[quaddriver]

Originally Posted by ivymike1031

That's correct, my degree is in mechanical engineering.

I do not believe that.

Originally Posted by ivymike1031

That is wrong. In fact, I have been involved in the design of valvetrain hardware for some recent US automobile engines that you are probably very familiar with, and some that you will no doubt become familiar with within a year or two.

name one. Its put up or shut up time. Since you and you alone have claimed to be THE expert, its time to prove it.

Originally Posted by ivymike1031

Because you clearly don't know what you're talking about when it comes to the relative noise levels of different timing drive schemes.

I have already stated that an OHV (which will perfectly suffice for a defn here, only a field mouse would not know what is being discussed) is quieter than any xOHC in same application. If you are sooooo sure of yourself and have done sooo much research, you will simply post sound measurements of the engine bay. Or are you now claiming that xOHC engines are soooo quiet that the manus use noisier alternators and PS pumps because they can?

Originally Posted by ivymike1031

I am an SAE member (since 1996), and I have several of their publications on my desk currently, mainly dealing with piston and ring lubrication, oil consumption, and recent developments in low-friction coatings. I also read their monthly magazine, Automotive Engineering, and I get the sectional newsletter. I get the idea that you really have no idea what automotive engineers do during the day (work), or what they have on their bookshelves (Roark's formulas for stress and strain, Shigley's Mechanical Engineering Design, and/or Heywood, typically, with a smattering of Timoshenko or Hartog texts as well). Do you have any idea how many papers come out of SAE in a year? I get abstracts from about 20 per month, specific to the areas of design that I'm responsible for. You try reading all that sometime (I usually don't).

Again, I do not believe this. Comments you have made here and in other threads do not belie this.

Originally Posted by ivymike1031

I don't need to "skirt" the subject of timing belt changes. You seem to be intent on misrepresenting the frequency with which they must be performed,

yes you do need to skirt it. As I am saying now for the forth? time, one needs changed, one does not. I even listed (correctly) which design that is an advantage to and I did not misprepresent the frequency, I *GAVE* the frequency and you later confirmed it. If we assume, as the 'industry' does, that a cars primary and secondary life is 10 years, and if we gather up all the models sold in 10 years (1994-2004) and averaged the timing belt change frequency, who is more correct? you or I? (hint: I would not bet on yourself)

Originally Posted by ivymike1031

Unfortunately, HLA-equipped pushrod engines (OHV is not an adequate description) typically rely on oil feed through an orifice in the HLA to the pushrod to get lube oil to the over-head area.

Besides being off topic, so? As I said and you have learned in the last 2 hours, the oil needed in the OHV heads' area is small.

Originally Posted by ivymike1031

Oil flow through that orifice is restricted to something in the neighborhood of several grams per minute (say 24gm/min @ 100degC).

No mikey, it is spec'd as a volume.

sidebar: I have to ask, because the answer I fear is apparent: you have never actually SEEN any of these systems in component form have you? Just ask and I will photo any of the components and upload them and explain to YOU how they work. the fact that oil travels up the pushrod is apparent. but how the flow is triggered you got wrong. way wrong.

Originally Posted by ivymike1031

Cams in the head often get oil drillings, and a much healthier oil supply.

I believe I mentioned that the oil system is different. And I beleive I mentioned that the supply requirements are higher. So you agree with me finally.

Originally Posted by ivymike1031

Not all overhead cam engines use aluminum heads (see Deere).

I didnt say they did, in fact I think I used the word 'most'. So aside from clouding the fact that I was, once again, not surprisingly right your point is? ps - iron on iron cam/boss contact is just as undesirable

Originally Posted by ivymike1031

Idle lubrication is the primary design factor for the oil pump for almost all engine configurations.

So? this was not the topic, other than the fact that I and I alone mentioned that xOHC have a greater need at idle than OHV designs and you have agreed with now twice.

Originally Posted by ivymike1031

Aluminum makes a pretty good journal bearing material.

Once again I ask not so rhetorically if you have ever seen the component pieces. I dont believe I mentioned any preference in bearing material (but I would prefer trimetal designs if asked), however, without, as I and I alone mentioned, ANY bearing between the cam and boss, loss of material is catastrophic. Unless of course you think it is a good design to have the cylinder head itself literally eaten away....its not the most bizarre thing I have heard.

Originally Posted by ivymike1031

Honda still uses mechanical lash adjustment, with a recommended adjustment frequency of about 60k miles. Mechanical lash adjustment is also used in a number of high-perf applications, and on a very large number of heavy duty diesels.

I didnt say there wasnt, for this other off topic presentation. I did say however that manus have moved away from mechanical systems, which I notice you do not dispute.

Originally Posted by ivymike1031

Wear is definitely not neglible at the cam-follower interface on pushrod engines. Ask a mechanic.

LOL, you get funny, OK, I asked one, myself. What is the wear then mikey? how much have you measured? on engines without oiling problems using hydraulic systems cams usually only need polished and the lifter bottoms reground. On mechanical systems, the lobes are ALWAYS deformed and the cam itself needs reground, IF it can be saved, often however with a smaller base circle. Again, it is hideously apparent that you have never observed first hand the components.

Originally Posted by ivymike1031

Pressure is never measured in ft-lbs (duh).

yes, I should have just said lbs. try to get as much mileage as you can out of that because it is the only error I have typed to date.

Originally Posted by ivymike1031

With a hydraulic lash adjuster, the expansion spring preload is not very large (say 40N or so), but the force that the lash adjuster exerts against the cam & pushrod on the base circle when the engine is running is much higher (say 150N).

I know what you did, you looked at the torque spec for a zero net lash hydraulic motor, but since you have never actually seen one, failed to realize that the plunger was as fully depressed as far as it would go long before the target torque on the rocker stud was reached. nice try. And when running, because of HOW oil is force up the pushrod, when the valve seats (return pressure zero) and the cam returns to base circle, there is an instant where the plunger actually rises to the lash point, and the lifter fills. at this point the pressure on the cam base circle is neglible.

Originally Posted by ivymike1031

If you'd like, I can explain to you how a typical HLA works.

Given previous errors, I doubt that. But also given that I use, assemble, disassemble, modify and improve same, Id be happy to do the reverse.

Originally Posted by ivymike1031

There are often collase and pump-up issues with HLAs during development, usually they're sorted out by the likes of me before the likes of you get an engine.

they were sorted out perhaps 30 years ago mikey. The automotive community pretty much trusts the hardware as bulletproof

Originally Posted by ivymike1031

A properly adjusted mechanical system will have less force on the cam-follower interface over the base circle than a HLA valvetrain (close to zero).

Boy, must be that CLEARANCE I was mentioning. Clearance=gap = no pressure. I never said this was a problem, I did however point out that the take up of said clearance IS a problem. But then again, you seem to feel that mechanical camshafts suffer less wear than hydraulic cams. Not only does that fly in the face of well, nearly everything learned to date, but pretty much defines the quality of the techincal responses received to date.

Originally Posted by ivymike1031

Roller followers are used on both overhead and in-block cam valvetrain configurations (as noted in my MUCH earlier post).

I dont recall saying they were not. In fact, I think to date my only comments about roller followers is that they seem to wear very well (meaning slightly if at all) - but again, that comes from actually SEEING the parts, using them etc. the whole gamut.

ps- GMs newest valve train technology, the VVT used on one of its 660 motors, hmmmm, is it mechanical or hydraulic? Not that this was ever the topic, but it shows which direction the industry continues to travel.