Rage

I am looking for the full specifications on the stock Merc 425hp 496HO cam to include at 0.006" valve opening.

Hydrocruiser

I would bet the guys at Rayler know the answer to that.

Rage

Yes, I suspect that Ray does. Also RMBUILDER may likely have that information. I would be gratefull to whoever can take the time to share.

Hydrocruiser

This appears to be it...(mechanic's best guess)....a mild/moderate grind.


Advertised Duration (Int/Exh): 285/295
Duration @ .050 (Int/Exh): 226/236
Gross Valve Lift (Int/Exh): .554/.575
LSA/ICL: 114/112
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 1800-5500

Rage

Thanks Hydrocruiser.

From that same source would you happen to also have the IVO and EVC timing as well as the 0.006" valve duration numbers?

I had some values recorded for the stock 496HO cam, I thought from an old Rayar post but not sure at this point, however they are way milder than those you mention. ie in/exh lift .480/.483 and @ 0.050" duration for int/exh of 204/209 with 118 speration.

I also have a quote, apparently from Crane cams as follows
"Crane Cams BBC Eight of the 11 gasoline powered offshore boats that won their individual classes at the 2003 A.P.B.A. World Champion Offshore Races in Orange Beach, Alabama were powered with Crane cams, Crane roller lifters and Crane rockers! Crane Cams offers all of the power and performance you need for any of your marine needs. See your marine engine builder or nearest warehouse distributor and ask for Crane when you want the best for your marine engine.

We offer cams for both the marine Gen 6 big block Chevy (454-502) and the 8.1L big block Chevy. You can also use the 8.1L Crane hydraulic roller tappet, Part No. 26535-16, in both engines, but you cannot use the Gen 6 hydraulic roller tappet, Part No. 16535-16, in the 8.1 engine because the oil gallery location is different and you will lose oil pressure.

Interestingly, the camshaft in all Mercury Marine’s 400HP, 420HP, 425HP and 525SC is the same cam, Crane Part No. 132561.

The Crane cams used in the Mercury Marine 525HP carbureted engine are different from the 525HP EFI engine. The 525HP carbureted engine uses Crane Cams Part No. 169621 and the 525HP EFI engine uses Crane Part No. 16HR00004.

You can change your G.M. Marine GEN 6 engine to adjustable rocker arms by using Crane Part No. 99152-16 studs and No. 13750-16 rocker arms. This is a fairly simple, bolt-on installation!

To change the G.M. Marine 8.1 liter engine to adjustable rockers use Crane 99155-16 studs and 13750-16 rocker arms. This is also a simple, bolt-on installation."

But I do not know if that is correct or not either regarding the stock 496HO engine's cam.

Rage

Looks like the Crane info is correct per attached timing card for the Crane 132561 cam. Thanks again for the help Hydrocruiser.

TWIN-SPINS

i tried to find the 525 efi cam using crane part#16HR00004 and couldnt find it,,,,anybody have a number for the 525 efi cam????

Alex

Just to make sure you're not comparing apples to pears.
The HP 400/420/425/525SC all uses a flat tappet cam while the other ones mentioned uses hydraulic roller cams.
I don't know if you were comparing them at all but I was a little confused over mixing in the old HP engines ... maybe too tired

rmbuilder

Rage,

The standard marine 8100 cam is:

204º/209º @ .050”
.282”/.284” Lobe
.480”/.483” Valve
118º

The HO cam:

224º/233º @ .050” (222º/232º)
.300”/.300” Lobe
.510”/.510” Valve
114º/115.5º

The cams are ground on the C swap core.

Bob

koutroullos

Hello
I am looking for replacement for the stock camshaft of the 496 MAG 375hp. The GM part is 12565075.
Also if I put different camsaft I will need to change any other parts like the cam bearings?