Roller Cams

[Joe C.]

Re: Roller Cams

Hey, wait a minute! That was MY story at the beginning of this thread. So now you agree with me?

Well........yes and no. Initially, you stated:


"We discussed roller cams/rocker arms here a while back and I think a few have forgot what I posted.
The true benefit of roller cams and rocker arms for newer cars doesn't really have anything to do with power. Not directly, anyway."

I never disagreed with you regarding the power losses derived from driving the oil pump, and the savings achieved by going rollerized. I DID disagree with you about the roller bearings not providing any DIRECT benefit. As you can see, there is a direct benefit, which is not insignificant.

[Duke W.]

Re: Roller Cams

Joe - I guess you've never spun a freshly installed crank in a set of new oiled journal bearings.

I'm gonna let you girls finish working this one out.

Duuke

[Michael H.]

Re: Roller Cams

Joe - I guess you've never spun a freshly installed crank in a set of new oiled journal bearings.

I'm gonna let you girls finish working this one out.

Duuke

I think it's dead now. (I hope) Joe kinda sorta half way agreed with me.

[Stuart F.]

Re: Roller Cams

Michael;

I thought it was you who said in an earlier post that you were going to sit this one out when Duke and Bill got going on it. Now it appears you hung in there and are the eventual winner.

Interesting posts fellows. I enjoyed and learned a lot, specially about that miracle additive ZZDP (?)

Stu Fox

[Jim L.]

Re: Roller Cams

Guys,

How about quantifying the significance or insignificance, as you view it, of the change in friction due to a roller cam instead of the "is too", "is not" discussion you've been having. Then the rest of us who have been paying rapt attention to this thread can decide for ourselves if the difference is "significant".

As for a suitable metric, I propose measuring the torque required to rotate the engine by the crank with all valve train present and all plugs removed.

Jim

[Stuart F.]

Re: Roller Cams

Too deep for me. I'm folden.

Stu Fox

[Duke W.]

Re: Roller Cams

Roller bearings can operate with very little oil. In fact, they can have higher friction than plain bearings if flooded with too much oil.

They are particularly well suited to small crankcase scavenged two-stroke engines where the oil aerosal mixed with fuel provides adequate lubrication.

However, roller bearings on multicylinder engines require built-up cranks, which makes them inherently weaker than single piece cranks, so they have to have larger sections and the roller bearings themselves require more room. As a result, automotive size engines with roller bearings would be bulkier and heavier than the same displacement plain bearing engine. There would also be a signficant increase in cost.

Over the years many automotive suppliers have come up with "ideas" to promote their products, but rarely are they embraced by the OEMs, and I expect roller bearings are one of them.

About 80 percent of internal engine friction is ring drag, so I question Timken's friction reduction claims.

Myself, I would not bet that we will see a roller bearing automotive engine in the foreseeable future.

Duke

[Dick W.]

Re: Roller Cams

/
Read it carefully, especially paragraph 16:
"Finally, Timken says an engine with reduced friction is able to produce more power. This is an aspect that had been exploited in motor sports, where Timken has close associations in NASCAR. But Deane says the rollerized engine was subsequently banned for having an unfair advantage."
.

The engines I have seen on the dyno with needle bearings for rods and mains did not exibit any hp increase. To quantify this, the observations were made in the mid to late 60's on Ford side oiler engines, maybe technology has changed.

[John H.]

Re: Roller Cams

The old Porsche 1600 Super engines had roller-bearing main and rod bearings, with Hirth built-up cranks; continuous high rpm never bothered them, but lugging them at low speed would destroy the bearings in short order - there were major warnings in the owner's manual about NOT lugging them, or severe engine damage would result. A neighbor of mine in Ohio had two of them - a 356 coupe and a Speedster.

[Duke W.]

Re: Roller Cams

Those were very interesting engines, and they are probably the reason why even to this day some Porsche owners think their engines should never run below 3000 revs. (My recent experience with a '70 911S, though, taught me that below 3500 it won't get out of its own way, but absolutely screams from 5000-7300. It makes a 30-30 cam engine seem "torquey" by comparison.)

