Pushrods vs DOHC

[FreddyG]

That is correct. But one more important thing is the ratio of bore/stroke.
An engine with a long stroke should have more torque than an engine with equal displacement but shorter stroke (and wider bore) because of the longer distance of the crankpin to the crankshaft centerline (leverage effect).
This is one reason why diesel engines usually have relatively high torque compared to gasoline engines. (Diesel engines are usually designed with a rel. long stroke.)

Good points...and to add to this, a short stroke motor will rev higher because of the lack of leverage of the arm (crank throw that the rod bolts onto). As far as diesels, turbos don't hurt for torque either (not too mention their high compression ratios too).

Here is a neat picture showing these high displacement ohv engine are actually small compared to a dohc

Here's another one with a 4.6 next to a Small block Ford (which is similar in size to an LSx motor and the 4.6 is supposedly smaller than a Coyote motor (don't know this for a fact, since Fords are new to me, but I'm sure there is someone smarter than me that can set the record straight):

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[thePill]

Pushrods are ok...

But investing $820,000,000 in that type of architecture in 2013 was a dumb idea.

 

[Erik427]

F1 regs don't favor the use of pushrods. That's why they're not used. The FIA says 1.6L displacement and 15000 rpm. Valvetrain stability goes wonky on pushrods far before that, even w/ pneumatic springs.

Sorry pro-pushrod guys, but the same goes for Top Fuel...only reason they use pushrods is due to rules that simply don't allow ohc. Although I'm not sure about tear down times on one between rounds, anyway...yikes.

Pushrods were banned because they cannot hit the rpm and do not breath nearly as well. 4 valves vs two valve. The pushrod motors when they were allowed to run, always needed a rule concession on cid in order to compete. 4 valve dohc motors have a huge advantage over two valve pushrod motors. FIA banned the pushrod design because nobody would run them. It cost money and other resources to research and develop rule packages that would make them competitive.

 

[Strokerswild]

Pushrods are ok...

But investing $820,000,000 in that type of architecture in 2013 was a dumb idea.

This.

And back to the 427 SOHC, that engine was very successful in Top Fuel during the '60s and into the early '70s after getting banned from NASCAR. The cylinder block was only good for 750-800 HP though, and was the limiting factor running supercharged with nitro (well, that and keeping the cams phased with a 6' timing chain). The guys that figured out the quirks loved them and preferred them to the Hemis.

FYI, Hot Rod did a great article on them a month or so ago. I used to have a pair of Cammer valve covers hanging on my shop wall.

Ever looked at a 4.6 SOHC and the old 427 SOHC side by side? Lots of similarities.....

 

[Norm Peterson]

FIA banned the pushrod design because nobody would run them.

If that's true, such a rule wasn't inserted for technical reasons.

The only reason I can think of for actually banning a configuration that isn't inherently competitive at equal displacement is to reduce administrative workload by eliminating entirely having to deal with requests for displacement or other concessions.


Norm

 

[Shawnski]

The one and so far only year that 4 valve heads were allowed in the highly respected Engine Masters competition; the top 3 finishers were DOHC 5.4 based motors.

http://forums.hotrod.com/car-craft/70/9574728/car-engine/dohc-dominates-2013-amsoil-engine-masters/

http://www.hotrod.com/events/coverage/1309-2013-amsoil-engine-masters-challenge-friday-coverage/

The formula for this competition is not peak power (although there is a trophy for this usually a 500+ cube BB), its about the power band, a combo of usable torque and HP.

The past 10 years of winners have all been right around 400 cubes. The top three 5.4 based winners were in that sweet spot, something that "conventional wisdom" said was not possbile with the mod motors small bore and long stroke.

All three used factory blocks and heads. Big 3 + AMC including LS engines always run aftermarket heads and many cases blocks. The most exotic part on the DOHC motors was the intake manifold from the rare 2001 Cobra R.

The winner Jon Kaase noted that it was remarkably easy engine to build (using factory valvetrain). So easy that he took the time to make a custom set of headers that splits the exhaust port in 2. Tuning is very flexible since you can degree the intake cam and exhaust cam.

Well that sweep prompted a change to outlaw 4v heads and this past year a new gen Hemi won it. An LSx motor has never won this competition.

Most people assume that its so expensive to build a DOHC engine, actually the beauty is that you can use factory heads, block, crank and valvetrain for 1000= hp motors. The other thing that most people don't realize is the strength of the block is inherent to not having holes down the center for a cam. I know that the first place you break an OEM SBF block is in the valley where the lifters reside.

"but its so big" - well if size is such a big factor we should all still be running flat head ford V8s!

 

[Herr_Poopschitz]

The one and so far only year that 4 valve heads were allowed in the highly respected Engine Masters competition; the top 3 finishers were DOHC 5.4 based motors.

http://forums.hotrod.com/car-craft/70/9574728/car-engine/dohc-dominates-2013-amsoil-engine-masters/

http://www.hotrod.com/events/coverage/1309-2013-amsoil-engine-masters-challenge-friday-coverage/

The formula for this competition is not peak power (although there is a trophy for this usually a 500+ cube BB), its about the power band, a combo of usable torque and HP.

