There are more moving parts in a pushrod engine, but if those extra moving parts aren't under a lot of stress then they aren't going to wear out. I have never heard of a 5.0/5.8/etc. breaking down because the push rod wore out or because the rocker arm had excessive wear. I have 220k miles on my 5.0 and if I pulled it apart today the push rods would be in just as good shape as the day they were made.

That's like me saying my 5.4 is more durable than your v10 because it has less moving parts. Or that my 2.3 four cylinders are more durable than my 5.4 and your v10 because it has less moving parts. Having less moving parts will make it more efficient and get better mpg's, but the durability is based on the quality of parts and the quality of the build. I have four 2.3's with less than 125k miles sitting in my garage right now waiting for a rebuild and those are OHC engines with half as many moving parts as my 5.0 with twice the miles.

 

And that was exactly what I was trying to illustrate with my example.

Maybe you can answer. Why SOHC or DOHC?

 

Depends on the design criteria. Space for the engine, power output per liter, bore, stroke, etc, etc, etc.....it's all about the necessary airflow for a desired HP output, and the packaging necessary to achieve that.
JL

 

Don't quote me on it, but I believe for the DOHC ISX, one cam shaft actuates the valves normally, while the other is dedicated for the jake brake. In which case having the cams up top could be an advantage for simpler packaging of the engine brake.

 

If you are talking to me, go back and read my posts. I never said OHC engines were only good for high revving and didn't make low end torque. I said OHC engines were much more stable at high rpms and able to withstand rpms that a push rod engine can't. I even made a point of pointing out that the mod motors make good low end torque and high rpm hp, but that it is because of the long stroke and high flow heads, not because of the OHC. What I did say is that for normal street driving, none of us will ever reach an rpm where a push rod engine is unstable, so an OHC is not necessary or beneficial from a durability standpoint.

 

Like I said earlier, OHC engines have an advantage in that they are more efficient and get better mpg's than a pushrod engine. From a durability standpoint, there is absolutely no benefit to it though. Valvetrain problems associated with a push rod engine don't become an issue until you start talking about 9-10k rpm's. Then there are simple mods that can be done to hold up to 12k. Once you start getting above that, an OHC is the only way to go. I'll hold a push rod 5.0 at 5-6k rpm all day long just as quickly as I would hold an OHC 5.4 or 6.8 there and won't worry about either one of them having issues.

 

Now that's just strange! I went and did some digging, and you're close. This is from the Cummins website:

In this case with an MEUI injection system it makes lots of sense.

I see what you're saying Josh, but is increased efficiency a product of overhead cams or just more advanced engine design? I'm really trying to grasp the advantages here!

 

I would say it's a little of both. There are plenty of advantages to an OHC engine, but none that make it necessary on a street car. People just want things on their car/truck that make them believe that is better than the competition. Like the Kenworth daylight door on our super duties. It serves no purpose what so ever on a truck the size of ours, but people like to be able to say "Kenworth" and "my truck" in the same sentence because it makes their truck seem more big rig like than the other brands.

Or the Dodge tow mirrors that stick out 20 feet on each side. I don't even have the Ford tow mirrors and I have no problem seeing what is around me no matter what I am towing. Back in about 2002 when I was living in Boone there was a woman walking on the sidewalk and a Dodge truck went by ON THE ROAD and his mirror hit her in the back of the head and killed her. Tractor and trailer mirrors don't even stick out as far as the Dodges do, but people like to say "my mirrors are bigger than yours." Properly adjusted and positioned mirrors are much more effective than mirrors that stick out really far, but "best adjusted mirrors in its class" just doesn't have the same ring as "biggest tow mirrors in its class." It's all about ego, not function.

 

Like insisting on a diesel in your truck,eh?
JL

 

Ooooh man!! I tried to rep you for that one but was denied. Funny how all the guys I see locally are looking down their nose at my gasser, yet seldom (if ever) tow anything more than a small quad trailer or 6x6 utility trailer.

 

It's not the V10 they're looking down at, it's your 4R100!

 

man, ain't that the truth!!! i HATE the 4R100 in my 99.5, and would give ANYTHING if it were a 6 speed (short of swapping one in, or trading the truck), but i didn't realize how bad i'd hate it until after i bought it. the E4ODs in our half-tons over the years didn't feel anything like this POS, but are supposed to be an older version of the same trans... i drive a 5R110 Torq-Shift in an 8+ ton '07 F-550 at work, and LOVE it. that thing truly is the answer to every problem (i personally have) with the 4R100. oh well... i'll be gettin' an '07 auto when the ol' 7.3's body rots out from under it and i swap it's heart into a bronco

 

Maybe it's not the truck at all, it's probably me!!!

 

For some people that is exactly right. No one NEEDS a diesel in their truck when all they haul is a bass boat or groceries. I know plenty of people that have diesels that have never even had a trailer hooked to them. For those of us that do tow and do the majority of our towing in steep areas, the diesel is not just for ego. Less downshifting, better mpg's, easier towing, etc. Your 3v v10 may have more hp than my 7.3 and beat me in any kind of shootout you want to run, but I promise you I will do less downshifting under normal driving from point A to point B and I promise I will get better mpg's too. That is function, not ego.

 

if they got 2 more cylinders then we got they better have more power then, otherwise it's just the 5.4, 4.6 motor