Opinion needed on a 496 cam
 

This is a friends motor in a single engine 26 foot sleekcraft
The motor started out as a 365 mag motor, upgraded to eagle 496 ratator.
compression 10-1
ported rectangle steel heads (really opened up!)
single plane intake
850 holley carb
full MSD ignition

The cam they recommended was as follows
Hydrolic roller
610/610 lift
230/242 duration
112 center

What do you guys think?

What exhaust and do you have flow numbers on the cylinder heads after the work?

no flow number right now
The exhaust is the older CMI two piece tube top. No silent choice

Who's they ?

That made me chuckle. Good question.

The guy that said it ran good in a car!
Which made me chuckle

Another quesion, what are your HP goals and how many RPM's are you planning to run?

I just read your post over again. I see its your buddies boat, tell him to call Bob RMbuilder. The car guys dont know s--t about boat engines.

Dude! I told him to call Bob, he wouldn't listen.

Always talking 600 HP area at whatever RPM it takes.
The previous non roller setup ran at 56-5800

I'd rather see it down in the 52-5400 area. Something with more torque, especially with a single engine.

Compression ended up more like 10.25-1

Let me start by saying I shouldn't say what I'm about to say, are we clear!! Since your friend has no interest in listening to an expert he clearly is smarter than everyone. If he was spinning a mag motor 5800 WOT he was making noise not power, that cam can't support it. A hydraulic roller combo should not turn above 5400 or you risk valve float. The cam he suggests is not large enough for 5800 rpm and needs to be mechanical roller anyway for that rpm. I think what he really wants is a boat he can talk about. He should put a large duration camshaft with a 108 LSA so he has the most knarly idle in the marina, spend his money on a really cool sticker to put on the engine that says 600 HP or heck even more if he wants. The boat will likely barely come on plane and run terrible but it will sound really cool and show great when it is broke down. I'm sure he doesn't need a 3X18 oil cooler, or a quality oil pump, or upgraded fuel system either but it's a suggestion. Let me know when the maiden voyage is, I'd like to bring a cooler and a chair to watch it get on plane. Good Luck.

:lolhit::angry-smiley-038::evilb::eek::drink:

Now that's a good read!
The oil cooler comment is really funny since it has the stock little 330 cooler on it. I was able to talk him into changing that.

I'll work on getting him to call Bob again.

I agree with almost everything listed here except that a hydraulic roller is only good to 5400 rpms. Now, with that said, in order to go above that number you need really good parts that are matched. RM Builder designed my entire valvetrain and most of my motor for that matter and I was told to prop my boat to run at 6100. I've had no issues with valve float. Again Bob designed the engine and only the best parts were used. It can be done and last, but your buddy is going to have to listen the the experts and be willing to spend $$$$. Also 10.25 compression is too high for an iron headed engine, 9.5 is the realistic "on the edge" limit!

Wow, tough crowd here! :D You forgot to tell him to install an old school tunnel ram with dual Holley's for the ultimate visual effect. I agree with the other poster who said 10.5:1 is way high for a marine engine, unless he has an inside line on racing gas. That cam has too much overlap unless he is running headers that are dry most of the way to the transom.

I stand corrected on my hydraulic roller rpm limit recomendation, please allow me to correct it. You should not turn a hydraulic roller combination that has been specified by the experts at Summit or Jegs racing that utilize the specified springs and have been installed in the cylinder heads carefully under the highest quality tool steel retainers, above 5400 rpm. No measurements or checks are necessary because these are proven high performance kits that guarantee amazing performance with the value and convenience of kit pricing. They are flying off the shelf but if you hurry they have one kit left. Glad to hear he is willing to upsize the oil cooler, he probably found a great used 8" long one from a 502 MPI that blew up to use. Good luck, can't wait to hear the speed increase reports.

We are beating this guy up pretty bad and he is not even here to defent himself. Have your friend register on the forum, that would be more intertaining. :drink: Actually I hate to have somone repeat history and waste a bunch of time and money. I broke a lot of parts before I figured out what I was doing wrong. There is so much more to it than throwing in a cam kit.

