Roller lifters/cams VS. flat tappets

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matty169

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#43- Trouble with Flat Tappets Reher-Morrison Official Blog

Now these guys build some of the most powerful engines in ANY form of racing. I believe the last ADRL race in the mountain motor nitrous cars they took 4 of the top 5 positions. You WILL NOT find cams with more aggressive lift numbers than those cars. FYI, some of these engines EXCEED 1 inch lift.
 
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matty169 said:
#43- Trouble with Flat Tappets Reher-Morrison Official Blog

Now these guys build some of the most powerful engines in ANY form of racing. I believe the last ADRL race in the mountain motor nitrous cars they took 4 of the top 5 positions. You WILL NOT find cams with more aggressive lift numbers than those cars. FYI, some of these engines EXCEED 1 inch lift.
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One thing to remember is an engine that runs 9000 rpm needs a little more spring pressure than an engine that turns 4500 or so.
 
I am in the process of building two pulling motors right now that will be spinning over 5000 rpm's. I am wondering what would be a good setup to run on these motors with this high of rpm's. My pump is going to be set up to turn around 5200 rpm while the other pump will have an ag gov assembly put on.

Would it be benificial to run a roller cam in these motors? One will be running a 2.6 class and the other a 2.8 or possibly a 3.0 class. Would there be a difference between the two? Just want to get some ideas on this.
 
shortbusdriver said:
I am in the process of building two pulling motors right now that will be spinning over 5000 rpm's. I am wondering what would be a good setup to run on these motors with this high of rpm's. My pump is going to be set up to turn around 5200 rpm while the other pump will have an ag gov assembly put on.

Would it be benificial to run a roller cam in these motors? One will be running a 2.6 class and the other a 2.8 or possibly a 3.0 class. Would there be a difference between the two? Just want to get some ideas on this.
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FWIW I have been told by a few people that if you aren't turning over 6k, the flat tappet will out perform the roller.

Any idea on lift?
 
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We have not decided on any specific cam, lifter, pushrod, or valve springs yet. We are just doing pump work and gathering parts for the bottom end so far.
 
j-rod said:
FWIW I have been told by a few people that if you aren't turning over 6k, the flat tappet will out perform the roller.

Yes ,you are correct. You just have to watch for the wear on the flat tappet cams, more so than on a roller. And now that we have this crappy oil out there it's even more of an issue.
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Sort of, but.......

zstroken said:
One thing to remember is an engine that runs 9000 rpm needs a little more spring pressure than an engine that turns 4500 or so.
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Weight of the valve and retainer being much higher in a dodge evens out the spring pressure actually. How much spring pressure do you think we run in a SBC with steel valves, flat tappets, steel retainers? .643 and .672 lift cam. FAST ramps and long duration. 1.7 roller rockers. Roller bearing cam and 9300 RPM. Rules forbid roller lifters and any Ti parts.
 
Wanna bet?????

j-rod said:
FWIW I have been told by a few people that if you aren't turning over 6k, the flat tappet will out perform the roller.

Any idea on lift?
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Back to back on a dyno. How much you wanna lose?:Cheer:

Taking the exact same engine, the area under the curve will be higher in a roller VS. non roller every time. Friction is friction, whether it be at 5k rpm or 9k rpm. You lessen friction, YOU WILL GAIN H.P.
Tell me why you think a flat tappet is going to gain on a roller set-up?
 
matty169 said:
Weight of the valve and retainer being much higher in a dodge evens out the spring pressure actually. How much spring pressure do you think we run in a SBC with steel valves, flat tappets, steel retainers? .643 and .672 lift cam. FAST ramps and long duration. 1.7 roller rockers. Roller bearing cam and 9300 RPM. Rules forbid roller lifters and any Ti parts.
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Does the weight even it out? Isn't velocity^2 used?
 
shortbusdriver said:
I am in the process of building two pulling motors right now that will be spinning over 5000 rpm's. I am wondering what would be a good setup to run on these motors with this high of rpm's. My pump is going to be set up to turn around 5200 rpm while the other pump will have an ag gov assembly put on.

