Overhead cam VS pushrod design? Which is better?

[jmortensen]

Well professor, how is it not a logical argument? Because I'd much rather drive a Nissan than any Chevrolet or Ford. Now if you are trying to break it down just as a mode of transportation, then I can see your complaint of illogicality. However, if that's the case then why would I waste so much time at a Classic Z Car site?

No need to get nasty. I wasn't trying to get nasty with you.

Emotional argument: "I'm gonna go with it's a "Nissan Thing". Personally I never said I was a purist, I consider myself a loyalist." Being loyal is a fine and good characteristic, but it isn't a logical argument. "I'd much rather drive a Nissan than any Chevrolet or Ford" is not logical either. WHY would you rather drive a Nissan? If there is not a logical reason, then it too is an emotional statement.

Chevy motor or Nissan motor makes no difference to the car, as long as the car goes. Both are clearly capable of making the car go. That's why it's not a logical argument. Similarly Chevy vs Ford is not a logical argument. Also "I hate Camaros" is a statement, not an argument. "I hate Camaros because they're overweight and undersuspended and have a tendency to explode the tiny 7.5" differential." Now there's an argument. We can break that down and decide whether these points are true or not. If they're not, then the argument isn't a very good one, so the best thing to do is either to re-examine why you don't like Camaros, or consider changing your point of view.

I don't know why you're here or why you like Z's. If you like Z's because someone told you when you were a child that Z's were great and Chevys suck, then I guess that would be illogical too. I personally like the Z because it is a great inexpensive lightweight car to modify and race. The emotional part for me is that I like the way it looks (see, I'm not a Vulcan either ). If the emotional part for you is an attachment to the L6, that's fine. I'm just pointing out that it is an emotional argument, and much like the theoretical arguments of why the OHC is superior to OHV it isn't rooted in facts.

On a personal note, I love to argue and I'll do this all week if you want to keep going, but I don't want to hurt your feelings. We can stop whenever you want.

[ecp48]

Jon,

Not to get religious, but thats what I alway liked about the Jehova's Witnesses at the Door, you could argue (discuss) all day.

[e_racer1999]

i think a more fair argument would be comparing a chevy v8 with the v8 from say a titan. if we go putting an L6 against a V8, of COURSE there is going to be some discrepancy.

[jmortensen]

I drove a Titan and was VERY impressed with the engine. What exactly did you want to compare Jason? Redline? 6100 in the Titan. HP is 305, torque is 385 IIRC, and that's in truck tune. I'm sure it will be capable of a heck of a lot more. I hope they put it in a car and develop it some more for that application. Cg will be higher due to the DOHC, weight of the engine ??? uh, what else should we be comparing...

[thehelix112]

I'm not sure if you get what I'm saying Jon. I'm not saying, nor did I ever, that an L6 will make as much HP as a V8 (or any other engine that has around twice the displacement!)

I also specifically said that whatever engine is a personal choice. Whether you want to make that on a purely rational basis or an emotional basis is entirely up to you because <MAIN POINT>

You can get more hp from either an L6 or a V8 or a rotary or just about whatever you damn well want with enough work.

</MAIN POINT>

I should note that I'm completely and entirely pro forced-induction. N/A seems like trying to wizz out a house fire.

A point that is entirely secondary to this is that an L6, due to its OHC design, will (with the right modifications) have a higher rev limit than an OHV design. IMHO the only way to compare it is stock, once you start comparing race engines you reach the stage of making up arbitrary rules like, on you're not allowed to change the timing drive etc etc, where do you stop? FYI, thought this might interest you:

http://nkondo-web.hp.infoseek.co.jp/Kameari_L6_2.htm using your favourite web translator if you want to read it, worldlingo.com works. Now I'm not going to say that means much as I've never seen any proof, but why would you advertise it as being 13000rpm capable if you hadn't tested it?

Dave

[jmortensen]

I get it. I'm just presenting the opposing viewpoint. You say again that OHC will rev higher than OHV, and again I have to say that this is not correct with regards to all V8's vs the L6 stock vs stock or modified vs modified. LS7 or 1968 Camaro 302 (that one takes care of the modern vs old part of the debate) have redlines of 7000, and I'm not a pony car guy but I'd guess that there were others.

I love that Kameari chain tensioner. What a great idea. I think Alan HS30-H has said that they tested it on a machine to 13,000 rpm, not on an engine BTW.

