[Muck]

I dont know that much about V8s, as we just dont get too many of them in Europe, Rover/Buick V8 aside, but for a 4-pot Id go for (D)OHC every time. I think the fact that manufactuers like Volvo, who moved from OHV to OHC on thier B23/B230 engines, is a good indication. Six of one, half a dozen of the other I guess.

[Notorious B.i.G.]

I guess Volvo saw that amazing billboard too!
God knows there wouldn't be anyother reason.

[Thunderhawk]

^^ - Volvo is owned by Ford, and Ford is trying to save money around the world by having more common parts through out their brands.


(on a side note, Volvo had joint GDI/DI research with Mitsubishi a while back, leading to some common engines)

[Muck]

Volvo is owned by Ford, and Ford is trying to save money around the world by having more common parts through out their brands.

It was pre-Ford that they changed. My point is that many manufacturers appear to have moved away from OHV for smaller engines.

[hannu]

My point is that many manufacturers appear to have moved away from OHV for smaller engines.

Where do they stick the valves now then?

I used to ride a Panther. That didn't have any valves on it's head.

[Muck]

Where do they stick the valves now then?

Eh? Under the cam?!

I used to ride a Panther. That didn't have any valves on it's head.

Did it look like this,



or this?

[hannu]

My point is that many manufacturers appear to have moved away from OHV for smaller engines.

OHV = OverHead Valve

SV = Side valve

http://en.wikipedia.org/wiki/Flathead_engine

Side valve engines tend to give a lot of torque at low revs & were nicknamed 'Sloggers'. BSA M20 was a side valve I think?

The Panther I used to ride was a motorcycle made in Cleckheaton.

http://www.pantherownersclub.com/PantherPage/

[Muck]

That bike is the dogs. I know next to nowt about bikes, and haven't even heard of Panther bikes, but loved the Enfields I saw in India, which look like they are from a similar mould, and a lot more charismatic than the FS1Es my friends had when I was younger, who all ride plastic bullet clones now, while I get laughed at because I cant tell them apart.

Anyway the side valve thing! I think most cars gave up with them many years ago, although I'm all for being corrected if wrong. To be honest I'm not even sure how relevant my views are on this thread, as it appears to be about V engines, but the European straight engine manufacturers, like Vauxhall, Ford and Volvo off the top of my head, all went to OHC many years ago, which I'm sure you'd know. The in-line ricers are predominately OHC as well I believe. I know its not a definitive argument, but I found it interesting that people are still debating OHC vs. OHV on the Vs, while the straight engine debate appears to have died long ago. I'd have expected one or the other to be 'victorious' by now. Horses for courses I guess. Man, I'm full of cliches today.

[hanno]

Pushrods, accept no substitutes. Much is made of fuel economy with OHC, to my mind the units don't check out - parasitic losses to widen the power band, sounds like licking up the cost-of-poor-quality to me - I mean, even in a 4-cyl, if it has to be rough-mannered so what, only way I like my cheap cars is cheap.

This new Camaro is supposed to get 26 highway-mpg with a 300HP DOHC V6 - ludicrous, 300 is a lot and the EPA keeps reshuffling the deck on their end, but I don't know how they can make a back-wheel-drive car burn that much gas if the driver don't want it to. I mean, give me a 350 and it'll idle 75 mph in a car - as much is made of small engines for fuel economy, if you're going to use the horsepower as opposed to just tell people about it, displacement is a more efficient way to get it. And the scary part is, after having 30-mpg Camaros for a decade they're calling it 'the fuel sipping Camaro' and such - reminds me of how Hitler said something like 'if you repeat a lie long enough people will believe it'. I mean, piss up my back and tell me I'm sweating.

It's alright - tonight we pray to the gods of chaos - I'm hoping ethanol will rattle them up a bit - give them a goal other than 'sell more parts per car'.

[Dr House]

Pushrod valvetrains are outdated. Aside from fuel efficiency conserns (which are meaningless considering the kind of cars I like), they don't allow for very high revving engines, because of valve float. Pushrod engines tend to be powerful due to sheer size alone, but all else equal, an OHC engine would pack more punch than a pushrod engine.

