Roller Cams

[Michael H.]

Re: Roller Cams

This is one of the WORST posts I have seen on the TDB in some time - spelling, grammar, composition, layout, but most importantly - FACTS!

For those who have short memories, The Summer 2008 Corvette Restorer has a factual article on current motor oils.

It also lists a number of Internet references including the API 1509 document. I suggest that unless you want to make a fool out of yourself, read the article and references before you pontificate on motor oil. There's absolutely no excuse for anyone on this forum to be ill-informed about current motor oils.

Merry Christmas!

Duke

We gots us a spell check but we don't gots no grammar, composition and layout checker or BS detector here.

Merry Christmas Duke.... and everyone else here.

[Bill C.]

Re: Roller Cams, ZDDP, EOS and grammar

My, My!
It appears I have offended the first responder to my post and stepped on some probably tender defensive toes. He fails to mention he is the author of the "factual" article he references, so I can understand his being defensive, as far as the personal attacks on grammar and such, excuse me, I thought this was a Corvette technical board, my hands are greasy from building the cars so maybe my priorities are different. I restore these cars for a living and consistently turn out Top Flight cars above 98 points. For myself and others. I build the engines also, and I repair the problems others have. I work very closely with my engine machinists with over 50 plus years of experience on everything from current engine technology back the early 60's drag motor builds and back to model T engines. Ask any reputable experienced engine build shop how they feel about current motor oils. I do my own "hands on assembly work" to ensure reliability as I have to stand behind what I do. I also own 6 66-67 BB cars and two 65 sb cars, all but 2 complete frame offs done in my shop, with my own hands. I have not had any failures with any engines I have built or service. So as far as BS goes, I guess I can push plenty of it, and do it quickly without using the spellchecker, again focusing on priority. And experience. References to the API 1509 document are a good reference and a guide, and very enlightening, please link to that website and you will see that the disclaimer to the information provided is in no way gauranteed or warranted (read that as BS may be enclosed). I recommend everyone should read the api document and understand it clearly and also understand they require royalties to use their "seal of approval" on any product advertised and sold. And they clearly say so.
Marketing world at work, aint it great?
And the only thing I am promoting is ensuring durability, reliability and what I know works for a proven fact.
Mama taught me early not to believe everything I read, dig in, learn for yourself, in this case api recommends you use good ,sound, engineering judgement in conjunction with the information they provide, which, in a good engineers character includes good common sense, not getting anal tunnel vision on printed words.How many times do we find what was drawn and planned in the AIM did not translate to practical common sense on the assembly line and the boys did what worked, quietly, without documenting it, for us to dig up later and realize, hey, that was just common sense! How come the engineer behind the desk did not know that? Read between the lines and follow timelines and events. I enchourage all to link to any camshaft manufacturers home page such as Crane or Comp Cam or Isky. Read the break in procedures AND oil recommendations for continued use. Educational, enlightening, and hopefully helps you to be more "informed" I would hate for anyone to be "misinformed". I stand by the facts and opinions I currently and previously quoted, of course at the risk of making a fool out of myself. I would hate for anyone now or later be looking at their detailed engine compartment and have to be told that it all needs to come apart to replace your camshaft because they were not willing to spend a few extra bucks on gauranteed protection. Again I enchourage all to do some further research and make some "fully informed" decisions, ask yourself why the changes were made to oils or EOS products in the first place and what changes are coming. And the real facts behind it all. And remember this does not only affect Corvettes but ANY flat tappet engine built by ANY manufacturer anywhere.It appears a fine line we are all walking between auto manufacturers current needs and ours and of course the waltzing done in the meantime between them, us, cam manufacturers, marketing dept's and API and what any of them can or cannot legally say. ( Corporate lawyers worry about grammar, marketing departments worry about sales). Read between the lines!
The post responder and author of the referenced restorer article refers to "what is best currently as of that date". I personaly am not convinced by the quoted "minimum satisfactory amounts supplied" facts and I stated that. I prefer to err on the side of gaurateed safety and not trust other quoted facts, its only a $30 or so added investment at each oil change. Not anything to be concerned about unless you are also kept up at night worrying how to improve the gas mileage of your 427 car.
Unfortunately, its the narrow minded personal attacks that harm the hobby in so many ways, and intimidate potential new members or posters to participate in any discussion board or meet. Enjoy your cars, learn all you can about it , share your enthusiasm to enchourage others. Share what you have learned and experienced. Remember whats important, it may not be your spell check or layout, hopefully its the car and the people who share your feelings for them.

