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powbmps

Camshaft Upgrade

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powbmps

Thinking about replacing my distributor and DUI was asking me for my cam specifications.  Looks like there is a Melling 22221 in the 5.7 Vortec reman motor I have.  

Specifications @ 0.50 Cam Lift - duration int. 197, exh. 206, gross valve lift - int. .433, exh. .450

Any performance to be gained by just swapping out the camshaft (and springs if necessary), or is this cam okay?

 

Edited by powbmps

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Woodski

@powbmps:  I found a performance gain by going from GM Marine cam to ZZ4 cam.  GM Marine cam specs:  196 / 205 degrees duration @.050" lift, gross valve lift = .431" / .451".  ZZ4 = 208 / 221 degrees duration @ .050" lift, gross valve lift = .474" / .510".  Appears your cam is close to GM Marine version.  With that, the GM Marine cam is actually very good and delivers plenty of torque off idle where it is needed.  My combo, which also includes a set of fast burn aluminum cylinder heads makes a noticeable difference from 1800 on up, it spools up pretty quick compared to previous and added a fair amount at the top end.

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powbmps

Thanks Woodski.  Being that I am not making any other changes, I will just stick with the one I have.  

After doing some additional research, I'm a bit more confused.  They supply this cam as an OEM replacement for Mercury, so it is typically used in motors like mine.  However, the suggested operating range is 800-4,000 rpm, with peak torque by 2,500 rpm.  How does the engine make peak hp at 4,800 (and peak torque at 3,600) if that is the case? 

Edited by powbmps

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Woodski

@powbmps:  If you look at the power curve for the standard Merc Tournament ski engine, the torque curve is very flat or constant from 2500-3600 rpm with a peak at ~3200 rpm but the level is very flat across that range so a subtle difference in cam may shift the curve slightly.  I would think they mean it is peak within a window, say 10% but actual peak is probably in the 3k range.  Hp is a function of engine speed x torque so it will continue to climb until the torque really falls off to offset the speed increase.

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powbmps
On 11/15/2016 at 2:16 PM, Woodski said:

@powbmps:  I found a performance gain by going from GM Marine cam to ZZ4 cam.  GM Marine cam specs:  196 / 205 degrees duration @.050" lift, gross valve lift = .431" / .451".  ZZ4 = 208 / 221 degrees duration @ .050" lift, gross valve lift = .474" / .510".  Appears your cam is close to GM Marine version.  With that, the GM Marine cam is actually very good and delivers plenty of torque off idle where it is needed.  My combo, which also includes a set of fast burn aluminum cylinder heads makes a noticeable difference from 1800 on up, it spools up pretty quick compared to previous and added a fair amount at the top end.

Looks like I had the wrong information.  The cam is actually a Speed Pro CS-1079R.  198/210 degrees duration @ .050" lift, gross valve lift 433/462.  Suggested operating range of 1,500 to 4,500, so that makes more sense. 

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