Help with cam choice
 

Hi I was wondering if I could get some advice on a good hydraulic roller profile... I'm currently building a pair of 540
engines with a 9.5 cr.... will be using a dual plane air gap/ 850
and EMI manifolds and pipes. have been considering Comp cams
Dur @ .50 Lift lsa
299 319 243 257 .570 .554 107°

Thanks in advance Ed

I would say no way on the cam you posted. Too much duration, not enough lift and 107 lsa will need dry exhaust.

Crane #168741 or similar would most likely be a good choice.

We have a nice Ultra-Dyne hyd rollers ground up for our 540/650hp's .600 lift, 236 @ .050 and 112 centerline. We sell them for $295-Mark

243*/257* on a 107* lobes sounds like you might be headed for some grief....sounds kinda big. For about the same price you would pay for an off-the-shelf cam you can Call or pm "RMBuilder"/Bob Madara of Marine Kinetics in N.Y. He is an expert at taking all your engine specs and producing a custom cam profile specifically for your application. Bob specializes in marine offshore hi-perf cam applications and has does them all the time for guys with our kind of boats for several years.

Bob's number is...(585) 654-8583

Also, what kind of boat do you have? You might get away with running with a single/open plane intake manifold on a 540cid engine vs the Air-Gap dual plane intakes you plan on using.

I've got a 34 Scarab Ninja.... The reason I was choosing a Dual Plane manifold was in an effort to keep the torque up
however I appreciate all of your feedback and am open to any suggestions..... Ed

I would think that with a pair of 540cid engines in a 34' boat you should notice a big difference in torque just in cubic inches alone vs a 454 or 502cid engine....so, you should be fine with a single/open plane intake manifold such as a Dart.

The extra 1/4" of stroke of a 540 will give your boat a real kick in the pants.

Thanks for the info.... the boat currently has a pair of 454 / 420's and I was looking for a little more

I too am building a copy of a 420 but wanted a little more. i went with 230/238 @.050 .544/.544 witha 114. We shall see what it brings on the dyno.

I doubt you'll see much change with that cam.

Cannot go wrong with RM builder. He helped me with a cam set up that was based on what I was doing with boat. Pleasure to work with. Rebuilt 454 mk 4's with roller setup that dynoed 469 hp at 5200 rpm. Think I'm right on rpm. Used dual plane and eldebrock 750.

I agree with Griff.....you can try it, but you may not be happy with the results of that cam.

If you really want to see a little more of a kick, then replace the stock Merc cam with a hydraulic roller cam that will peak the engine at 5400-5500rpm, a mild bowl/pocket port of the heads while paying special attention to the shortside radius. Depending on the cam you use and the exhaust system you have you may even get away with replacing the GM dual plane intake manifold with an open/single plane intake. (I think the stock Merc 420 came with a dual plane intake manifold).

Also, (if you can) replace the stock Merc cast iron exhaust manifolds with something like a Stainless Marine aftermarket aluminum exhaust manifold system which will help the engines breath even better. Either way, it takes the right combination of parts to get the right results. Do this and you may see 475-500+hp from a 454.

Call RMBuilder/Bob Madara....he can help you with your cam app and engine combination.

Have the heads checked so they are not cracked between the seats. GM rectangle port heads are notorious for cracking between the seats at random.