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Cam and valvetrain longevity....??? low duration high lift...

Old 09-16-2016, 06:58 AM
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Originally Posted by dunnitagain View Post
Looks like another Cam thread. What most don't realize is when the lift increases on a Lobe , the Duration also has to increase . Because of Valvetrain Stability. The magic bullet , high lift low duration cams, have a built in flaw . There is not enough Duration on the lobe to control bounce and loft. Everyone thinks that a lifter follows the lobe exactly. Not true. You have what is called Loft , at increasing RPM , the Lifter does not want to follow the lobe . Inertia takes over and objects in motion tend to stay in motion.
Thus the lifter jumps the nose of the lobe , and tries to land gracefully on the backside of the lobe. If it lands to far down the lobe , it bounces. Which sets up a Harmonic through the whole Valvetrain , The only solid points to dampen the Oscillations are , the Lifter and Lobe interface , and the Valve to Seat Interface. Resulting in Valves and Valve Seats that have been beaten to **** , Or Lifters that break due to the severe harmonic ( Bounce ) that is placed on them.
I know the theory , and the brain trust , behind the Magic Bullets. Trust me there is no magic bullet. If a name brand cam company doesnt have the lobe
configuration your looking for, There is a good reason why. That Reason is Thousands of Hours , and Millions of Dollars of R&D into Master Cam Lobe developement. That
actually works .
Well put,

Last edited by F-2 Speedy; 09-16-2016 at 07:41 AM.
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Old 09-16-2016, 06:59 AM
  #42  
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Old engines 557 ci or 565 can't remember was 4.375 stroke, 6.385 rod .060 flat tops 9,5:1, pro comp heads 320 cc, cam was 236/[email protected] and .578 lift on a 114, same intakes, hp500 carbs 800 CFm [email protected], [email protected] boat went [email protected] flat water actually was the best speed day, might have had more

New engines [email protected], 630hp @5900 best I seen 73.1 one time mostly low 72mphs

Another mistress with Trs I know of went 73.5 with 509's making 600tq and 540 hp.... Not sure rpm on Dyno

Now my boat may be heavier then his a little with AC, stereo or whatever but gotta be close...

