ratman

i need some advice from rmbuilder or one of you other engine builders. i am building blown 588ci under square engs. 4.625 stroke 4.500 bore . crane cam 139661 was recomended. the cam has .632 lift 256/264 @ .050 . the cam card states recomended rpm range 4000 to 7200. i don't plan on turning me engines over 5600 with a 5800 rev limit. im running dart 360 cnc heads. do you think this is to much cam for my planned rpm range? thanks in advance for any advice you can offer. wanna cam it right the first time. ratman

Linster

I would back that cam down a size. A blower seems to mellow a cam out but with something that large, the motor is not going to want to idle under 1200-1400 RPM. If you have bravo's that will be an issue. That engine combo will be an issue with a Bravo as well. With that much idle, docking is going to be tough. The surge on that engine is going to increase with a larger cam. Also it will take a lot of blower to fill that large cam & those huge heads. I would think it would take a 12-71 to make that combo work. A 10-71 may do it, but you will be spining it real hard.

I did a 572, 8-71 blower motor last year for a buddy of mine. I used a 244/252 cam . That worked real well. It sounded good and would idle down to 900-1000. It really needed a 10-71 but we got it to work with 7% overdrive.

Good Luck

ratman

i am running 1071's with 2 850 cfm carbs, thx

cstraub69@comcast

You need no where near that much cam, something in the 240's max.

Chris

10x

Linster gave you good advice. The # 139651 cam with 244/256 works excellent for your situation. We have used that grind and VERY similiar ones with great success. My 557's would idle down to 900 rpm and not stall in gear at 650 rpm.
For the rpm's you're lookin to turn, make sure you have atleast 160#'s on the seat, and around #425-440 at 635 lift. This cam has a perfect cruise speed between 3500-4000 rpm. Install it on a 114 lobe separation, and you'll be fine.
BTW, I hope you don't intend on installing these engines in front of Bravo's?

PatriYacht

I have 2 of those 651 cams that I'm taking out right now. Very low hours maybe 40 total. Look like new. Cheap to a good home.

10x

Why are you replacing them, and with what other?

ratman

10X , im running ssm#3a's 1.5 ratio with 11 plate trans. i think the drives will hold up with three blade props.

PatriYacht

Frank, they don't work well with my heads in my aplication. 540 n/a with AFR heads. Check out the threads about AFR heads. Those guys are using less duration.

Edward R. Cozzi

Linster's right on the money. A cam that starts at 4000 will never let you load it at idle rpm. Who ever told you to use that cam in an offshore boat?