Pushrod or Overhead Cam?

[Predator86]

Now of course all the f-body drivers here have pushrod V8s but im wondering what most people think is better and would prefer given the choice.

I myself prefer the traditional pushrod setup but there are lot of people who say they are outdated and that SOHC and DOHC engines are way better.(even thought i notice the opposite in performance wise)

Any opinions?

[69BirdX]

LS1 one proves them OHC engines wrong................for performance OHV all the way. i would be really upset if GM changed over to OHC design. Now automakers are talking about getting rid of cams completly and have the valves electronicly controlled to open and close. Which would mean a tune could do so much more.
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[Predator86]

Oh ya ive heard of eletric valves...im not sure how i stand on that.

But ive heard from another forum that GM is considering putting two cams in the next generation of LSX engines...but here the kicker...both cams will be through the block one over the other....sick

[Noodles]

Rotary!


if you want your **** to break every 5 seconds

lol

[Mike]

Oh ya ive heard of eletric valves...im not sure how i stand on that.

But ive heard from another forum that GM is considering putting two cams in the next generation of LSX engines...but here the kicker...both cams will be through the block one over the other....sick


*the next gen of lsx is out, and its still pushrod and single cam

[Ian]

top fuel cars make 7000 horsepower with pushrods, I'd say that makes it a pretty valid performance platform ;)

[Predator86]

*the next gen of lsx is out, and its still pushrod and single cam

True but from what i heard its on the drawing board....

[johnjzjz]

top fuel cars make 7000 horsepower with push rods, I'd say that makes it a pretty valid performance platform ;)

hey formula one 1.5 L motor 22,000 RPMs 1200 HP with no adders in the fuel and is on the track all day almost all the time wide open - 4 valve 4 overhead cams the cams advance and retard 20 years ago was the norm who knows now -- jz

[Noodles]

^ i think thats rotary dude...

[69BirdX]

Rotary!


if you want your **** to break every 5 seconds

lol

ughhh roatary got to love when they blow up on the track
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[qwikz28]

IIRC pushrods were designed AFTER OHCs were.

another reason GM might stray away from OHC designs is that pushrod engines are generally smaller than OHC engines

[Predator86]

IIRC pushrods were designed AFTER OHCs were.

another reason GM might stray away from OHC designs is that pushrod engines are generally smaller than OHC engines

ya think so? Cuz i mean the mustang engine is only a 281 4.6L...and northstar engines are in the 4 liter range....meanwhile GMs got the pushrod powered 5.0,5.7,6.0,7.0 etc.

[Ian]

hey formula one 1.5 L motor 22,000 RPMs 1200 HP with no adders in the fuel and is on the track all day almost all the time wide open - 4 valve 4 overhead cams the cams advance and retard 20 years ago was the norm who knows now -- jz

true, F1 motors are insanely efficient. I think from a cost standpoint though, the pushrod motors will get the nod.

[NJSPEEDER]

it really depends on the control system. GM uses push rods in a lot of stuff because it is a more economical system for them to produce and they have such good electronics that they can meet federal and international fuel economy and polution requirements easily.
i am sure in the future there will be a move to overhead cams in more GM platforms, but i think it is a good bit of time away still.

[qwikz28]

ya think so? Cuz i mean the mustang engine is only a 281 4.6L...and northstar engines are in the 4 liter range....meanwhile GMs got the pushrod powered 5.0,5.7,6.0,7.0 etc.

size does not equal displacement

[GP99GT]

OHC would yield more efficient motors in my opinion....but it costs more to produce so its kinda meh

[Predator86]

size does not equal displacement


good point..

[BigAls87Z28]

OHC engines were designed before OHV. When Caddy launched its first OHV engine back in the early 50's, it was held as one of the most powerful and smoothest running V8's. Soon after Chevy launched the first Small Block, and the rest is history.
What made OHC engines "advanced" was the technology added to it such as Variable Valve timing where the timing of the cam or cams could be advanced as the engine climbed in rpm. GM and now the Viper have a variable valve technology on thier OHV engines.
OHC engines are also physicly larger then your average OHV engine. Displacement is just bore x stroke. The Mustang 4.6 OHC engine looks like it could hold a SBF inside it.
OHC and OHV engines have advantages and faults. OHC tends to have less noise/vibration/harshness due to less valvetrain parts. With that, its RPM band tends to be larger then an OHV. OHC also has great advantages with smaller engines, such as 4 and 6cyl. If you look at the new MB 6.2 V8, its a OHC engine that makes 505hp.
GM wont replace the Gev IV with an OHC engine any time soon, they have kept the pushrod, but remember they also have an OHC engine in the Northstar and upcoming Ultra V8 engines that will find itself in new Caddys in the next year or so.
As for a Twin-Cam OHV engine, GM already produced a concept of the engine called the XV8. Displaces 4.3 liters and was shown in the 2001 Opel Signum.
http://www.acarplace.com/brands/gm/xv8-engine.html

