Just wondering which one you prefered, discuss the pros and cons of each.
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Just wondering which one you prefered, discuss the pros and cons of each.
i think the pro of pushrod is simplicity of design and it weighs less
I rather DOHC for its better breathing and ability to rev
Personally I think Push-rods sound better, but if you want something more modern and advanced, go for the DOHC.
[QUOTE=fpv_gtho]I rather DOHC for its better breathing and ability to rev[/QUOTE]
This has been a point of discussion all the time when the corvette C6 was being set off against european cars. Protagonists of the C6 invariably claim that pushrods are the best solution, only when you needed revs (and smaller engines) SOHC and DOHC would be a plausible solution. Of course in the US you don't need revs, as there is no replacement for cubic inches. European car tax systems have in some countries been based on displacement (a classic example of the consequences thereof is the existence of the Ferrari 208 turbo, which was the small displacement version of the 308 destined for the Italian market), resulting in optimising smaller sized engines.
So if you don't need revs you would go for pushrods. Fine, but there have been some developments in engine construction have largely escaped the avarage american (and australian) car nut. During the last ten years diesel engine developments have taken off like a space shuttle, and see what happens, these low revving engines (maximum 5000 but never necessary to go over 3500 or maximum 4000) are all fitted with one or two OHC's and 4 valves are now common as well. Why should that be? Is it because it always allows for a much better combustion process because you can place the valves in almost any position you wish? Coould well be, but for me it puts an end to the myth that pushrods are the way to go if you don't need revs.
Well the main thing i like about DOHC is its ability to have 4 valves rather than 2, afterall you'll cover more area with 4 valves rather than 2 so you should be able to get better breathing out of the engine from that
[QUOTE=fpv_gtho]Well the main thing i like about DOHC is its ability to have 4 valves rather than 2, afterall you'll cover more area with 4 valves rather than 2 so you should be able to get better breathing out of the engine from that[/QUOTE]
you are now not talking any more about abaility to rev?
Well....ability to rev is more of a secondary preferance to me. I dont NEED a car to do 7000-8000rpm, where DOHC would have its main advantages over OHV but i'd appreciate the extra valve area moreso. Having the DOHC there anyway makes the engine easier to extract power from by increasing the revs if the situation calls for it
OHC avoids the pushrod which can flex.
because OHC acts directly it is better suited for HIGH lift and high spring rates for valve closing and preventing spring bounce.
OHC has no friction from chanig angle as in 'rods, especially if valves are at an angle to the head.
Desmo can ONLY work with OHC thus avoiding springs issues completely.
DOHC enables variation of timing overlap on exhaust and inlet.
OHC doesn't need rockers or pushrods so can have less moving weight than pushrods ( rotating objects in engines are fine, mass going up and down are bad : ) )
Less materials technology required for high performance OHC versus pushrods
DOHC makes the head larger than a pushrod with 2 vlaves/cyl
OHC may make the head slightly larger - but not always as the valves and rockers are still there for an in-block cam. :)
Pushrod single cam is simpler to time. ( but so is single OHC :) )
depends on what i want. if i want a complicated but hi reving design, but would probably create a little more power, id take the ohc. if i wanted simplicity, lower revs, and othger things that describe pick up trucks and muscle car-type engines, id instantly take the pushrod
[QUOTE=CdocZ]depends on what i want. if i want a complicated but hi reving design, but would probably create a little more power, id take the ohc. if i wanted simplicity, lower revs, and othger things that describe pick up trucks and muscle car-type engines, id instantly take the pushrod[/QUOTE]
what you described as your second option is best fulfilled with a diesel engine and yet all modern diesel engines run one or two OHC's. Got an explantion for that?
kind of. not too good with words. ill try to rephrase
depends on what you want, hi revving hi tech engine, or low rev low tech but most likely more reliable.
See, the "complexity" one gets repeated so often adn yet isnpt true !!
The crankshaft has a gear/chain/belt drive to the camshaft in BOTH.
Each lobe on the cam drives a bucket, pushrod to rocker to valve stem.
OR each lobe on the cam drives a bucket to the valve stem.
So often folks talk about complication because there are MORE cams with DOHC.
But they're there for a reason.