Exactly. I'm being funny but his wallet won't think it's funny at all. I don't think it's funny either, just for the record.

I gave him Bob's number tonight. I may have gotten his attention.
Actually I tried Bob today to order a set of cams for my motors and couldn't get through, I'll give it a try tomorrow.

I would list my motors for opinions but I'd hate to get beat up on here :)

You wont get beat up if you are willing to listen. I was joking about him not listening to people that are clearly in the know. I'm no expert by any means, but I know a lil bit. I also know when to ask for help. No matter what your building someone has done it, blown it up, and done again until they got it right. There is no need to re-invent the marine engine at these power levels. Good Luck.

Feel free to list your engines. I got a lot of grief because I was building a short stroke BBC last summer. With the help of Bob M, I ended up with a 439 C.I. BBC that will hold its own against any HP500. There is always more than one way to do things but the key is to do it right and talk to the RIGHT people. Bob Mandera is one of those people we should be thankful is available to help us. My Formula 242 is a heavy boat and needs big power to go fast. I finally got mine out and with an exhaust swap and a different prop I was able to pick up 7 MPH for a total of 69 MPH over my best of last year. Most guys with formula 242's are building 540's to get that speed. My point here is that it's not all about Cubic Inches and Torque as most will lead you to believe. Its about correctly matching the parts to your goals and your boat. A smaller engine can make big power and torque if designed and built correctly.

Congrats on your build, the numbers speak for themself!

I know how hard it was to trip the 70 mark with a 242 LS. Took a lot of fine tuning of an aluminum headed 502 (about 525+ HP) and a shortie to get there for us. Best GPS speed was 73.4 in the end. Actually Bob was very helpful in tuning the motor to get there, even without me ever spending a dime with him at the time.

Anyways, on to the new project
Motors started out as 1995 Gen V 502 mag motors (EFI)
Bored to 509 - 9.2-1 JE pistons
H beam Rods
Stock heads
Crane Roller rockers
HP 500 intake
HP 500 Carb
Thunderbolt IV Ignition
Gil Exhaust without silent choice

Now the cam was setup for the origional EFI setup that I removed, sorry I like the carb better for me. I can work on it, and my goal was to remove this flat tappet cam and go to a good roller from Bob.

Billet Racing Cam
550/558 lift
231/239 Duration
114 Seperation

I have no idea where I am HP wise and I am pretty sure the cam and intake combo are not the best setup. But, that should change when $$$ works out.

So the cam listed is flat tappet that you have now, or the proposed hydraulic roller? Have the heads been prepped for .650 lift at the valve, and what are the springs.

I think that is the spec from his current flat tappet cam. Bob can get you one with way more lift and less duration.

jeffswav is correct, the listing is for the existing flat tappet cam.
I plan to upgrade springs, hydrolic roller lifters, and cam from Bob eventually.

I pulled some old dyno sheets, found a 509 basically started as carb 502 MAG, GM rectangle heads, GM dual plane I cut the divider down 3/4", Holley HP 950, stock ignition, the cam was Ultradyne flat tappet with your same duration specs but .570 lift both sides. Engine made 508Hp @ 5200 rpm and 538 ftlbs @ 4300 rpm. A good roller cam with same other parts except simple port work to the exhaust side runner floor and short turn, makes 565HP @ 5400 and 575 ftlbs @ 4400 rpm. Fuel distribution is better with a single plane manifold, it is easier to maintain consistent EGT with a single plane. Hope this helps.

That is great information, thanks for the follow up!!!
My goal was anything around 525 HP

Ok, so he didn't listen to Bob (RMbuilder) or me and went with the cam I mentioned in the 496. Honestly what should this thing run like? I think his boat is very forgiving on combinations as far as getting on plane.

No ideas?
He didn't upgrade the oil cooler either

He's a idiot, he should right a song. "Things that make it go BOOM !!!! "

I was thinking it would live, but run poorly.
Really think it won't live?

This thread has been going on for a while. I see he has the mag oil cooler, if it were the 330 oil cooler it would not last long. Not sure if the mag cooler will work, someone else may have tried it and give some input.