[Duke W.]

Re: Roller Cams

A solid screen of single spaced text is nearly impossible to read. Try hitting the return key a couple of times to separate paragraphs, and make the paragraphs small.

The API source documents and other references I used as a basis for my article are listed. I suggest you read them.

Duke

[Joe L.]

Re: Roller Cams

It's certainly possible to design/manufacture a lobe for roller lifters that yields the exact same lift-crank angle specification as any flat tappet cam.

But such a design would offer the exact same performance characteristics as the flat tappet cam, so there would be no point, given the higher cost.

Roller lifters can sustain higher lobe contact pressure, so a roller lobe can have more aggressive dynamics and lift with the necessary higher load valve spring to control the greater inertia forces without loss of durability. This facilitates similar top end power with shorter duration/overlap than a flat tappet cam, and the shorter duration/less overlap can yield better torque bandwidth and a more tame idle than the OE flat tappet SHP cams.

But now the engine, other than top end power, has significantly different performance/operational characterisitics. In short, it's a completely different engine.

It's like trying to have a cat act like a dog, but still be a cat.

Duke

Duke-----



I think the primary advantage of roller cams, both the hydraulic variety used in PRODUCTION engines since the mid 80's and the aftermarket mechanical variety used in racing for as long as I can remember involves the ability to utilize cam profiles not possible with flat tappet cams. In turn, the ability to use cam profiles not possible with flat tappet cams opens up "whole new worlds of possibility" with respect to engine performance. In the case of profiles for street engines, better performance, fuel economy, and emissions can be achieved all at the same time.

Certainly, the cost of roller cams and lifters was a MAJOR added expense for the auto manufacturers when they were introduced for PRODUCTION engines. Without major benefits, I don't think that cost would have been incurred.

[Stuart F.]

Re: Roller Cams

I haven't followed roller cam developments too closely for many years, unlike my hot rod days in the 50's and 60's. Back then I recall much of the concerns were for the roller lifters themselves, relative to the design/mechanisms used to hold them in alignment with the cam. I recall different "links" and "guides", including the "straddle" type.

What design or designs have "won out" for either OEM and aftermarket?

Stu Fox

[Michael H.]

Re: Roller Cams

Think I'll just sit back and watch this one. This is getting very interesting. Not accurate or informative at all, but interesting.

[Clem Z.]

Re: Roller Cams

I haven't followed roller cam developments too closely for many years, unlike my hot rod days in the 50's and 60's. Back then I recall much of the concerns were for the roller lifters themselves, relative to the design/mechanisms used to hold them in alignment with the cam. I recall different "links" and "guides", including the "straddle" type.

What design or designs have "won out" for either OEM and aftermarket?

Stu Fox

lubing roller lifter needle bearings was the big problem back then because of "splash" oiling to the needle bearings but now solid roller lifters have full pressure oiling to the needles. using a "rev kit" will also add the the roller lifter life as it prevents "skipping" of the roller on the cam lobe. before we change out solid roller lifters every 150 hours to prevent needle bearing failures. GM now has a hyd roller lifter good for 8000 RPMs in the LX series engines. with some fabrication they can be used in old chevy engines. there are still several choices of roller lifter alignment available. GM has the price of "standard" hyd roller lifters down to $121 and the special racing ones $226

[Duke W.]

Re: Roller Cams

I agree and the OEMs also claim improvement in fuel efficiency due to both roller lifters and roller trunnion rocker arms. The improvement is slight, but it combines with many other detail design improvements over the years to make modern engines very fuel efficient.

Roller cams can offer equivalent top end power as flat tappet designs while making better low end torque with better idle stability, and idle stability and less cyclic variation at low speed/load is absolutely critical to meeting today's low emissions targets, so relatively low overlap is a must, which is why LS-engine cams have LSAs on the order of 119-121 degrees versus 112-116 of vintage engine cams.

For these reasons (and cost) I don't recommend roller cams for restoration engines because they will noticeably alter the engine's performance characteristics compared to the original, but they are okay (if you can swallow the conversion cost) if you are building an engine from vintage components, but don't need to offer the same performance characteristics including idle characteristic as a vintage OE engine.