THAT is a choice the engine designer makes. If he/she just wants one cam then it's dead easy - the Ford Pinto's been doing it for 20 years in competition. In SOHC , multi-valve you usually have to add rockers to prevent twist..
So IN FACT all things being equal - valves/cylinder - there are MORE parts with pushrods.
The ONE plus in a V8 configuration is the designer can get away with only one camshaft, whereas with a OHC there MUST be one per bank. However, that is counter-acted that if an 'event ' causes damage and the cam needs replaceing ( usually along with bent valves, rockers and followers ) it's a LOT easier on overhead as only one bank needs stripped.
Where does complexity come into it ?
I reckon it's because so few folks have actually STRIPPED and rebuilt and engine. So from pics OHC looks "complicated" because you can SEE most of the parts that are hidden deap in the engine with 'rods.
Maybe one of the folks who think it IS complicated coudl explain to me, please, I do need to understand because it gets used ALL the time as a drawback that isn't matched by the reality.
[QUOTE=CdocZ]kind of. not too good with words. ill try to rephrase
depends on what you want, hi revving hi tech engine, or low rev low tech but most likely more reliable.[/QUOTE]
it it not a matter of how you described things. Diesel engines provide great amounts of low end torque and will very rarely have to go over 4000 revs. In fact they show all the charactistics of a traditional "lazy" petrol engine, and yet, all modern ones are fitted with OHC's. So both modern high revving and low revving engines produced in Europe (and Japan) are fitted with OHC's. In my opinion this means that for choice options you describe OHC's provide the best option.
yeah.........i really need to do some more reading on deisel cars
You gotta like pushrod engines for their superior performance for the money. You can get a 550+ hp fordracing crate motor for well under $10,000. If you want a dohc motor with that much power your gonna have to spend a lot more. If money is no object then the dohc motor is definately the better choice.
[QUOTE=NAZCA C2]You gotta like pushrod engines for their superior performance for the money. You can get a 550+ hp fordracing crate motor for well under $10,000. If you want a dohc motor with that much power your gonna have to spend a lot more. If money is no object then the dohc motor is definately the better choice.[/QUOTE]
That is because they are based on mass produced engines, the marginal costs for tuning them are relatively low. If the Northstar was produced in similar numbers as the small block Chevy, your costs figures would more or less correspond. It has nothing to do with the having pushrods or ohc's, it is just about the numbers
i think i have made my views of pushrods clear
[QUOTE=targa]i think i have made my views of pushrods clear[/QUOTE]
but not in this thread. Enlighten us please :D
The overiding factor between the two has always been COST.
Performance wise DOHC are superior.
Over head make the heads much more expensive to manufacture.
It's what you get for your money. That's what drives car companies at the end of the day. Money.
Corvette is different when tradition has overtaken sense on all fronts.
Has to be designed and built in Detroit and has to be push rod. No exceptions made.
So they do their push rod engines with magnesium and titanium bits everywhere. Stupid!
Like harleys, has to run like shit and rattle your teeth out. Not because they can't make better engines but because of tradition.
GM make some great DOHC engines. The Northstar V8 for example. And their racing engines.
It's just a cost issue.
Bang for your buck.
You want a better engine and cost isn't a factor - DOHC.
[QUOTE=90ft]The overiding factor between the two has always been COST.
Performance wise DOHC are superior.
Over head make the heads much more expensive to manufacture.
It's what you get for your money. That's what drives car companies at the end of the day. Money.
Corvette is different when tradition has overtaken sense on all fronts.
Has to be designed and built in Detroit and has to be push rod. No exceptions made.
So they do their push rod engines with magnesium and titanium bits everywhere. Stupid!
Like harleys, has to run like shit and rattle your teeth out. Not because they can't make better engines but because of tradition.
GM make some great DOHC engines. The Northstar V8 for example. And their racing engines.
It's just a cost issue.
Bang for your buck.
You want a better engine and cost isn't a factor - DOHC.[/QUOTE]
If cost is an issue why are then all engines of smaller cars, where costs are much more critical due to the lower margins, being fitted with S-or DOHC engines?
I wonder if the cost issue is as big as it once was.
The heads used to need more machining which USED to be a manual task.
Now with semi-automated casting and fully automated machining I wonder if the price is significant anymore.
