Cam Tech Talk on Custom Grinds
#11
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Just getting back into this, what a weekend. Between St Pats day and the OPA Kart 2 Kart bash, I just woke up from a nap. ![Big Grin](/forums/images/smilies/biggrin.gif)
Thanks for the input guys. Here's the problem I'm trying to solve; my current cam setup makes great power, tq comes on strong with 550+ at 3000 rpm. It also stays fairly flat with a peak of 625 at 4700, peak hp at 5400. This torque band was my stated goal with my the 04/05 winter upgrades, and I was and still am satisfied with the results. After all, I run P-class, and I am right at peak performance for my class. Just for clarification, hydraulic roller, spinning at 54-5600 rpm.
Ok, so that's not a problem... the real issue here is I had a problem last fall where a lifter tie bar rivet popped off, lifters rotated in the bore, lobes knocked off the rollers, lifters dug into cam, cam dust through motor, and All Bad from there. In trying to analyze the failure, there was a contingent from the various manufacturers and engine folks involved (let's leave names and brands out of this) looking at my numbers, and the concensus was I needed to make changes due to the "agressiveness" of the Xtreme Energy lobe profile (inverted ramp). There was no real evidence of valve float or lifter toss, so the solution was a theoretical one. The gist of those changes were to change springs to a pacalloy(sp?) based design, lighten up sprung weight with titanium retainer hardware, and increase spring pressures to 175 on seat and 415 over the nose. They were originally set to 150 on seat and 390 open. Of course, both motors had these changes applied.
Now that I'm putting things back together for the season, I'm revisiting my cam selection. Things to consider are moving away from the inverted radius ramp profile to ease valve train abuse, but my main question is what changes would need to be made in duration and lift to "make up" for less aggressive lobe profile. Avoiding another valve train meltdown is now my primary goal, preferrably without sacrificing my torque band.
And there's another option: be happy with how it runs now, and write off the previous incident as a fluke, which has since been adjusted and corrected. Pucker factor has set in, however.
I've got about 2 weeks before dyno sessions begin, so I'll be making a decision what to do this week. The cobwebs should be cleared out by the morning,
so I'll call a few of your suggestions tomorrow.
Thanks again for the help,
Brian
![Big Grin](/forums/images/smilies/biggrin.gif)
Thanks for the input guys. Here's the problem I'm trying to solve; my current cam setup makes great power, tq comes on strong with 550+ at 3000 rpm. It also stays fairly flat with a peak of 625 at 4700, peak hp at 5400. This torque band was my stated goal with my the 04/05 winter upgrades, and I was and still am satisfied with the results. After all, I run P-class, and I am right at peak performance for my class. Just for clarification, hydraulic roller, spinning at 54-5600 rpm.
Ok, so that's not a problem... the real issue here is I had a problem last fall where a lifter tie bar rivet popped off, lifters rotated in the bore, lobes knocked off the rollers, lifters dug into cam, cam dust through motor, and All Bad from there. In trying to analyze the failure, there was a contingent from the various manufacturers and engine folks involved (let's leave names and brands out of this) looking at my numbers, and the concensus was I needed to make changes due to the "agressiveness" of the Xtreme Energy lobe profile (inverted ramp). There was no real evidence of valve float or lifter toss, so the solution was a theoretical one. The gist of those changes were to change springs to a pacalloy(sp?) based design, lighten up sprung weight with titanium retainer hardware, and increase spring pressures to 175 on seat and 415 over the nose. They were originally set to 150 on seat and 390 open. Of course, both motors had these changes applied.
Now that I'm putting things back together for the season, I'm revisiting my cam selection. Things to consider are moving away from the inverted radius ramp profile to ease valve train abuse, but my main question is what changes would need to be made in duration and lift to "make up" for less aggressive lobe profile. Avoiding another valve train meltdown is now my primary goal, preferrably without sacrificing my torque band.
And there's another option: be happy with how it runs now, and write off the previous incident as a fluke, which has since been adjusted and corrected. Pucker factor has set in, however.
