Cam bushings

Believe what you want..........

You say rollers are used because, "most stock cams have _much lower lift and much higher duration than that of a cummins performance street cam." Earlier you say, "In a most instances unless you are going with some really high duration, _high lift profiles, in my opinion flat tappets are superior." So when are rollers better, high lift or low lift? Rollers work with long or short duration cams, fyi.
Roller lifters allow for faster valve action than a flat tappet, and you can control it. You want to compare a short duration, medium lift cam that would require high spring pressures in a flat tappet in order to keep the tappet on the cam, which in turn creates friction and wear on the nose of the cam, which then wears the lobes faster. Why did you go to wider lobes??? I dont get it. Have you ever worked in other forms of racing? I have not seen a Cummins cam that has anything close to what I call a fast ramp. We have a fuel bike cam that has around a 1.2 inch base circle and 1 inch LOBE lift, JUST AN EXAMPLE. Can you picture that cam? Do you think that will work with a flat tappet? I WILL BET YOU THAT A ROLLER WINS THAT $50K RACE. Then you can go tell him you will make him a flat tappet cam that will make it faster. lol.... If you are after all out performance, which is what I thought this was, a roller set-up with lower friction, lower oil volume needs which reduces windage, longer life, and allows cam profiles that you cant match, WINS everytime. I will give you our fuel bike cam specs and you come up with a flat tappet that would provide the same valve action and live. You can make EXTREME valve action with a roller set-up in relation to crank angle. In any form of racing that allows roller cam set-ups have you ever heard of someone saying, "jeez, I think I will switch to a flat tappet cam and kick some azz."??? NOPE!!! BUT QUITE A FEW GUYS DO THE OPPOSITE. Fuel type or form of racing doesnt matter. Its all about friction. I dont have all the answers, but I know that if a roller set-up is an option, I want it. Just my opinion, but find me a engine builder that says if you want the most power possible to use flat tappets.
 
Good reading!!!

I would have to favor a roller hands down! I also agree I havn't seen any fast cam rates. Zach I have a question. What is the highest intensity rate lobe you have? Once again good reading. Jeff
 
Matty169
I guess what I was saying is that in roller cams that drive 200,000 miles or so, they are typically have larger duration by quite a bit and lower lift than say a hot daily driver roller cam for the cummins would be. THis is prone to sideloading the lifter which can cause a net increase in friction in the system even though there may be a decrease at the lifter/cam. BTW most every shop I have been to that messes with performance cams has at least one roller cam with a wiped lobe on the bench. THey are not a cure all or magic in any way.

What I was refering to on the larger lift, larger duration, I would not run a high lift roller cam unless it had a pretty good amount of duration because there would be a lot of sideloading on the lifter.

Like say a .360" 207@.050" I would not run in a roller due to stresses. I would not think about a roller cam with .360" until about 215 or 220@.050" Just my opinion, and I respect yours.

I can see you were not really looking to have an intelligent discussion about the benefits of each design in differing lift vs durations so I won't try to have a civil back and forth with you. I guess you just wanted to beat your chest and say I suck and that flat tappets suck and roller cams rule the universe and the 50k race. You win, I suck, as do all flat tappet cams goodluck on the 50k race. Just to let you know, there are a few flat tappet cams in cummins over 2,000hp without nitrous, but I'm sure they suck too.

Sting puller, in what regards, lift and duration or lift at varrying degrees of crank rotation?



Zach
 
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Cam

Open rate of lobe vs. lifter. I'm not a cummins guy by no means but on a duramax with the wheel dia. and lifter dia. I would think they could get pretty fast on the rate on the lobe. I have had limited ex. with flat tappet other than ceramic lifters from Shubeck. I just remember without welding the lobe and ceramic lifters we couldn't get very wild without destroying stuff in a hurry. That stuff was three times the price of roller stuff but I had to run it because of rules. Thanks i'm just trying to learn the diesel stuff. Jeff
 
Didnt say you suck.........

Hamilton Cams said:
Matty169
I guess what I was saying is that in roller cams that drive 200,000 miles or so, they are typically have larger duration by quite a bit and lower lift than say a hot daily driver roller cam for the cummins would be. THis is prone to sideloading the lifter which can cause a net increase in friction in the system even though there may be a decrease at the lifter/cam. BTW most every shop I have been to that messes with performance cams has at least one roller cam with a wiped lobe on the bench. THey are not a cure all or magic in any way.

What I was refering to on the larger lift, larger duration, I would not run a high lift roller cam unless it had a pretty good amount of duration because there would be a lot of sideloading on the lifter.

Like say a .360" 207@.050" I would not run in a roller due to stresses. I would not think about a roller cam with .360" until about 215 or 220@.050" Just my opinion, and I respect yours.

I can see you were not really looking to have an intelligent discussion about the benefits of each design in differing lift vs durations so I won't try to have a civil back and forth with you. I guess you just wanted to beat your chest and say I suck and that flat tappets suck and roller cams rule the universe and the 50k race. You win, I suck, as do all flat tappet cams goodluck on the 50k race. Just to let you know, there are a few flat tappet cams in cummins over 2,000hp without nitrous, but I'm sure they suck too.

Sting puller, in what regards, lift and duration or lift at varrying degrees of crank rotation?



Zach
Click to expand...

Didnt say you suck or your product. Didnt say that at all I dont think. Matter as a fact I was considering trying one of your cams, as I have heard they are great in comparison to what I have in my turd. (Helix II and Mach 6 sticks). Also, I am NOT entering that race. My truck could win if all the others broke, but thats about it. It only runs 12 sec. at 123mph at 6000 feet with street tires in 2WD.(traction issues abound) Your argument about crank angle really doesnt make sense to me though. With a flat tappet you have to account for valve lash being taken up before the valve even moves(wasted crank angle) Whereas with a roller you can move the valve quicker without having to account for valve lash clearances and you can run. As for wiped out roller cams, sure it happens, but how many wiped out flat tappets do they have? Here is the specs on our fuel bike cam FYI. base circle .940 inch, lobe lift .462 1.6 roller rocker, .74x valve lift, 340 degrees at .020, valve stays wide open for 35 crank degrees before starting to close. Theres a high duration cam for ya.
 
I agree, there are some very insane roller cams out there, just higher duration than what we need for a street driven cummins. Lash is still part of the equation on rollers. We design a lash ramp into all of the cams we work with. We have a lash ramp designed factoring for rocker ratio.

Very high duration on that bike, sounds like a crazy grind. I guess I was hoping you had something similar to the profile I described in the 207 @.050" .360" lift.

Sting puller. I think I might be able to quantify it for you we have a 190@ .050" .290" lobe lift duramax grind with 1.34 to 1.35 rocker ratio, I could compare lift at the valve with different degrees of crank rotation to our 188@.050" .290 lobe lift and a 1.35 to 1.36 intake rocker on a flat tappet 24v.

I will see if I can find the time in the next week or so.

Zach
 
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