Defending the Pushrod

[funny]

Wednesday, June 08, 2005
The Redemption of the Pushrod? Various pundits occasionally slap GM for selling pushrod engines. I have even been known to do it myself. But I have come to understand and respect GM's use of OHV designs, and the critics should stop and think about it for a few minutes.

Staying with OHVs makes good business sense for GM because the designs and tooling are mature. The enthusiast community, and the automotive press both tend to be hard on the low-end pushrod engines, describing them as "buzzy" and "low tech". However, does the average consumer care? Does your father-in-law the pediatrician know if he has an OHV or DOHC engine in his car? Does your mother-in-law know? If someone is buying a car as an appliance, they may not even care if they are buying an I4 or a V6 (see: Toyota Camry). Many people just want a reliable car at a good price, and won't care about a pushrod design. Some of them might even enjoy the throaty roar.

GM's pushrods are not all primitive, and are getting more advanced, picking up many of the high-tech features. Cylinder de-activation is relatively simple and cheap with the OHV architecture--bleed oil pressure from valve lifters using a solenoid valve. Cylinder deactivation on a OHC design requires some complicated mechanics and electronics, such as BMW's throttle-less Valvetronic engine. The added complexity adds cost and reduces reliability. (Anyone seen a valve de-activation system from Ford yet?)

Read the rest here:

http://theautoprophet.blogspot.com/2...f-pushrod.html

[327]

actually enthusiasts like OHV better than OHC, its only the news media that criticize them. OHV was invented after OHC

[IAMCANADIAN]

Great review, interestingly enough people say ohv is older than ohc when both actually were in cars around the same time, look at the Pontiac tempest i think with the OHC v6 in the 1960's!!! and as 327 said, ohv was invented after ohc

[01Sunfire]

Originally Posted by 327

OHV was invented after OHC

Really, I didn't know that! So the low tech was invented after the high tech?

[327]

Originally Posted by 01Sunfire

Really, I didn't know that! So the low tech was invented after the high tech?

Have some reading material, http://www.motorera.com/history/hist03.htm

[IAMCANADIAN]

Originally Posted by GMCSonoma

All comments aside, OHV's are generally cheaper to fix than OHC's. Ask any service writer or parts person, no matter the car company, they'll concur, if they are honest.

That's why I bought my Alero with the 3.4L V6, also cuz it's faster than the ECOTEC or 2.4L twin cam and the GLS has nice stuff on it like mine has sunroof, power seats, leather seats, monsoon stereo etc.

[RWD60]

a good OHV is as good or better than any DOHC... IMO it comes down to what the company can do well and cheaply. Nissan for instance makes some nice DOHC V-6's: up to 300hp and 280lb-ft from 3.5L with decent, if not great economy and awesome reliablity. GM makes amazing OHV V-8's... i need not explain those here The problem I think is GM's OHV V-6's... they never seem to be that great anymore, and always seem to lack power or economy or quietness or something. What's doubly annoying is that GM has some great DOHC V-6's... more powerful, adaptible, just as economical and way more refined... yet still makes their lackluster OHV V-6's. use what works good... Nissan/Infiniti got rave reviews on their VQ engine, now 11 of their 16 US models have it in some form... DCX's Hemi is well recieved, and spreading through their line like a benevolent plague. IMO, GM should use the Ecotec (2.0, 2.2, 2.4) HF (2.8, 3.6), Northstar (4.6 and maybe the V-12) and LS (5.3, 6.0, 7.0) lines, with some FI, ONLY... that gives them hp ranging from 140 to 500+ with almost everything in between, from engines that have been widely lauded by enthusiast, critic, and consumer alike. it'd be cheaper in the long run to use less engines, though of course there is the short term cost of retooling some plants. tuning should be based on brand... Caddy gets most hp and trq, HUMMER and GMC get lots of trq, Pontiac and Saab get plenty of hp, Buick gets quiet tuning with good power, and Chevy and Saturn get fuel economy. Gm will have at least 7 different six cylinder engines on the market in 2006... based on at least 4 engine styles. pick one type, and make it the best engine around, period.

[W.A.F.U.]

Originally Posted by GMCSonoma

All comments aside, OHV's are generally cheaper to fix than OHC's. Ask any service writer or parts person, no matter the car company, they'll concur, if they are honest.

Just as an example, a 2.2 ohv Cavalier would take about 4-5 hours to do a head gasket. A 2.4 dohc Cavalier Z24 would be in the 10 hour range. Keep in mind those are labor guide times not how long it would actually take a knowledgable tech.