[QUOTE=90ft]
Corvette is different when tradition has overtaken sense on all fronts.
Has to be designed and built in Detroit and has to be push rod. No exceptions made.[/quote]
Gm already tried DOHC in a Corvette, it failed immensely, it gained 200lbs over the same year LT1 engine'd Corvette, and the LT5 was 100lbs heavier than the OHV LT1, and 200lbs heavier over the current LS1, and even more so heavier than the LS6/LS2 (and probably LS7).
[quote]
So they do their push rod engines with magnesium and titanium bits everywhere. Stupid![/quote]
What engine is using magnesium? And only the LS7 is using titanium, and thats only on the pushrods. Even with that its STILL cheaper than most same power'ed DOHC engines.
[quote]
Like harleys, has to run like shit and rattle your teeth out. Not because they can't make better engines but because of tradition.[/quote]
How do Harleys "run like shit"? They "rattle" because of the lobey cams they have, and long stroke for nice torque and a beautiful exhaust not. Its not about tradition, its about what people want, they want that "rattle."
[quote]
GM make some great DOHC engines. The Northstar V8 for example. And their racing engines.
It's just a cost issue.
Bang for your buck.
You want a better engine and cost isn't a factor - DOHC.[/QUOTE]
The Northstar is a great engine, but the LS1 is smaller, lighter, more powerful, more gas efficient, and most of all cheaper, so which do you want in your car?
Yes Slicks the Corvette is using pushrods, virtually all other constructors for high revving, low revving and very competitive cars all use OHC, my god are these people stupid. :D
[QUOTE=Slicks]How do Harleys "run like shit"? They "rattle" because of the lobey cams they have, and long stroke for nice torque and a beautiful exhaust not. Its not about tradition, its about what people want, they want that "rattle."[/QUOTE]
having ridden one, the comment was about rattling your teeth out, not valvetrain rattle.
"not tradition" -- "what people want" erm that IS tradition isn't it ??
it's what Harley have alwys sold on.
Harley are the only bike maker to have patented their engine sound they feel ThAT sstrongly it's why people buy there product. The famous "potato-potato" sound :)
Like the big cars on US freeways, if I had to sit on a bike at 55 for 4 hours I would prefer the Harley. Anywhere else and it's not the favourite.
The engines run fine, they are designed to maintain the harley sound and good on the company for identifying their unique selling point and adhereing to it. Shame that British bikes in the 60s USP was leaking oil and they satayed with that till they went bust :)
[QUOTE]The Northstar is a great engine, but the LS1 is smaller, lighter, more powerful, more gas efficient, and most of all cheaper, so which do you want in your car?[/QUOTE]
What are the relative sales volumes of these respective engines.
It was previously raised that the LS1 is cheap because of volume.
You're never going to get a cheap Ferrari engine for as long as they stay with low volume and hand-engineered/built.
It woudl be interesting to conjecture WHAT-IF on a Ferrari or Lambo or BMW engine if it coudl be made in the same numbers and factory costs as the LS1 :)
[quote]This has been a point of discussion all the time when the corvette C6 was
being set off against european cars.[/quote]
the corvette uses pushrod motors because that is the best solution for that car, its what the buyer wants. in that car it is a more compact, lighter design which produces all the torque and power that is required(well mabe a smidget more... ;)) for cheap. i cannot think of a better motor to go in a corvette. and sure heritage is part of it. the LT5 was DOHC and it was a good motor, but as slicks said it was heavier and cost kept it from being much of a success. pushrod may not be the best design alone but it is the best solution in many sitations, such as the corvette. especially considering the corvette is one of the best high end sports car values today compared with the likes of the viper, M3, 911, etc.
