Cam suggestions for 383 build
 

I would like a custom ground but is out of the budget. The boat is a 98 glastron gs205 and weighs 2600 lbs dry. We will be doing a little fishing and skiing both. It also has a Volvo penta sx duo prop out drive. Plans are to run exhaust out the stock leg. I'd like to make as much torque as I can with this set up. The heads on this 383 are 23degree EQ heads with 180cc intake runners with with both intake and exhaust runners ported and 64cc fast burn combustion chambers and compression at 9.3. Any ideas? I don't want to worry about reversion but do want a strong cam.

Cams that I have looked at are Lunati voodoo hyd roller 20080721 and Comp cams extreme 270xm. Would either be strong out of the hole all the way to 5500 rpm and free of water reversion problems?

Lunati 20080721 (Formerly Part Number 60121) Chevrolet Small Block LT1, LT4, & 1987-Present Hydraulic Roller Voodoo Camshaft RPM Range 1800 - 6000 Lift .515"/.530" [email protected] 219/227 LSA/IAC 112/106
Strong power increase in mildly modified engines with excellent throttle response. Will work with stock converter in 383+ c.i.. Likes 2000 RPM converter in 350 or less c.i. applications. Likes 3.23-3.73 gearing. Largest choice for inboard/outboard marine applications. Has noticeable idle and likes headers.

Voodoo: Lunati's Voodoo series of camshafts deliver more area under the curve than any other series of camshafts. This means more throttle response, quicker acceleration, more vacuum and better efficiency. These factors, combined with maximum horsepower and torque, make Voodoo camshafts the perfect choice for a wide range of high performance applications.

RPM Range: 1800 - 6000
Lift with 1.6 Rocker: .515"/.530"
Duration @ .050": 219/227
Advertised Duration: 270/278
LSA/IAC: 112/106

The cam change may not do much with the stock exhaust, the 270XM in my brothers 383 crapped out at 5000 rpm. You might look at the 276 XM.

That's what im afraid of. I like the advertised 6000 rpm of the lunati cam but not at the cost of water reversion. I think the 276 xm would force me to buy headers.

I built twin 355 Vortecs two years ago with the comp XM 264 Roller.Here are my results:

SuperFlow
Dynomometers and Flow Benches
SF-902S

355 MARINE CHEVROLET Result Summary Date 12-20-2012 1:46 PM Temp 80 Deg F. RH 74%

RPM TQ* HP*
2600 399 198
2800 408 218
3000 421 240
3200 430 262
3400 436 282
3600 440 302
3800 444 321
4000 448 341
4200 451 361
4400 450 377
4600 443 388
4800 438 401
5000 431 410
5200 421 416
5400 409 421
5600 396 422
5800 373 411
Max 452 422
Avg 426 339

* Test Exhaust 1.5" Diameter Dyno Tester Supplied Headers.

355-cid VORTEC SPECS

Bore / Stroke / CID: 4.030 / 3.48 / 355 cid
Compression: 9.4:1
Block: GM factory four-bolt 350 L-31 VORTEC
Crank: SCAT forged-steel PN 1101-11133
Pistons: Probe forged (PN 130212334-030)
Rods: Probe (PN 1201-10062) 5.7"
Rings: Total Seal Moly
Bearings: Clevite
Gaskets: Mr. Gasket and GMPP
Cam: COMP Cams (XM264HR) 212/218 at .050, .488/.495 lift, 110 LS
Lifters: COMP (PN 875-16)
Chain: COMP (PN 2100)
Pushrods: COMP (PN 7372-16)
Rockers: COMP 1.5:1 (PN 1417-16)
Heads: GMPP Vortec (Scoggin-Dickey PN SD8060A)
Manifold: Edelbrock Performer RPM Air Gap (PN 7516)
Carb: Demon (PN 1402010VE)
Distributor: Davis Unified Ignition DUI-7000
Spark Plugs: Autolite AR103
Oil System: Milodon HV (pan PN 31505)

I am running stock Mercruiser OEM Exhaust with y pipes in the boat so I'm loosing power on the top for sure. running 1.5 Ratio Bravo I's with 23" Mirage I have all the power and torque I can use. i have no reversion issues and make BIG TQ numbers down low.

Your limiting factor is not the fact that it is a stock exhaust manifold, or worrying about reversion, but rather trying to exhaust out the outdrive. That is your choke point. The Lunati cam would likely work but not trying to push it out the prop. Keep the LSA wider as you go up in cam size and utilize thru-hull exhaust with the stock manifolds and risers. Crower has some nice hyd roller cams that would work too. Don't pick a cam that makes peak power at 6000 rpm as you will likely never see that in a boat. Some drives don't like that.

Target an LSA in the 112-114 degree range.

FWIW, I'm running a cam nearly equivalent to the 276XM, stock exhaust with thru-hull and no reversion.

True. Many 383's and 350's out there with the Comp 270 HR extreme marine. Performance heads and Most afmkt exhaust.

218/224 at .050" on a 112LSA.

Top usuable rpm in boats 5k for 383's and 5200 or so for 350's.

Great all round cam though. Makes real good power with good heads.

Gm LT4 hotcam

Sprink, looking at your dyno readout, something just didn't look right. That motor had a peak torque RPM of a bigger cam and continued making power higher than the cam listed should. That cam should have had peak torque at 39-4100 tops and ran out of steam at 5200. Your dyno guy might have screwed you because those dyno numbers are exactly the same as this one listed in Popular hot rodding. http://www.popularhotrodding.com/eng...ec/index1.html . Not saying you don't have a good set of motors, just wanted to point that anomaly out.

So what are you implying? That two nearly identical engines one built in 2006 and the other in 2012 can not yield the exact same results? :lolhit: :lolhit: :lolhit:

The details in this case do not point to shenanigans by sprink's builder.

Looks to me that a good recipe was copied. Where was the magazine engine built?