Roller lifters, Anyone tried them? Options

[r_towle]

Has anyone tried roller lifters in a type 4, or any flat motor?

[Jake Raby]

The mechanical tendency of the lifter is to rotate as it travels up the opening ramp of the cam lobe. I found that this tendency occurs at roughly .175" lobe lift with most profiles. It's much easier for the lifter to try to turn, than for it to ascend up the ramp, the more lift it sees, the more valve spring load it sees, and the quicker the issue at hand becomes apparent.

None of the photos that you have seen are of my final lifter/ indexing design. In fact, it's a far departure from those designs, in every way. I abandoned that, and sold the lifters, and tooling on thesamba. The lifter is now indexed with two control surfaces, sharing noting in common with previous attempts.

If one believes that a roller lifter can self index, and maintain alignment with the cam lobe with no mechanical limitation, they haven't studied the fundamentals of roller lifter and cam evolution. The challenge that everyone has had stems from this same issue. Some use dowels, some use links between lifters, and others use tunneled bushings. All of these have caveats. If you just throw a roller lifter in the mix, and expect it to follow the cam lobe, you'll be disappointed before the engine is even assembled. The lifters will roll sideways and crash the lobes before you get all the valves adjusted on the bench.

Once you get the roller mechanicals figured out, then you'll need to pony up for custom springs, retainers, and valves, so you can net dramatically increased spring pressures that will allow for more lift, while handling the insane opening and closing speeds of the roller actuated lifter, and pushrod. Once you tackle that, then you'll learn that the pushrods that are readily available are deflecting under load, and costing you valve timing. You won't notice this at first, but maybe after 3 months of beating your head against the wall you'll remember this post.

If someone has head leaks that bad, less time needs to be spent on the crazy stuff, and more on the elementary level elements of T4 modification. There's a possibility that the engine had a tendency for head leaks due to the cam profile that was used, as it's easy to build too much dynamic CR and cylinder pressure with a roller arrangement. Been there.

The dynamics associated with utilizing a roller lifter impact the entire engine combo. Don't be one of those guys that says "I'll not worry about any of that, because I'll keep it mild". Guess what? You'll hit all the same issues as the engine I have running .700" valve lift.

The last set of ceramic lifters I sold went for 2k, I have one more set that I'd take that amount for, the other 10 sets I'll be selfish and keep for my own cars.

This post has been edited by Jake Raby: Oct 31 2015, 09:30 PM

[r_towle]

The mechanical tendency of the lifter is to rotate as it travels up the opening ramp of the cam lobe. I found that this tendency occurs at roughly .175" lobe lift with most profiles. It's much easier for the lifter to try to turn, than for it to ascend up the ramp, the more lift it sees, the more valve spring load it sees, and the quicker the issue at hand becomes apparent.

None of the photos that you have seen are of my final lifter/ indexing design. In fact, it's a far departure from those designs, in every way. I abandoned that, and sold the lifters, and tooling on thesamba. The lifter is now indexed with two control surfaces, sharing noting in common with previous attempts.

If one believes that a roller lifter can self index, and maintain alignment with the cam lobe with no mechanical limitation, they haven't studied the fundamentals of roller lifter and cam evolution. The challenge that everyone has had stems from this same issue. Some use dowels, some use links between lifters, and others use tunneled bushings. All of these have caveats. If you just throw a roller lifter in the mix, and expect it to follow the cam lobe, you'll be disappointed before the engine is even assembled. The lifters will roll sideways and crash the lobes before you get all the valves adjusted on the bench.

Once you get the roller mechanicals figured out, then you'll need to pony up for custom springs, retainers, and valves, so you can net dramatically increased spring pressures that will allow for more lift, while handling the insane opening and closing speeds of the roller actuated lifter, and pushrod. Once you tackle that, then you'll learn that the pushrods that are readily available are deflecting under load, and costing you valve timing. You won't notice this at first, but maybe after 3 months of beating your head against the wall you'll remember this post.

If someone has head leaks that bad, less time needs to be spent on the crazy stuff, and more on the elementary level elements of T4 modification. There's a possibility that the engine had a tendency for head leaks due to the cam profile that was used, as it's easy to build too much dynamic CR and cylinder pressure with a roller arrangement. Been there.

The dynamics associated with utilizing a roller lifter impact the entire engine combo. Don't be one of those guys that says "I'll not worry about any of that, because I'll keep it mild". Guess what? You'll hit all the same issues as the engine I have running .700" valve lift.

The last set of ceramic lifters I sold went for 2k, I have one more set that I'd take that amount for, the other 10 sets I'll be selfish and keep for my own cars.

As always, you raise an interesting set of related factors.
I believe you when you say they turn.
I can't visualize it at the moment, but I will see it over the winter when I go to replace the camshaft....
Most likely won't go down this road unless I can achieve my goals.

After all is said and done, what is the benefit of going this way from a torque perspective?

Ideally, having better tolerances, and less adjustment maintenance would be my personal goal.

[DBCooper]

After all is said and done, what is the benefit of going this way from a torque perspective?

Ideally, having better tolerances, and less adjustment maintenance would be my personal goal.

With a roller you can have steeper ramps on the lobes to open and close the valve faster. Means you can get the cam profile closer to what you want rather than what's possible. You've got an aircooled engine, though, so unless they're hydraulic lifters you're still going to be adjusting valves in the same intervals.