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camshaft change?


medicdiver

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Just wondering if there would be any big power gain from changing the camshaft on a Monsoon engine? I know comp cams makes some pretty big cam profiles for marine use, just wonder how big the stock one is already. Anyone have the stock specs on a 335hp Monsoon engine Camshaft?? Lobe/ lift??

Any other suggestions to add just a little power to it? Always in the quest for more power.

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No one really does any heavy mods to these engines. You can put alot of horsepower in a ski boat and it will only ever go so fast.

-Chris

Yeah, but a lumpy cam sure would sound good.

If I had a direct drive carb engine and was board one afternoon I might do it.

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Prop change is better money spent than trying to make more hp on a boat.

Plus1.gif If you want to increase your lift you can also just change out your rocker arms to 1:85 ratio. That would be much cheaper and would do the exact same thing, plus you wouldn't really have to have the pcm tuned from anybody your stock pcm should allow enough monitoring for the air/fuel ratio adjustment.

Plus if you were to go bigger with a cam, how would you know the increase in HP you'd have?

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There has to be a few 05 sportys out there with the 383....bet that would be fun.

I never drove it myself, but there was an all black sporty with the LS1 that supposedly screamed...especially at the high revs that LS1 put out.

-Chris

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No one really does any heavy mods to these engines. You can put alot of horsepower in a ski boat and it will only ever go so fast.

-Chris

Yeah, but a lumpy cam sure would sound good.

If I had a direct drive carb engine and was board one afternoon I might do it.

Cam + Captain's Call! Testosterone is already flowing ... but let's not make it as loud as the jet boat that sank in a recent post.

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Larger then stock rockerarms are nice but you must be carefull with them on stock heads. To big and you could end up with coil-bindding spings and wearing the edge of the valve tip. Sometimes you are better off to go with a roller tipped aftermarket rocker and a longer pushrod to keep things happy. But the biggest thing is to make sure your valve springs can handle more lift before giving it to them. A floating valve can do a bunch of damage!!

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Larger then stock rockerarms are nice but you must be carefull with them on stock heads. To big and you could end up with coil-bindding spings and wearing the edge of the valve tip. Sometimes you are better off to go with a roller tipped aftermarket rocker and a longer pushrod to keep things happy. But the biggest thing is to make sure your valve springs can handle more lift before giving it to them. A floating valve can do a bunch of damage!!

I'm only talking .150" depending on the stock lift of these cams they are normally about 5-6% increase in lift, not enough to worry with stock valves or springs. When you get into 20-25% increase then you have to take all those precautions, piston to valve clearance, spring pressure and height which includes the angle of the rocker arm which then determines the length of push rod you need!

A longer push rod does not net you anything as far as lift, it actually sits the lifter lower in its designed location and eliminates valve clearance. Unless you have solid lifters, and as far as I know all our motors have hydraulic lifts and self adjusting.

When I was into LS1 based motors just the change in rockers arms (non roller tip) gained 12rwhp without a tune, granted that is on LS1 designed engine with an LS2 intake manifold with a much more accurate PCM control and fuel/map control that our motors do not have.

Edited by 68Slalom
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If you use your boat for skiing, boarding or footing, you do not want to go with too much cam as you will lose the low end or pull up region of the power band.

A really nice cam for an upgrade is the ZZ4 cam PN: 10185071. Adds a little lift for both intake and exhaust and adds to the 2500-5000 rpm power range. Adds about .050 lift to the cam and 10-15 degrees of duration. Prod cam is .431/.451 lift vs. .474/.510 for the ZZ4 cam.

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If you use your boat for skiing, boarding or footing, you do not want to go with too much cam as you will lose the low end or pull up region of the power band.

A really nice cam for an upgrade is the ZZ4 cam PN: 10185071. Adds a little lift for both intake and exhaust and adds to the 2500-5000 rpm power range. Adds about .050 lift to the cam and 10-15 degrees of duration. Prod cam is .431/.451 lift vs. .474/.510 for the ZZ4 cam.

