Curiouser and Curiouser

RE- valvetrain design generalities- it has far more to do with the cam events and valve shapes than if it's (D)OHC or OHV....

It's not that hard to make an OHC engine run just like an equal OHV engine if the heads are the same and the events are the same.

Where OHC gets an "advantage" is that it's cheaper to get engine speed out of it. But, as GM has shown many, many times, OHV engines are not really re-limited, either.

Just want to point that out.

In reply to tuna55:

The simple answer is that Ford bet the bank on the 4.6 modular and had no funds left to build an updated pushrod engine.

The long winded version... In the same time frame, GM built the North Star and the LS.

Financially, GM went from its best sales year to bankruptcy in less than a year. They spent more than Ford and everyone else so they ended up with two engine families instead of one. GM made a lot of other decisions that landed them in bankruptcy, but this is pretty symptomatic of how they went broke. GM built two complete architectures when one would have sufficed.

The North Star was direct competitor to the mod motor. The mod was designed to fit in the front wheel drive Lincoln Continental and the rear wheel drive Mark VIII. For this reason, the bore spacing is compromised for such an eternally large engine. A few millimeters of bore would make a world of difference, displacement, shrouded valves, etc... The mod would still be "ginormous" but it would make silly power at say 6.0-7.0 liters.

Having said all that, I believe that a modern, aluminum Windsor would have been a better decision which would have ended up looking a whole lot like an LS.

I've been on record as a mod-motor hater (and someone who has owned many of them) for years and years. However, I must say I dearly love the Coyote in my Mustang. Tons of power everywhere in the rev band, loves to rev, and sounds amazing. In contrast, the LS2 I had in my GTO was slower-revving and sounded good, but not as good. Both engines make roughly the same power, but the Coyote feels faster to me.

Having said all that, if I was doing an engine swap into something that didn't already have a V8, it'd be an LS motor all week and twice on Sunday.

Kreb wrote: One thing to consider also is that the LSX series mills are extremely well developed. One would be hard-pressed to improve upon them with a clean sheet pushrod design.

Except for the whole sustained high-G oil starvation thing...Which not only did they not even bother fixing when 'upgrading' from Gen III to Gen III.5 ("Gen IV"), but rather they actually let it get worse on the later engines. Ironically enough, the engines typically seem to grenade during left hand (NASCAR direction) corners.

Other than that though, yes, they're pretty phenomenal engines.

Driven5 wrote:

Kreb wrote: One thing to consider also is that the LSX series mills are extremely well developed. One would be hard-pressed to improve upon them with a clean sheet pushrod design.

Except for the whole sustained high-G oil starvation thing...Which not only did they not even bother fixing when 'upgrading' from Gen III to Gen III.5 ("Gen IV"), but rather they actually let it get worse on the later engines. Ironically enough, the engines typically seem to grenade during left hand (NASCAR direction) corners. Other than that though, yes, they're pretty phenomenal engines.

Plus chronic piston slap no the LQ4's, and maybe others.

DaewooOfDeath wrote: I recently watched a comparo of the LS3 and Coyote engines and it seemed that the Ford engine had literally no advantages. It's physically larger, it's heavier, it's less powerful, it's more expensive and it's not as efficient. Is there some reason Ford doesn't just build a pushrod LS copy that I'm missing? Smoothness? An aura of "high tech?" Factory constraints?

"High tech", that's it. Ford committed itself to OHC/DOHC everything in the 90s and has been eliminating all pushrod engines as they get out of their product life cycle.

GM said, screw that, OHV makes a more compact package for V engines, so they have stuck with pushrods for V engines except for "premium" models. They catch hell from technology fans for having "low tech" engines.

I giggle and point out that DOHC is a far older technology than OHV...

If it wasn't for the Corvette, GM might have abandoned pushrods as well. Imagine a Corvette with the hoodline required to clear a Coyote.

DaewooOfDeath wrote: Yeah, it seems weird with Fords OHC/DOHC V8s. Like, in the mid nineties, I don't really understand how the 4.6 was in any way an improvement on the 5.0 and I can think of LOTS of ways it was worse.

