Oil, flat tappet cam failures, and what I learned - 09/05/06 08:14 AM
In the building process on my GMC 302 project, I was hearing and seeing bits and pieces of flat tappet cam failure. I was very concerned about this and set to trying to identify the cause. There was a lot of conjecture about the source, but often fingers pointed to reformulations of engine oils and the reduction of ZDDP, a lubricant.
You roller bearing guys don't have to worry about this, but us flat tappet guys should pay attention.
First, understand that my motor is not high performance engine. I built this engine for longevity and high rpm continuous operation. I am planning to make a Boston-San Francisco Cannonball run next year to commemorate Cannonball Baker's famous non-stop transcontinental run in a 1927 GMC 2.5 ton truck. To do that, I wanted to build a motor that looked stock, but had more balls than the original 228, but more importantly I was attentive to balancing the motor very carefully at each step of the build. My motor is a military 302, but I went to great pain to "convert it" to a civilian appearing model all the way down to cutting the fuel pump boss and mounting a mechanical fuel pump. I am running stock spring pressures because this engine will not wind out much past 3500 rpm, but may run for days at 3200 rpm. So my valve spring pressures are within original spec because float is not an issue for me in this engine at the rpm's I'm planning on running it.
I digress. Flat tappet cam failures.
What I found was that engine oils have been reformulated to reduce certain bi-metallic additives such as ZDDP because they were finding their way into the insides of catalytic converters and causing pre-mature converter failure by placquing up the insides with metal salts rendering them ineffective.
After a lot of reading, I stumbled into an article in Hot Rod Magazine that beautifully summarizes this issue (as I see it) and correctly identifies the source and offer an alternative that I had already settled on but was pleased to see it confirmed in the article.
I am a Castrol GTX man. Have been for as long as I've been serious about engines. You'd have to pry that quart from my dead hands if you wanted it prior to my research, but now, I've "upgraded" to Castrol Tection, which is formulated for diesel engines. Since there are no catalytic converters in diesels (real trucks don't have spark plugs!) it's not an issue and the diesel engine oils have copius quantities of the goodies that croak catalytic converters and add decades of life to vintage flat tappet motors.
I copied the article from HotRod and have it stored on my oldgmctrucks.com server and you guys might find this information helpful if you don't know it already.
http://www.oldgmctrucks.com/photos/FlatTappetCamTech.htm
Hope you find this information helpful. This is only an issue for us flat tappet engines. Good argument for roller bearings!
You roller bearing guys don't have to worry about this, but us flat tappet guys should pay attention.
First, understand that my motor is not high performance engine. I built this engine for longevity and high rpm continuous operation. I am planning to make a Boston-San Francisco Cannonball run next year to commemorate Cannonball Baker's famous non-stop transcontinental run in a 1927 GMC 2.5 ton truck. To do that, I wanted to build a motor that looked stock, but had more balls than the original 228, but more importantly I was attentive to balancing the motor very carefully at each step of the build. My motor is a military 302, but I went to great pain to "convert it" to a civilian appearing model all the way down to cutting the fuel pump boss and mounting a mechanical fuel pump. I am running stock spring pressures because this engine will not wind out much past 3500 rpm, but may run for days at 3200 rpm. So my valve spring pressures are within original spec because float is not an issue for me in this engine at the rpm's I'm planning on running it.
I digress. Flat tappet cam failures.
What I found was that engine oils have been reformulated to reduce certain bi-metallic additives such as ZDDP because they were finding their way into the insides of catalytic converters and causing pre-mature converter failure by placquing up the insides with metal salts rendering them ineffective.
After a lot of reading, I stumbled into an article in Hot Rod Magazine that beautifully summarizes this issue (as I see it) and correctly identifies the source and offer an alternative that I had already settled on but was pleased to see it confirmed in the article.
I am a Castrol GTX man. Have been for as long as I've been serious about engines. You'd have to pry that quart from my dead hands if you wanted it prior to my research, but now, I've "upgraded" to Castrol Tection, which is formulated for diesel engines. Since there are no catalytic converters in diesels (real trucks don't have spark plugs!) it's not an issue and the diesel engine oils have copius quantities of the goodies that croak catalytic converters and add decades of life to vintage flat tappet motors.
I copied the article from HotRod and have it stored on my oldgmctrucks.com server and you guys might find this information helpful if you don't know it already.
http://www.oldgmctrucks.com/photos/FlatTappetCamTech.htm
Hope you find this information helpful. This is only an issue for us flat tappet engines. Good argument for roller bearings!