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#1
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Roller lifters on a non-roller cam?
Hey all,
I have a friend that asked me this question, and I really don't think it can be done, but it did make me curious. He asked me if roller lifters from an LA engine be used on a non-roller cam that's in a B/RB engine? Since the later LA engines could be retro-fitted with a regular hydraulic/mechanical cam that uses the same lifters as a B/RB, then he thinks there shouldn't be any issue with putting the roller lifters from the LA into the B/RB block, of course, assuming that you can modify or fabricate one of those metal "webs" that holds the lifter crossbars in place. I was thinking that the lobes on a non-roller cam are ground on a slight taper so that the lifters rotate, and therefore the rollers on the lifter would probably cut a groove into the cam lobe after a while from only making contact on one edge of the roller. I don't think it can be done, but it did make me curious. Any ideas on whether this can work or not? I think it'd be great if it could work somehow, but I don't see how you'd get around the cam lobe taper. |
#2
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Absolutley NOT!
Your correct in your assumption, the taper on the cam lopes will twist the roller lifters in the bore and destroy the lifters bores as well as the roller on the lifter..... |
#3
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I thought so
Thanks for the verification, but I knew that if it could be done, someone would have done it by now.
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#4
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Your welcome
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#5
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im not sure if it will fail or not probably will, but there is no point to it. the idea of running a roll lifter solid or hydrolic is the rate of the lift. the have such a step ramp that the nornal lifter would dig into it. this type profile is very desirable faster rate of lift at a point of duration. there would be no gain running a non roller profile cam with roller lifters. kinda like when you take a shower and put on dirty stained underware, whats the point.
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#6
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Don`t even think about it!
Besides there wouldn`t be any performance gaine anyway. |
#7
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...at least turn the underwear inside out....
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#8
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Actually, have you ever taken a look on the different style cams. I know cuda66 is a big favourite of the real mopar lifter cams (ground by Racer Brown ) and you could think about the roller lifter as a 0.001" diameter lifter. It will only touch the ramp of the cam right from the middle unlike a flat tappet which climbs the cam up further from the center of the lifter and therefore opens the valve way quicker than a similar lobe with a round ended roller lifter. That's why the roller cams are more squary looking than flat tappets; they have to even with the same rate of lift per degree. So using the roller lifter with a flat tappet grind would make the valves open & close way slower. But there is more to it. The flat tappet lobes have built in taper. This would cause it to touch the roller lifter only from one edge killing the lifter very soon. And there is still some; the surface pressure of the cam with the rollers very narrow touching point is way higher than with flat tappets. That's why the rollers are heat treated steel insted of cast like the flat tappets; a flat tappet cam can't take the surface pressure put on by a roller lifter.
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#9
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Wait there`s more
Quote:
Iam sorry to have eliminated much of your post as a Quote. My intentions are not to cause an However from what I have experianced . You are right the HYD cam lobes are taperd. This causes the cam to walk toward the back of the block. And you are correct it would definetly shorten the life of the roller lifter. However I would have to disagree with the rest of your post as I understand it. The reason the rollers are made of billet steel is the same reason you need a bronze distributor gear. As the roller cams are ground from billet steel. Wich would eat regular steel and or cast. This would fill the engine with shaveings in no time . And you know what that will do. As for valve opening and closeing speeds this is dictated by lobe design, rather then lifter type. Once again dart66 ,my intentions are not to start an . If you feel Iam mistaken in my post . tell me where and when. |
#10
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Well DD, I have to disagree with you. Changes in the lifter diameter will result in changes to both the valve timing and the rate of lift. As a large diameter (Mopar) lifter turns on the base circle, it is the center of the lifter which is making contact. As the cam rotates, it is now the leading edge of the lifter which begins to contact the opening ramp. In just a very few degrees of rotation, the contact point of the lifter has moved almost 1/2 inch across the cam lobe (one-half the diameter of the lifter). This does not happen with a roller lifter, requiring a radically different camshaft profile to obtain the exact same valve action. I'm not sure I explained this adequately for you to visualize the effect, it is easier to see with a picture. Maybe someone else has a graph or diagram?
