I had a 201 liberator with 350 mag and I built the motor several times. The last time I installed a brand new bow tie block .040 over balanced assembly dart heads 2.02 valves roller tip rockers (comp roller tips would not oil correctly they would squirt the oil up onto the valve cover not down into the socket) I ran crane and comp 270 cam center risers manifolds(threw away the log type) crane billet chain and gear eldelbrock performer rpm, electronic ign, stock q-jet carb this engine has over 600 hours on it runs great and has over 1200hours on the king cobra drive and it has never been apart just 2 u-joints and a shift cable. The boat is quick and nimble and runs very good

Liberator21-If you can post those vids, that would be great. I have alumnium GLM manifolds with internal runners and stock Mercruiser stainless steel center rise manifolds. My mods for the winter are as follows-clean up the ports on the Vortec Heads, port match the intake, send the heads out and have Ferrea stainless intake and Super Alloy Valves Exhaust valves installed, convert to screw in studs, roller cam, Marine Demon Carb, and I would like to go to an EMI DRY system, but I will likely run out of $ before that.

I'm not sure if it would be too much cam, I guess we will see. I would love to see you post results with your XM270 before I decide to try the XM276.

Do you have any signs of reversion? My current LSA is 114, and I would hate to get reversion going to 112, but the EMI dry would cure that, altho $ is the problem...

My boat at idle
http://www.youtube.com/watch?v=5q-rbQZyUVU

My boat WOT (shows how easily it gets on plane with only light throttle)
http://www.youtube.com/watch?v=eo2hdwzHrMo

azk4536, The boat sounds good.
I have the video of the 270 cam posted, but not the 262 yet. the 270 was done with a digital video camera, so it was easy to transfer. the 262 was taped on an 8mm camera, so I've got to get it off there first.
This video is right after the cam break in (about 1 hr total on cam).
The engine is idling around 700 rpm. I have about 12 degrees initial advance. The exhaust manifolds are GLM, and there's Rex marine slip in silencers in the pipes. I think the sound levels were about 80db around 10 feet behind the boat (I don't remember exactly what I measured).
If you have a sub, turn it up. It sounds pretty throaty.
http://media.putfile.com/XM270Cam

From what I understand, the XM270 doesn't suffer from reversion with a stock exhaust. Any idea if the XM276 does/would with a stock manifolds, risers, and thru hulls w/ S-bends? THe reason I ask is that I may end up using the exhaust I have now until I can save for another...I tried to figure out the overlap, but wasn't sure how to use the fomula...
Here are the cam specs
Grind Number CS XM 276HR-12
Description

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Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.503 0.51
Duration At 0.006 Tappet Lift 276 282

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Valve Timing At 0.006
Open Close
Intake 28 68
Exhaust 75 27

--------------------------------------------------------------------------------

These Specs Are For The Cam Installed At 110 Intake CL
Intake Exhaust
Duration At 0.05 224 230
Lobe Lift 0.335 0.34
Lobe Separation 112

--------------------------------------------------------------------------------

Since overlap is ° both intake and exhaust are open together you add the °'s between IVO and EVC.

Say at .006" IVO is 28°BTDC and EVC is 27°ATDC, your overlap is 55° .

Also remember, some cams seat ° is measured at .004" and some at .006" so it's hard to compare the two different points.

[QUOTE=azk4536]From what I understand, the XM270 doesn't suffer from reversion with a stock exhaust. Any idea if the XM276 does/would with a stock manifolds, risers, and thru hulls w/ S-bends? THe reason I ask is that I may end up using the exhaust I have now until I can save for another...I tried to figure out the overlap, but wasn't sure how to use the fomula...
Here are the cam specs
Grind Number CS XM 276HR-12
Description

QUOTE]
I've built two 383's using the XM276HR. 55 degrees overlap would definately be questionable with stock exhaust. I've got Stainless Marine exhaust, no reversion issues at all. My motor would idle @ about 800 in neutral and about 650 in gear through a Volvo SX drive.
Are you running an Alpha or Bravo? Might be an issue with an Alpha.

Its an alpha, and its a weak link...
LMAC, is your exhaust a stainless marine with the long or short risers?
How do they run with the XM276? Where is the power, up top down low? Does it have a lumpy idle?
What kind of speeds, rpm's, and prop are you seeing on what kind of boat.
Thanks in advance!

Standard risers. On the dyno, that motor made 421 H.P. @5400, 451 Tq. @4400.
I propped for that RPM, 23pitch Powertech, through a Volvo SX drive with 1.6 gears in a 20' Crownline.
That was the 05' motor, which I still have. Now I am running a 410 ci. SBC. It's a latemodel 350 block with a 4.00 stroke. Why build a 383 when you can build a 408-410 for the same money?

Thanks for the info.
What does the idle sound like?