Roller cams, cons.....pros???
 

Ever wonder why the 575SCI runs a flat tappet cam? I sure do, and never got a real answer from the Merc rep at the Miami show.

Late last season, I had destroyed a motor from a roller lifter tie bar breaking and the roller got loose at 5500 and totally ruined the entire long block.

Today I had the other motor torn down for inspection and found a cam lobe going away because of a skidding roller. Fortunately there was no other damage. How often does this happen? I have been told that synthetic oils can cause the rollers to skid instead of spin but this motor has always been run on Kendall petroleum oil and changed every 10-20 hrs.

If Merc is still running flat-tappet hyd cams in their 575 they must be still working well. Can I run flat tappet cams in my 468" 671/Supercooler 8 lbs boost BBC?

At this point, I'm not sold on the roller cam. Seems like too many things to go wrong.

Kurt

What kind of roller?

Kurt,
Running a flat tappet cam on a S/C application does not require the same optimization of lobe profile that a N/A cam requires. The addition of forced induction negates the necessity of inertial ram and overlap that are the keys to making power in atmospheric engines. Roller lifters accommodate acceleration rates that are not possible with flat lifters, but not necessary with boost present in the induction column. V.E. numbers of 100%+ are routine with superchargers, but not directly related to cam timing.
In my experience I have yet to see a cam lobe going away due to a “skidding” roller. Burnished rollers and lobe degradation are nearly always the direct result of improper or failed valve springs. Synthetic oil is not a contributing factor. Both street and endurance racing engines routinely run roller lifters with synthetic oil successfully.
Bob

Thanks for your reply, they were Comp Cams components.

Kurt

every type of set-up has some lemons once in a while....
 

On a side note, I am doing a cam swap/ head work on my bike. At tear down and inspection, I had a roller lifter skidding on the cam lobe. Cam was ok but lifter seemed to be a little tight in the roller bearings. Must have gotten some crap in there. Initial thought was to high of spring pressure. New lifter and cam being installed and double checking spring pressure.

Might have lost rollers due to SMALL contamination or needle bearing failures...

Zack

The only "skidding" rollers I've ever seen or heard of were eventually traced to the needle bearings in the roller tips themselves.

Anybody got more info on those "needle-less" roller lifters that use a trapped oil film for the roller to run in? They look pretty cool.

Mike,
They are made by Schubeck. You can find the info here:
http://www.schubeckracing.com/rollerx.html
Bob

The Schubeck lifters seem to be the answer to the sticky roller problem and I like their method of retaining the lifter in a Mark IV block. Nice stuff!

I just got a call from my engine builder and he said everything else looks great. I guess I'm lucky that a little preventative maintenance found a big potential problem :D

Back to the 575 SCI, I find it interesting that Mercury feels the flat-tappet hyd cam is the way to go on this application. Phil @ Lip-Ship tell me that even Zul retains the flat-tappet on his 575 upgrade. I just don't understand why I need roller cams in my application.

Kurt

We are in the process of rebuilding a 575 that wiped out two lobes on stock cam. I like the hydraulic rollers, so far 0 failures with comp lifters.

Kurt,
Two of the factors determining the necessity for roller lifters are camshaft intensity (the lower the number the more aggressive the ramp) and lift. By comparing two Crane blower grinds of similar adv duration, one hyd flat, the other hyd roller, you can illustrate the point.

CRA 134561 Hyd flat
Adv...... .050........ lift
296/306 236/246 .553/.571
Lobe intensity 60/60

CRA 138781 Hyd roller
Adv.... .050 ........ lift
296/304 246/254 .615/.636
Lobe intensity 50/50

The roller grind has a significantly more aggressive ramp as compared to the flat and has .062/.065 more lift. The need for the change from flat to roller is dependent on the aggressiveness of the grind you choose. Hope this helps clarify the question.
Bob

Anyone used these yet ?

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

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.

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

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.

