May C&D
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From: Phoenix
It's not a totally in-depth article, more an editorial on his opinion of OHC vs. OHV. He comments on how the Hemi is a new pushrod design that goes counter to what most manufacturers are doing now, which is moving toward SOHC AND DOHC setups on their engines. He also comments on GM's decision to stay with pushrod designs, and throws in a couple quotes from one of GM's people about why pushrod is king there.
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From: Foster City, CA
Originally posted by Slamnasty
I read this article, and Webster makes a decent, if not bulletproof, point. OHV engines are much simpler and save on materials and cost for sure (although GM's car prices hint otherwise).
I've noticed that OHV engines don't sound as "elegant" when idling...OHV engines sound much less refined and sophisticated. Anyone who's ever listened to the GM 3.4 run probably knows what I'm talking about.
I wonder what ever happened to Chevy's idea to put variable valve timing on the pushrod the LS2...
I read this article, and Webster makes a decent, if not bulletproof, point. OHV engines are much simpler and save on materials and cost for sure (although GM's car prices hint otherwise).
I've noticed that OHV engines don't sound as "elegant" when idling...OHV engines sound much less refined and sophisticated. Anyone who's ever listened to the GM 3.4 run probably knows what I'm talking about.
I wonder what ever happened to Chevy's idea to put variable valve timing on the pushrod the LS2...
http://corvettemechanic.com/board/index.ph...t=ST&f=23&t=843
You will have to make an account. I can't paste the article here...sorry.
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From: mount airy
Originally posted by Slamnasty
It's not a totally in-depth article, more an editorial on his opinion of OHC vs. OHV. He comments on how the Hemi is a new pushrod design that goes counter to what most manufacturers are doing now, which is moving toward SOHC AND DOHC setups on their engines. He also comments on GM's decision to stay with pushrod designs, and throws in a couple quotes from one of GM's people about why pushrod is king there.
It's not a totally in-depth article, more an editorial on his opinion of OHC vs. OHV. He comments on how the Hemi is a new pushrod design that goes counter to what most manufacturers are doing now, which is moving toward SOHC AND DOHC setups on their engines. He also comments on GM's decision to stay with pushrod designs, and throws in a couple quotes from one of GM's people about why pushrod is king there.
Why does GM make "northstar" OHC? They were a little coy on that. The GM folks said customers want refinement etc..
I'm a little fuzzy about this. If I was buying a XLR I'd rather have 400/400 than whatever the quad cam northstar is putting out.
My question is, what would happen if they made the northstar 6.0L? It would be stronger than the OHV engine.
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From: Phoenix
The Northstar is a bit of a different animal. It dates back to the very early 80s, and it pioneered a lot of things other companies are using now (like the cylinder shut-off technology D-C is using now on the Hemi 300C, and the 100,000 mile tune-up cycle).
I think the Northstar was an experiment in bringing GM into the 20th century after the ugly 70s, and the experiment happened to work out remarkably well. The Northstar is a great example of what GM can do when it doesn't hinder itself.
I agree with GM's quote that luxury buyers want "high-feature" engines. Notice GM is using the same buzzword in harping its new 3.6 (Northstar-based) V6. I don't know that I'd personally buy a non-OHC-engined car if money was no object. It's the sense that something more is there that goes a long way in selling an $80k car. Just me maybe, but...
I wouldn't mind 400/400 either, but then again if I am looking for a car with that kind of power, I'm likely not in the market for an XLR anyways.
I think the Northstar was an experiment in bringing GM into the 20th century after the ugly 70s, and the experiment happened to work out remarkably well. The Northstar is a great example of what GM can do when it doesn't hinder itself.
I agree with GM's quote that luxury buyers want "high-feature" engines. Notice GM is using the same buzzword in harping its new 3.6 (Northstar-based) V6. I don't know that I'd personally buy a non-OHC-engined car if money was no object. It's the sense that something more is there that goes a long way in selling an $80k car. Just me maybe, but...
I wouldn't mind 400/400 either, but then again if I am looking for a car with that kind of power, I'm likely not in the market for an XLR anyways.
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From: Palo Alto
Slamnasty
I thought the new 3.6L was a ground up new engine. I know they made a 90 degree V6 "Shortstar" that was used by Olds but I was under the impression the new engine was a 60 degree unit.
I thought the new 3.6L was a ground up new engine. I know they made a 90 degree V6 "Shortstar" that was used by Olds but I was under the impression the new engine was a 60 degree unit.