It might be possible to replicate the performance and idle characteristics of a OE SHP flat tappet design with a roller, but it would take a custom design and experimental development, which would be an expensive and time consuming project.

As for what is on the market today for retrofit roller cams I have the same criticism as I have for aftermarket flat tappet cams - too much overlap to achieve maximum torque bandwidth and fuel efficiciency in a road engine with a reasonably legal exhaust system, but since most guys seem to choose cams based on "how they sound at idle" rather than any objective criteria such as torque bandwidth and fuel efficiency...

Duke

[Joe L.]

Re: Roller Cams

I haven't followed roller cam developments too closely for many years, unlike my hot rod days in the 50's and 60's. Back then I recall much of the concerns were for the roller lifters themselves, relative to the design/mechanisms used to hold them in alignment with the cam. I recall different "links" and "guides", including the "straddle" type.

What design or designs have "won out" for either OEM and aftermarket?

Stu Fox

Stu-----


I consider that the OEM design is best. However, this design can only be used in blocks designed for roller lifters. In this design, the tops of the lifter bodies are machined flat on 2 sides. A retainer fits over each pair of lifters which mates with the flat-sided lifters and positively prevents their rotation. A stamped steel "spider" bolts to bosses in the lifter valley and maintains the anti-rotation retainers. In addition, the camshaft thrust is controlled via a thrust plate at the front of the block which is designed to work with the specially machined front camshaft journal.

RETROFIT aftermarket rollers, either of the hydraulic or mechanical variety, use articulating anti-rotation bars between pairs of lifters. There are several different designs but the most popular, especially for hydraulic roller set-ups, is a simple flat bar pivoting on pins attached to the upper lifter body. Camshaft thrust control, very important for roller lifter set-ups, is usually provided by a bronze or aluminum "button" installed at the center of the cam sprocket and bearing on the timing cover (or plate attached to the inside of the timing cover). In my opinion, the OEM camshaft thrust control is FAR superior to the button system. However, it can only be used with cams and blocks designed for the OEM system.

[Stuart F.]

Re: Roller Cams

Clem and joe;

Thanks for the enlightenment. Lately I have been reading more about the LS series of GM engines, and I saw so many performance versions at the recent PRI show here in Orlando. GM certainly has come a long way with the old push rod "cooking machine" engine designs. It's hard to convince the proponents of the overhead cammers that the push rod engines aren't dead yet, but they sure have made quite a case.

Stu Fox

[Joe C.]

Re: Roller Cams

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.
If there was actually enough friction to reduce engine power by 15 horse power, just exactly how long would a flat tappet lifter or rocker arm last? Not very long, at all. Enough friction to robb 15 HP would quickly destroy these components. Rocker arms and flat tappet lifters can last hundreds of thousands of miles and still be shinny on the contact surfaces when removed. That should tell us something about how much frictional loss is created at these points.

What it does have to do with is fuel mileage and emissions. While it's true that these components, by themselves, do not robb power, they DO require a lot of lubrication, which requires oil pressure, which gobbles up power. It takes a LOT of energy to spin an oil pump, especially at road speed RPM.
By reducing the amount of pressure required, the power required to turn the oil pump can be reduced.
Some Pro Stock engine builders go as far as using needle bearing cam bearings but not because there is any power to be gained because of less friction. It's because they require less oil flow/pressure. Less power loss at the oil pump.

Roller cams/lifters in race engines were used for two reasons. One, because of the incredible valve spring pressure required to prevent valve float at high RPM and... and two, because an longer duration, faster action cam profile was available with the roller design.
If you increase the duration of a cam lobe, you eventually get to the point where lifter to lobe contact no longer occurs on the face of the lifter. The point of contact would move off the face of the lifter.
There are two ways to correct the problem. Either use larger diameter lifters, (or mushroom lifters) or use roller lifters.
Roller lifters cured both problems which is another reason why so many racing engines used them.
However, in Nascar, for example, roller cams/lifters are not allowed so todays Nascar engines usually use wide base or larger OD lifters.