The past 10 years of winners have all been right around 400 cubes. The top three 5.4 based winners were in that sweet spot, something that "conventional wisdom" said was not possbile with the mod motors small bore and long stroke.

All three used factory blocks and heads. Big 3 + AMC including LS engines always run aftermarket heads and many cases blocks. The most exotic part on the DOHC motors was the intake manifold from the rare 2001 Cobra R.

You musta missed post 88, where I addressed this issue already.
"That's a political...as in sales...maneuver. Nothing else.

I responded to this in a previous thread about it. Kaase comes in w/ exotic parts...worked over Cobra R intake ($$$), worked over Ford GT heads that had already been prepped by Yates for a Daytona prototype ($$$), and the most unique headers that would never fit any car ever ($$$) and as you say, mops the floor.

How does the average guy building an engine in his garage relate to a build like that? If they have too many builds featured like that, people would lose interest and no longer buy the magazine. Be glad there are sponsors willing to fork over money and time for something like EMC...if it went to all 4V, all the funding would go away. No one makes aftermarket stuff for 4Vs...there's no real money in it compared to everything else. Maybe if 4V swaps were even remotely as popular as LS swaps you'd see them included. Facts don't lie...they just aren't. Hell, seems the most popular combo right now for cheap thrills is an LS powered Fox...best chassis for the $, meet best engine for the $...

Also, how many guys really do internal mods to their 4Vs? Not many are taking them apart...most are bolt on and/or blown and that's it."

The winner Jon Kaase noted that it was remarkably easy engine to build (using factory valvetrain). So easy that he took the time to make a custom set of headers that splits the exhaust port in 2. Tuning is very flexible since you can degree the intake cam and exhaust cam.

'Easy'. Sure. BS on factory valvetrain. If it were so easy, why aren't there tons of similar garage builds happening...let's be realistic.

Most people assume that its so expensive to build a DOHC engine, actually the beauty is that you can use factory heads, block, crank and valvetrain for 1000= hp motors.

No. You can use these items, but be prepared to spend big $ on machining. Not sure about 1000 hp NA engines...even more realistic 600ish hp builds will require expensive valve jobs and porting...since there are twice the ports/details and valves...the valves 'might' be able to be reused, but not wise...replace twice the valves....replace twice the valve springs....hell, just upgraded tensioners, guides and chains add up...

"but its so big" - well if size is such a big factor we should all still be running flat head ford V8s!

Size is a factor. Small cars are typically faster...a lot of times you can't fit engines w/ large external dimensions in them.

 

[Shawnski]

I think the bottom line is; would the S550 Mustang be better served with a pushrod engine? I think the 2.3, 3.7, and 5.0 DOHC motors aquits themselves well, and can be modified for more. No going back.

 

[Herr_Poopschitz]

I think the bottom line is; would the S550 Mustang be better served with a pushrod engine? I think the 2.3, 3.7, and 5.0 DOHC motors aquits themselves well, and can be modified for more. No going back.

Been tempted to pick up a wrecked V6 and do an LS3 6 speed swap...

 

[pietran30]

I think the bottom line is; would the S550 Mustang be better served with a pushrod engine? I think the 2.3, 3.7, and 5.0 DOHC motors aquits themselves well, and can be modified for more. No going back.

Of course ford isn't going back. Stick a 430lb pushrod in a mustang and I'd be hard pressed to believe it wouldn't be slightly faster.

That said, there really isn't a reason for Ford to change. The Coyote makes good power, and has good fuel economy. No sense spending a ton of money to basically have the same performance. Same with GM or Dodge.


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[Catfish]

Been tempted to pick up a wrecked V6 and do an LS3 6 speed swap...

How original.....

 

[Herr_Poopschitz]

How original.....

Interesting, I have yet to have seen this done...

Please share any info you have on it since your sarcasm implies it's really common...

 

[Grimace427]

Interesting, I have yet to have seen this done...

Please share any info you have on it since your sarcasm implies it's really common...

He used a SBF, not an LS3, but still a sweet as hell conversion.

http://paddedwall.org/2012mustang/Default.aspx
http://www.fastfordmuscle.com/index.php/topic/3193-ahhhh-that-glorious-noise/

 

[B-52 Jetman]

He used a SBF, not an LS3, but still a sweet as hell conversion.

http://paddedwall.org/2012mustang/Default.aspx
http://www.fastfordmuscle.com/index.php/topic/3193-ahhhh-that-glorious-noise/

Daaaaamn...love that big cam sound! Especially when the camera goes around to back of the car....

 

[Herr_Poopschitz]

He used a SBF, not an LS3, but still a sweet as hell conversion.

http://paddedwall.org/2012mustang/Default.aspx
http://www.fastfordmuscle.com/index.php/topic/3193-ahhhh-that-glorious-noise/

Well, that's also a '12...not a '15....

That is a nice car, and sounds great.

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