[quote]So both modern high revving and low revving engines produced in Europe (and Japan) are fitted with OHC's. In my opinion this means that for choice options you describe OHC's provide the best option.[/quote]
best option no, as i described above with the vette "best option" is a reletive term. "best" for a bimmer or a civic doesnt mean its "best" for a corvette or GTO. im under the impression that modern diesels use OHC designs because of the more precise control needed for a more efficient combustion process. and the inherent design of diesel blocks makes weight pretty much a non-issue. at least not enough of an issue to justify not using an OHC design.
cost is also an issue. pushrods are cheaper, possibly both for the reasons henk posted and for the manufacturing process. it is more expensive to have a OHC head ported than a pushrod head, it cheaper to cast/grind one cam than 4. 16 valves/springs as oposed to 32. and with advancements in pushrod head design such as those used on modern chevy LS engines the advantages of OHC are hardly worth the cost(both monetary cost and weight/volume)
engines such as the DOHC northstar and the SOHC/DOHC ford modualr motor have been mass produced for over a decade now. they can be had for reletivly cheap. and are used in replacement for the likes of LS and LT motors. but the fact still remains that it is easier and cheaper to buy an LT1 or LS1, build and make power out of than it is for en equivelent mass produced DOHC motor such as the mod' or northstar. its just the way things are.... ;)
[QUOTE=megotmea7] pushrod may not be the best design alone but it is the best solution in many sitations, such as the corvette. [/QUOTE]
Interesting contribution Meg, I won't dwell on all your points, but I would like to be told more about why the Corvette is so unique that a pushrod is better there. Aren't there any other comparable sportscars that could also benefit from the perceived advantages of the pushrod? Or is it still the case that the engine can be made cheap because the majority of the LS engines is being sold in truck in less tweaked form.
I am not downplaying the qualities of the C6, in fact I just read a comparison between the C6 and the 911S done by the French magazine Echappement, whereby the Porsche was a tat faster in all departments (including the 1/4 mile) but that was due to a much better gearbox which really has 6 gears while the C6 has a 5 plus 1. Also the C6 engine picked up slightly less alert than the Porsche. With a price of more than 30000 US$ less in Europe this is not a thing that prospective C6 buyers would worry about.
Cost issues need to be further investigated, if all cost advantages that pushrod engines appear to have (if what you said is correct) then I really don't understand why so few engines still run on pushrods. Can you name one new design less than 10 old that is running OHV? (not the small block derivatives)
[quote]I would like to be told more about why the Corvette is so unique that a pushrod is better there. Aren't there any other comparable sportscars that could also benefit from the perceived advantages of the pushrod?[/quote]
no, the corvette is not unique at all. there are comparable cars, such as the 911 and the M3. both using more "advanced" DOHC 6 cylinder powerplants and producing comparable power to a vette. the main reason i see however that the vette still uses a big OHV V8 aside from heritage is the fact that it gains nothing by going to an OHC engine aside from a couple hundered pounds and a more cramped engine bay. im sure the M3 could (and has in some cases) benifit from a small compact OHV V8 but who wants their ultimate driving machine to be pushrod powered? ;) im sure it would shed a few pound but it wouldnt be a bimmer. the small block is a better motor for the vette not only from a engineering perspective(light weight, good power, good torque, good gas mileage, cheap to build) but from a buyers perspective (power/torque, ease of driving, gas mileage, ease of moding, vette heritage, etc.). just as the case with the M3 owner, he/she wants a high tech motor to go along with his/her cutting edge chassis design and overacheiving handling. but what advantages do you see the M3's I6 having over an LS2 or even an LS1 smallblock fitted in the vette?
[quote]I just read a comparison between the C6 and the 911S done by the French magazine Echappement[/quote]
ive not actually seen a comparison between the C6 and the new 911 but ive heard from a friend (who happenes to be a big porsche and german car fan, he loves the E30 bmw) where those 2 cars were compared, and the C6 beat out the porsche in every criteria, but the porsche won in overall because of its more inspiring feel and being more controlable and stable, making you want to pushn it further than you'd want to in the vette(which i can apreciate). but im not going to argue the vaildity of either claim. they are both great cars, and has their individual merits; price, performance, and feel.
