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496 Cam Recommendations

Old 01-29-2020, 09:01 PM
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Default 496 Cam Recommendations

Been window shopping for a cam for a 496 build I'm working on. Any recommendations for a proven off the shelf hydraulic roller cam that works well in a 496? Boat is a 23' single engine Nordic, 3500lbs. TRS drive. Interested in the Crane 741 but not sure if it might be a little too much. Planning on running a Gen 6 cam in my Mark 4 block. 6K rpm max. Also what roller lifters do you guys like? I'm thinking of the Isky HPx Silver Series made by Johnson. What do you think about the Short Travel lifters?
496
Mahle pistons 10.2 CR
6.385" rods
Lunati crank 4.25"
Brodix Race Rite BB2 Plus 312cc 119 cnc chambers 2.25"/1.88"
RPM Air Gap w/850 DP
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Old 01-29-2020, 09:57 PM
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A 741 would fit the bill well on this setup. Id expect peak hp 57-5800. Short travel lifters are excellent. Triple check your preload though. Also plan on the possibilty of custom pushrods through a company like Manton ( meaning up to 16 different lengths). The benefits of short travels far out way the added costs of proper setup especially with heavy valvetrain

Last edited by mggdoors; 01-29-2020 at 10:02 PM.
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Old 01-30-2020, 02:37 AM
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The 741 should work well in a 496 stroker.
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Old 01-30-2020, 08:54 PM
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I've had great luck with these. An old time drag racer spec'd it out for me...


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Old 02-01-2020, 09:55 AM
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What exhaust will you be running? The 741 cam will not be too big. For a 6k rpm combo, it will actually be a bit small for a 496ci. Id also lean towards a single plane intake on a combo like this.
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Old 02-01-2020, 11:30 PM
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MT, I'm running a pair of old school Hardin P1000 headers.
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Old 02-02-2020, 09:05 AM
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Pickle, here is a build that had a similar cam as the 741. It was borgies 496 build. Cam was a madera 237/246 112 lsa with 650ish lift. Very similar to the 741 crane. Afr heads

made nice power. Definitely not a 6000rpm engine though in my opinion . While it technically "peaks" at 5900, you can see there really isnt much point turning it past 5500 for a 10 hp over a 400rpm increase. Stepping up a bit, to something in the 242/248 range, would have likely netted additional power above 5500rpm, and made it worth turning to 6000. Likely at the expense of a little less low end tq. Either cam would work well, just depends what youre looking for. I certainly wouldnt go smaller than a 741 on your build. I think the 741 is better suited for 4" stroke combos like a 454 or 502.
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Old 02-02-2020, 01:37 PM
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Default Peak hp

I had a 244/248 hyd roller in a 496 combo and it peaked at 5,800 however that was after advancing the cam 4 deg. With solids and spring swap peaked at 6k. Definitely to much duration for that combo. Considering I was wanting to peak near 5,800 to 6k. In a 540 CI peaked at 6k with same cam installed straight up.

Just throwing it out there for some info.

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Old 02-02-2020, 01:56 PM
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I dont really care much about the point of peak power (within reason that is). My 468s kept making power to 6500rpm on dyno. I ran them at 6200 in boat though.

If you were to look at volumetric efficiency on a dyno sheet , one must simply ask where he wants his greatest volumetric efficiency. Alot of builds, the VE plummets after peak torque. The engine might be 100% VE at peak torque, and nose dive where you might think the best wot rpm is with your prop setup. This is why sometimes, a guy might find his boat goes faster with more pitch and less wot rpm. No point in spinning it past the point of good returns.

If you look at the above dyno sheet, you can see the HP is still climbing after 5500, but the torque is falling off substantially. It gained 11hp over that 400rpm, but dropped 30ft lbs of torque. The fact the bsfcs climb, shows the engines efficiency is going downhill. I cant say for sure, but id be willing to be, a bit more duration, and torque between 5500-6000 would have increased, as well as improved the bsfc there also. In order for HP to increase after 5252rpm, the torque has to increase as well. No way around that math.
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Old 02-02-2020, 06:25 PM
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I get it completely especially when you look at the numbers. Why throttle 500 + - more rpm on your engines/drives for an extra 10-15 hp.

I wonder how the old worked over 049's would perform in a 496 with either of two cams mentioned with the single 2904 eddy intake or airgap. Twin app heavier boat. 5,500-5,700. Stock heads are pretty much done at .520 lift or so but with the right port job can get get half way decent numbers up to .600 plus or so. Not looking for any serious power but I would think you could achieve some decent numbers for some budget builds.
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