Flat-Tappet Cams and Worn Down Engines - The Perfect Storm

Flat-Tappet Owners Beware: Your Motor May Be Silently Grinding Itself Away

John Pfanstiehl Aug 7, 2010 0 Comment(s)
Corp_0808_07_z Worn_down_engines Crankshaft 1/27

Good news, bad news. The crankshaft journals were not damaged, but the bearings showed some contamination by metallic particles. One factor that helped save the engine from further damage was that we were alerted early to a problem by the particles picked up by the magnetic drain plug.

Another oil option is buying racing oils, such as Valvoline Racing Oil, Joe Gibbs, or Brad Penn. Look for a label that specifically states something like "contains added zinc." It may also state "not for passenger cars" and explain that it may damage catalytic converters. This is not a problem for pre-'75 cars or other vehicles that don't have a catalytic converter.

Another option is buying from a specialty oil company that formulates oil with antiwear additives similar to the good old days. Call them with a credit card and they can ship oil to your door.

The second way is to supplement modern oils by pouring in a break-in additive from a camshaft manufacturer at each oil change. These can be ordered from cam manufacturers, from speed parts distributors such as Summit Racing or Jegs, or picked up at local speed shops. Because formulations change, the safest policy is to check with suppliers of diesel oil, racing oil, or cam break-in additives to learn the current concentrations of their antiwear additives.

Corp_0808_10_z Worn_down_engines Oil_filter_mount 2/27

This modification of the oil filter mount helped protect the rest of the engine from the metal particles. The oil bypass valve opening was cemented shut with an epoxy to prevent any oil from bypassing the filter. The valve was originally intended to prevent oil pressure from dropping if the filter became clogged, but it's unnecessary when the oil is changed frequently.

Synthetic Oil
There are two sides of the argument about the danger of running synthetic oil in a flat-tappet cam engine.

The pro-synthetic oil argument is simple: thousands of people have run synthetic oil in flat-tappet motors with no problems (yet). But remember this is anecdotal; there are no long-term real-world tests across a variety of engines, and almost certainly there will never be any. Plus, just because many have run synthetic oil without a problem, that doesn't prove there isn't a higher risk factor.

Corp_0808_08_z Worn_down_engines Drippy_rear_man_seal 3/27

With the pan off, this was a good time to change a drippy rear main seal, particularly since the bearings were also being replaced. A common problem with a rear seal is that its lip can wear into the crankshaft, and this area is not cleaned when the crank is ground. Felpro solves this by offering an offset seal (PN BS 11829-1) that has the seal lip in a slightly different location.

The "be wary of synthetic oil" argument has a couple facts. First, we know that synthetic oil is more slippery than conventional oil (which oil-heads nickname "dino" oil for dinosaur). This sounds good but actually may not be good for flat-tappets. For some background, flat-tappets are not completely flat. They have a very slight crown ground into their face. Also, each cam lobe is slightly tapered toward the front, and the lifter bore is slightly off-center on the cam lobe. These three things are done to make the lifter turn when the cam lobe slides on it. If the lifter stops turning, the cam lobe wears on the same area of the lifter and both wear down soon thereafter. Synthetic oils are so slippery that there is less force to turn the lifter. So, theoretically, synthetic oil could cause problems for flat-tappet cams.

The real-world warning comes from cam manufacturers. Who has better experience than the people who make cams, test them, and learn of failures because they warranty them? Major aftermarket cam manufacturers state not to use synthetic oil during break-in, and one states not to use synthetic oil for at least 5,500 miles after break-in of flat-tappet cams.

Corp_0808_11_z Worn_down_engines Rubber_oil_pan_gasket 4/27

The one-piece rubber oil pan gasket from Felpro has been praised by a number of rebuilders. It comes with clever plastic studs to hold the gasket in place on the block while the pan is being installed. Silicone gasket sealer is used only on the four corners. The '74-and-up pans used a different thickness end gasket.

This writer switched to synthetic oil well after break-in, and subsequently lost a cam lobe at 4,500 miles. Inspection of the wear pattern on the other lifters showed three that were not turning.

Amsoil, the inventor of true synthetic oils, is aware of the flat-tappet cam problems and offers several oils with high phosphorus levels (over 1,250 ppm) and zinc levels (over 1,350 ppm). AMO 10W-40 and ARO 20W-50 Synthetic Premium Protection oils are recommended for flat-tappet and late-model high-performance motors. Amsoil's TRO 20W-50 Premium Synthetic Racing oil is recommended for highly modified, high-horsepower street or race motors. AHR Synthetic SAE 60 Racing oil is recommended for nitro- or alcohol-burning motors to protect from oil dilution by fuel. HDD Series 3000 Synthetic 5W-30 diesel oil also offers extra protection from high soot loading and acid generation in modern diesel engines.

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