2020 11:33 am

pdq67 wrote: ↑Wed Jul 29, 2020 11:00 am Where is 540Rat at??

He can tell you in a NYM!!

pdq67

540 rat and his blog is the laughing stock of the tribological community. Film strength testing is not relevant to engine oils, and he doesn't even reveal what machine he uses which is a red flag for anybody that deals with ASTM testing. He keeps it proprietary to ensure nobody can validate his testing. Sequence IVA 100 hour cam wear tests (real world engine tests, ASTM D6891) have repeatedly shown no correlation between cam wear and film strength. It's just something that some oil companies use as a marketing point. The only time it has merit is high powered nitrous enignes, but even then, the pressure-viscosity coefficient is more important than the film strength. Film strength is more for gear oils where you have teeth sliding pasts each other at high shock loads.

Krooser wrote: ↑Wed Jul 29, 2020 4:13 pm

RDY4WAR wrote: ↑Wed Jul 29, 2020 11:33 am ...

540 rat and his blog is the laughing stock of the tribological community. Film strength testing is not relevant to engine oils, and he doesn't even reveal what machine he uses which is a red flag for anybody that deals with ASTM testing. He keeps it proprietary to ensure nobody can validate his testing. Sequence IVA 100 hour cam wear tests (real world engine tests, ASTM D6891) have repeatedly shown no correlation between cam wear and film strength. It's just something that some oil companies use as a marketing point. The only time it has merit is high powered nitrous enignes, but even then, the pressure-viscosity coefficient is more important than the film strength. Film strength is more for gear oils where you have teeth sliding pasts each other at high shock loads.

He uses the old fashioned " one arm bandit"!