[hanno]

Forgive me, but are you sure you’re following the right script? I mean, looking at your stats, a secular humanist I know spent four figures on a bassoon – there’s this idea of doing one’s thing, self actualization and all that – but being a puritan-flavored atheist, my question is without some concrete functionality, if not to tie it into other goals at least to provide a basis for critical evaluation, how do you know it’s your thing and not something else? Like this boy-racer culture or harley-davidsons – they try to make the vehicle something that makes them what they want to be, which tends to be quite amusing - put them in an Amish family and they’d get excited about draught horses.

By displacement OHC does better, but the curb weight comes out closer and then I’m thinking what’s this metal going to do for me now that I paid extra and assume liability to have it piled on top instead of in the block itself – if I’m half of who I think I am a wide power band is a crutch. What’s it going to do for GM though – smaller castings, design for manufacturability, crawl up the EPA’s corn chute, put consumer expectations where they keep an eye on 'em, brochure lust – there’s always free cheese in a mousetrap.

[Leo2]

There are several reasons why twin overhead camshafts per cylinder bank has been the choice of the manufacturers of high performance engines for the best part of a century.

Overhead camshafts allow the following of the camshaft profiles more accurately, particularly in engines with non-hydraulic cam-followers - such as Ferrari, BMW, Lamborghini, etc.

There are fewer parts and no pushrods to bend, break, or wear.

The configuration of twin overhead camshafts allow hemispherical combustion chambers with inlet and outlet valves on opposing sides (or variations thereof) thus promoting maximum airflow, and avoiding 'hotspots'.

Contrary to opinions expressed here, overhead camshaft engines are not appreciably heavier than pushrod engines with hydraulic tappets.

BHP, torque characteristics, and fuel efficiency are related to a myriad factors not directly related to the location of the camshafts, so are not a direct indicator of the superiority of one type over another.

But as a generalisation, Australian and US pushrod V8 engines do not have as high specific outputs as European and Japanese DOHC engines. They are designed for 'lazy' torque characteristics, and are usually to be found in large and quite comparatively thirsty vehicles.

Example: A 3.8 litre 6-cylinder Holden Commodore Calais produces 171 Kw (235bhp), and returns 13.5 litres/100km (21 mpg) in mixed city/highway running. By way of comparison a 3 litre BMW 5301 produces 200 Kw (280 bhp), and returns 9.5 litres/100km (29 mpg) in mixed city/highway running. The Holden boasts a specific output of 61.8 bhp/litre, while the BMW produces 93.3 bhp/litre - a considerable difference.

The proof of the pudding tends to be in the eating.

[hanno]

Broken example - those engines barely even have the same number of cylinders.

[Leo2]

Broken example - those engines barely even have the same number of cylinders.

If you are referring to the comparison between the Calais and the BMW 530i; the one has a V6 and the other an in-line six. I am no maths genius but that would appear, at first glance, to be the same number of cylinders.

[hanno]

Right you are, but beyond the reality of which you speak, that of cylinder-count, there is a second which to my mind causes the first to act in the manner of an illusion. Were you to extract the metaphorical DNA of a 3.8 Liter, place it in an egg-gamete, fertilize it with the metaphorical seminal fluid of the 3.8 (radiator gunk perhaps) and cram it in some sort of in-season female jungle-cat, the resulting offspring would be a small V8.

The 3.8’s six-cylinder-ness is phenotypical you see, to save working capitol they’re built much in the manner of a V8; at 90-degrees and with uneven firing order. The 4.3L in fact is 75% of a 350. I don’t view this as a fault, in it’s time and place it worked nicely and of all the ways to cut costs it's just slightly less stompy than where they put the gas tanks in Pintos. There are of course suboptimalities to doing it that way, whereas the straight-6 like BMW makes is an entirely elegant, deliberate configuration. Too bad they’ve taken a shine to aluminium sleeves reminiscent to my beady little mind of the Chevy Vega, which they know can’t take a turbo-chargin’, and of course DOHC which I see as worse than usual in that case as it adds to the great disadvantage of straight/vertical engines – height.