Another benefit of ohv is that the valves and pistons don't usually occupy the same space. So, if your timing chain breaks, you aren't replacing the heads and pistons as well.

[IAMCANADIAN]

If you look at the 60 Degree V6's from GM, the 3.5 and 3.9L V6's are the best, they have horsepower ratings that don't seem as embarassing as the 3.4L, 2.8L and 3.1L seemed logical but the 3.4L could've gotten 190 HP, where my alero has 170, but i'm not complaining about power since it has a great 0-60 time of 7.8 Seconds and the 2.8L in the 89 Grand Prix I drove (see my review) had plenty of power. Also the fact that the 3.5 and 3.9 have newer technology which helps. 211 HP (MC and Impala) out of a 3.5L OHV V6 is quite good and competes well enough with the competition

[AdmiralViscen]

Originally Posted by IAMCANADIAN

If you look at the 60 Degree V6's from GM, the 3.5 and 3.9L V6's are the best, they have horsepower ratings that don't seem as embarassing as the 3.4L, 2.8L and 3.1L seemed logical but the 3.4L could've gotten 190 HP, where my alero has 170, but i'm not complaining about power since it has a great 0-60 time of 7.8 Seconds and the 2.8L in the 89 Grand Prix I drove (see my review) had plenty of power. Also the fact that the 3.5 and 3.9 have newer technology which helps. 211 HP (MC and Impala) out of a 3.5L OHV V6 is quite good and competes well enough with the competition

Too bad the 3.9's mileage is absolutely pathetic.

[cooguyfish]

I don't have anything against pushrods, but so far with the limited engine's I've driven, I much prefer the powerband of a DOHC, and I am an enthsuiast. That's just my preference though, and I think that OHV's definately have their place in the automotive world too.

[Globalist]

To be fair, let's compare two engines with same displacement, one is ohv (2v/cyl) and the other is dohc (4v/cyl).

Pontiac G6 GT: V6, ohv, 2v/cyl, 3498 cc, 200 hp, 220 lb-ft, 4A, 0-60 mph in 7.9 sec
Nissan 350Z :V6, dohc, 4v/cyl, 3498 cc, 300 hp, 260 lb-ft, 6M, 0-60 mph in 5.6 sec

Even the G6 GTP with a bigger engine (3900 cc, V6, ohv, 2v/cyl, VVT, var intake, 6M) gives only 240 hp and 245 lb-ft.

Why?

[nailhead425]

Originally Posted by Globalist

To be fair, let's compare two engines with same displacement, one is ohv (2v/cyl) and the other is dohc (4v/cyl).

Pontiac G6 GT: V6, ohv, 2v/cyl, 3498 cc, 200 hp, 220 lb-ft, 4A, 0-60 mph in 7.9 sec
Nissan 350Z :V6, dohc, 4v/cyl, 3498 cc, 300 hp, 260 lb-ft, 6M, 0-60 mph in 5.6 sec

You can't compare two different models with different weights, transmission ratios, and final drive reductions (gearing) based solely on the engines. To really compare these engines, you need to look at the total torque (not horsepower) under the curve.

[Globalist]

Originally Posted by nailhead425

You can't compare two different models with different weights, transmission ratios, and final drive reductions (gearing) based solely on the engines. To really compare these engines, you need to look at the total torque (not horsepower) under the curve.

I understand the integration part. And, I am not comparing Laurel and Hardy here
These two cars have almost the same weight (few lbs difference). The other differences are engineering choices. And please don't tell me that people buying cars do a torque curve integration before their purchase.

We can't integrate visually any curve. So, what most people retain is:
max Hp
max torque
0-60 mph
mpg

[RWD60]

Originally Posted by nailhead425

You can't compare two different models with different weights, transmission ratios, and final drive reductions (gearing) based solely on the engines. To really compare these engines, you need to look at the total torque (not horsepower) under the curve.

from everything i've seen, the Nissan VQ has a pretty flat torque curve (especially for a DOHC engine) and therefore would win a integrated test too because it peaks higher and is flat... but Globalist is right, no normal consumer, or even a mild enthusiasts, even looks at a dyno reading, much less finds the total area under either curve. i personally object to that comparo cause one is a flagship sports car and one is a mainstream sedan... at very least compare the G6 motor to the altima version of the nissan motor (the G6 still come out behind, but not as bad, Altima SE has 245hp and 250 lb-ft or there abouts). most important of all is end result... who's faster and/or more effecient... from what i've seen, the altima will win that test, if only by a second 0-60 and a MPG.