It sounds the same too! (Sorry, I couldn't resist. I'm kidding you know... I used to work on a ranch where we had a 1957 Ford tractor with an aftermarket hydraulic front loader/back hoe set-up. Definitely unique sounding.)

 

Again, valvetrain doesn't define the power curve; cam timings, along with valvetrain profiles and piston design define that. So you can get an I6 with either SOHC or DOHC and design it to be a stump puller. The European diesels (ANY flavor) have IMMENSE amounts of torque coming in at or below 2000rpm, and decent higher-end power peaking around 3500-4000, and they are ALL OHC multivalve designs. So it stands to reason that a gas engine can be designed to do what you want in an OHC design.

The biggest tradeoff they have right now is trying to widen the power bands for driveability. This is why they are pushing hard to develop CVTs: you can narrow the powerband considerably, which makes the engine MUCh more efficient, with the added bonus of more power and torque available in a narrow powerband than what can be gotten over a wide powerband (think WWII v12 or radial engines: they didn't run for s**t until they hit their sweet spot, between 4500 and 6000rpm in some cases).

Now imagine some of the crusties around here screaming bloody murder if Ford develops a CVT for the superduty!!



>Good response Tex Arcana. You are right any camshaft/head
>configuration can be designed/tuned to do the same thing.
>My understanding is that the main advantage of overhead cam
>is in greater efficiency in high rpm operation since you
>don't have to run pushrods and rockers at high speed. OHC
>is not bad and Ford did it right on the new V8s with a chain
>drive. Wish they would chain drive the four bangers too.
>The old 70s Ford Courier pickup had a chain drive 4 banger
>(1800 and 2000 cc, but the 2300 was rubber band). In the
>20s there was an overhead cam automobile with a shaft drive,
>which I think would be way better than the chain. But when
>they put OHC in an engine, they tend to use its advantage
>and go to a higher rpm band as evidenced by the new Ford
>V8s. Thats why I like my 300 I6--it is sort of like a
>tractor engine.

 

Inefficiencies in transferring mechanical power to electrical and back again. That, and you need a HUGE amount of current to deliver enough power to electric motors to get a boost of acceleration, like you do when you floor it and get all that acceleration and power, like in passing. That requires a LOT of electricity storage. Locomotives aren't limited by size or weight, so can use poweer cables the size of your torso and motors the size of an Escort. Plus, they are limited to the amount of traction they have--which isn't much, steel-to-steel, so they need HUGE amounts of torque at very low rpm, and alot of current. So they can deliver that current, and not worry about efficiencies and losses.

Now, see my reply to your previous message, where I discuss why a CVT is useful, and you'll see why manufacturers are working on it. It's even useful in electric applications. Hell, take a gas turbine and gear it way down and hook up a CVT to it, and you have a VERY efficient drivetrain.


>I am trying to figure out why they would bother with a
>continuously variable transmission in the first place. Why
>not an electric transmission? Engine powers a generator.
>Wheel motors power the wheels. No gears needed, just hike
>the voltage. I think it would be very efficient--no drive
>shaft, no gears. Works in locomotives.

 

[updated:LAST EDITED ON 08-Jan-03 AT 10:05 PM (EST)]If I reiterate what was already said, please disregard or take it as a compliment.

Actually the ->"BASE"<- torque has nothing to do with valves or their timing. Torque is a factor of the length of the Conn rod and the piston height (ie stroke), and mildly due to the angle they sit in the engine (gravity). Torque is basically the force applied to cause something to turn. You apply torque to the end of a wrench (or anywhere along it's length) to get the nuts to turn. The further up the handle and the longer the wrench is, the easier it is to turn.
The length of time that a valve is open is purely in the cam shaft lobe design and the object following that lobe. In the overhead case is may be a direct drive pin or rocker. In the old pushrods it could be a hydraulic or solid lifter located under the pushrod and the rod pusheing the rocker arm. Either way it depends on that cam lobe 1st and foremost. Either engine type could have a valve open for as long as the designer willed it to, either through mechanical advantage or the height of the lobe.

Flow rate through the head will also tell the tale of an engine, but this is secondary to the stroke. That long stroke is your torque and you build upon that. You can alter the flow rate through valve size/lift and the timing/duration, this will alter things like HP and torque bands and where they are fall on the RPM scale. The OHC's do have the advantage of less moving parts in the valve train (I'm including cam to valve here), so you can't bend a rod or have a lifter stick to cause bad things to happen.

People have had the misconception about the torque of an overhead engine being always in the high end of the rpm band. This is due to the short stroke 4 bangers put in the light econo boxes, you didn't need a large amount torque to move a 2000lb car, like you need torque to move your 5000lb+ truck and it's equally large trailer. The lighter 4 cyl engines weren't designed in the way that the mod motors were. *There are those exceptions.* I think auto manufacturers stayed away from the long stroke OHC's for many reasons, I think the bigger engines weren't OHC's because of the cost of a piston going through the head (new head if not new engine, as the piston would tear everything up on it's way out). Ford did have the 427 OHC from the 60's, though, I'm not sure what its stroke was, but being a 427 it had to have been pretty long. As we don't see a lot around (I recall T-birds having them), they must not have been successful, so they didn't sell well?

