Lifter re-ginding or turning

[earntaz]

With roller lifters you would expect to use a thrust plate of some sort ... TAZ

[VintageMusclecar]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: L78steve</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: VintageMusclecar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: L78steve</div><div class="ubbcode-body">Just the (constant) load of the oil pump is enough to keep the cam pulled rearward in the block. </div></div>

If that were the case there would be no need for a thrust plate or thrust button on an engine equipped with a roller cam. </div></div>

Exactly. Unless there is a remote oil pump installed. Think about it the angle cut of the pump/Dist. drive gear will thrust the cam rearward.

If I'm wrong please tell me why. </div></div>

Straight from COMP cams (emphasis added)

<span style="font-style: italic">&quot;Roller Cams

Several points must be considered when installing a roller cam in an earlier block designed for a flat tappet cam. Flat tappet cams are ground with taper on the lobes to force the cam to the rear of the engine. Roller cam lobes are ground flat, <span style="text-decoration: underline">so a thrust button must be used to keep the camshaft to the rear of the block.</span>&quot;</span>

Additionally:

<span style="font-style: italic">&quot;When installing a hydraulic roller cam in an early model block, it is necessary to use a special hydraulic roller lifter with a link bar assembly to keep the lifters from rotating in their bores. In addition, appropriate- length pushrods must also be used. A roller lifter, being physically longer, has a pushrod seat that sits closer to the rocker arm than a flat tappet lifter pushrod seat –necessitating a shorter pushrod. <span style="text-decoration: underline">A thrust button is required to keep the cam from “walking” forward in the block.</span> A wear plate is also a required (though inexpensive) part, which serves to prevent the rear of the camshaft gear of the timing set from excessively wearing the engine block as it works to keep roller cam walk under control.&quot;</span>

The oil pump gears <span style="text-decoration: underline">will not</span> keep the cam pulled back in the block.

I'm really not trying to be argumentative, I just don't want to see anyone get tripped up on a build over erroneous information. If you try to run a roller cam w/o some means of thrust control (either a plate, button, or a belt drive which uses thrust shims), the cam <span style="font-weight: bold">will</span> move in the block during operation and the results will probably be catastrophic.

Think about this: all modern engines that came from the factory with a hydraulic roller cam have some form of thrust control--in `87 when the original SB Chevy went to HR cams they also added a thrust plate behind the cam gear. If the oil pump drive was sufficient to keep the cam from walking, why would they (GM) have went to the trouble &amp; investment to make the thrust plate and all the requisite tooling changes if it wasn't needed?

[L78steve]

The taper ground into the lobes is for lifter spin. I may have a secondary effect of pushing the cam back I don't know.
The reason I believe this is that every cam (flat tappet) Ive installed with a button never made any contact with the cover after disassembly many runs later. The clearance set was the gasket thickness. So I have assumed the cam was held rearward by pump load.
Roller is another issue the plate is needed for insurance that the cam will not walk.
Don't mean to be a PITA just info gathering.
Also i have seen blocks run with high pressure pumps worn from the cam gear contact surface.
Pumps put one hell of a load on the cam gear. You can feel it when pre-lubing. Also oil pumps are loaded weather spinning up or down in RPM.