Well, I don't know either. All I know is, when I owned my '99 OHV 4.0, I test drove a SOHC 4.0L '01 model with the manual tranny and was not impressed at all. Later I test drove an '02 4.0 with the automatic and it was also a disappointment. So I bought a brand new one (see sig.) and it's really not much better. I wish I could take my '99 and line it up with this SOHC just to see for sure. But from the seat of the pants feel, my "old" 4.0 would whip these new ones.

And you know, if you really think about it there isn't a power advantage even in the numbers. The SOHC only makes 10 lb./ft. of torque more, and needs more RPM to do it. And you don't get the 207 HP until it's redlined. At "normal" driving RPM, the SOHC is only making 160 or so HP as well. If you drive a healthy OHV 4.0 and then drive a OHC 4.0 it's real noticeable how much more torquey the "old" one is.

If the OHC was so great, Ford wouldn't have kept using the OHV as long as they did in the pickup application. Anyway, what difference does it make now? We don't have a choice anymore.

 

WxBoy, I agree. The current OHC engines by most of the automakers have to turn in excess of 4500-5000RPM in order to make their peak output. IMO, these engines do not belong in trucks and SUV's. In the Mustang, etc...,they're probably better than the old 5.0 and other engines as racing requires the engine to make maximum power at the highest RPM. But in towing or in heavier vehicles, the OHC is going to maintain higher RPM's at times, thus putting more stress on the engine. OHV engines won't have to work as hard to do the same task and they'll maintain lower RPM's while achieving the same speed when towing something. As for durability, I can't really name a common problem in the history of OHV engines (roughly 40 years). Yet, in modern times, OHC engines that are fairly new and supposed to have the latest design technology are left burning oil at less than 150K (some of the Towncar's, etc..), blowing spark plugs out of the head, and having head gaskets replaced. Clearly, all of these can't be the owner's fault in every case. I wouldn't be surprised to see if there have been more problems with the modular engines in 10-15 years than in the entire lifespan of OHV engines. There really isn't much to do, complaining won't help, as the HEMI and GM 5.7 and maybe one or two other engines are the only pushrod engines left. Just my $0.02.

 

I own a modular, and it si decent, but really is no better than the other competitors. Currently, the competitors make mor HP and More torque, while meetng the same emission standards. The GM engines make more hp, their pushrod. The hemi makes more HP, it's pushrod. They all meet the same emission standards. They all get similar fuel economy ratings, what is the rael advantage? The GM motors are still much easier and cheaper to repair. I see no real real world advantage witth the modular OHC engines, they are more expensive, make similar or less power, get the same fuel milage, are no more relyable and are more complex.

 

But what motors are you comparing? I'm not talking about OHC vs pushrods, this is about motor size. What size motors are you comparing?

Looking around, I found these numbers, I think they say it all for the competitors HP figures at such high RPM and peak torque says a lot about how high reving these motors are, to get these numbers. These numbers are straight from Chevy and Dodge's 2004 web sites, the Ford #'s have been around a few years.

Chevy 4800V8 285@5200 295ft/lbs@4000
Chevy 5300V8 285@5200 325ft/lbs@4000
Chevy 6000V8 300@4400 360ft/lbs@4000 (2500/3500 HD series)
Chevy 8100V8 330@4200 450ft/lbs@3200
Dodge 5.7V8 Hemi 345@5400 375ft/lbs@4200
Ford 2V 5.4L 260@4500 350ft/lbs@2500
Ford V10 6.8L 310@4250 425ft/lbs@3250

Compare Ford's 2-valve (and the 3-valve is coming) 5.4L to the Chevy 5300V8. On the Chevy peak HP is 700RPM higher, peak torque is 1400RPM higher! Chevy HP is 25 more than the Ford, but for torque Ford beats Chevy by 25ft/lbs, and does it 1400RPM lower. 5.3L vs. 5.4L, near enough. Their 6.0L V8 comes in with only 10ft/lbs more torque than a 5.4L - that's 600cc's difference! Guess where the extra low-end torque comes from? OHC? Hmm... that "reciprocating mass" theory starts to rear it's ugly head again...

Compare the Dodge Hemi 5.7L to the Ford 5.4L - Hemi makes 345HP vs Ford's 260, but at 5400RPM vs 4500. The hemi puts out only 25ft/lbs more torque, but at a whopping 4200RPM vs. the Ford at 2500RPM, 1700RPM higher! Which makes a better truck motor?