[firehawk1120]

who is this guy posting above me???

[Predator86]

The pushrod engines have a very limited RPM range due the extra mass of the pushrod putting stress on the valve spring. But i think theyve overcome that when I look at the corvette and GTO spoting these 6500 and up redlines.

But OHC engines have a more likely chance of snapping the timing chain and when that happenes in those engines its more violent..the pistons start striking the valves and you gotta huge mess.

[Tru2Chevy]

But OHC engines have a more likely chance of snapping the timing chain and when that happenes in those engines its more violent..the pistons start striking the valves and you gotta huge mess.

It's never good when a timing chain (or belt) gives way, but not all motors are interference motors.

- Justin

[Ian]

The pushrod engines have a very limited RPM range due the extra mass of the pushrod putting stress on the valve spring. But i think theyve overcome that when I look at the corvette and GTO spoting these 6500 and up redlines.

built right, you can spin a pushrod motor over 10K RPM's. but even then, pushrod motors will NEVER come anywhere close to F1 motors as far as RPM capabilities are concerned.

[Predator86]

It's never good when a timing chain (or belt) gives way, but not all motors are interference motors.

- Justin

my bad i forgot to specify that

[Pampered-Z]

The OHC engine have allot of advantages but more so on the smaller displacement motors as they have far less reciprocal mass and as such can be spun to higher RPMs.

Remember with a typical V8 engine you moving 50lb cranks and heavy rods and pistons compared to a 2.0 liter. Look at the monster motors they spin above 8,000 RPMs and price out those the parts they need to achive that power and RPMs compared to our little 4 bolt blocks and after market cranks! You must use parts light enough and strong enough to control that much mass. With a V8 you take advantage on the CI ability to make torque in the lower RPMs

So putting OHC on a V8 doesn’t gain you that much, if GM did build an engine like this ( LT5 ) you would pay allot more $ of little HP gains.

[Mike]

GM does build a OHC V8...its called a Northstar.
The supercharged 4.4 motor makes 470hp.

[Batman]

Pushrods in big motors, OHC in little motors. I think the OHC engines get the nod for high RPM use but pushrod engines make a better powerband. Basically for something like drag racing I think the pushrod engine has a big edge because they make so much low end power, but for some kind of all out wide open racing I think the efficiency of the OHC engines is going to take the cake.

[Pampered-Z]

GM does build a OHC V8...its called a Northstar.
The supercharged 4.4 motor makes 470hp.

Yah, but it's a half~hearted attempt. Not that it isn't a good motor, but compare that to an LS1 with the same SC and how much power would it make, or compared to something like a HP import engine or Motorcycle. 1400CCs and almost 200HP. GM didn't really take full advantage of the OHC on the Northstar.

[BigAls87Z28]

Yah, but it's a half~hearted attempt. Not that it isn't a good motor, but compare that to an LS1 with the same SC and how much power would it make, or compared to something like a HP import engine or Motorcycle. 1400CCs and almost 200HP. GM didn't really take full advantage of the OHC on the Northstar.

MB's 5.4 supercharged engine makes the same power with 1.0 more liter. Not saying it was a sad engine, its a monster, but the Northstar is somewhat still relivent considering its a 15 year old design....
The new Ultra V8 should bring the GM OHC V8's up to spec with the new BMW and MB V8's.

[Pampered-Z]

but the Northstar is somewhat still relivent considering its a 15 year old design....
The new Ultra V8 should bring the GM OHC V8's up to spec with the new BMW and MB V8's.

Point well taken, I forgot how long it's been around.

[Predator86]

An extra overhead cam definetley makes a bigger difference in those little 4 bangers than in the big V8s