Would it be benificial to run a roller cam in these motors? One will be running a 2.6 class and the other a 2.8 or possibly a 3.0 class. Would there be a difference between the two? Just want to get some ideas on this.
Click to expand...

j-rod said:
FWIW I have been told by a few people that if you aren't turning over 6k, the flat tappet will out perform the roller.

Any idea on lift?
Click to expand...

Diehard Ram said:
j-rod said:
FWIW I have been told by a few people that if you aren't turning over 6k, the flat tappet will out perform the roller.

Yes ,you are correct. You just have to watch for the wear on the flat tappet cams, more so than on a roller. And now that we have this crappy oil out there it's even more of an issue.
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If you are using the EXACT same grind the flat tappet may somehow be better but I just cant see a flat tappet being better than a roller cam with optimized ramp angles, lift and duration... The roller cam should always win in those situations because the cam can be set up to open and close the valve faster and allow for more open time because of that...

Now I am not sure if anyone builds optimized cams and roller lifters for our diesel applications but I would think they would definately allow for better performance...$.02
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O.K.

zstroken said:
Does the weight even it out? Isn't velocity^2 used?
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Sort of, but there is alot more to it than that. You have to take into consideration valve weight, retainer weight, angles, rocker arm ratio and weight over the valve, etc. How quickly are you trying to open the valve, and more important, close the valve in a controlled manner so it gets out of the way of the piston, but doesnt bounce off the seat. We use a 2.08 intake valve and 1.7 exhaust valve(moved) and have under 125lbs. of seat pressure.
As for the other person wondering about specific cam profiles, well, I cant think of a profile that a flat tappet would be preferred. Fast ramp, slow ramp, long or short duration, I WANT A ROLLER every time. Did you guys read that link and actually think about what is going on in that engine? Most of these things are answered in there.
 
matty169 said:
Sort of, but there is alot more to it than that. You have to take into consideration valve weight, retainer weight, angles, rocker arm ratio and weight over the valve, etc. How quickly are you trying to open the valve, and more important, close the valve in a controlled manner so it gets out of the way of the piston, but doesnt bounce off the seat. We use a 2.08 intake valve and 1.7 exhaust valve(moved) and have under 125lbs. of seat pressure.
As for the other person wondering about specific cam profiles, well, I cant think of a profile that a flat tappet would be preferred. Fast ramp, slow ramp, long or short duration, I WANT A ROLLER every time. Did you guys read that link and actually think about what is going on in that engine? Most of these things are answered in there.
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I understand that there are many things to consider, my point was just because the cummins stuff may weigh 2 times as much but travels at half the speed, doesn't mean it needs the same spring rates.
 
matty169 said:
Back to back on a dyno. How much you wanna lose?:Cheer:
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Reread my post. I have been researching this topic for quite some time. I am not making these claims...it is what I have been told by Cummins engine builders. Period.

Chris Tobin said:
If you are using the EXACT same grind the flat tappet may somehow be better but I just cant see a flat tappet being better than a roller cam with optimized ramp angles, lift and duration... The roller cam should always win in those situations because the cam can be set up to open and close the valve faster and allow for more open time because of that...
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I don't know why you would use the same grind on a flat tappet that you would a roller. That makes absolutely no sense. Again, you guys want to quote what I said, you should reread what I posted.
 
I read it, but........

j-rod said:
Reread my post. I have been researching this topic for quite some time. I am not making these claims...it is what I have been told by Cummins engine builders. Period.