I'm pulling my hair out trying to see where these builds went wrong and it seems the cam....biggest issue
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Old 09-16-2016, 07:20 AM
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Just for the hell of it, list every spec of your engines
Deck height
Quench height
Installed cl of cam etc
Let's look at everything
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Old 09-16-2016, 07:22 AM
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Forget about the old engines. They are gone. Forget about other Mistresses. No two boats will run the same. Obviously your goals were not met with this build. Are you not at the point now where you pull the mills, take them to reputable builder, give them your performance goals/budget, and let them do all this heavy lifting for you? And at the end of that road if your objectives are still not met at least you can finally rest your mind knowing that it is what it is?
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Old 09-16-2016, 07:46 AM
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Pistons .010 in hole square decked
Not sure how to figure quench, head gasket is .039 compressed marine gel pro, non figured .030 cosmetics but I went over that way back and decided regular was fine.
540ci dart 9.5:1 flat tops
Cnc afr 325's
Cam 241/246 681/663 on 112 I have to find degree paperwork I can't remember off top of my head I think came in at 107.5? Don't hold me to that been a while lol
Scorpion 1.7
Trend .135 pushrods
Pro comp single plane intakes
Quick fuel 1050's
Gutted 3" flame arrestors, plenty of air to hatch, monitor mid to high 11's to a 12.0 air fuel at WOT
TIMING at 35
Originally Posted by Unlimited jd View Post
Just for the hell of it, list every spec of your engines
Deck height
Quench height
Installed cl of cam etc
Let's look at everything
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Old 09-16-2016, 07:48 AM
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Originally Posted by Knot 4 Me View Post
Forget about the old engines. They are gone. Forget about other Mistresses. No two boats will run the same. Obviously your goals were not met with this build. Are you not at the point now where you pull the mills, take them to reputable builder, give them your performance goals/budget, and let them do all this heavy lifting for you? And at the end of that road if your objectives are still not met at least you can finally rest your mind knowing that it is what it is?
why would I redo it all for another 30,000 plus to have a guy build what I can myself? That's dumb, I cannot spec my own combo from heads up, I can build engines clearly, that being said... I relied on Bob to design my setup like he did other, it did not work and that's not my fault, I am taking a cam change to make it last and maybe gain Hp not a complete start over here, it's easy for others to say that but in the end it's my bank getting spent.... I can simply add 5 lb pro chargers and gain 150+ hp all day, that's not the issue.... Longevity concerns are....
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Old 09-16-2016, 07:50 AM
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I know old engines and other boats different, doing that for example and as far as comparing to other mistresses yes it give you idea, I am not comparing to a cafe, gun, apache, Baja or fountain... Comparing to closest things possible ... MISTRESS
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Old 09-16-2016, 07:51 AM
  #48  
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As far as reputable builder or spec? Thought Bob was.... You see how that worked out... Fail!
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Old 09-16-2016, 08:25 AM
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Originally Posted by dunnitagain View Post
Looks like another Cam thread. What most don't realize is when the lift increases on a Lobe , the Duration also has to increase . Because of Valvetrain Stability. The magic bullet , high lift low duration cams, have a built in flaw . There is not enough Duration on the lobe to control bounce and loft. Everyone thinks that a lifter follows the lobe exactly. Not true. You have what is called Loft , at increasing RPM , the Lifter does not want to follow the lobe . Inertia takes over and objects in motion tend to stay in motion.
Thus the lifter jumps the nose of the lobe , and tries to land gracefully on the backside of the lobe. If it lands to far down the lobe , it bounces. Which sets up a Harmonic through the whole Valvetrain , The only solid points to dampen the Oscillations are , the Lifter and Lobe interface , and the Valve to Seat Interface. Resulting in Valves and Valve Seats that have been beaten to **** , Or Lifters that break due to the severe harmonic ( Bounce ) that is placed on them.
I know the theory , and the brain trust , behind the Magic Bullets. Trust me there is no magic bullet. If a name brand cam company doesnt have the lobe
configuration your looking for, There is a good reason why. That Reason is Thousands of Hours , and Millions of Dollars of R&D into Master Cam Lobe developement. That
actually works .
Some good text book info but last comment regarding lobe design I don't agree with. Theres is always improvement and power to be made especially with all the cnc heads and different heads and combinations available currently. Most the cam books from the major cam manufactures have been lazy over the last decade or two. Most offshore label flat bottom jet boat. No comparison what so ever. Lunati has probably kept up the most but regardless my point being is there is a need for ongoing r&d that I feel most have slacked off. Look at computers for instance. Just sayin...
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Old 09-16-2016, 08:27 AM
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Its not often, a guy has a similar cubic inch engine, with decent aftermarket heads, cam, intake , carb, etc, then basically builds another similar combo, but with different brand parts.

If you had gone from your 420hp 454 mercs, to these builds, you would probably be nominating bob m for president. Youd be happy gaining almost 10mph with your new build . Unfortunately, you arent the average guy who calls bob to upgrade his stock engines that run on 87, have stock heads, small cams, built for longevity merc engines, gains some power, and is happy as a clam. Or the guy whos building his first high performance blower build, and is amazed at the dyno sheet.

At the end of the day, its a 540ci chevy. If you cant make decent power with a aftermarket head like afr, dart, brodix, EQ, a decent induction combo, cam, etc , you really shouldnt be in the engine business. These combos been around for decades now. You can pretty much slap together a 540/650hp combo right out of the summit catalog, and have all the parts in stock and to your door in a couple days. A secret ramp profile , .040 extra valve lift, or any of that fancy talk, isnt going to do chit for your speedometer, if you way off on the cams timing events.
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