WAGS382

Chris,
Do you think even the 761 is too big? What cam would you use?
RLW
I will be leaving the stock pistons and going with the 114cc combustion chamber option, I hope to get about 9.2:1.

cobra marty

I've allways like it when peak HP = peak TQ at about 5600 and 4700 rpm respectively, thats a tough marine motor.
6100 rpm is a bit high and would benefit from a smaller cam to move the peak lower. Although 605 HP is 1.33HP/CID and is nothing to sneeze about. You could give up a little HP for more TQ and be happier.

RLW

I will be leaving the stock pistons and going with the 114cc combustion chamber option, I hope to get about 9.2:1.

That clarifies my thinking.

WAGS382

Cobra Marty,
The dyno numbers are from a 454, I will be using a 502. Don't you think the peak tq and hp will come in at a lower rpm?

mcollinstn

Your 502 torque will be higher (prolly 30 ft lbs). It should come at 200 less revs, give or take.

This will give you a 5300 rpm hp reading of 598HP 593T
a 5800 rpm reading of 617HP 559T

Just guesses, but they should represent a pretty close apples-apples comparison between the 454 tested and a 502 in exactly the same dress.

WAGS382

BadDog,
The 731 has a 10* I/E split in duration, I would like to see 6* or less. From what I seen so far I think the 761 is the best off the self crane cam for this combo. I will be talking to Crane Cams this week again. I talked to Crane last week and the person I was talking to recomended the 761 but he didn't have any interest in the flow numbers from the heads. Maybe a custom ground will be the way to go. Jeff

articfriends

iTrader: (1)

Jeff,you can also call kip at cam motion,thats who ground my cam.A little smaller company where your not dealing with just a salesman on the phone.Smitty

HPJunkie

I currently am running that 741 griind on a 114 l/s vs. the stock 112 and I am very happy with it. It does have a procharger on it so It may idle better but its very tractable. Greg

rmbuilder

Wags,
The shelf cams (marine) available today were designed around flow numbers from cylinder heads designed 25 years ago. This is particularly true of marine catalog grinds that haven’t been updated in years due to the relatively small market share they bring to the larger companies. Simply put they will not come close to optimizing the flow capabilities of today’s AFR/Canfield type cylinder heads. The durations are to long and the splits to wide given the near 80% I/E ratios that are commonplace today. Much of the potential HP/torque increases available are underutilized by improper camming of these engines. It doesn’t make sense to bolt on a set of CNC AFR’s and cam it with a piece that was designed around flow #’s that aren’t even close and send those increases “out the pipe”. Due to advanced modeling and software, custom cams (designed around your particular parameters) are now affordable and readily available option to the marine market. There is extensive development going on today in marine camshaft design especially in the 502/540+ displacement area that is making high, flat torque numbers on the dyno, easier on the valve train, with much better VE and BSFC #’s. This is all done while keeping peak torque/HP numbers right where you need them. In your case approx. (without having all the numbers) 2*- 4* split around 228*- 230* @ .050 with intake approx .600” on 112* LSA and 108* ICL
One footnote, Jon Kaase just won his second Engine Masters competition by making the most average torque/HP under 6500 RPM. His cylinder heads had the highest flow #’s of the top 3 finalists and his cam the shortest intake duration. The flow maximizes the cylinder fill and the shorter duration valve events optimize charge trapping. It’s a win/win.
Bob

Turbojack

RmBuilder
What would you say is the amount of HP & torque that is being thrown away with say using the Crane 741 cam & Afr heads compared to the new type cams?