The DOHC cams on these "Carrera" engines (a flat-four that began at about 1500 cc and was later expanded to two-liters) were driven by shafts with bevel gears, and it took an extraordinary amount of time (and patience) by a master mechanic to set them up with shims to get the proper backlash, but when setup properly the engine was virtually indestructible and gained Porsche a reputation for exceptional reliability in endurance racing.

Alas, Porsche realized that the labor intensiveness and cost of this engine did not justify the benefits, and later engines - both for road cars and race cars - were conventional with plain bearings and chain driven overhead cams.

The last Carrera engines - expanded to two-liters - originally powered the 904 in the early to mid-sixties, but many surviving 904s have been repowered with various versions of the 911 flat-six.

Duke

[Patrick H.]

Re: Roller Cams

Roller bearings can operate with very little oil. In fact, they can have higher friction than plain bearings if flooded with too much oil.

They are particularly well suited to small crankcase scavenged two-stroke engines where the oil aerosol mixed with fuel provides adequate lubrication.

However, roller bearings on multicylinder engines require built-up cranks, which makes them inherently weaker than single piece cranks, so they have to have larger sections and the roller bearings themselves require more room. As a result, automotive size engines with roller bearings would be bulkier and heavier than the same displacement plain bearing engine. There would also be a significant increase in cost.

Over the years many automotive suppliers have come up with "ideas" to promote their products, but rarely are they embraced by the OEMs, and I expect roller bearings are one of them.

About 80 percent of internal engine friction is ring drag, so I question Timken's friction reduction claims.
Myself, I would not bet that we will see a roller bearing automotive engine in the foreseeable future.

Duke

Exactly what I was thinking when I watched the demo.

I've had a crankshaft placed in an upside down block, with no rods or pistons, and it spins very easily. Try the same thing with rods and pistons installed, and there is a lot more resistance. Unless they can come up with roller rings I would not expect much of a benefit from roller bearings as compared to traditional bearings in a Chevy V8 engine.

Patrick

[Duke W.]

Re: Roller Cams

Ring drag is most noticeable at very low speeds, where, at best, they have only boundary lubrication.

At normal speeds and loads they probably experience full hydrodynamic lubrication over most of the travel - except where they slow to zero speed and reverse, especially at the top on the compression/power stroke where gas pressure increases radial loading, and this is the major source of internal engine friction.

On a well maintained engine, often the only noticeable wear at overhaul is the taper at the very top of the bores due to this wear. That was the case with my 327/340 at 115K miles notwithstanding the badly cracked #7 connecting rod!

Duke

[John M.]

Re: Roller Cams

Craig,
Here's a short story about flat tappet cams. In 1999 I replaced the cam in my L71 with the Crane copy of the GM original. I used the black Moly lube that comes with the cam and filled the crankcase with 10W-30. I drove the car with nothing but 10W-30 until 2006, well over 10,000 miles, when I started to hear a lot about Zinc. I then started using 15W-40 diesel oil and have until now. The engine's out of the car and while it's out I've checked the cam very carefully. It's basically unchanged since installed. All max lifts are the same within the accuracy of the method, measuring directly on the lifter.
I think if you break it in with the zinc additive, EOS, and use the 15W-40 Diesel you'll be fine with the flat tappet cam.
Regards,
John McRae 30025

[Duke W.]

Re: Roller Cams

John is exactly right as long as you stick to OE equivalent camshaft and valvetrain components from quality vendors (which includes Crane), but if you use some aftermarket cam grind and gorilla valve springs...

Duke

[Joe R.]

Re: Roller Cams

Here's a link to an interesting article about solid lifter cams and modern oil from the Pontiac crowd:

http://www.highperformancepontiac.com/tech/hppp_0802_pontiac_performance_engine_oil/index.html

I don't intend this to be a recommendation, but I plan to use the Brad Penn oil during my initial break in of my L-72 (427 / 425) rebuild. After that I will use Shell Rotella T, probably with the Comp Cams additive or the GM EOS.

Joe