Ratchet

Anyone used these yet ?

Panther

I believe the Merc 800SC even had a flat tappet hyd. cam.

You don't need to run the wild cam specs in a SC motor to achieve the power, you get it from the blower.

It is my understanding that more emphasis is on the exhaust lift/duration in an SC setup. You still need to get the gasses out, nothing is forced out on that end.

Panther

tomcat

Optimum timing of a SC cam may need to be different, but within that timing event a roller cam with more area under the curve is going to be better than a hydraulic lifter. Why doesn't Merc use roller lifters in the 575? Maybe because they already reached the desired power level (within the drive torque capacity) and don't need to spend the extra coin.

cstraub69@comcast

Roller cams aren't the problem, roller lifters are. With boat in no wake zones, canals, and other "idle only areas the roller lifter takes a beating. Without the use of dry sump oiling systems for higher pressure, the needle bearings get beat to death during these low idle times.

You don't need a roller to make the power these Merc. factory plants are doing, so a flat is much more user friendly and more reliable. I would recommend the flat route to anyone wanting "factory warranty" type power.

A second choice is to run mech roller lifters on a hyd. roller profile. This has been done for years in racing. Due to the softer opening and closing ramps and less agressive flanks, lighter spring pressure can be used and the solid lifter does not get as beaten in "idle" mode as with a solid roller. Light lash is run but these still require maintenance.

Solid roller for those of you that want ultimate power. The new 2 piece cam cores will offer you the extended running time without the loss of distributor gears. . .damn those bronze gears. As Tomcat said the roller gives optimum under the curve power and for the guy wanting ultimate performance their is no other way to go.

I would recommend the Morel lifter ultimate reliability.

Chris

PatriYacht

Autos run roller lifters for years without failure. It must have something to do with the high spring pressures required by bigger cam grinds and higher rpm that our boats are using. Tomcat brings up a point that hyd. rollers are expensive. About 800.00 to 1000.00 more per engine when you get the required lifters, pushrods, springs.

SB

iTrader: (1)

I know this is an old post but I would bet the breakage and the 'skidding' where more than likely do to not enough spring psi.

Trends have been going with higher rate springs and stiffer pushrods. Things do not like to be bounced around !!

Biggus

iTrader: (1)

Wow.. old thread up from the dead

Since posting this thread, I went with Isky hyd. roller lifters and appropriate valve springs (Isky) for the cams I'm running. It has worked flawlessly the past 3 seasons (300+ hrs)

This fall the motors will be dissasembled and inspected. I'll post my finding when done.

Kurt

bcarpman

As long as we're digging up a dead post, I'll add my two cents.

Roller cam valvetrains are WAY more durable than flat tappet. This is especially true of intial run-in.

It took years for the auto industry to finally adopt roller cams, even though they were a win-win advance. Added power, fuel economy, emisions, ect.. But they were expensive. I'd heard at one point that they were finally implemented only after the bean counters realized they could SAVE money on warrenty repairs by going roller.

SB

iTrader: (1)

They where actually forced to by internal + external forces. External forces where mandated (by our Gov and EPA)100K 7 yr warranty's on cat converters. This meant oil additives such as ZDDP had to be severly limited or removed since they could / would cause converter problems by this time.

The flat tappet ridng over a cam lobe is the most severe lubrication point on any engine - this called for these oil additive packages.

By going roller and eliminating this 'by far most extreme wear / contact point' the oil did not need these additives.

So yes, if the manufacurers kept the flat tappet with the newer oils, warranty issues would be huge and catastrophic ! We see this issue almost everyday on the non-OEM level because of continued use of flat tappets.

Note: There are some oils out there that still have these ZDDP packages. Won't find them for 'on highway auto's' though - you'll have to luck in the race oil, diesel truck oil, and motorcycle oil sections.

Panther

I think tomcat was 100% correct when he posted this!

As they say, hindsight is 20/20...and if I could do it all over again I would have put a roller cam in my motors when we rebuilt them.