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From: Phoenix
Actually you're right Rockville. I didn't pay attention when I read C&D. C&D says that this 3600 V6, debuted in experimental form in the Buick Velite show car with twin turbos, will be OHC with VVT when it hits the streets.
GM has a lot of new engines lately. The new OHV 3500 in the new Malibu is basically a bigger 3400 (which is also still around even though they need to retire it). They should've used the Shortstar IMHO. I hear their truck-based straight range of engines, the 4, 5 and 6 cylinder versions, are all really good. They should dump the 4300 in the base Chevy 1500 for the straight-6 IMHO. They should do a lot of thing IMO I gsuppose...
GM has a lot of new engines lately. The new OHV 3500 in the new Malibu is basically a bigger 3400 (which is also still around even though they need to retire it). They should've used the Shortstar IMHO. I hear their truck-based straight range of engines, the 4, 5 and 6 cylinder versions, are all really good. They should dump the 4300 in the base Chevy 1500 for the straight-6 IMHO. They should do a lot of thing IMO I gsuppose...
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From: Rochester
I've been waiting for some discussion of this here. It looks like GM is taking this on the road as I've seen similar articles in a couple of other places. I think the points are accurate:
1) Pushrod gives lower hp/displacement, but...
2) It is cheaper
3) It can be physically smaller. See: Mustang 4.6L DOHC v 5.0 OHV
4) It can be lighter
5) It is simpler, which may imply durable
6) It has less friction which may lead to better mpg
Conversely:
7) It is considered "low tech" and marketting matters. Which may in part explain why GM also makes OHC engines.
8) For same hp, requires more liters which usually means more pumping loss in normal driving, thus lower mpg (counters #6 above).
9) They do seem to be less refined. I love the mechanical sound of high reving DOHC engines such as in Hondas and BMW's.
I used to be a DOHC snob, but lately I've come to accept that pushrod engines do have many benefits. The Corvette is a solid existence proof. So, I did appreciate Webster's column
1) Pushrod gives lower hp/displacement, but...
2) It is cheaper
3) It can be physically smaller. See: Mustang 4.6L DOHC v 5.0 OHV
4) It can be lighter
5) It is simpler, which may imply durable
6) It has less friction which may lead to better mpg
Conversely:
7) It is considered "low tech" and marketting matters. Which may in part explain why GM also makes OHC engines.
8) For same hp, requires more liters which usually means more pumping loss in normal driving, thus lower mpg (counters #6 above).
9) They do seem to be less refined. I love the mechanical sound of high reving DOHC engines such as in Hondas and BMW's.
I used to be a DOHC snob, but lately I've come to accept that pushrod engines do have many benefits. The Corvette is a solid existence proof. So, I did appreciate Webster's column
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From: Foster City, CA
The push-rod design is a great design for a engine. It is true that they will not rev as high as DOHC or even a SOHC engine because of the fact the pushrods will always be longer then their corresponding parts on an over-head cam engine.
The new CTS-V race car is using a variant of the LS7 and is running a redline of right around 8000. They have just hit them with restrictions to lower that, but at 8000 is had been deemed very reliable by GM engineers. I think 8k at anywhere from 5.7 to 7liters is more then enough for any street cars. You will be hard pressend to find too many DOHC engines with 6-7 liters running up to 8k. There is a lot of new info coming out about the LS2 and LS7 engines. The only thing "un-high tech" about them is maybe the fact they use push rods, but even that is a stretch. The rest of the engine is as high tech as it gets. The computer system in the new C6 is amazing. It has something like ~23 computers or some crap in it.
edit: The CTS-v which is running a 5.7 liter version of the LS7 was turning over at greater then 8k, but scca put restrictors on them to 7900 and I think they have lowered it even more now because it kicked so much @ss in it's first race.
The new CTS-V race car is using a variant of the LS7 and is running a redline of right around 8000. They have just hit them with restrictions to lower that, but at 8000 is had been deemed very reliable by GM engineers. I think 8k at anywhere from 5.7 to 7liters is more then enough for any street cars. You will be hard pressend to find too many DOHC engines with 6-7 liters running up to 8k. There is a lot of new info coming out about the LS2 and LS7 engines. The only thing "un-high tech" about them is maybe the fact they use push rods, but even that is a stretch. The rest of the engine is as high tech as it gets. The computer system in the new C6 is amazing. It has something like ~23 computers or some crap in it.
edit: The CTS-v which is running a 5.7 liter version of the LS7 was turning over at greater then 8k, but scca put restrictors on them to 7900 and I think they have lowered it even more now because it kicked so much @ss in it's first race.