What Are The Advantages of Pushrod Engines Over OHC?

[tt 383]

See it gets thrown around they respond to boost better but nobody can give an actual fair assessment, or any technical reason why. How does a 4v mod motor do better than an ls when the you go from 1 - 2 - 3 - 4 bar? Why don't the 2v mods respond equally?

[turbo2256b]

4 valves for one have the best combustion chamber shape and more air flow than a 2 valves. Why do the current mod motors with cam advance and retard do so much better. remove either or both and hp drops big time.

[Truckedup]

The world's fastest piston engine wheel driven car is powered by........A turbo supercharged two valve SBC.....

[tt 383]

4 valves for one have the best combustion chamber shape and more air flow than a 2 valves. Why do the current mod motors with cam advance and retard do so much better. remove either or both and hp drops big time.

That's what let's smaller displacement be equal to the larger, doesn't explain how it supposedly boost better.... 5.0 Coyote vs 6.2 ls3 not too dissimilar hp ratings, at 2 or 3 bar what happens respectively assuming they are not having catastrophic failures?

I also wonder in 1/8 or 1/4 mile racing how much the dohc phasing actually is used or helps a high hp engine say in the 800-1200 hp range. Seems like it's more for driveability and economy than anything... If anyone would like to share data log info to give some insight I would appreciate it.
For a better chamber the fuel mileage isn't there either with less displacement...

[tt 383]

The world's fastest piston engine wheel driven car is powered by........A turbo supercharged two valve SBC.....

What style head wedge or hemi?

[ptuomov]

The world's fastest piston engine wheel driven car is powered by........A turbo supercharged two valve SBC.....

In the 1980s and 1990s, a well-known advertising and marketing firm built both normally aspirated and turbocharged engines for their cars. For a long time, the turbocharged version continued to use a 2-valve head while the normally aspirated version had already been moved to a 4-valve head.

[Ron E]

Like already mentioned. There are 2 advantages to pushrod engines. Neither are about performance. If its a V 6 or V8 the packaging is a huge advantage.
Add to that a no maintenance cam drive.
The push rod motor is cheaper to build. If you're talking about performance, it depends on what you're after. I'm still amazed that a LS3 isn't even close in width as the DOHC V6 in my car. Plus its lighter. More power, easy serviceability, simpler. No, it's not going to be a Indy 500 contender heads up. However, I don't drive a Indy car during the week. Even a wide headed 6.4 hemi with it's 485 HP isn't as wide as my V6.
So, it depends on hat you're going to do with it. I'd rather drive a torquey bigger engine on the street. But, that's a personal thing. To each his own. But, there's plenty of room for push rod engines. If you think they're beneath you go ride in SRT8. At 4400 lbs. they still have entertainment value. If you're hard to impress try a boosted version. Same with the LS engines. Different strokes.

[turbo2256b]

4 valves for one have the best combustion chamber shape and more air flow than a 2 valves. Why do the current mod motors with cam advance and retard do so much better. remove either or both and hp drops big time.

That's what let's smaller displacement be equal to the larger, doesn't explain how it supposedly boost better.... 5.0 Coyote vs 6.2 ls3 not too dissimilar hp ratings, at 2 or 3 bar what happens respectively assuming they are not having catastrophic failures?

I also wonder in 1/8 or 1/4 mile racing how much the dohc phasing actually is used or helps a high hp engine say in the 800-1200 hp range. Seems like it's more for driveability and economy than anything... If anyone would like to share data log info to give some insight I would appreciate it.
For a better chamber the fuel mileage isn't there either with less displacement...

Read a dyno test on the mod motor were the advance was disabled then the retard disabled then both were engine lost about 150 HP with both disabled. also test of the truck mod motors year after year won the passing tests but chevy , dodge won the off the line and top end runs.

[MadBill]

The world's fastest piston engine wheel driven car is powered by........A turbo supercharged two valve SBC.....

What style head wedge or hemi?

The pix I've seen, Speed Demon looks like it has SB2.2 canted valve heads.

[bigpoppapreston]

https://www.mechadyne-int.com/products/duocam/

The Dodge Viper uses...at least the gen 4 and 5 Mechadyne cam technology. Which is described as a cam inside a cam. It allows VVT to improve idle quality, torque, and top end horsepower. With the Viper, it had VVT on the exhaust only but allowed the gen 4 v10 to make 600hp and the gen5 640hp both naturally aspirated and with converters and full exhaust and passed emissions. Take a Hemi pushrod engine with the Mechadyne camshaft technology and it could make a good street deal.

[Truckedup]

The world's fastest piston engine wheel driven car is powered by........A turbo supercharged two valve SBC.....

What style head wedge or hemi?

The pix I've seen, Speed Demon looks like it has SB2.2 canted valve heads.

From a website...

he engine is based on a Dart Little M block with an 8.5” deck height and splayed valve Dart Little Chief heads with an 11 degree valve angle, oval intake ports, 325cc intake ports and 50cc combustion chambers for a high compression ratio. With a 4.125” bore and 3.25” stroke, the twin turbo powered engine is designed for huge top speeds without the massive torque output you’d see in such a fearsome big block. That’s not to say that it doesn’t make plenty of torque, of course. On the dyno it puts out well over 1,200 ft./lbs. at around 8,800rpm.

HP estimates are around 2200 HP...

[peejay]

What Are The Advantages of Pushrod Engines Over OHC whether SOHC or DOHC?

There are none. Zero, Nada, Zilch. Overhead cam, with finger follower will out-perform any pushrod valvetrain.

A too-broadly posited question gets a too-general answer. If one interprets it as "max performance", then Mike, as usual, is correct. As others have mentioned, pushrod OHV engines are more compact, less expensive.

And over time, DOHC belts drives will need replacement and it's not an inexpensive job on some vehicles...Chain drive may also need replacement and this may also be a lot more expensive than a pushrod cam chain...

In my experience, chains last about as long as belts do, in some cases a lot shorter (have been replacing Honda K-series chains as low as 60k miles), but they are a lot more expensive and labor intensive to replace.

The timing belt for my '89 VW was $7 and was two hours, tops, to replace. A timing chain set for a W8 VW is over $1800, and requires splitting the drivetrain to access. Both last about 90k miles.

The good news is, VW has discontinued most W8 parts, so if you are fortunate enough to own a W8 Passat (one of the best cars of the 2000s), you won't even have the option of repairing it anymore. Suck it up and buy something new that is heavier and slower and less efficient, consumer.

[MadBill]

I understand belt replacement on some Ferrari models is $20 k+...

[CamKing]

In my experience, chains last about as long as belts do, in some cases a lot shorter (have been replacing Honda K-series chains as low as 60k miles), but they are a lot more expensive and labor intensive to replace.

You've got some krappy experience
My experience is, most chains are good for at least 150k miles

[Brian P]

Timing belt replacement on my 1996 VW Passat TDI took me about 2.5 hours in the driveway. But that engine, even though transversely installed, had somewhat traditional engine mounts on either side of the block (i.e. one towards the front of the car and one towards the back).

The newer ones (I had a 2006 Jetta TDI next) use a different engine mount arrangement (common to most newer cars) in which the engine mount is on the front end of the engine and passes through the path of the timing belt, which means you have to support the engine and take that engine mount off to do the timing belt. I didn't do it myself any more, I paid a local VW specialist shop to do it.

Timing belt in my current car is not due for replacement until 240,000 km, at which time I'm expecting to be finished with it anyhow.