Unicorn: a 4 Valve Head Pushrod Engine

[nicholastanguma]

As Ford and GM were moving away from their older v8 engine designs and consolidating engine families they chose 2 very different paths. It seems to me like Ford has gone through a bit more experimentation and growing pains with their modular design than has GM with their LS. It is interesting that when Ford decided on a clean sheet truck engine not to be shared with their car line that they decided on 2 valve pushrod rather than OHC. I believe that the engineers in those 2 companies know far more about engine design than any of us do.

The new corvette would be a perfect showcase for a 4 valve pushrod engine if Chevy wants to push the envelope and finds enough of a performance advantage in the design.

Back when GM was releasing the LS crate engine lineup one of the program's engineers recounted how the team had experimented with OHC configurations in the R and D phase, but found that they could build an engine about 400.00 USD cheaper by sticking with pushrods instead. I think they found a way to make the LS 2 valve magic happen because of nothing more than necessary bean counting, not because "4 valves really isn't better."

 

[nicholastanguma]

Packaging had a lot to do with it imo. A OHC 7.3 would be massive.

Yes. For example, a GM 7 liter LS V8 is much much physically smaller than a Ford 5 liter Coyote V8.

 

[85_Ranger4x4]

Not really untimely, have you ever driven a triton personally, V10 or V8? They have to be revved to the hilt to get power out of them and the changes in CAFE and CARB regs made them obsolete, can't meet those requirements at the rpm triton series need to make power, that's why ford went ecoboost and godzilla.

I have daily driven the one in my sig since 2005.

I like Fords route for the future better than the problematic one GM took for the half tons.

 

[javajoe79]

A 4 valve will out breathe a 2 valve but with variable cam and ignition timing it mitigates some of that ultimate advantage. 4 valves shine more and more as rpm's increase. Overhead cams shine more as the rpm increases. If this was a sports car or drag racing forum I would think the discussion would have a lot more merit than it does in a forum where people are mostly interested in smooth low end power and torque. OP what advantage do you think you are going to see in an overlanding rig with a 4 valve pushrod head? How is it going to make your rig better?

The out breathing part and better with more RPMs isn't even much if any advantage when a 2V pushrod engine does just fine in both departments when properly equipped. I'm not the OP but I don't see any advantage for our use.

 

[javajoe79]

Back when GM was releasing the LS crate engine lineup one of the program's engineers recounted how the team had experimented with OHC configurations in the R and D phase, but found that they could build an engine about 400.00 USD cheaper by sticking with pushrods instead. I think they found a way to make the LS 2 valve magic happen because of nothing more than necessary bean counting, not because "4 valves really isn't better."

Yes but the LS wins at everything it does so why does it need to be more complex and expensive to build if it already dominates in every sector?

I also think packaging and center of gravity are often overlooked. You can't package on OHC engine as well or achieve as low of a center of gravity as an OHV engine.

 

[85_Ranger4x4]

Yes but the LS wins at everything it does so why does it need to be more complex and expensive to build if it already dominates in every sector?

I also think packaging and center of gravity are often overlooked. You can't package on OHC engine as well or achieve as low of a center of gravity as an OHV engine.

Emissions/economy, it takes a bigger LS to compare to a OHC engine. Mustang/Camaro trade blows for hp and they are always pretty close. One has a DOHC 5.0 and one has a pushrod 6.2. Nobody is sure if the Challenger RT with a pushrod 5.7 is really even trying, for the heavier car they also lag behind on hp. And of those three only one does not have variable engine displacement... the Coyote.

 

[javajoe79]

Emissions/economy, it takes a bigger LS to compare to a OHC engine. Mustang/Camaro trade blows for hp and they are always pretty close. One has a DOHC 5.0 and one has a pushrod 6.2. Nobody is sure if the Challenger RT with a pushrod 5.7 is really even trying, for the heavier car they also lag behind on hp. And of those three only one does not have variable engine displacement... the Coyote.