Using the formula HP=Torque*RPM/5252, I figure that the hemi is making 335.54ft/lbs at 5400, and the 5.4L is making 303.45ft/lbs at 4500, at their max HP. There's only a 32ft/lbs difference, and that should be easy, revving at 900RPMs higher and having 300cc's extra displacement.

Do the same thing with the HP formula above for the Chevy 5300, and you have at peak HP, 287.85ft/lbs of torque, while the 5.4L Ford has 303.45ft/lbs, but at 700RPM lower. Chevy 6000 is 285 peak HP at only 4400RPM, giving 358ft/lbs at 4400RPM, while Ford's 5.4L is only 303.54ft/lbs at 4400RPM. 600cc's difference will do that, but it seems here, Chevy is pulling more than the difference in cubes would indicate.

I'm not even going to try to compare the V10 to anything in the above list except maybe the 8.1L Chevy, but the displacement difference far outweighs the V10 anyway.

Looking at the above numbers, the Ford OHC modular motors do NOT rev high at all... they are real grunty powerplants, just like you want in a truck (or a streetable car for that matter).

Again, I'm going to ask this question - why do you think modulars are more complex than any Chevy or Dodge pushrod motor these days? What? Two cams? More timing chain details? Please be specific... take a look at a Hemi ... two rocker shafts per head? Two spark plugs per head? This makes the modular MORE complex?

 

How can you say the overhead camers have to rev. If you want to compare pushrod 4.0 to OHC 4.0, the OHC gets it's torque peak at 3000 RPM compared to the pushrods 2750, a 250 RPM difference, and it holds it very well through the rest of the powerband whereas the pushrod seems to reun out of breath. And especially in comparison to the competion the Ford OHC's don't rev near as much. Also look at torque/liter, that tells you how well an engie is designed, the only one better than the ford 5.4 is the DOHC 5.6 that the Titan has. The pushrod hemi makes its power by revving, not the OHC Tritan.

 

This horse is about dead.

 

Amen! Some good points have been made though. This thread actually seemed to stay very technical up to this point also which I sure appreciate.

 

The only true advantage of a pushrod motor is simplicity. Also there is some truth to better low end torque with a push rod motor. With hydraulic lifters at low RPM the valve lift and duration are shorter, increasing velocity. Also less valve overlap at low rpm.

 

Overlap duration and lift are just as easily controlled in a OHC engine. They have the ability to run the same profiles with less spring pressures. The modular engines are limited to around a .530 lift with the stock valve guides at this time but that can also be changed. OHC engines use a hydraulic mechanism also just like a lifter. It takes up the slack the same way.

Solid lifter engines on the other hand can make more torque across the whole band but aren't preferred for daily driving by most consumers as they require periodic adjustments. This is where hydraulic rollers come in to play. They offer an even greater ability to use a more agressive lobe profile. Roller setups are also used in some OHC apps. The rocker arm (follower) has a roller that rides the cam instead of bare metal.

 

I vote for pushrods

 

Same here

 

More compact. More cubic inches. I'll stick to the pushrod design. Whatever works for you.

 

More compact? Are you running out of space under your hood? Are you stuff thsi V8 into a Yugo?

More cubic inches? An OHC engine can be designed to be as big as you need it. There is no limit to the size that an OHC engine can be.

 

I've seen a lot of arguements but not many facts...

http://www.machined.net/Articles/2003/09/EngineDebate/
http://www.datsuns.com/Tech/ohv_vs_ohc.htm

Good information...

 

I single handedly covered most of the facts covered in these two articles... others here either preceded or overlapped my information. The long-stroke vs. short-stroke is something not really covered in this thread. Thankfully, Ford decided on a long-stroke motor for their trucks and cars...

It's been so long, was this a Ford modular vs. pushrods, or the entire OHC design vs pushrods?

Again, I'd like to know. WHAT is so simple about a pushrod design when compared to the Ford OHC modulars? Piece for piece, the valve train is SIMPLER, two cams, one roller-tip follower per valve, and a hydraulic valve-lash adjuster. With pushrods, add a pushrod for each valve to the formula, but drop only ONE cam. That's LESS parts for the OHC than the pushrod motor.

Add in the extra timing chain tensioners, and you about break even.

WHAT IS SO COMPLEX ABOUT AN OHC? Someone please answer this simple question. PLEASE!