[e_racer1999]

what i was getting at: it's a little unfair to match a 6 to an 8 (for the 8, of course! j/k) so i figure let's match an 8 to an 8. i know that in the truck world the titan is the new king (according to car and driver, etc.) so i would go so far as to say that maybe the DOHC titan motor would be a better comp engine to say a chevy OHV v8.

[thehelix112]

Jon,

When I say OHC will rev higher than an OHV, where did I mention 6 vs 8? They are two entirely seperate issues IMHO. An OHC engine WILL rev higher everything else being equal simply due to less reciprocating weight, not to mention it will make more power as there is less mass that the valve spring has to move hence lighter valve springs can be run, hence less parasitic losses.

That is not an emotional argument.

Dave

[jmortensen]

what i was getting at: it's a little unfair to match a 6 to an 8 (for the 8, of course! j/k) so i figure let's match an 8 to an 8. i know that in the truck world the titan is the new king (according to car and driver, etc.) so i would go so far as to say that maybe the DOHC titan motor would be a better comp engine to say a chevy OHV v8.

It looks like a kick arse engine by all accounts. The issues that I can see are: cost, availability, aftermarket support, weight, size, transmission options. I'm sure the first three will be overcome with time, the last 3 might be a problem, might not.

When I say OHC will rev higher than an OHV, where did I mention 6 vs 8? They are two entirely seperate issues IMHO. An OHC engine WILL rev higher everything else being equal simply due to less reciprocating weight, not to mention it will make more power as there is less mass that the valve spring has to move hence lighter valve springs can be run, hence less parasitic losses.

What engines are you talking about then? I thought we were talking about Z's. As I've pointed out several times, despite the theoretical advantage of the OHC L6, the L6 does not necessarily have a higher rpm limit than a Chevy V8. Both of these engines are commonly found in our beloved Z's. If you're back to theory that's fine. Theoretically I agree with you 100%, which is why I voted that I prefer the OHC design in the poll. If you are saying that there exist OHC engines which spin higher than the fastest OHV redline I would agree with you. Why that relates to somebody's choice about an L6 which doesn't have those characteristics is beyond me.

Parasitic loss? How about having to spin 4 cams instead of one? Opening and shutting 48 valves instead of 16 uses less hp? How about the drag of the gigantic chain and the idlers and all that? Think of how much mass is in the chain(s) on a DOHC V engine, it's gotta weigh at least as much as all the pushrods put together, and thats not even counting the cams, cam gears, valves, springs, retainers and keepers. I don't know that I'm convinced on the parasitic loss argument. Maybe this is why OHC engines don't seem to have as much torque at as low an rpm as OHV (generalization). Maybe it's the parasitic losses from the valvetrain at low rpms that hold back the OHC engine, but it's higher rev capability and better chamber design and better flowing heads (another generalization) make up for these losses at higher rpms, not to mention VVT that some DOHC engines have. Could also have to do with the fact that the valvespring in the OHV engine is responsible for moving the rocker and the pushrod and since those pieces aren't in firm contact that makes keeping the valvetrain stable at high rpms is harder in the OHV. That's all pulled straight out of my butt, BTW, I haven't researched it at all, but I don't think parasitic loss from the valvetrain is an argument for OHC.

[CoastGuardZ]

Emotional argument: "I'm gonna go with it's a "Nissan Thing". Personally I never said I was a purist, I consider myself a loyalist." Being loyal is a fine and good characteristic, but it isn't a logical argument.....

"I'd much rather drive a Nissan than any Chevrolet or Ford" is not logical either. WHY would you rather drive a Nissan? If there is not a logical reason, then it too is an emotional statement.....

.....I don't know why you're here or why you like Z's. If you like Z's because someone told you when you were a child that Z's were great and Chevys suck, then I guess that would be illogical too.....

...On a personal note, I love to argue and I'll do this all week if you want to keep going, but I don't want to hurt your feelings. We can stop whenever you want.

To answer the question of why I like Z's... I just do. Emotional or Logical?