Re: Roller cams, cons.....pros???
 

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 !!

Re: Roller cams, cons.....pros???
 

Wow.. old thread up from the dead :D

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) :D :D :D

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

Kurt

Re: Roller cams, cons.....pros???
 

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.

Re: Roller cams, cons.....pros???
 

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.

Re: Roller cams, cons.....pros???
 

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

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.

Re: Roller cams, cons.....pros???
 

Oil is a huge problem right now with flat tappet cams. Shell Rotella is what a lot of pro stock guys and engine builders are reccomending for flat tappet cammed engines. All of the additives that help prolong the life of the flat tappets has been done away with in most off the shelf oils. All has to do with EPA stuff. Thats why a lot of people went to the diesil oils.

Re: Roller cams, cons.....pros???
 

So why did my 420's w/ flat tappet cam get 852 hours without any adjustments in 17 years running Quaker State 20W50? :eek:
Why would I want to go roller when I do the rebuild?

Re: Roller cams, cons.....pros???
 

I'm not 100% sure about the oil stuff but the lifters are now being produced in China. Let's just say the quality isn't the same and there has been a lot of lifter/lobe failures on new engines. :(

Do yourself a favor and upgrade to a hyd. roller cam, you may get another 30-50 hp out of it anyway! :cool:

Re: Roller cams, cons.....pros???
 

There are better cam cores available, lifter's too, but you must find someone that can get them for you.

As far as the oil................it is the truth. You just have to believe us on that one !!!

Two decent threads - I have more if you want, but you'll get the idea. Oh, don't mind that CFM guy, he's a pain in the azz. :D

http://www.speedwake.com/upload/show...lat+tappet+oil

http://www.speedwake.com/upload/show...lat+tappet+oil

Re: Roller cams, cons.....pros???
 

If you believe that some/most of the lifter/cam issues are related to wear at idle due to poor oiling...check out the KE spray bar solution

Re: Roller cams, cons.....pros???
 

3th try...

Re: Roller cams, cons.....pros???
 

First time I saw that oiler was at PRI last winter. So it takes me a little while sometimes - doh !

Fantastic idea - should really keep them rollers happy. :D

Re: Roller cams, cons.....pros???
 

Ya got THAT right..... :cool:


Doug

Re: Roller cams, cons.....pros???
 

HERE!!! :drink:

Re: Roller cams, cons.....pros???
 

I agree there is no reason not to go roller.

Re: Roller cams, cons.....pros???
 

Kurt, sorry to hear about your engine woes... Just my opinion, But I have no qualms about the roller cams, they just do require a little more time & $$ to do properly... The flat tappet stuff still works well for a lot of the moderate stuff. I too agree the spraybar solution in the lifter valley is a good idea if one is overly concerned about lack of lubrication there... But again that all adds to the cost, although its still easier & cheaper to add that then to redo the thing later... :bunny: jamie

Re: Roller cams, cons.....pros???
 

cstraub or anyone else,
Why do roller lifters take such a beating at low RPM? Are you saying it is a lack of oil pressure, or what is the reason?

Re: Roller cams, cons.....pros???
 

Anyone know of the correct roller cam replacement for a 575 SCi stock flat tappet.

Re: Roller cams, cons.....pros???
 

Cam lobes receive a lot of their lubrication from oil being splashed of the reciprocating assembly.

Add in high spring psi's and then typical windage trays, crank scrapers, etc,etc for better high rpm performance and the solid roller's are subject to a lot of abuse from lack of oiling.

Street mechanical (solid) rollers use gentler profiles and thus lower spring psi. The axle/wheel combo really likes this better during low speed low oil situation then the high spring psi combos.

But.............solid rollers are now available with pressurized oiling and companies like Keith Eickert are making oil sprayers aimed at this area. These make life much easier. Also, rev kits supposedly help by holding roller against lobe, not totally sure on this one...remember there is lash involved with rollers.