Here's a link to the original discussion.

https://www.forums.ncrs.org/showthre...leage&uid=5460

Michael,

Don't forget the lube oil, which forms the thin film boundary layer, preventing most contact between lifters, lobes, rings, bearings, journals, cylinder walls, etc, etc. Although the components themselves do not contact each other (except in certain rare and cyclic occurrences, which is when wear takes place), it is the shear forces set up in the boundary layer, which create heat at a rate sufficient to raise the temp of the lube, per unit of time. This consumes energy at a specific rate.

The lube oil in the crankcase "heats up" or, rises in temperature for two reasons, the first of which, is because it shares a part in carrying away heat due to the combustion process. The second reason, is due to the shearing, on a molecular level. This action is similar to the transmission fluid heating within the torque converter of an automatic transmission (fluid shear coupling). It is also similar to the fluid heating which occurs in a vane type pump which is idling for extended periods.

For example, for a crankcase containing 6 quarts mineral oil, losing 1 HP due to shear:

6qts (1/500 lb/gm) (.8 gm/cc) (1/.00105668 cc/qt) = 9.08 lbs.

The specific heat of mineral oil is 0.4 BTU/lb. deg. F.
1 HP = 42.407 BTU/min.

42.407 BTU/min = 0.4 BTU/lb-deg F. (9.08 lb) X deg F.
where X is the temp rise per minute, of the 6 quarts of oil
solving for X yields 11.67 degrees/min.

An oil pump does not create oil pressure, it pushes oil from one place to another. It is a positive displacement pump that moves oil as it turns. Oil is incompressible so once it leaves the pump it continues to flow until it encounters resistance in the filter, oil galleries and bearings. It's the resistance to flow that builds pressure in the oil system. Trying to force oil through a small opening creates more resistance and pressure than allowing it to pass freely through a large opening. As pressure builds in the oil system, it exerts pressure. A spring-loaded "pressure relief valve" built into the oil pump (or near the pump) opens when pressure exceeds a certain limit (typically 50 to 60 psi) and either reroutes oil back into the pump's inlet or the oil pan. At idle, most oil pumps do not produce enough flow to force open the relief valve. Oil pumps that are camshaft driven turn only at half engine speed so output isn't great at idle and low rpm. Even pumps that are crankshaft driven and turn at engine speed (or double engine speed in a few instances) don't pump enough oil to overcome the relief valve spring. The relief valve generally only comes into play at higher rpm when the pump's output pushes more oil into the system than it can handle. Then the relief valve opens to vent oil and limit maximum oil pressure until the engine returns to idle or a lower rpm.

A high volume pump, having larger lobes, requires more power to drive it at all times. High pressure pumps, being equal sized to standard pressure pumps, only require additional energy when running at speeds above that at which a standard relief spring would bypass........

Vehicle manufacturers have traditionally recommend a minimum of 10 psi of oil pressure for every 1,000 rpm of engine speed. Using these numbers, most stock engines don't need any more than 50 to 60 psi of oil pressure. With tighter bearing clearances, pressure goes up requiring less flow from the pump and less parasitic horsepower loss to drive the oil pump. In racing applications, the old school of thought was more oil pressure was needed to keep the engine lubed. That's true if bearing clearances are loosened up. But most engine builders today tighten clearances so less oil flow is needed to maintain adequate oil pressure. This approach increases the horsepower output because less power is needed to drive the pump at high rpm, but sets up higher shear within the boundary layer, which leads to more losses due to shear.

[Clem Z.]

Re: Roller Cams

with the proper valve train you do not need high pressure springs with hyd. roller tappets as the ZO-6 engine turns 7000 RPM with 100# on the seat and 310# over the nose spring pressure as the "beehive" type spring design allows this to happen

[Bill C.]

Re: Roller Cams

Read them, long ago, and have already commented on them,
have you read the ones I referenced?

[Clem Z.]

Re: Roller Cams

Read them, long ago, and have already commented on them,
have you read the ones I referenced?

were you speaking to me,sir ???

[Joe C.]

Re: Roller Cams

with the proper valve train you do not need high pressure springs with hyd. roller tappets as the ZO-6 engine turns 7000 RPM with 100# on the seat and 310# over the nose spring pressure as the "beehive" type spring design allows this to happen

"Beehive" springs lower reciprocating (inertial) mass, thus obviating the need for higher forces over the nose. A small amount of float is actually helpful, increasing lift. It's spring force on the seat which helps prevent valve bounce, especially with very aggressive closing rates.