Why still pushrods??
Thread Starter
Instructor
Joined: May 2005
Posts: 241
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From: Los Angeles CA
Why still pushrods??
Just wandering why you guys think chevy hasnt put an overhead cam in the vette by now?? I would have thought they would have to bring the vette into the next generation of sports cars
Le Mans Master
Joined: Jan 2005
Posts: 5,611
Likes: 5
From: Thousand Oaks California
The product team wants the Corvette to have a low cowl and engine compartment side rails. The cam in block/push rod engine design provides for a lower engine height which allows for a lower hood, cowl and side rails. The Corvette's cousin, the XLR, with the twin dual OHC design (Northstar), has a little higher cowl. Besides, the push rod LS7 is SAE rated at 505 hp, not too bad!
Safety Car
Joined: May 2005
Posts: 3,990
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From: Corpus Christi Texas
Originally Posted by zaccotner
Just wandering why you guys think chevy hasnt put an overhead cam in the vette by now?? I would have thought they would have to bring the vette into the next generation of sports cars
Safety Car
Joined: Sep 2000
Posts: 3,572
Likes: 420
From: Taildragers rule! USA1
Originally Posted by zaccotner
Just wandering why you guys think chevy hasnt put an overhead cam in the vette by now?? I would have thought they would have to bring the vette into the next generation of sports cars
The new LS series of engines is far more sophisticated than the LT5 engine in the ZR1. More power, less volume, lighter, better fuel consumption, and a wider smoother power band.
Just because it's "European" doesn't make it better!
Le Mans Master
Joined: Dec 2002
Posts: 7,588
Likes: 6
From: Montreal Qc
Originally Posted by ztheusa
There is nothing "next generation" about an overhead cam. Duesenburg had them in 1929.
The new LS series of engines is far more sophisticated than the LT5 engine in the ZR1. More power, less volume, lighter, better fuel consumption, and a wider smoother power band.
Just because it's "European" doesn't make it better!
The new LS series of engines is far more sophisticated than the LT5 engine in the ZR1. More power, less volume, lighter, better fuel consumption, and a wider smoother power band.
Just because it's "European" doesn't make it better!
sometimes the "kiss" system works best!
Race Director
Joined: Oct 2004
Posts: 10,089
Likes: 14
Originally Posted by zaccotner
Just wandering why you guys think chevy hasnt put an overhead cam in the vette by now?? I would have thought they would have to bring the vette into the next generation of sports cars
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Pro
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The Redemption of the Pushrod?
Burning Brakes
Joined: Nov 2004
Posts: 1,031
Likes: 4
From: Crete IL
People have been brainwashed into thinking the size of the engine is only related to the displacement. OHV allows GM to get more displacement out of a given overall physical size, which offsets the gains in HP you get with a OHC 4 valves/cylinder engine. The 5.7L LS1 OHV engine has higher displacement and is smaller and lighter than both Ford and Cadillacs 4.6L DOHC V8s. Granted I will admit, all else being equal, the OHC design is prone to being a little smoother.
I read an article where the author claimed(and had pictures showing) that the Ford 5.0 pushrod engine was hardly any bigger in overall size than the Ford 2.5L duratec DOHC V6. At an auto show I saw a 5.7 L LS1 pushrod engine on display in the Chevy section and I saw a Nissan 3.5L OHC V6 engine on display in the Nissan section. I was shocked that they looked similar in overall size. On another forum there was a heated pusrod vs OHC debate that came down to a few people providing data showing the 3.5 L Nissan and 5.7L Chevy engine not being that far apart in size and weight.
To sum it up I think GM is just as clever as everyone else in engine design.
I read an article where the author claimed(and had pictures showing) that the Ford 5.0 pushrod engine was hardly any bigger in overall size than the Ford 2.5L duratec DOHC V6. At an auto show I saw a 5.7 L LS1 pushrod engine on display in the Chevy section and I saw a Nissan 3.5L OHC V6 engine on display in the Nissan section. I was shocked that they looked similar in overall size. On another forum there was a heated pusrod vs OHC debate that came down to a few people providing data showing the 3.5 L Nissan and 5.7L Chevy engine not being that far apart in size and weight.
To sum it up I think GM is just as clever as everyone else in engine design.
Melting Slicks
Joined: Jul 2001
Posts: 3,284
Likes: 3
From: Southwest Florida
Originally Posted by AU N EGL
Correct.
as far as push rods, well It works very well, why change it?
as far as push rods, well It works very well, why change it?
tooPlease keep it the way it is. I'm quite happy that I don't have to do silly things like adjust valve timing on an OHC. Pushrod is better in many ways. It even offers some protection against overrevving (the valves will just float above a certain point). Not that it is much of an issue with a rev limiter, but more protection is better than less.