It was a lot smoother, and the bottom end was a lot more stable, and the bore sealing was a lot better, so it made a better production-car engine. Notice the pushrod engine was gone from cars before the emissions standard jump with OBD-II, and gone from trucks as soon as the Mod proved itself in cars.

None of this is related to being OHC, of course, but the new design engines were all going to be OHC so that's what we got.

BrokenYugo wrote:

codrus wrote: Also, OHC engines have an advantage in specific power (power/displacement) and in a lot of other countries cars are taxed based upon displacement, so an engine that makes the same power at 30% less displacement has to pay less tax to those governments.

Is this really relevant when you get up to V8 sized engines? When I think of displacement based car taxes I think of 660CC Kei cars.

Probably not, but it drives the adoption of OHC engines at the low end, which drives the R&D and tooling design, so it feeds into the "cheaper to make them all the same" thing.

codrus wrote:

BrokenYugo wrote:

codrus wrote: Also, OHC engines have an advantage in specific power (power/displacement) and in a lot of other countries cars are taxed based upon displacement, so an engine that makes the same power at 30% less displacement has to pay less tax to those governments.

Is this really relevant when you get up to V8 sized engines? When I think of displacement based car taxes I think of 660CC Kei cars.

Probably not, but it drives the adoption of OHC engines at the low end, which drives the R&D and tooling design, so it feeds into the "cheaper to make them all the same" thing.

exactly.. technically a V8 can be built of two I4s. In reality, it never works that way.. but if the cams, retainers, pulleys, cam bearings, valves, valve springs and retainers, and a whole slew of parts up to and including the valve covers can be shared between the I4 and the V8.. that is winning efficiently.

It may not make the most power.. but as far as building cars, the more parts you can share, the cheaper they become

bravenrace wrote: If it wasn't for the Corvette, GM might have abandoned pushrods as well. Imagine a Corvette with the hoodline required to clear a Coyote.

The trucks always drive engine choices. Not a small production car.

So thank all of the pick ups.

Really? So why doesn't Ford have pushrods engines in everything, since they are clearly superior in a truck? In fact I bought a Chevy truck for that excited reason. The fact is the Vette is GMs halo car, and they could never have fit an OHC engine in it.

In reply to bravenrace:

Considering how many more F150's sell vs GM's products, customers don't seem to care.

Still, engine plants are all driven by the large volume cars. So the plant that makes the Vette engine exists just because the truck uses the same basic engine. Which is why the mustang get's a DOHC v8, still. None the less- the fact that the truck has the same engine is probably about 90% of the reason the Vette is so reasonably priced for it's performance. It's why the Miata is still a reasonably priced car (main line car engine). It's why the S2000 died. It's why Lamborghini almost died 20 years ago, but an Audi V10 saved it's life.

If GM developed the Northstar family to THE engine for them, it would have fit in the Vette just fine- remember, at that time in it's life, it did have a DOHC V8 as an option. It would have progressed from there.

In reply to alfadriver:

I remember when the '97 F-150 came out. They started making it in January 1996, and they made the outgoing model until, IIRC, 12/96. A LOT of people refused to buy the new F-150s because the engines felt like they were struggling, and bought the outgoing model while they still could, even though it was a thorough POS to drive relative to the new one, even when new. Truck buyers are afraid of engine speed.

Chevy vs. Ford isn't a pushrod vs. OHC thing, it's an engine displacement thing. Ford had/has the 4.2, 4.6 and 5.4 (which replaced the 4.9, 5.0, and 5.8) Chevy has the 4.8, 5.3, and 6.0 (which replaced the 5.0 and 5.7, and did they continue making the 4.3 V6 models? I haven't ever seen one post-1997) So in a way, Chevy went BIGGER while Ford downsized.

