Off the shelf cam options for marine engines
02-14-2016, 04:12 PM
#121
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Location: Olmsted Falls,Ohio Marblehead,Oh
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why back to 741's?
I had one of bobs cams in a 548 a couple boats ago. I had no issues with it, made excellent power and killer throttle response. Alot probably had to do with the iron eagles from valako. Built another with one of his cams that had issues with a leaky header, but the cam was fine. My current builds I went back to 741's.
02-14-2016, 04:14 PM
#122
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Hyd. rollers used to be limited by available lifters but that's not the case these days. We have hyd. roller lifters that can take solid lobe profiles and spring pressures capable of >8K rpm. Comp's biggest BB Chev hyd roller is only .680", but 271/283 @ .05. That's a very mild lobe with such low lift and long duration. I did a pump gas 532 last year with a 55mm .903 lifter hyd roller that was .768/.744 262/264 on a 110 and it turned 7800 on the dyno with no issues.
02-14-2016, 04:16 PM
#123
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Short duration with high lift -as a rule- can be asking for trouble but if the lobes are designed right and the supporting valve train is there it can be done reliably. If that's really the need then one needs to start looking at rocker ratios and not the lobe.
02-14-2016, 04:26 PM
#124
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It be nice to have some data on these custom lobes other than .050 numbers and lift number.
I think the other thing to consider, is at what point, is the extra lift, or increased acceleration, a benefit to the speedometer? These offshore boats arent drag cars looking to gain a tenth or two. Like my boat for example, 20hp per side isnt going to do squat for top speed, nor is making gobs of torque at 2400rpm, at the expense of upper rpm power.
I think the other thing to consider, is at what point, is the extra lift, or increased acceleration, a benefit to the speedometer? These offshore boats arent drag cars looking to gain a tenth or two. Like my boat for example, 20hp per side isnt going to do squat for top speed, nor is making gobs of torque at 2400rpm, at the expense of upper rpm power.
02-14-2016, 05:10 PM
#126
Just my opinion from what I've seen and run, and broke, the faster ramps with shorter seat timing give you better idle quality while making excellant power. But the springs, pushrods and all of the valve train must match the cam profile or you will trash everything.
02-14-2016, 05:54 PM
#127
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i am willing to bet my last dollar that any cam designer or cam grinder knows the damage that lobe ramps that slam the valves open&closed will cause in a marine endurance engine.also,imo a .680 lift hyd roller cam is going to be hard on even the properly set up valve train,the customer who buys this cam should be aware of that .things that will fly in a drag race engine that is done in 1320 feet won,t work for long in the marine world.i reciently built a pro charged 565 but used a solid roller cam and the lift&duration is more than i feel any hyd roller lifter can handle.
02-14-2016, 06:14 PM
#129
I feel like this thread is getting a little off topic. For marine 454's to 555's, we know the Crane 731, 741, 651 are all proven performers in a pretty wide range of combos. I have had really good luck with Lunati 20110669 234 / 244 .629 / .612 The 20110670 works awesome 238 / 248 .640 / .629 As well as the 0671 242 / 252 .640 / .629 All of those run with average spring pressures, and the smaller two I've used with stock gm lifters no issues. Any other known reliable Isky, or Howards grinds, etc. post em up. The comp XM lobes work well but don't make as much power as the lunati.
02-14-2016, 06:17 PM
#130
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