Flat tappet lifters
 

Hi all

Looking for advice on solid flat tappet lifters for a maximum effort sbc 311" with factory cast iron heads restricted to a maximum tappet diameter of 0.904" and mushroom tappets are not allowed as per class rules (Australian Superstock). Whilst we have used Schubek/Smith lifters in the past with one failure (what a mess) were looking at going a different way. Given the rpm (8500-9500) and the aggressiveness of a newer style camshaft we are running (Cup style cam) we are looking to get some recommendations on lifters. I have read in some older forums that racers have had good results with DLC tool steel lifters. So i would just like to get some feedback and past experience with these and if they require any special break in or oil to be run with them. The cam shaft is a steel core 55mm cam with all the latest surface treatments for increasing surface hardness. Any input would be highly appreciated.

Re: Flat tappet lifters
 

Schubecks have a history of catastrophic failures for many.
Your choices are NASCAR Nextel Tool Steel lifters with the DLC coating made by Trend, PPPC and Ferrea.

The PPPC tool steel lifter can be sent back to PPPC for resurfacing later on.

For your application, make sure to get a lifter for an AMC application since they have the proper pushrod oiling for a Chevy engine. Both Trend and PPPC make the oiling modification. Ferrea already has a modified lifter under P/N LF1004.

http://trendperform.com/b-94213-1149...rformance.html

https://www.pppcenter.com/06Catpgs/C5.pdf

Re: Flat tappet lifters
 

Thank you for the input, will definitely take this into consideration, all our schubeks ran this type of setup for correct oiling via the pushrod. How do these hold up in terms of spring pressures? What has been safely run with these seat/over the nose pressures? I have read that some these lifters have had issues with DLC coatings delaminating, however all seem to have been related to cast cores and wrong oils being used. Have coatings improved over the years?

Re: Flat tappet lifters
 

Yes, you can run DLC coated tool steel lifters on an 8620 steel core camshaft. I strongly suggest the high end finish that Comp Cams has recently introduced. I use and sell only Trend lifters. I suggest you ask your lifter supplier about motor oil, as certain DLC coatings do not always work with just any motor oil.

We use the Trend tool steel lifters (without DLC) with as much as 550# open pressure on 0.842" lifters. We do this on nitrided cast iron core cams, and we do not use the EDM oil hole.

Re: Flat tappet lifters
 

Thanks Alan for the response! It seems Trend are the way to go and have had a lot good reviews from racers. Have you had any feedback or reviews regarding there DLC coated lifters from any racers? Will definitely be in contact with them regarding correct break in procedures and oils. Does the latest comp cams finish have a particular name? Can you recommend someone to talk to at comp regarding this? Thanks

Re: Flat tappet lifters
 

We're not using DLC coated lifters, we may try them in the future.

The guy to talk to at Comp is Dave McCarver. The new finish is one actually developed for the LSx series roller cams. However, the idea behind it is to provide the smoothest possible surface, so that more of the roller contacts more of the lobe. The gain for a flat tappet application is that the breaking is pretty much a process of burnishing and polishing. So the more polished a surface is to start with, the easier it is to finish the break in.

Realize that DLC is just like the foot on a Schubeck in that it absolutely does not tolerate impact or abrasives. That's the reason DLC does not work on cast iron, cast iron is a really nasty abrasive.

Re: Flat tappet lifters
 

Thanks again Alan forthe response. Given the want to remove the chance of any nasty abrasives going through the engine due to a lifter failure, could a non coated tool steel lifter from trend be used instead with this application, with a tool steel cam and the finish discussed above? Thanks

Re: Flat tappet lifters
 

Can a cast iron camshaft be dlc coated?

Re: Flat tappet lifters
 

Both the Trend and PPPC lifters operate well with high spring pressures and the DLC coating is a plus to prevent wear. DLC coatings have improved and most of the high end solid and roller lifters are DLC coated including, Jesel and Morel.

My Boss at my place of employment, was the engine shop manager for 30 years in several NASCAR teams. He used and we continue using both the Trend and PPPC, DLC coated lifters with no issues.

As regards to the engine oil and DLC coating compatibility, a few have experienced issues with the Driven oil. My recommendation would a synthetic oil such as Mobil 1, Lucas or Amsoil.

There are many SAE Engineering papers that have tested the compatibility and it appears that the recommendation for best wear is to use 5W-30 weight synthetic oil with DLC coated parts.

Re: Flat tappet lifters
 

Thank you for the response, starting to get a lot more confident with this type of setup. Given your Boss' past experiences within NASCAR would you be able to comment on a camshaft specific question? My question relates to cup style camshafts being apparently designed to loft the lifter and hence giving the valve additional "dynamic" lift whilst running. Is this something that you or he has encountered and if so how would a DLC coated lifter hold up in this scenario? As Alan mentioned above you don't want a DLC lifter bouncing around so to speak because it will have the same result as a Schubeck, thus it seems strange to want to design a camshaft to loft the lifter with this potential catastrophic result. Any input would be highly appreciated.

Re: Flat tappet lifters
 

NASCAR cams have never been designed to have an inherent loft or separation at the nose of the camshaft lobe. This type of event would damage or destroy the valvetrain and engine, especially during a 500 mile race. Just imagine the end result of the engine due to lofting taking place at a constant 8700 to 9400+ RPM's during a race.

The main root cause for a lifter to loft or jump the camshaft nose is inadequate open valve spring pressure. Dwell nose camshaft lobe designs have less propensity to loft.

Nevertheless, in a nutshell, the key is proper selection of valve springs to prevent lifter lofting.

Re: Flat tappet lifters
 

That is the answer I thought I was going to get, doesn't seem right at all to have an inherent loft at those engine speeds and the given operating times. It seems that our past Schubeck lifter failure was the result of swiping the ceramic puck off rather than a valve float/loft issue. Looking at the failed Schubeck lifter it seems the failure mode of the puck has been due to a shear load rather than an impact load. Correct spring pressures and lash settings have always been constantly maintained with approx. 250-300# seated and around 700 over the nose with PAC springs. The remainder of the valve train has no shortcuts, with titanium valves and retainers used, jesel high end rockers and correct pushrod sizing. Do you have a preferred camshaft supplier for using the recommended DLC lifters with? Again thanks for the advice.

Re: Flat tappet lifters
 

For starters, I would go with PSI springs in lieu of PAC springs. During an NHRA divisional race a few weeks ago, we were experiencing issues with PAC springs loosing pressure every other run on a Comp Eliminator engine.
Yes, your forensic assessment on what took place with the Schubeck lifter is correct.
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