[quote]Cost issues need to be further investigated, if all cost advantages that pushrod engines appear to have (if what you said is correct) then I really don't understand why so few engines still run on pushrods. Can you name one new design less than 10 old that is running OHV? (not the small block derivatives)[/quote]
im no engine manufaturer, im giving my opinion based on what ive seen when it comes to cost of engine building, theres a reason the LT5 failed miserably, and it was ebcause of price, beacuse they could make the OHV engines for cheaper and acomplish the same thing while taking up less space and weight. i too would like to know why pushrod motors are dying out but my theory is its the consumer. ppl want high tech, they want cutting edge, even on their base model econo boxes. OHC is a better design, more can be done with it in terms of economy(in a world where economy is becoming more and more important), just ebcause the vette has better gas mileage than a comparible sports car doesnt mean any car will get better gas mileage out of a pushrod motor. OHV also has a negitive stigma about it, esp. outside of the US. such as in the first supercar project, ppl wanted to see a 4.3 liter OHC lexus motor or a turbo 4 liter OHC I6 instead of the LS1 regardless of the increased weight/size from either of those motors. i belive its because they dont think pushrod motors are "good enough", their "old tech" even when the numbers prove them supirior for a given purpose. its just the way things are. like a diesel ferrari, if ferrari developed a diesel 4 cylinder that outperformed their V8 and V12's in every way, while sipping fuel and weighing about the same and put it in their next flagship, most ppl would have a heart attack(esp in the US where opinions on diesels are even lower than in europe, esp. in the performance dept). and it wouldnt be just because of ferraris history of high revving V12's either, it would be just because its a deisel, visions of huge big rigs whistling by on the free way come to mind. like with pushrods, big muscle cars that cant really handle come to mind. and unfortunatly ppl dont realize alot has changed since the 60's pushrods included. well thats my theory anyway.
and about the new example of a pushrod only one i cn think of off the top of my head is the 4 cylinder used in the ford ranger. not sure where/when it came from tho. just know it is used in rangers to this day. but leaving out small block derivatives leaves out alot of new motors ;) coarse theres the new 8.1 liter big block used in chevy trucks ;)
Basically it is therefore a psychologic issue, which I can understand on the supercar and luxobarge market. However, if you would ask the average
Joe in the street about the valve drive of his car you would be met with a blank stare. A mass produced engine could do very well without OHC's for image purposes, but obviously there are other technical advantages which even exceed the perceived cheaper construction costs. Matra has mentioned a few and it is difficult to understand why these advantages would not be vaid for any engine.
I don't know what the price differences were at the time, but what was the additional costs of the ZR1 compared to the pushrod version? Was the difference substantial enough to prevent the ZR1 from becoming a commercial success?
A ferrari 4-pot diesel I could probably afford. :D , and you may have heard that Maserati is developing a V8 version of the Fiat multijet diesel engine to be installed in the QP. The Brera will have a 5 pot 200 BHP diesel, you can buy BMW 3 coupe with the 330d engine, Audi delivered its previous A4 cabrio with a diesel and the list is endless.
i prefer DOHC...i will leave it at that
i cried when a pontiac powered DP won daytona
the ZR-1 package was an almost $30k option. cars were sold for around $100k in some cases, compared to the $35k base price for the vette at the time.
[quote]obviously there are other technical advantages which even exceed the perceived cheaper construction costs.[/quote]
granted there are, as i said it is a better design, but speaking on end result regardless of the makup of the engine or technical advantages over the next, even regardless of displacement. comparing the LS1 to the M3 I6 for simplicitys sake, the LS1 is a smaller lighter engine, producing more power, more torque, and a flatter torque curve, and acheaiving better gas mileage. with those advantages does it matter where/how many cams there are, how many cylinders, or displacement, how efficient the head design is, how many valves? what advantages does the M3 motor have over the LS1? and this isnt taking into account the cheapness of the LS1 either
[quote]Maserati is developing a V8 version of the Fiat multijet diesel engine to be installed in the QP. The Brera will have a 5 pot 200 BHP diesel, you can buy BMW 3 coupe with the 330d engine, Audi delivered its previous A4 cabrio with a diesel and the list is endless.[/quote]
dont get me wrong, i never said anything about the deisel, i was just trying to demonstrate the stigma against pushrods with ppls attitudes and perceptions against diesels
[QUOTE=targa]i prefer DOHC...i will leave it at that
i cried when a pontiac powered DP won daytona[/QUOTE]
theres that aformentioned "psycological" issue. . .
[QUOTE=megotmea7]theres that aformentioned "psycological" issue. . .[/QUOTE]
...huh?
