cstraub69@comcast

You wont need that much duration. All it will do is raise the powerband to the upper rpm range and not make useable power. . .IE Narrow power band. Lift is to small. Blower like to get the air in and out quick. A lobe with a more aggressive lifter velocity would be a better choice.

Chris

rmbuilder

Fastlane40,
Because the 2 cams you listed are Hyd-Flat, do you intend on staying with the flats or converting to roller?
GPM,
What would be the advantage to running the 3299/3295 lobes in this application?
They are the Cheater HR Lift Rule Competition family, which are extremely aggressive competition profiles that are clearly categorized as a "Race Only". They were designed for "lift rule" racing with very fast opening rates and clearly present a durability issue in a marine engine.
Bob

Notched_Baja

I think the Crane 741 would work well. It's been a proven favorite.

GPM

Over the last 15 years or so I found better power with the "Race Only" cams, I've had no durability issues when matched with the proper componants. I would rather see more lift, but I don't know if this application will alow it, the above cam may already be to big. It was only an option, the same as the Crane. Staying with the flat tappet hydraulic would be much cheaper. How much lift can he run in stock condition?
What's your recommendation Bob ?

rmbuilder

Some suggestions for a blower Cam.
A wide lobe separation (112*-115*) to reduce overlap and blow through.
Blower engines need less (2*-4*) advance. An early IVO is unnecessary. The intake column is pressurized and early openings increasing overlap. A 110*/112* ICL on a 114* Lobe sep would work well.
Increased exhaust volume requires blower cams to have additional ex duration to rid the cylinder of spent gasses. This is dependant upon the efficiency of your exhaust port. 8*-10* spread is a baseline reference.
Stock exhaust ports need an earlier EVO to blow down the cylinder. The negative of and early exhaust valve opening is the loss of some of the increased cylinder pressure. The negative of a late EVO is increased pumping losses. Optimizing your exhaust port will help, allowing you to delay the EVO, negating the pumping losses.
If you choose to go with a custom profile you need to determine your head flow and mechanical parameters, your peak torque/HP range, and then the cam can be calculated. I agree, staying in stock configuration with a flat tappet will limit lift
If not, (2) proven OTS flat tappet cams that provide reliable power(peak@ approx 5500 RPM) with moderate boost, valve train stability, and durability:

Lunati 02005
302*/308*…224*/234*….534”/.559”…114* LSA
2°BTDC 42°ABDC /
55°BBDC -1°ATDC

Crane 132561 H-228/312-2S-14 T1.2 (525 SC)
298*/306*…..228*/236*……530”/.551”…..114*LSA
5°BTDC 43°ABDC /
57°BBDC -1°ATDC

fastlane40

GPM and Rmbuilder.Thanks for taking the time and helping me out.Will the 525SC cam fit in a 502HO GenV crate motor?If it will fit will it provide benefits over the standard cam?

Panther

RM, I went with the next step up from that Lunati cam in my 580" motors we are building. I believe it was 234*/244* and .557/.595 with a 114* LSA or something close to that. Don't have the cam card in front of me but I think it's going to work out well.

GPM

Look at the cam and the power MESA is getting out of a blown 383 small block, does it tell you anything.

rmbuilder

That its not a 502 crate motor
Bob

GPM

I'm not saying to go as big as the 383, but a 502 crate motor with forged crank, rods, and pistons, 1/4 more stroke, 119 more cubic inch can take a decent size cam and make good power in a useable power range. I disagree with the 114 lobe separtion, from what I've seen on the dyno,they may idle just a bit smoother, they do extend the power range a 100 or so rpm but they cost low and mid-range torque, vrs a 112.