Overhead cam VS pushrod design? Which is better?

[CoastGuardZ]

I'm gonna go with it's a "Nissan Thing". Personally I never said I was a purist, I consider myself a loyalist. Quite frankly, I'm very impressed with all the well thought out answers and I can see everyones reasons for their choice. My first car building experience was an '84 Monte Carlo SS. I built a 350 , no brainer, with 374hp at the wheels. Not bad for a 19 year old on a budget. It also got about 10mpg. Anyways... When my project is all said and (in 5-10 years or so) my anticpation is to have an L28 with tripples and a 5spd.

Nissan Nate

[jmortensen]

Heh. Maybe I'll sell you mine when I swap to V8...

[260DET]

'day Dave There is a particularly significant problem with a turbo L, at least in a hot climate. Heat, although IIRC Dave has his turbo away from the side of the engine.

Having a non crossflow head your are stuck though with a hot exhaust manifold under and next to the inlet equipment. Bad! Having a turbo only adds to that problem. Badder than bad

[thehelix112]

I thought we already did on the other thread. The 350 has a higher potential redline than an L6. OHC in theory has more potential for higher rpms, but the L6 in particular can't handle the extreme rpms. I don't know whether that's because of the non crossflow head or the crankshaft harmonics issue or what. Regardless of why, V8s actually can do better than an L6 at high rpms and that's the truth. If you're going to push either to that kind of limit you're already talking about a high dollar engine.

My point was only that OHC engines (in general) have higher theoretical RPM limits than OHV engines (in general). That is all. BTW, I believe there are several issues with a L6, some of which were covered by phred in other topics. It makes me wonder if you are comparing apples to apples here. Sure maybe some big budget top fueler V8s will pull past 9500, is that the type of engine you are comparing an L6 to? Please be more specific because I'm not convinced yet.

Most people use these arguments when talking about relatively stock engines, where the V8 might have a rpm limit somewhere in the 500-1000 rpm slower than the L6. IIRC my original L24 had a redline of 7000, and the L28 I replaced it with had a redline of 6500 from the factory, my new Sierra pickup has a readline of 6000. So then you're talking about the relative benefit of another 1000 rpm and 150 fewer hp than the V8, which again leads me to believe that the advantage still goes to the V8. Now we're talking about a displacement thing more than anything else, but the power advantage is there for a rpm disadvantage that's pretty minor.

See previous comment. You have successfully compared stock to stock and the L limit is higher. And if we are going to compare race engines we should use those from a similar application as a drag engine that only has to live for 540 revolutions or so can't really be compared to a circuit race engine.

You're talking boost, so are you swapping in an L28ET or are you driving a ZX Turbo? If you're swapping the motor into an early Z, then I really don't see the distinction between doing that and putting in a V8. Is it a Nissan thing? If someone swapped in a Nissan V8 (the old 70's pushrod limo engine for instance) would that be "better" than a 350? If so why? Just trying to understand.

The L28ET is a MUCH better match up to a V8, and it makes a lot of sense to do a turbo swap IMO. Obviously you've seen the limitations of the NA L6 and chosen to do something about it. In that sense we're in agreement.

I never said I was using an L24. I've always said L6 I think. And if you don't see the difference between that and a V8.. well.. thats your err.. decision I guess. Yes its a Nissan thing for me. But at the same time I'm not going to go to any effort for a reduction in power/potential.

Your taste is your prerogative. Taste is subjective, and there certainly is no need for anyone else to tell you how to build your car. You like the L series, build an L series. I would still argue that an early Z with a ZXT engine is also a "mongrel" in technical terms. If it ain't stock, it's a mongrel, right? Isn't that the purists' credo?

I suppose it depends by what you mean by `breed'. I consider Nissan a breed. Also I consider an L6 to be an L6 whether it has webbers or turbos or whatever. The induction system is distinct from the engine in my opinion.

Look forward to your reply.

