TomZ

I'm going to be changing the cam in my 383 to something a little wilder to make up for the difference in displacement over what Comp recommends. The current cam is a Xtreme Marine 262H with these specs:

XM262H 262*/268* Adv dur, 218*/224*.050 dur, .462/.477, 112* LOA

Comp advises that this is the biggest that one should use with an I/O. The rest of the cams listed in that line are designed with a jet in mind. My builder thinks it's too mild for the displacement and that there is definitely some hidden useable power to be found there. Due to the set budget requirements set forth by "the one who must be obeyed," I cannot go the roller route which was what I had planned originally.

I will definitely be going with Comp as I can get a sweet deal on anything that I get through them (through the shop).

With the first motor that I had built it made 390hp and 450 ft lbs of torque. 400 ft lbs was on tap from 2500 RPM and on. We did not dyno the replacement, but I'm told that it should put out as much if not more power than the first since the bottom end was straightened out. All of this was with a 385 CID, 9.8:1, ported Vortec heads, and the above listed cam. The boat was on plane by roughly 2k RPM (not even breaking a sweat).

What do you folks think? Suggestions? What about reversion with bigger cams... any threshold? I use Marine Power center-riser manifolds with 4" risers which are not extended. They do seem to exit water a little farther down the pike though than the old three inchers did.

Oh, the boat is a 23.5 ft cuddy... I guess more like a runabout than anything. Weight is 3415 dry and holds about 80 gallons of fuel, no water and an Alpha One drive.

Thanks!

TomZ

I saw the other cam post farther down the line. With the 262H I do not see any problems with reversion using the manifolds that I have now. I boat in salt and semi salt water and as such I think that cast iron manifolds will be the best for my situation (God help me if I mention needing to buy a new set of stainless manifolds and risers).

With that said... please go on.

traviss

for a Idea..I am going to run the Crane roller cam #109831. 222/230 at .050 duration...509/528 lift....112 LSA
I choose this one and to get a peice of mind I called crane and they set me up with the same one I had choose.

383
4340 eagle crank
H beam eagle stroker rods
forged full floating dished srp pistons 9.9:1
edelbrock air gap intake
750 holley w/1" spacer
vortec heads, 7/16 screw in studs, with guideplates.
Crane full roller valvetrain

stock exhaust so far.. running outta money


This thing is built like brick ****house

it is going in a 18.5' powerplay tippin the scales at 3000 lbs. with a alpha..

There is one more cam above this, they say this is the biggest one to be used in a marine motor. it is crane #119641... 234/242 .050 duration.... 539/558 lift on a 112 LSA..

traviss

I just read a little more info and I am going to run the 1.6 roller rockers. so my cam will be ..222/230... .543/.563 lift at a 112 LSA..

jr

Tom, I'll bet that the reason that Comp Cam said that cam is the biggest for I/O's is not because of the lift or reversion, but because of the idle. Remember that alpha of yours needs a momentary "stall" to get out of gear. If you go with something too wild you might start stalling out when youre trying to shift out of gear. Also make sure you have enough clearance to the pistons. My guy was saying youre okay until you get up around .520 then you may need reliefs or dishes to get the clearance. But I also had the blocks and heads decked.

Now are you going to end up like me with a boat all torn apart over the summer. Mine is finally in one piece. My wife is already asking how all the other projects are going to get done if the boats in the water this year. I told her what projects!

TomZ

I think I'm good with the valve-to-piston clearance. The stall issue is something I didn't think about though. I guess I'll have to keep in mind the idle characteristics and such.

I'm not going to have a dead boat this summer! I'll have it running before the spring thaw and as soon as the river water starts warming up we'll be out there.

Thanks on the stall issue though... I totally forgot about that part of the equation. I would have been pissed if every time I had to shift the engine died!

jafo

TomZ- I know you're going CompCams and have a stroker- this is what I came up with for my 355's and they work great ( a little lumpy on the non-stroker but no problems with the Alphas and their shift interruptor)-would work great on a stroker motor as well. I've always had good luck with Iskendarian Cams. This a little similar to the 280H?
Isky Dual Pattern MegaCam
270 intake, 280 exhaust
221 intake, 232 exhaust @ .050
.465 lift intake, .485 exhaust
112 degree lobe center
Running Comp Magnum Rockers 1.6 on intake only for a intake lift of .498"
All in all it's a pretty impressive marine grind. No reversion problems at all either on EMI Thunder exhaust.
Jim

[ 02-10-2002: Message edited by: jafo ]

TomZ

That's the same cam I was running in my 355 a while back. I thought it was a bit much for the 355 and the heavy boat BUT the motor was also a bit worn out as well so that might have been part of it.

Do you have a grind number for that one? If not I'll just look it up when I get the chance.

Thanks!

TomZ

The grind number is an Isky 281-12.

jafo

TomZ- The tired motor may have been some your problem-I used them on complete OH's. It's an aggressive grind for a 355, but the torque still comes in at a low RPM and stays with it on up. The 1.6's on the intake help as well.
It probably is more suited for a stroker, but I really like these cams. My 355's are in a VERY heavy boat as well ('86 Formula 242LS), but I have the advantage of two engines. I'm sure Comp can match it up or grind something for you very similar.
Jim