After the recent premature destruction of my flat tappet cam in a basically stock motor, the thought of going to a roller conversion sounds appealing.

My primary hesitation is that the bar/linkage that is riveted or swedged to each roller looks like Mickey Mouse engineering.

Has anyone put many miles on this system, or more importantly has it failed on anyone?

Any input is appreciated.

To be clear, I'm NOT talking about stock roller lifters, just the aftermarket conversion for flat tappet motors.

 

stock rollers don't have "retrofit" mickeymouse linkbars ... because stock rollers have a stock block, dogbones & spider that's alot better design than retrofit.

There are some other retrorollers that employ a keyway affair that's superior to linkbars ... keyway is much more $

 

Ask yourself this..what pressures or forces are applied to these link bars and where do these forces or pressures originate ?

I put over 20,000 miles on the first design Comp Cams solid roller lifters. THey have no direct oiling to the rollers like most do now. I would imagine hydraulic rollers would last many thousands of miles more as they don't take the beating and high spring pressure the solids do

 

I have never had problem with a retro fit roller lifters, I wouldn't but a flat tappet cam in anything I didn't have to...

 

15K miles here, and still running strong.

 

Flat tappet lifters roll around their axis because the contacting surface is not completly square. Rollers don't have this design incorporated because you wouldn't want them to turn in any condition. That is why the bar is there : to prevent them from turning, that's all. Don't worry about the bars, because the presure on them is small.
Because of this you also need something to control end float on the cam, as in a flat tapet cam the cam has a tendency to walk towards the rear of the block, which does not exist in the roller design.

 

I saw result of a failed linkbar in a busch motor ... of course cam & lifters wrecked ... but it was very fortunate it took only $800 of repair, bush & machinework to save that block ... I pulled the motor down & took block to machinist in virginia & it matters not it was a ford. I cannot adequately describe where those forces come from nor quantify them ... but let one of those linkbars let go ... thus let a lifter rotate in bore ... & you'll have a me$$.

Most folks have good results w/ linkbars ... my point is that I think OE roller setup is more robust & better suited for street use ... opining.

-edit- BTW ... yes flat taper induces cam walk ... but motor w/ helical cam/dist gear that also runs oil pump (sbc & BBC) will have cam walk induced by dist/op drag ... regardless if flat or roller.

 

I recall at least one or two posts in this forum by members who had link bar failure. It is certainly rare and not something I would worry about overly.

But clearly unless those were instances of just plain cruddy lifters from the MFR then there is some kind of force on them, albeit minimal.

I run a OEM setup for the reasons of reliability and parts availability...they have been clearly shown to be plenty reliable with dozens of models running for countless combined miles.

If you dont have the option of OEM parts (because you dont have a block set up for it..by all means run the link bars, any sort of problem with them is very rare.

 

I appreciate the input. The way it sums up to me is:

1. 2 or 3 forum members have had link failure (and I'd guess a minority of members run aftermarket roller systems).
2. Link failure can cause catastrophic engine damage when the lifter spins. I don't want to risk scrapping my original block. If a flat tappet fails, I'll notice it by seeing (once again) metal on my magnetic drain plug -- not by the motor grenading.
3. There's not much experience on whether aftermarket roller system links will last 40, 60 ,80 or 100k miles. Even though there's not a lot of force on them, each of the 16 ends pivot 2500 or so times per minute on the highway. And I guess they are not directly lubricated or bushed.

And I sure agree with Jackson re: "... yes flat taper induces cam walk ... but motor w/ helical cam/dist gear that also runs oil pump (sbc & BBC) will have cam walk induced by dist/op drag ... regardless if flat or roller. " Anyone who has oil-primed a motor knows how much torque that takes, and that really pulls the cam rearward. I can't imagine why a roller cam would need end float control on our motors.

Your experiences regarding aftermarket roller cam longevity have been a big help in working through this decision.

Thanks,

John

 

My original solid roller motors had Crane Horizontal lifter cross bars and now I went to the vertical Crane ultra pro in both of my SR motor.

I have never seen bar failure in all of the damaged race motors that i have looked at.

 

The least of your worries with a full roller valvetrain are the linkbars, plenty of other things will fail first

 

This week Im putting in a roller cam set up. With the high cost of the lifters, I was not concerned about them failing. I figured they were well built hence the price. Now you guys got me wondering. I am going to go ahead with the roller cam anyways and wish for the best.
I have a set of Comp Cams roller lifters I will be using.

 

Have fun wiping cam lobes.

 

That's why it pays to go with high quality roller lifters. I trust Crower in my motor.
Eddie

 

I think the advantages of the roller cam far outweigh any possible problems you might have.

 

Setup, run and broken in properly a flat tappet cam will provide thousands of trouble free miles. Use the right oil and break it in correctly and you will have no trouble, A roller cam certainly has it advantages and someday I will install one but not because I can't keep a flat tappet cam alive. I think going to a roller just because you flattened a lobe on a flat tappet is a bad reason to go to a roller. If your looking for more HP and cost is not a consideration than go roller.

 

Roller cams always have an advantage towards the area under the lift curve, but it gets more important with long duration cams. Thus if you are running your engine in the higher rpm's you will need a roller cam, since you will also be using heavy spring forces to avoid valve float. In this situation you will certainly need rollers that can withstand the higher spring pressures. Plus ... a roller definatly needs to avoid valve float, so higher spring rates are even more important.

I would say, once you go much over 6000 rpm, go roller (mechanical that is)

 

For years solid flat tappets have run at 7500+ rpm. You don't need dump truck springs with a solid flat tappet like you do with a solid roller. I agree that the area under the curve is much better with a roller cam but I run my solid flat tappet all the time to 6500+ rpm and my spring pressure is not near roller cam spring pressure.

 

Why? When Crane makes a Hydraulic roller that revs to 8500!!

 

I appreciate the input and realize this is a controversial judgement call.

On one hand, we know for a fact a lot of flat tappet cams have been prematurely wiped recently. Probable causes include off-shore lifters, changes in oil and perhaps switching to synthetic oil (Crane warns against this for at least 5500 miles). But we also know that for decades Detroit put out many millions of cars each year with flat tappets and no break-in -- and the cams went way beyond warranty.

On the other hand, we know roller cams don't have a break-in issue but there is no history or long warranties or objective data on the (after market) link/bar failure rate, only anecdotal info. But we know that if a link joint fails, the lifter turns and can destroy an original number-matching block (and other parts).

I certainly would not risk the original block to make the car a few tenths faster. But I did break the (GM) cam in properly (as with all the other motors I've rebuilt), used EOS, ran Castrol dyno oil but switched to synthetic before 5000 miles. One lobe was wiped but the wear pattern on 3 other lifters showed they were not turning, also. I can send pics if wanted.

So I haven't decided yet but believe (1) I probably have a very good chance of a flat tappet cam lasting if I avoid the above three items or (2) the aftermarket roller cams on the market probably don't have a high failure rate.

Thanks for joining the discussion.