I've got about 2 weeks before dyno sessions begin, so I'll be making a decision what to do this week. The cobwebs should be cleared out by the morning,
![Roll Eyes (Sarcastic)](/forums/images/smilies/rolleyes.gif)
Thanks again for the help,
Brian
#12
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Originally Posted by Nordicflame
Don't forget to look at the Extreme Energy XFI HR grinds as well. (they're not just for EFI setups) These have even slightly more agressive ramps as well.
<stuff deleted>
Oh yea...It was $249 for any grind you want from Summit
Dave
<stuff deleted>
Oh yea...It was $249 for any grind you want from Summit
![Evil](/forums/images/smilies/evilB.gif)
Dave
And thanks for the Summit tip. Good to know.
Brian
Last edited by p4-33; 03-19-2006 at 10:33 PM.
#13
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Originally Posted by cstraub
Without knowing what the cam has to work with (airflow) all you can do is guess at a profile.
Along with airflow the combination and the rpm range is then considered. Lobe selection looking at duration on the seat, .050", .100", .200, .300 and so on can be catered to the engines requirements.
If this is a competition OEM headed BBC then you may want to look at grinding cams with 2 intake lobes, 1 for the good runner and 1 for the bad runner. This is old Pro Stock stuff but works very well on class limited engines. These cams are expensive but will squeeze more power out of the engine.
Along with airflow the combination and the rpm range is then considered. Lobe selection looking at duration on the seat, .050", .100", .200, .300 and so on can be catered to the engines requirements.
If this is a competition OEM headed BBC then you may want to look at grinding cams with 2 intake lobes, 1 for the good runner and 1 for the bad runner. This is old Pro Stock stuff but works very well on class limited engines. These cams are expensive but will squeeze more power out of the engine.
Please explain what you mean about 2 different intake lobes for "good runner and bad runner".
Thanks,
Brian
#14
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Originally Posted by BenPerfected
Hi Brian,
Consider talking to Dave Generous at Cam Techniques. Dave throughly understands the marine needs...all of them.
<stuff deleted>
As you know, I run my boat hard and I spend significant time above 6000 RPM. This package is excellent at top end, acceleration and idle.
I never checked my valve lash last year. As the engines sit on the shop floor, neither the intake or exhaust lash changed .001 in 2005.
Consider talking to Dave Generous at Cam Techniques. Dave throughly understands the marine needs...all of them.
<stuff deleted>
As you know, I run my boat hard and I spend significant time above 6000 RPM. This package is excellent at top end, acceleration and idle.
I never checked my valve lash last year. As the engines sit on the shop floor, neither the intake or exhaust lash changed .001 in 2005.
I've chased your boat while you were spending "significant time above 6000 rpm"
![Cool](/forums/images/smilies/cool.gif)
![Big Grin](/forums/images/smilies/biggrin.gif)
Thanks for the tip,
Brian
#15
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Originally Posted by Pantera28-650HP
Contact Bob Madera at Marine Kinetics. He set me up!!
RMBuilder on the board.
RMBuilder on the board.
Thanks,
Brian
#16
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Originally Posted by cstraub
.
.
.
Bullet
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.
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Sometimes the smaller guys can spend more time with you.
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Bullet
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Sometimes the smaller guys can spend more time with you.
Thanks,
Brian
#17
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Originally Posted by Nordicflame
Might as well swap 4 and 7 lobes while your at it
Comp does this for a minimal charge.
![eureka](/forums/images/smilies/eureka.gif)
What does swapping 4 and 7 do for you?
Thanks,
Brian
#18
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Originally Posted by p4-33
I've talked with Bob on a number of occasions, and he will be another call tomorrow,
Thanks,
Brian
Thanks,
Brian
#19
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Now I remember this project. Brian as much as RMbuilder helped you last year with your issues with the one engine I would highly suggest working with him.
BBC have 2 intake runners. These runners are different from each other. Grinding a specific lobe for each style runner can optimize the combination.
BBC have 2 intake runners. These runners are different from each other. Grinding a specific lobe for each style runner can optimize the combination.
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