[QUOTE=megotmea7]the ZR-1 package was an almost $30k option. cars were sold for around $100k in some cases, compared to the $35k base price for the vette at the time.
granted there are, as i said it is a better design, but speaking on end result regardless of the makup of the engine or technical advantages over the next, even regardless of displacement. comparing the LS1 to the M3 I6 for simplicitys sake, the LS1 is a smaller lighter engine, producing more power, more torque, and a flatter torque curve, and acheaiving better gas mileage. with those advantages does it matter where/how many cams there are, how many cylinders, or [B]displacement[/B], how efficient the head design is, how many valves? what advantages does the M3 motor have over the LS1? and this isnt taking into account the cheapness of the LS1 either
dont get me wrong, i never said anything about the deisel, i was just trying to demonstrate the stigma against pushrods with ppls attitudes and perceptions against diesels[/QUOTE]
I put displacement in bold, because that's what the M3 is lacking compared to the LS1. LS1 is cheap because of the numbers. M3 is expensive because it is a BMW :D
I rambled on about the diesels just to show what is going in Europe, and mentioned a few cars that also in Europe had to fight against prejudice, but I'll buy you a drink of Ferrari ever comes up with a 4-pot diesel :D
[quote]I put displacement in bold, because that's what the M3 is lacking compared to the LS1. LS1 is cheap because of the numbers. M3 is expensive because it is a BMW.[/quote]
the point i was making tho was despite its greater displacement, it is an overall smaller engine, this is due to it being OHV, demonstrating this advantage. and i understand the price difference im mostly because of its brandage.
[quote]I'll buy you a drink of Ferrari ever comes up with a 4-pot diesel[/quote]
i used the example of a ferrari 4-cyl diesel to demostrate, how feelings towards a type or configuration of an engine may deture ppl away even if it proves superior in real world and performance scenarios. but i have the feeling you may have picked up on that. :)
[QUOTE=megotmea7]it is more expensive to have a OHC head ported than a pushrod head,[/QUOTE]
Don't see this one meg ( and a few others - stay tuned :) )
I can think with soem heads that porting them is more difficutl becase there are more valves or are already optimised with minimal wall thicknesses.
Not sure I can think of a head where porting makes a BIG difference and it's harder whre all other things are ketp the same.
Can you maybe expand ?
[QUOTE]it cheaper to cast/grind one cam than 4.[/QUOTE]
A brand new custom cam from one of the top engineering companies in the UK for one of the strongest Ford competitions engines out there is the pricely sum of £140 ( about US$200 ). Now as they make a healthy profit too, then casting and machining price isn't really a major issue for those parts.
Yes, it's cheaper but does 300 quid REALLy make a difference ?
[QUOTE]16 valves/springs as oposed to 32.[/QUOTE]
That assumes going to DOHC on a V8.
The choice to go for 3 or 4 valves per chamber is drven by other factirs and NOT the cam. only IF the engine needs the larger valve openeing area does it NEED the D in DOHC and the extra springs valves etc.
They often get put together becuase it is difficult for a pushrod system to operate on more than 2 valves per combustion chamber as they have to be angled and pushrods don't work well with multiple angled valves.
It's another discussion on multi-valve that coudl explore that decision.
[QUOTE]and with advancements in pushrod head design such as those used on modern chevy LS engines the advantages of OHC are hardly worth the cost(both monetary cost and weight/volume)[/QUOTE]
erm, there aren't any "advancements" :)
Competition cars have used esoteric materials and billet components for rods, buckets, follwers, tappets including rollers etc etc
If any "advance" it's been in better fluid dynamic modelling to improve the flow of air in and out the combustion chambers - but OHC heads have benfitted from that equally so.
We are porting a 295 head for the Mini and it's funny reading what was written 40 years ago about porting it and what is known to be best today :)
[QUOTE]engines such as the DOHC northstar and the SOHC/DOHC ford modualr motor have been mass produced for over a decade now. they can be had for reletivly cheap. and are used in replacement for the likes of LS and LT motors. but the fact still remains that it is easier and cheaper to buy an LT1 or LS1, build and make power out of than it is for en equivelent mass produced DOHC motor such as the mod' or northstar. its just the way things are.... ;)[/QUOTE]
Thanks meg, I had wondered if it was order of magnitude differences in volume - esp if the block is shared in trucks - or just 10% more. Another thought was does country of manufacture make a difference ? Labour costs coudl be significant - hence why the MINI ended up with a cruddy Mexican POS instead of a decet motor :( Any ideas ??