My first encounter with Z's was a black 280ZXT when I was younger and I've been hooked ever since. Of course my father said it was Japanese garbage and I should "Buy American". My position on the Z and Nissan is just simple choice and personal taste partially based on old technology and shoddy build quality. Are you aware that the Big 3 use the consumer as their Q/A? Compare a new Japanese vehicle (most of which are built in the USA) to a new American vehicle and you will see my point. I've owned my share of American cars and trucks and I'm through. The Jap cars and trucks I've owned have all been extremely reliable and easy to maintain. This doesn't just apply to Datsun/Nissan but to cars like my wifes 174,000 mile Acura Integra, still going strong and holding up well too.

Aftermarket support when talking about the V8's will never be anywhere near the same... the CSB has been around since when, 1955? Where as the Titans 5.6 has been around only a few years. Sheer quantity alone and the extremely wide range of placement will always guarantee the CSB a better aftermarket support. But for my taste I'll be plenty happy If my Z makes 200hp. - I reckon that's emotional.

My feelings aren't hurt :hurt: , I'm just a smartass by nature. :devious:

Nasty Nissan Nate

[jmortensen]

My first encounter with Z's was a black 280ZXT when I was younger and I've been hooked ever since. Of course my father said it was Japanese garbage and I should "Buy American". My position on the Z and Nissan is just simple choice and personal taste partially based on old technology and shoddy build quality. Are you aware that the Big 3 use the consumer as their Q/A? Compare a new Japanese vehicle (most of which are built in the USA) to a new American vehicle and you will see my point. I've owned my share of American cars and trucks and I'm through. The Jap cars and trucks I've owned have all been extremely reliable and easy to maintain. This doesn't just apply to Datsun/Nissan but to cars like my wifes 174,000 mile Acura Integra, still going strong and holding up well too.

Yeah, I had similar experiences. My Toyota P/U has 208,000 and my dad had a 85 S10 Blazer that broke down every 3 weeks that turned me off of American cars for a LONG time. My Z had ove 200,000 when I got it, but that's not a fair comparison since it's had 2 L6's, a tranny swap, 2 diff swaps, etc. The thing is that the 70's and 80's were CRAPPY for American car manufacturers. Quality was LOW. Very LOW. Power was down. Cars struggled under smog restrictions and plain ol bad engineering. The big 3 really didn't know what to do about smog. My friend's dad had a 78 F150 with a 351W or M or whatever engine in it, and we tried to pull his 510 to a race some 4 hours away. Took us 8 hours and we were doing 35 miles an hour up ANY sort of grade. What a horrible POS truck! During this time the Japanese cars had a major advantage in that they didn't try to redesign the same car over and over and over. They were able to make designs that passed smog but weren't quite as badly affected in the power or reliability areas, and they took over huge portions of the market share deservedly so. Even in the 90's American car manufacturers were still making pretty cheesy interiors, with switches and gauges that were cheap and crappy in aesthetics and functionality. Times are changed though. GM cars have come up significantly in quality and in design. If you choose to still remain wary of American cars, I can't say that I blame you one bit. But they are better and more efficient and more reliable and more powerful now than they have ever been. http://www.theautochannel.com/news/2005/06/30/136286.html

Aftermarket support when talking about the V8's will never be anywhere near the same... the CSB has been around since when, 1955? Where as the Titans 5.6 has been around only a few years. Sheer quantity alone and the extremely wide range of placement will always guarantee the CSB a better aftermarket support. But for my taste I'll be plenty happy If my Z makes 200hp. - I reckon that's emotional.

This is one of the strongest selling points for an American V8. I can buy 8 forged CSB pistons for less than the cost of 6 forged Nissan pistons. I can also get 8 connecting rods for less than the cost of 6 Nissan rods. Everything in the aftermarket is geared towards the CSB in particular, and that is a huge advantage. Imports are getting increasing aftermarket support as time goes by, and I for one really hope that the Nissan 5.6 gets a wide array of aftermarket parts to choose from. We'll have to wait and see.

If you're happy with your 200 hp more power to you. If I could be happy with that I would have saved 100s of hours in labor and 1000s of $$$.

[thehelix112]

Jon,

Are you capable of comprehending the HYPOTHETICAL? I'm not talking about ANY engine. When I say `everything else being equal', I mean, everything else being equal. Imagine an L6 with an OHV design, and then a standard OHC L6. Which do you think would rev higher, and which do you think would make more power?

I have no idea why you keep comparing I6 to V8 in conjunction with OHC and OHV. And then where did this comparison involving a 6 valve per cylinder V8 (48 valves), or are you talking about a 4 valve per cylinder V12 now? Would make about as much sense.

Dave