Nordicflame

iTrader: (4)

After looking at the recent dyno tests that have been posted showing results in naturally aspirated 540s with the Crane 741 cam I have a couple of questions.
In the dyno sheets I have seen the motors are still climbing the hp curve at 5700 rpm plus while the peak torque shows to be around 4600 which would leave one to assume that by most input you would have to prop at ~5850 for optimum speed. This is based on Hydromotive’s and several others steadfast rule that you must prop at 1250 rpm over the peak torque number to achieve optimum speed. (I see that this rule is also applied in all of the Merc motors also)
1. So, assuming that this rule is correct and that most don’t want to spin their 540’s at near 6000 rpm all the time, is this too much cam or should it be installed 4-6 advanced to bring the peak torque down to say 4200-4300?
This would allow one to prop at 5500 rpm and be more efficient. By efficient I’m thinking more bottom end, better cruise torque and possibly even a few more hp at ~5500 rpm.
2. Do you think this is the best cam for a ProCharged 540?

Thanks,
Dave

mcollinstn

741 comes ground on a 5 degree advance. If you install it with zero offset timing components, it "should" be 5 degrees advanced already.

Haven't knowledge of what dyno curves you refer to, but keep in mind that "most" dyno sheets are on dyno headers which will usually allow freer high rpm flow and skew results towards the top end versus in installed marine application.

Beak Boater

We used the 741 cam in our whipple charged 540's with AFR aluminum heads and CMI exhaust. Idled at 700 rpm had plenty of low end torque and the motors pulled very hard from 3300 rpm up to 5800. The motors were set up with a compression ratio of 8.3 to 1. The transom stayed clean, which caused me some concern that it was lean, but Whipple did the ECU and they were set up just perfect. Dont know much about the procharger system, but that cam worked well in my application.

KNOT-RIGHT

I have run the 741 cams for the last three seasons
normally aspirated.
540 ci. Dart tall decks.
merlin cast Iron fully ported heads.
9.5 to 1 comp ratio
merlin single plane intake
dominator 9377
prove to be reliable.
Idled at 900 and pulled to 5200rpm.
Motors were never dynoed but the boat came to life at 3300 and held to about 4900. From 4900 to 5300
the props needed to brake loose to get the 5300.
(Surface drives 1.33 to one 17x28 rollas)
Cams were straight up.

I am Keeping the 741 crane cams..

Installing super chargers with intercoolers for the new
season.


Here is a copy and paste of the 741 specs.
Notice "aftermarket dry pipe exhaust systems"
Notice "454-502+ cu inch.

Rough idle, for 454-502+ cu. in. modified engines in performance applications with aftermarket dry pipe exhaust systems, 10.0 to 11.5 compression ratio advised. Basic RPM 2500-6000 PowerMax
Hydraulic Roller
HR-296-2S-12 IG

Cam Specifications


Degrees Duration @ .050 Int./Exh. Degrees Advertised Duration Int./Exh. Degree Lobe Separation Open/Close @.050" Cam Lift Int./Exh. Lash Hot Int./Exh. Gross Lift Int./Exh.
234
242 296
304 112 10 44
58 4 .000
.000 .610 .632

I would Install it straight up.
I wouldn't spin a hydraulic roller past 5600 rpms.
I think the 741 is perfect for your application.

Just my 02.
Gerry