- Posts
- 83,296
- Location
- Embasinga stocæ
Just posted this because I thought this might be an interesting topic to many of you.
Extract from "MTA NZ Radiator Magazine, July 2009" - New Motor Oils Are Bad for Older Engines with Flat Tappet Camshaft
"The lobes on this 289 Ford Mustang flat tappet [Pic Below]
cam suffered excessive wear because the motor oil did not contain adequate levels of ZDDP anti-scuff additive. If you are driving an older classic muscle car or hot rod that has an engine with a flat tappet camshaft, you should be aware of the fact that today's "SM" rated motor oils contain much lower levels of anti-scuff additive called "ZDDP" (Zinc Dialkyl Dithio Phosphate). The level of ZDDP in current motor oils has been reduced to no more than 0.08% phosphorus to extend the life of the catalytic converter. Phosphorus can contaminate the catalyst over time if the engine uses oil, causing an increase in tailpipe emissions.
The lower ZDDP content is not harmful to late model engines with roller lifters or followers because the loads are much lower on the camshaft lobes. But on pushrod engines with flat tappet cams, the level of ZDDP may be inadequate to prevent cam lobe and lifter wear. In some cases, cam failures have occurred in as little as a few thousand miles of driving! This is even more of a risk in engines if stiffer valve springs and/or higher lift rocker arms are used.
To avoid such problems, you should add a ZDDP additive to the crankcase, or use an oil that meets the previous "SI" service rating, or use diesel motor oil or racing oil that contains adequate levels of ZDDP to protect the camshaft and lifters."
Extract from "MTA NZ Radiator Magazine, July 2009" - New Motor Oils Are Bad for Older Engines with Flat Tappet Camshaft
"The lobes on this 289 Ford Mustang flat tappet [Pic Below]
cam suffered excessive wear because the motor oil did not contain adequate levels of ZDDP anti-scuff additive. If you are driving an older classic muscle car or hot rod that has an engine with a flat tappet camshaft, you should be aware of the fact that today's "SM" rated motor oils contain much lower levels of anti-scuff additive called "ZDDP" (Zinc Dialkyl Dithio Phosphate). The level of ZDDP in current motor oils has been reduced to no more than 0.08% phosphorus to extend the life of the catalytic converter. Phosphorus can contaminate the catalyst over time if the engine uses oil, causing an increase in tailpipe emissions.
The lower ZDDP content is not harmful to late model engines with roller lifters or followers because the loads are much lower on the camshaft lobes. But on pushrod engines with flat tappet cams, the level of ZDDP may be inadequate to prevent cam lobe and lifter wear. In some cases, cam failures have occurred in as little as a few thousand miles of driving! This is even more of a risk in engines if stiffer valve springs and/or higher lift rocker arms are used.
To avoid such problems, you should add a ZDDP additive to the crankcase, or use an oil that meets the previous "SI" service rating, or use diesel motor oil or racing oil that contains adequate levels of ZDDP to protect the camshaft and lifters."
Last edited:
