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_14_z Worn_down_engines Roller_cam 2/27

If you think the lobes on the Comp Cams roller cam look meatier, you're right. Even though the duration and lift specs are similar to the flat tappet cam, the lobes are visibly wider at the top in profile on a roller cam.

Offshore Lifters
As roller lifters became the choice for auto manufacturers, the quantity of flat-tappet lifters that were needed dropped dramatically. The few companies making these lifters in the U.S. decreased their production, and one discontinued production. Eventually, flat-tappet lifters were in short supply and unbranded offshore lifters filled the void. Hold the mail, I am not saying that all U.S.-made products are perfect and all offshore products have problems. Japanese manufactured products have established a reputation for high quality, but many other offshore countries have not yet achieved such a reputation.

Corp_0808_15_z Worn_down_engines Valveguilde_seals 3/27

If your car occasionally gives a puff of blue smoke upon starting or after letting off on a long exit ramp, this is the perfect time to change valveguide seals. Choices include the umbrella seal that moves up and down with the valve, the original factory o-ring, and varieties of positive seals. The seal on the right presses onto the head's valve boss; in this case machined down to 0.500-inch diameter.

The point is, a change has occurred. Years ago, nearly all flat-tappet lifters sold in Amercia were made by a few U.S. companies that were well established, well respected in their field, and had decades of experience. Today, lifters from other companies are in the marketplace. make sure you know the source of the lifter and the reputation of the actual manufacturer, not the distributor. A lifter is a highly stressed part, and its demise can be very costly.

Our primary goal here is to warn readers who own flat-tappet cam engines that there are new choices to be made concerning the oil that's put in the crankcase in order to avoid premature cam failure. A second goal is to inform readers who are thinking about rebuilding their motors that there are new cam and lifter choices to help ensure long engine life using the newly formulated oils. One of these choices is installing a retro-roller cam. This is becoming more popular because it eliminates concerns about early cam failure caused by use of the newly formulated or synthetic oils, and it eliminates the flat-tappet cam break-in procedure. Follow along as we repair the damage from a premature failure of a flat-tappet cam and install a new Comp Cams retro-roller cam and valvetrain.

Corp_0808_16_z Worn_down_engines Degreeing_the_cam 4/27

Degreeing the cam is not essential, but it will ease any worries about a problem with the cam or the timing gear. With the heads on, degreeing takes a $10 TDC stop tool, and then buying or borrowing a $25 degree wheel and a dial indicator with base. An hour of work here can prevent diagnosis dilemmas or parts problems that are more costly in the future.

Installation And Break-In Tips
Clean and inspect parts thoroughly, even though they are new.Apply cam lube on cam lobes, distributor gear, and lifter faces (not on the sides of lifters).Apply engine assembly oil on cam bearings, crank bearing, pushrods, and rocker arms.Apply regular oil on the lifter sides and use it in the motor. Thirty-weight is a good choice.Oil-prime the motor until oil flows from the top of all the pushrods.Do not run synthetic oil during break-in.Change oil and filter immediately after break-in. (I recommend this after 30 minutes or less on any rebuild.)

Corp_0808_17_z Worn_down_engines Cam_thrust_button 5/27

Installation of a cam thrust button is recommended when switching from a flat-tappet cam to a retro-roller cam. In a flat-tappet Corvette engine, the taper of the cam lobe exerts rearward pressure on the cam, as does the distributor gear that drives the oil pump. Comp Cams offers stamped-steel covers that look original, but are reinforced inside for the thrust button.

The following extra steps are only for flat-tappet cams; they are not needed for roller cams.
Install only the inner springs or install softer springs for break-in if you are using high-pressure springs.Make sure the engine is ready to start immediately and run continuously thereafter.Start the motor and then raise the rpm to 2,000-2,500 for 30 minutes (per Comp Cams).Mark the tops of pushrods and watch to make sure they are spinning.If the pushrods aren't turning, try to turn them as a last-ditch effort to get the lifters to rotate.




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