Mike
Melting Slicks
Joined: Jan 2004
Posts: 2,158
Likes: 4
From: Henderson Nevada
Originally Posted by rfopt
Granted I will admit, all else being equal, the OHC design is prone to being a little smoother.
In addition, the shorter timing chain of a pushrod design eliminates one potential source of vibration (although companies like Toyota take a lot of care in this area).
Melting Slicks
Joined: May 2005
Posts: 2,143
Likes: 0
From: San Diego California
Originally Posted by ztheusa
There is nothing "next generation" about an overhead cam. Duesenburg had them in 1929.
The new LS series of engines is far more sophisticated than the LT5 engine in the ZR1. More power, less volume, lighter, better fuel consumption, and a wider smoother power band.
Just because it's "European" doesn't make it better!
The new LS series of engines is far more sophisticated than the LT5 engine in the ZR1. More power, less volume, lighter, better fuel consumption, and a wider smoother power band.
Just because it's "European" doesn't make it better!
Racer
Joined: May 2005
Posts: 257
Likes: 0
1. If you're curious what an DOHC multi valve engine feels like, test drive a Carrera 997. You'll find you need great handfuls of revs before it starts to pull. There is no down low grunt.
2. Torque is what really makes a car move, and the OHV engine gives you lots of torque both low down and all through the rev range. After you get out of the 997, test drive a C6 Z51 MN6. Just put your foot down and hang on to your hat. And you'd better have it pointed pretty much in a straight line before you light it off. I'll take an OHV mill with 400 ft lbs and 400 bhp anytime over a smaller, peaky DOHC design. Remember, Ford clobbered Ferrari in the mid 60's in a similar OHV/DOHC duel. And the OHV C6R Corvettes did the same thing to all the DOHC GT contenders at this year's LeMans 24.
2. Torque is what really makes a car move, and the OHV engine gives you lots of torque both low down and all through the rev range. After you get out of the 997, test drive a C6 Z51 MN6. Just put your foot down and hang on to your hat. And you'd better have it pointed pretty much in a straight line before you light it off. I'll take an OHV mill with 400 ft lbs and 400 bhp anytime over a smaller, peaky DOHC design. Remember, Ford clobbered Ferrari in the mid 60's in a similar OHV/DOHC duel. And the OHV C6R Corvettes did the same thing to all the DOHC GT contenders at this year's LeMans 24.
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Originally Posted by AraiGP4
1. If you're curious what an DOHC multi valve engine feels like, test drive a Carrera 997. You'll find you need great handfuls of revs before it starts to pull. There is no down low grunt.
2. Torque is what really makes a car move, and the OHV engine gives you lots of torque both low down and all through the rev range. After you get out of the 997, test drive a C6 Z51 MN6. Just put your foot down and hang on to your hat. And you'd better have it pointed pretty much in a straight line before you light it off. I'll take an OHV mill with 400 ft lbs and 400 bhp anytime over a smaller, peaky DOHC design. Remember, Ford clobbered Ferrari in the mid 60's in a similar OHV/DOHC duel. And the OHV C6R Corvettes did the same thing to all the DOHC GT contenders at this year's LeMans 24.
2. Torque is what really makes a car move, and the OHV engine gives you lots of torque both low down and all through the rev range. After you get out of the 997, test drive a C6 Z51 MN6. Just put your foot down and hang on to your hat. And you'd better have it pointed pretty much in a straight line before you light it off. I'll take an OHV mill with 400 ft lbs and 400 bhp anytime over a smaller, peaky DOHC design. Remember, Ford clobbered Ferrari in the mid 60's in a similar OHV/DOHC duel. And the OHV C6R Corvettes did the same thing to all the DOHC GT contenders at this year's LeMans 24.
There is nothing like the torque monster that is called a small block chevy.
: 
I have given several 996 and other p-car drivers rides in my car on the track. C5 with 400 rwhp and 405 rwtq. There is nothing like shifting from 2nd to 3rd at 120 mph and having that p-driver passanger lunge forward in the seat( when I shift out of 2nd) only to be pushed deep into the passanger seat when 3rd gear and all that torque takes over.
and the comments are," No wonder I cant catch you when shift to 3rd."
Last edited by AU N EGL; Jul 5, 2005 at 03:08 PM.
Instructor
Joined: Jan 2005
Posts: 171
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OHC vs Pushods
Hard to argue with the results Chevy has acheived with the LS2, 6500 PRM R/L, and LS7, 7000 RPM R/L; net HP output of well over 1HP / CID; smooth power delivery and broad torque band; outstanding fuel economy; compact, simple and lightweight and relatively inexpensive. Chevy has pretty much perfected its small block V-8. If it an't broke don't fix it!