[QUOTE=Matra et Alpine]
What are the relative sales volumes of these respective engines.
It was previously raised that the LS1 is cheap because of volume.
You're never going to get a cheap Ferrari engine for as long as they stay with low volume and hand-engineered/built.
It woudl be interesting to conjecture WHAT-IF on a Ferrari or Lambo or BMW engine if it coudl be made in the same numbers and factory costs as the LS1 :)[/QUOTE]
The LS6 is only in 2 cars (C5 Z06 and CTS-V, so its not "mass produced") and it can bought new for 2-3K over an LS1.
[QUOTE=henk4] Can you name one new design less than 10 old that is running OHV? (not the small block derivatives)[/QUOTE]
Saleen S7
BTW to clear somethings up OHV engines can have VVT.
Everyone stop and think about marketing here. Do you think that companies want people to buy their cars, or do they want to make the best performing car, ignoring customer wants and needs etc?
By a company that normally uses DOHC to switch to OHV that shows that they were previously "wrong" with the engine design, and gives even more credit to GM with sticking with that design. Its no surprise companies will go with a better marketing design, even if its less superior(not saying that it is) to keep reputiation points.
[quote]I can think with soem heads that porting them is more difficutl becase there are more valves or are already optimised with minimal wall thicknesses.[/quote]
ive seen shops charge supra owners upwards of $1500-$2000 for a decent port job on its DOHC 3 liter I6 head. the 'equivelent' port on a LS is around $1200-1400.
[quote]Yes, it's cheaper but does 300 quid REALLy make a difference?[/quote]
it is when your making 150,000 cars
[quote]That assumes going to DOHC on a V8.
The choice to go for 3 or 4 valves per chamber is drven by other factirs and NOT the cam. only IF the engine needs the larger valve openeing area does it NEED the D in DOHC and the extra springs valves etc.
[/quote]
the DOHC 4.6 mod' and the northstar are 32v engines, the LS1 is a 16 valve engine, i was indirectly comparing them
[quote]If any "advance" it's been in better fluid dynamic modelling to improve the flow of air in and out the combustion chambers - but OHC heads have benfitted from that equally so. [/quote]
my point being the LS heads are the highest flowing, non big block heads ever to come on a OHV production car, the LS heads are leaps and bounds ahead of the LT heads, which werent shy in the flow department either. OHV engines have come along way since the 60's. and the end result is apearent. dont take this as me saying OHC engines havent come along, its just that OHV engines are at a standstill with 1970's technology and some ppl belive
[quote]the northstar has been in production since the 80's, the ford modular motor came out in the mid 90's, and has been used in mustnags lincolns, and in ford trucks ever since. chevy has used the 350(5.7) in its trucks up untill 2002 when it switched to the 327(5.3) the LS motors and the truck 350's were never the same up until recently when the new iron block 6 liter LS based truck motor came out for its full size pickup. i guess you could call LS motor and ford modular motor production right about the same, altho it is highly probable that ford has made more OHC engines than chevy has LS's since the highest selling pickup in the US has been the F150 (fitted with a 5.4 liter SOHC mod' motor) and mustangs (fitted with either a 4.6 SOHC, DOHC, or supercharged DOHC, or a 5.4 DOHC modular motor in GT, mach1, cobra, or cobra R form) have been outselling LS1 equiped camaro's and trans ams 3 to 1 for years. not to mention lincoln LS, crown vic's, grand marquis, etc. being fitted withe the 4.6 or in the LS's case a very small version or the modualar motor(i think around 3 liters).
i would go pushrods myself personally. the LS1/2/6/7 only need to rev to 6500rpm to get their max power, as opposed to 7-8000rpm. the LS7 generates 500hp/373kw at 6200rpm and 644nm at 4800rpm, while the M5 V10 needs 8000rpm for the same power level. whats gunna last longer when pushed, i'll put my money on the LS7.
also, pushrod motors can rev hard, ie V8 supercars have 5litre pushrods motors, getting 630+hp at 7500rpm