waterbum

How about the 139651 from Crane.

139651 cam: at .050 lift
Opens Closes Max Lift Duration
Intake 13.0 BTDC 51.0 ABDC 109 244 °
Exhaust 67.0 BBDC 9.0 ATDC 119 256 °

These were put in my Dart tall deck 540s. 9.75 to 1 CR. Ported GM heads, dart tall intake, 1050 Holley carbs. CMI tube headers with dumps at end of pipes.

I'm not even sure what all these numbers mean. Engines run good, plenty of HP and torque. Needs 91 octane.

Max HP is around 5800 RPM.

Thanks,
Doug

rmbuilder

Tom,
The blower likes a late intake opening, good exhaust port (or go more ex duration)to reduce pumping losses from late EVO and a wide lobe sep and less overlap to reduce blowthrough.
Bob

PatriYacht

[QUOTE=waterbum]How about the 139651 from Crane.

139651 cam: at .050 lift
Opens Closes Max Lift Duration
Intake 13.0 BTDC 51.0 ABDC 109 244 °
Exhaust 67.0 BBDC 9.0 ATDC 119 256 °

These were put in my Dart tall deck 540s. 9.75 to 1 CR. Ported GM heads, dart tall intake, 1050 Holley carbs. CMI tube headers with dumps at end of pipes.

I'm not even sure what all these numbers mean. Engines run good, plenty of HP and torque. Needs 91 octane.

Max HP is around 5800 RPM.

See my comments above. This is the cam I was running in my 540's with Merlin heads. They ran great. Seems like a perfect cam for 540's with older style heads. When I switched to AFR heads the difference was night and day. The idle went to hell, they started reverting badly and they didn't power up the way I had expected. This winter I'm switching to a smaller cam.
Lift is .630
Ian

rmbuilder

John,
As Chris said look to your I/E ratio to set your duration. You dont want to over scavenge or you'll lose torque and your BSFC #'s.
Ian, Are you N/A or forced?
Bob

waterbum

Ian,
What improvements were you looking for when you switched from the Merlins to the AFRs? When you go to the smaller cam with the AFR heads, are you just cleaning up the idle and reversion issues or will you see more TQ and HP? I thought about some winter upgrades, but I'm kinda of afraid to change anything at this point! Hell, it took me 7 years to get the boat in the water. Might as well enjoy it for awhile before I rip it apart.

Good luck,
Doug

cstraub69@comcast

Doug,
Over camming will reduce the power range, make power range more peaky. I don't know whether the cam is correct for your application because I don't know what the heads flow.. . that will determine split and how long the valve needs to stay open to optimize the cylinder head flow to fill the cylinder. So I don't know. Can a smaller cam make more power. . .yes. . .peak and under the curve.

Chris

fountain333

there is a couple things that i don't understand here?? nobody knows what kind of piston, chamber volume ( compression ratio ) that this guy is running, let alone what kind of intake and everyone is giving him cam help ?? go figure?? The other question is can you explain in detail what over scavenging is rmbuilder?? if it were me i would get the afr 315 fully CNCed with the smallest combustion chamber you can get and run a flat top or dish piston if you have to and get the compression around 9.5 - 9.6 and run good rectangular port intake with a 4150 carb or maby a dominator a 238/242 comp solid roller on like a 110 and turn it around 5700 - 5800. then the motor would make some power!! and not just peak power either!!

articfriends

iTrader: (1)

fountain 333, you must not have read this whole thread,jeff (wags) is running a 502, 800 holley,dart 6200 single plane,114cc chambers,yields 9.2-1 with his pistons,his heads (afr 305ccintake w/cnc'd chambers)flow 344/268 at .500,367/284 at .600.
he is looking for a reliable,good running motor with decent midrange and good top end pull without crappy idle or reversion,Smitty

KAAMA

iTrader: (1)

fountain 333,

I don't think anything is always written in stone here---there's just other ways of doing things. I understand your frustration as you can get several differing opinions about all this engine stuff, but I think others will agree that rmbuilder and a few others who have been here for a while have always been willing to offer up helpful alternatives, and instruction to the guys here with pretty good/accurate info as they ask for it. I also don't believe their input is reckless either. Plus, I think everyone here pretty much understands that the person asking for the help has to weed out all the facts from the BS, etc, to ultimately make up their own mind, and decide what they're going to do.

PatriYacht

Very good questions. Right now I think that the engines are making peak horsepower at too high of an rpm for me to use. Going to a smaller cam will produce more hp and torque at a lower rpm. At some point going to a smaller cam is going to take away the airflow improvements that I spent big money on new heads to get. Hopefully there is a sweet spot where the engine runs pretty well and uses some of the airflow potential of the heads. RLW's dyno results lead me to believe that's possible.

A side benefit is improving the idle and reversion problems, although I would put up with them if the boat went faster.