It's a lot easier to work on the 300 without the computer controlled crap than my 5.4 with the OBD-II, I'll admit that I'd rather have the 300 with the same torque that the 5.4L has now... 325 lb-ft would be a real treat in that old truck, reguardless of the RPM (1800 vs. 2500).

-Kerry

 

i believe the 427 SOHC was a race only engine designed for NASCAR use. this may or may not be the version u are refering to, but it was a power house making around 625hp and near the same torque. i know they used these "cammers" as they were often called in drag racing a lot with the A/fx and B/fx (correct me if im wrong) cars. there was a 68 "cammer mustang and matching cougar i believe. god i love Mustangs and Fords mag

 

The 427SOHC, if it is was the 427 of NASCAR fame, had to have had a production run in stock form. The engine could be put into any vehicle in Ford's lineup, as long as you had a certain amount. I.E. the Boss 429 was a purpose built engine and was sold in Mustangs, but they didn't race the Boss 429 Mustang in NASCAR, as the engine went into Torinos for that.

Now that you talk about it, if you put that engine into a vehicle designed to run flat out at top speed for hours and take the punishment it did, then the 427SOHC must have been one heck of an engine.

-Kerry

 

yup ur correct about the limited production run, NASCAR found them to have to much power for oval track use. anyway u cut it, OHV, SOHC, DOHC, etc...can make power in any part of the power band, just the most OHC's are better up higher, but have a nice torque curve from pretty low on up.

 

>I heard that they were dropping the 4.6L V8 for something
>more substantial. And I also heard that the hp numbers on
>the gas engines were going to be raised quite a bit to be
>more competitive with C#$&* and D*@!&. Can anybody verify
>these rumors and if so, what is the new engine going to be?

Check out Ford's site for the 2004 F-150: the six-cylinder is out! Gone! History! The 4.6 is now standard as the BASE engine.

 

Is the 4.2 six gone out of production ?

 

if the 4.2L is gone maybe ford has something else planned...*crosses fingers* maybe its another inline 6

 

""Wrong on all counts. THe only reason the pushrods seem to produce more torque is because 1) they were an undersquare design, so they had longer strokes, which equates to more torque; 2) the pushrod setup actually makes for less overall airflow, because the time it takes for the valve to actually start opening is longer, and the same for closing, therefore not allowing as much airflow through the engine; 3) given the previous two points, more torque is created because the mixture burns more slowly, creating alot of force over a longer period of time. Hence more torque. Horsepower is sustained power over time (delivered torque over time, actually), or the ability to maintain a sustained power output, which means towing a trailer at 65 mph on a grade. Torque gives you pulling power, horsepower allows you to maintain a speed.

Now, overhead valve engines are more efficient overall because as you mention they can open the valves faster and hold them open longer. All things being equal, that equates to more airflow thru the cylinder versus the pushrod setup. And, yes, more airflow affects torque because the engine can already spin up faster becasue of the lower resistance from the intake/exhaust limitations, so it seems low end torque suffers.

Seems.

Truth is, you can tune any engine to produce power at any point on a powerband, overhead cam or overhead valve or flathead. Each has limitations, but I can bet you that I can design a OHC engine to respond exactly the same way as a dinosaur flathead. It's all in the piston design (oversquare vs. undersquare), induction design, and cam profiles and timing.

As for all of you who want the return of the I6, I agree, they're great engines for smoothness and power. However, it would still benefit from modern design, and can still put out the power and torque we all expect. The best I6 I ever owned was in my '79 Toyota Supra, 2.6L, single overhead cam, fuel-injected. This thing put out 140hp and 195 ft-lbs of torque, and would pull all day long from idle in damn near any gear. Hm, gee, OVERHEAD CAM producing lots of torque?? Not bad for #1 a ricer amd #2 a '79.


For the rest of you who want the pushrods to take over the world, I think you may be suffering from "good ol' days" syndrome, and I invite y'all to join the rest of us here in the new millenium.""

-Hey thanks for correcting me, I got the conjecture after reading an artical comparing flatheads, OHV, OHC, and DOHC. I re read it after and I realized I misinterpeted a few things.

 

>I got the conjecture after
>reading an artical comparing flatheads, OHV, OHC, and DOHC.
>I re read it after and I realized I misinterpeted a few
>things.

Sounds like an interesting article. Could you post the title and publication? Or is there a web address to access it? Thanks.

 

>That DOHC 5.4 from the Navigator would sure be a nice
>option. 300+ hp would make the trucks and expys move much
>better.

Isn't that what they are going to have while retaining a single cam set-up for simplicity? 300HP is 300HP...

 

Are you serious FordDude? I guess I'm old fashioned. It works.

 

The 4.2 isn't going anywhere, it's suspoes to be "upgraded" and avilable with the 4-speed auto, or 5-speed manual in 2005.