Cam upgrade?
 

When I took my engines (MCM 575, 540 cui) apart I found out that the factory cams was replaced with hydraulic roller cams. These motors are new to me, was never in my boat so I need some experienced advice how they will work with these cams.

The factory cam are Crane 131311 (replacement) Mechanical Lifter Cams.

New cams are Crane 139651 Hydraulic roller.

Degrees Duration @ .050 Int./Exh. 244 256
Degrees Advertised Duration Int./Exh. 306 318
Degree Lobe Separation 114
Open/Close @.050" Cam Lift Int./Exh. 13 51
67 9
Lash Hot Int./Exh. .000 .000
Gross Lift Int./Exh. .632 .632

I did run them in a desktop dyno, about the same hp but a huge increase in torque.

Will these cams be a problem to me or ????

I have headers with dry exhaust.

Thanks in advance!
/Torbjorn

No problem - the 114 lobe center is what you need. Good cams.

make sure you have proper valvesprings (not too stiff).
and replace lifters every 200 hours or so to be safe (300 max).

Good cams, hydraulic rollers always make more torque than flat tappets. Be sure you have the right springs, as mcollinstn suggested. We run about 140# on the seat with Comp Cams valve springs. Changing lifters after 300 hours is also a good idea. You should be very happy with this combo!!

Thanks!!

Lifters has 100-150 hours on them, I think I will follow your advice and change them. I will also take a look at the springs..

Thanks again!!
/Torbjorn

The cam is a good selection for the cubes.

Rollers, as 1500 said, will make more torque and hp degree for degree. The ramp speeds are faster. Also if you compare a roller lobe with a flat lobe you'll see the flat lobe has more of a peak and the roller lobe is more rounded. This translates to the valve being open faster, being held open wider, longer. That's how rollers make more torque and hp than flats.
The "downside" to the fast ramp speeds are stiffer spring pressures. Hence the good advise to check the springs.

With the dry exhaust however, the 114 centerline is of no consequence. If your exhaust is truely dry then you could run what ever lobe separation will give you the best performance from your engine and your hull.

DAVE

DAVE

cam choice
 

i have that cam in my motors sound great and run great i also
have stelling dry exhaust very loud

do the roller lifters have that short of a life span is there 1 brand that is better than others

Good question carreraboat. Has anyone had any experience with the Comp Magnums or Isky's hyd roller? I had a 100 hours on some Crane's and had a couple rough rollers running on a .632", 264/272 at .050". Appreciate any info!

Hi, another effect comparing my cams in the desktop is that max hp is at 5500 instead of 6000rpm and thats good!!

I have a pair of stelling dry but they have silencers (air actuated) and when they are closed water will mix at the very end of the tailpipe, could this be a problem at low rpms?

Have the same question as carreraboat, someone who have experience from other brands than Crane (100h above) ?

Have seen a pair of Isky with bad/rough rollers but I do not know the hours on them so...???.

There are some colour markings on the springs, will check it later today.

I will KEEP the cams!!
/Torbjorn

Hello, Guys!
Most all hydraulic roller lifters are made by the same company so there is no real difference in any brand.
Solid rollers are made by a few different manufacturers-Isky and Crower being the ONLY ones we use. No other brand we have tried will live like these-no matter whether they have bearing oiler provisions or anything else. Of course, you can break anything, and ANY valve float will destroy ANY lifter quickly!!!
Too much spring pressure shortens valve train life also. Be wary and always set up the valve train as recommended by the manufacturer!!:D

hey blown1500 what about the hour change just pulled mine out no visable wear the only weird thing is where my fuel pump push rod hit the cam it is munched can that be repaired

Hi Carreraboat!
I usually just check the rollers for proper, smooth, no-slop roller operation. If they feel good, use them! The fuel pump pushrod problem is not too common, but you probably used a stock type fuel pump pushrod on a steel roller cam. This is repairable, but not practical as you have to pull the cam and send it back to the factory to be welded and reground. I usually install a good electric pump or use a Mercruiser raw water pump for the Mark V
block. It has a fuel pump provision on it.
To avoid the problem in the future, special fuel pump pushrods are available with bronze tips for this application. They are available from most speed shops or mail order-like Summit or Jegs.
Good luck and if you need further info or I can help in any way, pm





1

thanks for the info you have been very helpful
bo

Had the same problem on one motor, the pushrod was damaged but the cam was ok. Will replace with electric fuel pumps to be on the safe side.

/Torbjorn