I didn't realize that these motors came with such a big cam, thats good to hear Thumbup.gif I never really did the research because it was never a concern of mine. Maybe I'll do the rocker upgrade myself now :)

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Larger then stock rockerarms are nice but you must be carefull with them on stock heads. To big and you could end up with coil-bindding spings and wearing the edge of the valve tip. Sometimes you are better off to go with a roller tipped aftermarket rocker and a longer pushrod to keep things happy. But the biggest thing is to make sure your valve springs can handle more lift before giving it to them. A floating valve can do a bunch of damage!!

I'm only talking .150" depending on the stock lift of these cams they are normally about 5-6% increase in lift, not enough to worry with stock valves or springs. When you get into 20-25% increase then you have to take all those precautions, piston to valve clearance, spring pressure and height which includes the angle of the rocker arm which then determines the length of push rod you need!

A longer push rod does not net you anything as far as lift, it actually sits the lifter lower in its designed location and eliminates valve clearance. Unless you have solid lifters, and as far as I know all our motors have hydraulic lifts and self adjusting.

When I was into LS1 based motors just the change in rockers arms (non roller tip) gained 12rwhp without a tune, granted that is on LS1 designed engine with an LS2 intake manifold with a much more accurate PCM control and fuel/map control that our motors do not have.

sorry, i was not trying to imply that the longer pushrod would give you more lift alone. The stock factory stamped sbc rockers are shy of thier 1.5 mark ( 1.47-1.48) and if you go to an after market roller tiped rocker you will get at least 1.52. Not worth the money to buy new rockers and stay with the 1.5 IMO. Go with 1.6 at least, and the longer(stronger) pushrods for proper tip placement on the valve.

Edited by txwakejunkie
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Larger then stock rockerarms are nice but you must be carefull with them on stock heads. To big and you could end up with coil-bindding spings and wearing the edge of the valve tip. Sometimes you are better off to go with a roller tipped aftermarket rocker and a longer pushrod to keep things happy. But the biggest thing is to make sure your valve springs can handle more lift before giving it to them. A floating valve can do a bunch of damage!!

I'm only talking .150" depending on the stock lift of these cams they are normally about 5-6% increase in lift, not enough to worry with stock valves or springs. When you get into 20-25% increase then you have to take all those precautions, piston to valve clearance, spring pressure and height which includes the angle of the rocker arm which then determines the length of push rod you need!

A longer push rod does not net you anything as far as lift, it actually sits the lifter lower in its designed location and eliminates valve clearance. Unless you have solid lifters, and as far as I know all our motors have hydraulic lifts and self adjusting.

When I was into LS1 based motors just the change in rockers arms (non roller tip) gained 12rwhp without a tune, granted that is on LS1 designed engine with an LS2 intake manifold with a much more accurate PCM control and fuel/map control that our motors do not have.

sorry, i was not trying to imply that the longer pushrod would give you more lift alone. The stock factory stamped sbc rockers are shy of thier 1.5 mark ( 1.47-1.48) and if you go to an after market roller tiped rocker you will get at least 1.52. Not worth the money to buy new rockers and stay with the 1.5 IMO. Go with 1.6 at least, and the longer(stronger) pushrods for proper tip placement on the valve.

Got it, that makes sense. I was thinking more like 1.65 from the 1.5 ratio. Plus I thought they had 1.6" stock? I may be wrong on this, haven't done any research what so ever on these. But I thought that all 2000 LS1 based motors came with 1.6" rocker arms and roller camshafts Dontknow.gif

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Larger then stock rockerarms are nice but you must be carefull with them on stock heads. To big and you could end up with coil-bindding spings and wearing the edge of the valve tip. Sometimes you are better off to go with a roller tipped aftermarket rocker and a longer pushrod to keep things happy. But the biggest thing is to make sure your valve springs can handle more lift before giving it to them. A floating valve can do a bunch of damage!!

