The hydraulic roller cam is on the way for my 541 build. It's a mild grind (235/241 .590/.571) and I plan on racking up the miles on this thing. Valve train components are already in motion.

I'm wondering about the timing gear. I know I'll need a thrust limiter (bearing/button) on the timing cover side but what about the back side between the gear and the block? Should I bother with a thrust bearing or washer back there? I like the idea of a bearing but don't like the idea of bearing failure involving scattered rollers.

This is a low RPM build (max 6000 rpm) and will be used for extended drives including occasional road trips.

Where would you put your money on this one?

I just did a nylon thrust button up front. I had to carve it some to get it to fit around the 3 bolts and for length but it was easy and has lasted.

used the Summit steel Billet that has thrust bearing made in and Comp Cam nylon button.

I’ve used the Rollmaster. Very nice quality.

Look at it this way, with a flat tappet cam the cam is loaded towards the rear of the engine and the block/gear live just fine. With a roller cam the rear thrust is practically nil. So why would you need anything exotic if the loading is reduced?

A thrust bearing should always be used between the gear and the block with any type of roller cam.

Dwayne, what’s the reason? I’d like to know also. Trying to reason why it’s actually needed.

I like the idea of a thrust bearing but undecided between an actual roller and a thrust washer.
The washer would likely wear quicker but it has no tiny hardened rollers to fall out and trash the engine.

The interface/interaction of the roller wheels and the camshaft can generate substantial thrust force....... either forward or backward.
For any particular build, you won’t really know if there is any, and if there is, how much there is, or in which direction.

So, to cover all bases....... incorporate some sort of thrust control in both directions, and some form of wear protection for the block.

Frankly I don't buy this. If a thin, stamped steel timing cover with a nylon thrust button can control forward thrust, there is no way that there is substantial reverse thrust. As to the rollers on the lobes, if the lobe face is ground parallel to the camshaft centerline and the rollers are cylindrical, the only way that there could be any thrust in any direction would be from lifter bore misalignment. To say this produces greater reverse thrust than the taper on a flat tappet cam that by design imparts substantial reverse load.... Again, I don't buy it.

I can see it happening.
Not only is the engine a bit of a mess when it comes to harshness and vibration it's also bouncing around inside a car that is doing anything but standing still. Inertia acts on everything.

Does the distributor drive gear rotation have any loading effect on thrust fore or aft?

Load from the distributor is insignificant. Load from the oil pump is considerable and would try to push the cam forward.

Ok,I was just wondering about the helical cut gears loading it.Thanks. Looking forward to seeing this one run!
RT

You don’t have to.

I have seen it happen first hand.
The stamped timing cover won’t hold the forward thrust if it’s on the high side, nor will the nylon button(which is why I won’t use them in a roller cam application).
The SBC community has reinforced covers, along with waterpump housings that have stop bolts to support the timing cover from being pushed forward.
However, that stuff only works to prevent cam walk from the cam moving foward.
There can just as easily be the same amount of force rearward as what there is when I timing cover gets bent outward.
The plain gear being pushed hard against the block wears a groove into the block........ like what happened recently to a customer of mine who has a roller cammed 505.
When he pulled it down for freshening, the area of the block where the cam gear rides is badly worn.
No thrust bearing on the back of the timing set.

http://www.iskycams.com/how-to-prevent-roller-cam-walk.html

https://www.hotrod.com/articles/cam-thrust-explained-killing-engine/

Just found this from a 10 yr old post, not sure if numbers are still good

If its a big block, here are the torrington part numbers you need:
qty 2 spacers TRA-3648
qty 1 torrington brg NTA-3648 (has steel cage)

If you look down the lifter hole on a flat tapper camshaft you will notice the cam lobe is not centered, plus the lifter is not flat but slightly crowned. This set up makes the lifter rotate on the cam lobe, if it does not rotate, it goes flat, quick. This arrangement also makes the cam thrust toward the rear of the block. A roller camshaft lobes are basically centered with the lifter, and they have no design to thrust only one direction, but a roller cam will thrust forward and backward as the engine is accelerated and deaccelerated. It you don't control the thrust, the cam can move enough that the sides of the lobe will rub on the lifter body of the next cylinder, causing all kinds of bad things to happen. All OEM roller lifter engine have some method of controlling the thrust of the camshaft, so it is not just a performance cam thing. I seen one guy put a roller into a small block Chevy and did not use a thrust button, it lasted less than a day. Lifter got into the next lobe, and it even busted the lifter bore out of the block.

Had this happen first hand on my 588, but had a different issue along with it. Jessel has both the torrington bearing set up, or washers, whichever you prefer. reasonably priced too. Jim.

I did the same, I have the set with a thrust bearing, so far about 6k street strip miles on it in Southeast Texas heat.