I don't know why you would use the same grind on a flat tappet that you would a roller. That makes absolutely no sense. Again, you guys want to quote what I said, you should reread what I posted.
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What I am telling you is this. Friction is friction. It doesnt matter if it is in a sewing machine, Cummins, Chevy, or the space shuttle. You reduce friction in order to reduce heat, gain power(EVERY TIME), etc. etc. Show me one instance where you can gain power with a flat tappet over a roller. JUST ONE. Roller cams allow MUCH more aggressive profiles to be used and controlled, but even if you run street cams, rollers WILL reduce friction, rev quicker, and run cooler. You can also restrict oil to the top end gaining a little more. You can run your big azz heavy flat tappet or a lite weight smaller diameter roller, even with the same cam profile, the roller wins. As long as you are running heavy valve train parts you will be severely limited in RPM potential. Your heavy flat tappet has to change direction very quickly, right? In order to control that you need heavy springs, heavy pushrods, etc. Try this... tie a tennis ball to a string and tie it to your pecker and drop it. NOW try that with a bowling ball. Feel the difference???? You need to stop that weight and reverse the direction. Lite weight wins.
 
Actually........

zstroken said:
I understand that there are many things to consider, my point was just because the cummins stuff may weigh 2 times as much but travels at half the speed, doesn't mean it needs the same spring rates.
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Might want to check your math on that. Parts with twice the weight may just take MORE than double the spring rate, depending on several factors, such as ramp rate and lift numbers, etc.
 
matty169 said:
Might want to check your math on that. Parts with twice the weight may just take MORE than double the spring rate, depending on several factors, such as ramp rate and lift numbers, etc.
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kE=(m*v^2)/2

Holding the ramp rates and lift numbers constant.
400lb seat pressure on a small block is not uncommon and the cummins can get away with much less? I am running under 150 on the seat on mine, motor can run 5000+.
 
j-rod said:
Reread my post. I have been researching this topic for quite some time. I am not making these claims...it is what I have been told by Cummins engine builders. Period.



I don't know why you would use the same grind on a flat tappet that you would a roller. That makes absolutely no sense. Again, you guys want to quote what I said, you should reread what I posted.
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Matty already made the point I was trying to make... Roller will be better than flat tappet every time. I do not see any case where you can show that a flat tappet would make more power than a roller cam... It just doesn't make sense!!! Maybe you are confusing hydraulic vs mechanical lifters... in those cases the non hydraulic will make more power but there is also more maintenance and for street engines most builders recommend staying with hydraulic lifters, with roller hydraulic being the best for street engines...
 
Wrong.

zstroken said:
kE=(m*v^2)/2

Holding the ramp rates and lift numbers constant.
400lb seat pressure on a small block is not uncommon and the cummins can get away with much less? I am running under 150 on the seat on mine, motor can run 5000+.
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400 lbs SEAT pressure DOES NOT AND CAN NOT happen on a flat tappet!!! EVER!!!! Thats even too much for a roller set-up. Pressure on the nose, well, thats different. Also, if you think your valve is controlled at 5000 rpm with those springs you are wrong. Guarantee you that it is lofted over the nose if the ramps are even REMOTELY fast. We even tried ceramic lifters with a flat tappet. Guess what, as soon as you loft it over the nose and the lifter comes back to earth shiiit goes WAY bad way fast. And ceramic going through the engine destroys EVERYTHING, EVERYTIME. $30-50K paper weight. Remember several years ago at the beginning of the Nascar season? 2 big engine builders were lucky to have 1 engine survive the race out of about 10. Needless to say, ceramic lifters didnt last long. LOL
 
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Chris Tobin said:
Matty already made the point I was trying to make... Roller will be better than flat tappet every time. I do not see any case where you can show that a flat tappet would make more power than a roller cam... It just doesn't make sense!!! Maybe you are confusing hydraulic vs mechanical lifters... in those cases the non hydraulic will make more power but there is also more maintenance and for street engines most builders recommend staying with hydraulic lifters, with roller hydraulic being the best for street engines...
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Again, I invite you to reread what I posted. I am not making these claims. Perhaps you guys should talk to a few Cummins engine and/or tractor engine builders since you seem to be "shooting the messenger" here.

And no, I am not confusing hydraulic and mechanical lifters. LOL
 
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