Ford also had the 6.8l V10, but then Chevy had the 8.1.

edit - And you mention the Audi V10, which, relevant to other commentary upthread, nearly shares a cylinder head with the Rabbit 2.5l engine. Same valvetrain and head geometry. The belt-drive Audi V8s DID share a cylinder head with the 16/20v four cylinder engine. I don't think they were side-to-side swappable the way the V6 heads are, so the left bank has a "unique" casting, but people have put right side V8 heads on the fours and turbocharged the V8s with a pair of turbo 16v manifolds.

alfadriver wrote: Considering how many more F150's sell vs GM's products...

2015 F-Series sales: 780,354

2015 Silverado/Sierra combined sales: 824,683

Driven5 wrote:

alfadriver wrote: Considering how many more F150's sell vs GM's products, customers don't seem to care.

2015 F-150 sales: 780,354 2015 Silverado/Sierra combined sales: 824,683

If I read it correctly, you're comparing the 1/2 ton Ford against all versions of the Sierra/Silverado. What are the numbers if you factor in the F0250s and F-350s?

In reply to Knurled:

GM did keep building/offering the old SBC based 4.3, until 2014 when it was finally replaced by a new gen V derived 4.3 with DI, AFM, VVT, and all that fun stuff.

In reply to Kreb:

Sorry, for the confusion. The drop down selected says "F-150", but the page actually reports "F-Series". It's an equal basis comparison.

In reply to Driven5:

Ok. But there are still almost 800,000 buyers who don't seem to mind the tech. Of those, about a 1/3 get the twin turbo V6.

Doesn't really say one engine is better than another.

alfadriver wrote:

bravenrace wrote: If it wasn't for the Corvette, GM might have abandoned pushrods as well. Imagine a Corvette with the hoodline required to clear a Coyote.

The trucks always drive engine choices. Not a small production car. So thank all of the pick ups.

This is interesting. I'd think that if any class of vehicle could deal with an externally huge engine it'd be a fullsize truck.

Is it just the fact that gm wanted a cheaper engine design or more room for crumple zones?

Engine bay choice has nothing to do with it. Unlike Ford, GM uses the same firewall-forward section on the half ton trucks as on the larger ones. If they're fitting a huge turbodiesel and attendant plumbing/coolers in the engine bay, an OHC engine won't matter. It's FORD who you would think would make engine choice based on engine bay size, because the F-150 and F250/350 are different, and the F-150 is cramped. You can remove an engine through the top but barely.

Possibly apocryphal: When Chevy was doing drivetrain testing for the C5, the engineers built various mules. The pushrod engined cars felt more Corvette-y. And when the pushrod engine line engineers said, hey, we can make as much power as the LT5 (the DOHC engine from the ZR1), they were just asked, well why aren't you? (Loose paraprhasing) And soon came to pass the LS6 engine, which made LT5 levels of power and much lower cost.

It's not really that complicated - Ford went to OHC because that is what direction they wanted to go, Chevy stayed with pushrod because that is what direction THEY wanted to go(asterisk), Dodge went OHC with the 4.7 then went pushrod with the 5.7 because they have no direction as a company.

Asterisk: Chevy just wanted to see if they could improve on the Ford Cleveland engine Seriously, the GenIII engines look way more like Ford engines than anything Chevy ever designed. Ford heads will even bolt on to the Chevy blocks.

In reply to Knurled:

That's what I'm saying. If a truck will swallow your quad cam 135 degree v12 no problem, why did GM go to all that trouble making the LS package well?

Money.

It's 70% money, 30% politics. It's cheaper to have one set of stampings for all the trucks you make. In theory, at least. At the volumes that GM and Ford makes trucks, I think they are well beyond that point where it actually matters that much.

But money driven politics.

DaewooOfDeath wrote: In reply to Knurled: That's what I'm saying. If a truck will swallow your quad cam 135 degree v12 no problem, why did GM go to all that trouble making the LS package well?

The LS engine was also transverse under midsized sedan hoods, and the C5 Corvette had a super low hood. There are other good reasons that a small footprint = less dollars.

For trucks and muscle cars, it certainly seems pretty much even today. When the mod motor was young it was a lot more lopsided.

It doesn't matter, both will be out of the job in 25 years when everything is electric!