Dave

[thehelix112]

Richard,

Quite right. I've also added some ACL heat shielding between the exhaust and intake sides.

Heat transferring between intake and exhaust is definitely bad and its definitely a weakness and not ideal. I'm not entirely sure how I'll go with dealing with that much heat in a track condition.

Dave

[jmortensen]

My point was only that OHC engines (in general) have higher theoretical RPM limits than OHV engines (in general). That is all. BTW, I believe there are several issues with a L6, some of which were covered by phred in other topics. It makes me wonder if you are comparing apples to apples here. Sure maybe some big budget top fueler V8s will pull past 9500, is that the type of engine you are comparing an L6 to? Please be more specific because I'm not convinced yet.

I've been trying to find a page that quotes the redline of a NASCAR V8. Man is that tough to find! I did find this one: http://www.fittipaldionline.com/current_season/buschcar.shtml but I believe this is a Busch series car and that they are less prepared than the full on NASCAR cars. I am not a NASCAR fan, so I might just not know where to look. Even so, 9000 rpm is the quoted rpm limit here for a Busch series car. I would swear that the major leaguers are pushing 10,500, and I got that from flipping past Speed channel and thinking, "Holy crap, 10,500 rpm!!!"

See previous comment. You have successfully compared stock to stock and the L limit is higher. And if we are going to compare race engines we should use those from a similar application as a drag engine that only has to live for 540 revolutions or so can't really be compared to a circuit race engine.

That is correct, but the V8 still has a 150 hp advantage over a stock L6. So you can take the 1000 rpm, but I'd prefer the 150 hp. I was trying to compare a NASCAR engine because it does have to live through qualifying and the race, and is not simply a 1/4 mile engine. Keep in mind, NASCAR races at Infineon Raceway and a couple other road race tracks, so it IS a circuit racing series at least for a couple races per year. I agree that comparing an engine that gets rebuilt every 1/4 is not fair, which is why I never brought up the 7000 hp of a top fuel dragster. A top fuel dragster isn't even remotely related to a Z car.

I never said I was using an L24. I've always said L6 I think. And if you don't see the difference between that and a V8.. well.. thats your err.. decision I guess. Yes its a Nissan thing for me. But at the same time I'm not going to go to any effort for a reduction in power/potential.

I suppose it depends by what you mean by `breed'. I consider Nissan a breed. Also I consider an L6 to be an L6 whether it has webbers or turbos or whatever. The induction system is distinct from the engine in my opinion.

OK so your ARBITRARY line is that the engine should be a Nissan engine. Other more severe purists' arbitrary line is that the engine number should match the chassis number. It is a purist thing, and you're just a little less of a purist than some others.

A short story: My roommate was selling chassis #472 about 7 or 8 years ago. A guy drove 7 hours to come take a look. He gets there and is checking it out. My roommate says, "You want to see a nice Z, you should look at Jon's Z over there." The guy walks over looks in the window of my car and almost wretches, I mean he looked physically ill. He then told me that I "ruined" a classic Z. What he saw was Recaro seats, Autometer gauges, and aftermarket carpet kit, camber plates, and a strut tower bar. That was enough to make the man physically gag. How do you think that guy would feel about my F54/E31/Mikuni/header engine? Something tells me if I had actually showed it to him I would have had to wash puke off of it. So what makes his level of purism wrong, but yours correct? Where is the arbitrary line correctly placed? Matching #'s? Same manufacturer? Period correct induction? None of the above?

I firmly believe that an engine is an engine. You may want an engine to perform a specific task, or produce a specific amount of power, or have a specific torque curve or whatever. I do not believe that an engine that says Nissan on it or has a particular cam configuration is automatically superior to any other. There are many engines that are not built by Nissan that have characteristics that would suit the Z well, and I'll stand by the idea that the engine that is easiest and cheapest to build and does what I want is the one I should buy. I understand you do not agree, and I'm not trying to make you. You have an emotional argument (am I mistaken?) and I'm just trying to point out the rational point of view.