I'm only talking .150" depending on the stock lift of these cams they are normally about 5-6% increase in lift, not enough to worry with stock valves or springs. When you get into 20-25% increase then you have to take all those precautions, piston to valve clearance, spring pressure and height which includes the angle of the rocker arm which then determines the length of push rod you need!

A longer push rod does not net you anything as far as lift, it actually sits the lifter lower in its designed location and eliminates valve clearance. Unless you have solid lifters, and as far as I know all our motors have hydraulic lifts and self adjusting.

When I was into LS1 based motors just the change in rockers arms (non roller tip) gained 12rwhp without a tune, granted that is on LS1 designed engine with an LS2 intake manifold with a much more accurate PCM control and fuel/map control that our motors do not have.

sorry, i was not trying to imply that the longer pushrod would give you more lift alone. The stock factory stamped sbc rockers are shy of thier 1.5 mark ( 1.47-1.48) and if you go to an after market roller tiped rocker you will get at least 1.52. Not worth the money to buy new rockers and stay with the 1.5 IMO. Go with 1.6 at least, and the longer(stronger) pushrods for proper tip placement on the valve.

Got it, that makes sense. I was thinking more like 1.65 from the 1.5 ratio. Plus I thought they had 1.6" stock? I may be wrong on this, haven't done any research what so ever on these. But I thought that all 2000 LS1 based motors came with 1.6" rocker arms and roller camshafts Dontknow.gif

I believe your right on the 1.6 rockers for the ls1 based motors, i will have to look when i get home, i have a set sitting in the tool box. The motor he has is not the ls1 based motor, it is just a gm 350 (should have the 1.5 rockers, not 100% on that though).

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http://www.compcams.com/Cam_Specs/CamDetai...id=203&sb=2

There is the link to the Cam I was looking at, not that far sifferent from the ZZ4 cam someone suggested.

Specs,

RPM range, 1500-5500

Duration 276/282

Lift .503/.510

Would this be a suitable increase in power for the $500 investment and 3-4 hours of time to do?? Does anyone know the specs on the monsoon stock cam?

how much change would be needed in the PCM, and how would I go about getting a new fuel map installed in it?? Goal is a little idle sound difference, and little more power.

Basically looking for a winter project to do on the new boat. I can only clean it so many times, and prop is already new as someone said to change that. I just cant leave things alone, and love to tinker with them. Also going to be looking at stereo upgrades to do this winter.

Any coments/suggestions welcome

Edited by medicdiver
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The monsoon uses the cam I listed above as that is the standard GM Marine cam for the small block. There are other restrictions in the system you probably want to change before you change the cam, although it does improve the performance in the 2500-5000 rpm range over the current cam in the engine and keeps the good start up torque needed to launch a skier.

The other limiters include the complete exhaust system from the manifolds out to the tips of the exhaust. There are several manufacturers of exhaust manifolds with improved tuning that will help (Stainless Marine, IMCO, Eddie's Marine, Hardin). The spark arrester might be a limiter, you need to check that first and it is pretty easy to improve. These changes will really wake up your small block and make quite the screamer out of the boat.

I will add that going to the ZZ4 cam or the Comp Cam listed above will not change the idle quality or sound. If you use the boat for skiing, I would suggest that you do not go after that as a "lumpy" cam will probably hurt the out of the hole pull needed to get up skiers or barefooters. You do have to twist the engine to change the cam as it will not slide out past the pylon in the installed position.

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If you guys want to read some interesting threads, go over to correctcraftfan.com. There's a few people that have built up engines in their boats. They're getting from the low 50's to up towards 60 mph.

I was at the CFF reunion in Lake George last weekend and there were some boats that screamed. TBenj, who is also a member here, has a '90 SN with a built up 351. Much bigger boat than my Sportster, but it screams. Much better hole shot and it pulls harder through the entire range than my Sporty. There were a couple other boats that had heavy mods and were rockets. All carb engines though. I haven't seen any built up with efi.

They also had a new CCF ski nautique at the show. 409 hp. It was fast, too.

Edited by 88Skier
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