Cam suggestions for 383 build
#32
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A lot of useful information from all of you, thanks. Is your engine loud all the time? I'd love to hear the engine loud but not all the time. I'm pretty green on terminology but could I run a cam like the 276 comp and quiet the engine when wanted or is that getting into a lot of expense? I need to get this project done before my 12 and 14 year olds are grown. My old job is gone that let me spend what ever I wanted on toys and I'm tempted to buy a mild hyd roller just to get it done and get everyone out fishing and skiing. It just seems a shame as well built as the motor is.
I can, and have run inline silencers and they do cut the dB by about 6-8 but also choke down the top end rpm by 300-500 so I almost always leave them out. With a milder cam you may not have that problem. There are several exhaust cut-out systems available which can also give you some sound options, but they should be avoided when cams get more aggressive since the butterfly valves diverting the exhaust down the Y-pipe when running closed can exacerbate potential reversion issues with performance cams. They also add expense. $600-800 just for the system, not including additional exhaust hose, thru hull tips, and the labor required to cut the holes.
To answer your question, I would be hesitant to run the Comp 276 with a diverter type exhaust system.
#34
Geronimo36
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FYI:
I did a top end on a high hour 350 Mag (260HP) in a 20ft boat (really 19ft) and about 2800lbs.
218/224 at .050" / 113LSA Comp Extreme EFI HR cam
180cc heads
Weiand Air Strike (like the Eddy Air Gap)
650 Vac BG Carb
Eddie Marine Exhaust Manifolds (already on boat)
Merc Alpha Outdrive
15mph increase was result. NO BS. I'm intimate with that boat. LOL.
It's also an animal planing if at WOT - so....that needs to be held back to take care of outdrive.
Reason why I mention above is that you have same size and near same weight boat + a bigger engine. Heads are pretty much the same performance wise.
So, even if you go a little smaller on cam, it should still be an animal compared to whatever was stock. Just remember what we said top rpm will be as far as best speed. That 212 at .050" cam from Comp will probably be 4600 rpm.
I did a top end on a high hour 350 Mag (260HP) in a 20ft boat (really 19ft) and about 2800lbs.
218/224 at .050" / 113LSA Comp Extreme EFI HR cam
180cc heads
Weiand Air Strike (like the Eddy Air Gap)
650 Vac BG Carb
Eddie Marine Exhaust Manifolds (already on boat)
Merc Alpha Outdrive
15mph increase was result. NO BS. I'm intimate with that boat. LOL.
It's also an animal planing if at WOT - so....that needs to be held back to take care of outdrive.
Reason why I mention above is that you have same size and near same weight boat + a bigger engine. Heads are pretty much the same performance wise.
So, even if you go a little smaller on cam, it should still be an animal compared to whatever was stock. Just remember what we said top rpm will be as far as best speed. That 212 at .050" cam from Comp will probably be 4600 rpm.
Last edited by 38special; 03-04-2014 at 11:46 AM.
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#37
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Is this cam doable in my 383 exhausting through the stock leg and would it actually reach the advertised rpm? What kind of hp and tq numbers could I expect from it?
Lunati 20080720 (Formerly Part Number 60120) Chevrolet Small Block LT1, LT4, & 1987-Present Hydraulic Roller Voodoo Camshaft RPM Range 1600 - 5600 Lift .507"/.515" [email protected] 211/219 LSA/IAC 112/106
Excellent choice for stock to mildly modified engines, works well with OEM style injection, great inboard/outboard marine cam for economy and sking. Good mileage and torque increase.
RPM Range: 1600 - 5600
Lift with 1.6 Rocker: .507"/.515"
Duration @ .050": 211/219
Advertised Duration: 262/270
LSA/IAC: 112/106
Valve Lash: Hyd/Hyd
Cam & Lifter Kit: 20080720LK
Complete Kit: 20080720K
Lifters: 72910-16
Springs: 73943-16
Retainers: 75742-16
Locks: 77003-16
Valve Spring Kit: 73943K1
Valve Seals: 78501-16
Timing Set: 93026
Pushrods: 5040-16
Rocker Arms: 85340-16
Lunati 20080720 (Formerly Part Number 60120) Chevrolet Small Block LT1, LT4, & 1987-Present Hydraulic Roller Voodoo Camshaft RPM Range 1600 - 5600 Lift .507"/.515" [email protected] 211/219 LSA/IAC 112/106
Excellent choice for stock to mildly modified engines, works well with OEM style injection, great inboard/outboard marine cam for economy and sking. Good mileage and torque increase.
RPM Range: 1600 - 5600
Lift with 1.6 Rocker: .507"/.515"
Duration @ .050": 211/219
Advertised Duration: 262/270
LSA/IAC: 112/106
Valve Lash: Hyd/Hyd
Cam & Lifter Kit: 20080720LK
Complete Kit: 20080720K
Lifters: 72910-16
Springs: 73943-16
Retainers: 75742-16
Locks: 77003-16
Valve Spring Kit: 73943K1
Valve Seals: 78501-16
Timing Set: 93026
Pushrods: 5040-16
Rocker Arms: 85340-16
#38
MarineKinetics
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You will likely incur pumping losses (both intake and exhaust) that will inhibit you from reaching 5600 RPM. It will be beneficial to address your exhaust lobe due to the downstream restriction the log manifolds present. The displacement has increased ~9% from the original spec, increasing the spent charge proportionally. I would suggest increasing intake duration, reducing your exhaust bias (from the new intake lobe) to: (1º-4º) It will also benefit you to pay close attention to your ECL.
Bob
You will likely incur pumping losses (both intake and exhaust) that will inhibit you from reaching 5600 RPM. It will be beneficial to address your exhaust lobe due to the downstream restriction the log manifolds present. The displacement has increased ~9% from the original spec, increasing the spent charge proportionally. I would suggest increasing intake duration, reducing your exhaust bias (from the new intake lobe) to: (1º-4º) It will also benefit you to pay close attention to your ECL.
Bob
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You will likely incur pumping losses (both intake and exhaust) that will inhibit you from reaching 5600 RPM. It will be beneficial to address your exhaust lobe due to the downstream restriction the log manifolds present. The displacement has increased ~9% from the original spec, increasing the spent charge proportionally. I would suggest increasing intake duration, reducing your exhaust bias (from the new intake lobe) to: (1º-4º) It will also benefit you to pay close attention to your ECL.
Bob
You will likely incur pumping losses (both intake and exhaust) that will inhibit you from reaching 5600 RPM. It will be beneficial to address your exhaust lobe due to the downstream restriction the log manifolds present. The displacement has increased ~9% from the original spec, increasing the spent charge proportionally. I would suggest increasing intake duration, reducing your exhaust bias (from the new intake lobe) to: (1º-4º) It will also benefit you to pay close attention to your ECL.
Bob
Or suggest an off the shelf cam that will let me get the most from this 383 that I can exhausting through the stock leg?
Last edited by 38special; 03-04-2014 at 12:55 PM.
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I have been offered a brand new hyd roller cam and roller lifters a long with new roller rocker arms, chain and gears. valve springs push rods from a 325 HP 5.7 mercruiser that is being reworked for opposite rotation. He is asking $375 for everything. I can't hardly turn that down. Will my 383 gain or lose running that hyd roller cam? Pretty sure he said it was a duel pattern cam. He also said the cam is a 5,000rpm cam. Everything is for my same year engine, a 98.
Last edited by 38special; 03-05-2014 at 02:04 PM.