olysan

Hey Guys,

A few years ago I built a 406 with vortec heads and a comp cams xtreme marine cam with the following specs
Advertised Duration: 262 268
Lift and Lobe Sep: .462 .477 112°

I'm thinking about going up going to a bigger cam, because I think that the larger displacement of my 406 (relative to a 350) can support more cam and still keep the boat manageable around the docks. Also note that the vortec heads have been modified to include larger valves than stock. My exhaust is standard merc with "silent choice".

1st choice would be two steps up to this cam:
Advertised Duration: 278 292
Lift and Lobe Sep: .498 .500 112°

2nd choice would be one step up to this cam:
Advertised Duration: 270 286
Lift and Lobe Sep: .480 .489 112°

What do you guys think? Is anybody running a similar combo?

Mike

FIXX

iTrader: (2)

call bob mandara and have one custom ground..

formula 382 sr-1

iTrader: (3)

We ran Bullet Racing Cams in our 383's Great around the docks and good power part # 501000 Grind # chs288/296-10HR duration @ .050 223/231 lift .530/.548 separtion 110.

getrdunn

iTrader: (7)

Personally I like option 1 or even slightly bigger. You have basically added 16% cubic inch so... you can do the math. I am a little gunshy on camshaft selections currently as I just made some costly mistakes in regards to my valvetrain. I went a little beyond my normal HP ugrade this time. Sometimes pride gets in the way a little but as mentioned CALL BOB. He will take you places you have never been before and learn more in 20 minutes than you learned all day. There are so many variables especially in Marine. Your call will cost you nothing and if you decide you want to wing it on your own so be it however I would rather see you make the call than be potentially very disapointed with your selection. Every component you have including heads, valve size, flow numbers, stroke, bore, pistons, intake, carb, springs, retainers, valve stem size, desired running RPM as well as your current exhaust and compression. I could go on and on however I think your seeing what I'm saying. Even with the two cams you mentioned, without seeing the cam card and know more about your build I would really hate to advise. Unless I had a proven combo with your exact specs I would hate to say.

NOTE there is a lot more to the lobes than duration and lift. I could go on and on however I would rather have you talk to an expert. Unfortunately that's typically not a cam manuf. tech line either. They also almost sent me down a destructive path also.

Call Bob....

Ryan00TJ

iTrader: (8)

I agree with calling Bob Mardera of Marine Kinetics. 585-654-8583. He's the man. He did my 383's cam and its just what I wanted and more. We made just near 500hp with a tame setup that idles @ 800rpm N and I can lug it down to 650rpms in gear with no stalling. I've ran large solid rollers before and around the docks only I could drive the boat to keep from stalling. Not with this bad boy. From 650 to 6300rpms its a dream.

With your 406 you can easily add a larger cam and keep idle quality. Your limiting factor will be the stock SC exhaust. Also remember that the more cubes the more it will want to revert. From my personal experience I would not venture over 224 @ .050 duration with stock exhaust.
A tight split hyd roller like the Comp XM270HR would work nicely and be reversion free. The larger XM276HR would be even better with the 406 but be on the edge for reversion.

MOP

There is a chance that you suffer reversion with stock Merc risers with the hotter cam, you may want to give some thought to headers.

Phil

olysan

Thanks for the feedback guys. I will try to call Bob later today. I think reversion will be my limiting factor, and budget. I'm not setup for roller lifters, and I don't really have the budget for retro rollers so I'm trying to limit my choices to flat tappet cams.