Not to knock the Coyote, I have 2 Coyote projects in my shop right now, but it's huge, expensive and complicated. LS engines get great economy when needed. They are also very dialed back in stock form. A 5 liter variant could easily match the HP of a coyote. It's all about state of tune and what you want from it. Just because one version of an LS has more displacement than a Coyote doesn't mean anything really. I helped build my friend's land speed truck that we ran at Bonneville. It was a 358ci LS, that revved to 10k and made 675hp at the wheels. It would also idle all day long on twin dominators and drive around town with no fuss. Compression was only 12 to 1. To accomplish the same thing with a Coyote would have probably cost him double the money also. People will always have their preferences that override other benefits but especially in the overland community it should be all about simplicity, ease of maintenance and lower cost IMO

 

[85_Ranger4x4]

People will always have their preferences that override other benefits but especially in the overland community it should be all about simplicity, ease of maintenance and lower cost IMO

Who started this rumor? LOL

 

[Buliwyf]

Overhead cams vs pushrod, has no effect on torque at all, by itself.

Overhead cams generally have bigger better valves, or more of them. So they can breath better at higher rpms, so might be combined with an oversquare revvy bore and stroke ratio. That combo, all together, makes a difference.

Everyone wanted torque in trucks. So Ford made some modular engines with good torque. They were dogs, or at least nearly everyone hated them. That's what happens when you listen to customers too much. So newer engines are more square strokes. Cutting away some torque for a better balance of horsepower. The 6.2 plain wastes every modular I ever drove. Real deal 400hp/400tq does that. I expect even more from the 7.3l. Make no mistake, even though the 7.3 makes good torque, they axed a huge chunk of it off during design, for better power. And the 7.3 is quite small, like any other pushrod engine.

 

[85_Ranger4x4]

I don't race mine, I tow with it. It is really rather enjoyable to tow with really.

There is a noticeable hump around 2k rpm, it is like the engine pulls down into that (OD off it runs around 2500rpm at 60mph) and it is like it draws a line in the sand... we pull down no more (to a point obviously) I can break any speed limit I see loaded with ease so to me I have "enough". It would probably struggle to haul my tractor over the rockies but I have yet to have the urge to try it anyway.

Our F-250 service truck at work with the 2v 5.4 is a dog, the thing is like a rolling dyno. But if you throw something in or on the back and it just takes it in stride. It is the same dog loaded or empty.

From what I gather talking to farmers the 6.2 is kinda boss of the mods... except for the 3V V10. And I think the 7.3 is coming to fill the hole the V10 left when it was dropped from the lighter Super Duty trucks.

 

[b dkw1]

Yes. For example, a GM 7 liter LS V8 is much much physically smaller than a Ford 5 liter Coyote V8.

That's Coyote VS 302 Ford. LS is a little taller deck but still not as wide as the Coyote.

 

[billiebob]

The joys of a 2 valve pushrod head are simplicity, low cost and compact design. Yes 4 valve dual overhead cams can provide better power and torque and likely be more fuel efficient but they will be bulkier, more complex and more expensive. If you can get all the power you need from a 2 valve pushrod engine why bother with the additional complexity and expense.

But if you are going for a 4 valve head, why bother with pushrods.

 

[nicholastanguma]

Yes but the LS wins at everything it does so why does it need to be more complex and expensive to build if it already dominates in every sector?

No, certainly the LS doesn't need 4 valve heads, as you're quite right in saying that it already dominates. But since it's just physics that 4 valves breathe better at all rpm than 2 valves, this simply means that a 4 valve head LS would be even better than a 2 valve LS.

In the long game there's no such thing as a static condition, so really evolution of a species is key to continued survival and not just dominance.

A 2 valve head pushrod can be a terrific engine; a 4 valve head pushrod can be a mo betta terrific engine.

 

[nicholastanguma]

That's Coyote VS 302 Ford. LS is a little taller deck but still not as wide as the Coyote.

Thanks for the correction.

 

[javajoe79]

The thing is, if it was worth doing, the aftermarket would have provided.