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#11
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[QUOTE]Originally posted by 72Challenger
[B]Well DD, I have to disagree with you. Changes in the lifter diameter will result in changes to both the valve timing and the rate of lift. Your right that will affect duration and valve timing when vompared to smaller lifter diameter. like those cheby guys. |
#12
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As the lobe turns
[QUOTE]Originally posted by 6 packin
Quote:
And I also agree that up to a limit,such changes will take place. When toying with lifter dia; But it would be a very small amount . What I was trying to point out was the differance between a roller set up and a HYD or SOLID set up. Set up meaning (cam&lifter) packages as desinged. The Hyd valve events or slow and mushy at best. The Solid valve events are a little Quicker and more brisk. But the roller goes from base circle to wide open with a slap! Then once the valve is wide open it has more hang time. Due to the faster openning and closeing valve cycles. That in my opinion will deliver much more effect then any lifter dia; changes. To me the differance in lifter dia; would make such a small amount of differance,that it`s hardly worth mentioning. Just my opion no more and no less |
#13
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Well, remember that the original question was if roller lifters could be used on a hydraulic camshaft. The radically different profile is one reason why you can't. And if you're talking about the differences in lifter diameter between a Chevy and a Mopar, yes, they're minor. Still significant enough for serious GM racers to convert to mushroom lifters however. And the difference in valve action between the tiny contact point of a roller lifter and an almost 1" diameter Mopar lifter on the same lobe would be huge.
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#14
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Didn't mean to cause such a stir...
I just wanted to get some feedback on the idea from people that I figured would know more than I do.
To make a long story short, how this all started was a friend of mine was helping me try to brainstorm some ideas of how to improve fuel efficiency on my 400, and if possible, improve performance at the same time. One of the first thoughts was to follow the lead of the factorys and see if we could duplicate some of the things that they had done to improve fuel efficiency. This lead to the thought about the roller lifters. We really weren't out for killer power as much as trying to make the engine as fuel stingy as possible while still delivering decent performance. We know that there are roller cams out there in the aftermarket, but the other constraint is money, as in, practically none. But, as I already said, I didn't think it'd work because I was pretty sure the taper on the lobes would mess things up with a roller. The thing that really started all of this was an issue of Hot Rod from a while ago. They had issued a challenge for cars to do 12's and still get a minimum of 20 mpg. Of the cars that made the list, all of them were some sort of fuel injected something or other, so Hot Rod made another challenge to see if any cars that were carbureted would be up to the task. So he and I just started looking for all the other ways to improve efficiency of my 400 and still leave it carbed and streetable. Anyway, thanks for all the effort and debate. I'll just have to come up with some other ideas for showing Hot Rod what a Mopar is capable of. |
#15
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thanks
thanks for the brain tickler.
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#16
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Didn't quite understand your explanation. The roller lifters roll on the cam unlike the bronze gear and flat tappet lifters. They do not care about the aterial, as little as the rubber tires care about rolling on the ground. It is the hardness why the steel is needed, not the fact that the cams and lifter rolls have to be the same material. It's the same thing with things like real roller rockers like Harlan sharp; you'll need hardened shafts with them since the surface pressure of the needle bearings against the shaft becomes so big. And the thing that the rate of the lift and the profile of the cam is dictated by the lifter design is true. You can build a similar rated cam as a roller and as a flat tappet and they will still look very different. That is, the roller looking way bigger.
I don't want to argue about this either, the thing that is important is that: no they can't be used together. |
#17
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mis under standing
Quote:
If what you are saying is,that the roller lifters don`t care what they roll over then I agree. If your saying both cam and lifter must be made of billet or hardend steel then again I agree. If the cam is ground from billet steel ,then it will require a bronze distributor gear. Because the billet steel will eat the factory cast gear in no time. This will fill the oil with metal shaveings . |
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