[e_racer1999]

a post on a different forum:

http://www.pistonheads.com/gassing/topic.asp?f=66&h=&t=153085

[CoastGuardZ]

You know - this whole Nissan Engine in a Nissan Car boils down to the old " I'd rather push a Ford than drive a Chevy" argument that the good ol' boys are always fighting about.

Of course the topic is OHV vs. OHC. Both have strong points, both have week points. The whole L6 vs. V8 almost doesn't apply though. Honestly how do you compare a 30+ year old Nissan 6 cylinder 2.4L to a 5 or so year old Chevrolet 8 cylinder 5.7L? That's 2 more cylinders and more than twice the displacement and another 20+ years of development.

Nate

Nate

[jmortensen]

You know - this whole Nissan Engine in a Nissan Car boils down to the old " I'd rather push a Ford than drive a Chevy" argument that the good ol' boys are always fighting about.

Right. Not a logical argument.

Of course the topic is OHV vs. OHC. Both have strong points, both have week points. The whole L6 vs. V8 almost doesn't apply though. Honestly how do you compare a 30+ year old Nissan 6 cylinder 2.4L to a 5 or so year old Chevrolet 8 cylinder 5.7L? That's 2 more cylinders and more than twice the displacement and another 20+ years of development.

I did mention my truck which has a 5.3 liter based on the LS1, but that doesn't have to be the V8 example. I believe everything that I've stated holds true for the old V8 a la 283, 302, 327, 350, 377, 383, etc with the exception of the redline, which moves up and down depending on the build of the motor and the car it was put in. I'm pretty sure that Busch car runs the old style V8, which is concurrent with the Z as far as age goes.

[CoastGuardZ]

Originally Posted by jmortensen

Quote:

Originally Posted by CoastGuardZ

You know - this whole Nissan Engine in a Nissan Car boils down to the old " I'd rather push a Ford than drive a Chevy" argument that the good ol' boys are always fighting about.

Right. Not a logical argument

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?

The 5.7L comment is derived from the ongoing nagging session that has transversed in this thread and at least one other thread in the last few days which the brunt of V8 debate has been centered around late model SBC's LT1, LS1, LS6 blah blah blah so on and so forth. If you chose to use a 5.3L that's fine, it's still 20+ years newer and more than half the displacement of an L24.

Busch cars may run an "old style" V8 but they use new castings developed with state of the art precision and their engine's cost more to build than restoring an entire Z car.

A comparable engine to place a Busch Car up against might be whatever Nissan is using in the Japan GT500 class. Of course this is speculation considering I'm not even sure what they are running.

Again, just stating my opinion. Not an expert by any means.

Nate

[CoastGuardZ]

Oh yeah, almost forgot. I noticed you left out the "power house"... Chevy's 305. We all know how great that engine was... My '88 C1500 made an astonishing 180hp and had something like a 5800 rpm redline. 5.0=180hp vs 2.4=150hp... there's a fair comparison.

[240ZX]

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?

The 5.7L comment is derived from the ongoing nagging session that has transversed in this thread and at least one other thread in the last few days which the brunt of V8 debate has been centered around late model SBC's LT1, LS1, LS6 blah blah blah so on and so forth. If you chose to use a 5.3L that's fine, it's still 20+ years newer and more than half the displacement of an L24.

Busch cars may run an "old style" V8 but they use new castings developed with state of the art precision and their engine's cost more to build than restoring an entire Z car.

A comparable engine to place a Busch Car up against might be whatever Nissan is using in the Japan GT500 class. Of course this is speculation considering I'm not even sure what they are running.

Again, just stating my opinion. Not an expert by any means.

Nate

Easy there big boy....lifes too short to get your panties in a bunch!

Nate, I think Mr. Mortensen was agreeing with your statement.