LS9 DOHC / LS8 / And end of life for LS7
02-23-2006, 10:28 PM
#62
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Originally Posted by slt200mph
Go and get your tape measure and see what an LT5 motor is and then measure the LS series motor and you will see what we are talking about..big difference in the size of those two power plants.. 
I know the physical dimensions are larger on the LT5 but they made that work. Too bad it didn't sell too well though. 
02-23-2006, 11:21 PM
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What if the next major small block from the general had no camshaft at all?
What if GM had been spending more money than the yearly total income of all members of this board made annually, on this project?
What if GM knew that a OHC motor would kill valve acceleration rates, and they knew that is what allowed pushrod motors to allow un-matched cylinder fill ability?
What if, there was a device that could open the valve quicker than anything we can grind today, but it was powered by 24 volts instead of a gun drilled piece of steel?
what if?
What if GM had been spending more money than the yearly total income of all members of this board made annually, on this project?
What if GM knew that a OHC motor would kill valve acceleration rates, and they knew that is what allowed pushrod motors to allow un-matched cylinder fill ability?
What if, there was a device that could open the valve quicker than anything we can grind today, but it was powered by 24 volts instead of a gun drilled piece of steel?
what if?
02-23-2006, 11:30 PM
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this is really one of the stupidest discussions ive seen on this board, right up there with the thread "which GM vehicle do you have" in the apperance section that never seems to die
02-23-2006, 11:32 PM
#66
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Originally Posted by TAEnvy
When you are talking about efficiency thats all that matters. And seeing as how this is an engine based thread not one about the whole car it seems that efficeincy would be what we are talking about. So the LS7 that all of you love so much makes 505hp with 7 liters the BMW M5 V-10 does it with only 5 liters.
On top of that it makes more torque at 2500RPMs than the V10's peak torque!
Oh yeah, and with one less gear the Corvette is getting better gas milage than the M5 as well.... Ouch...
02-24-2006, 02:41 AM
#67
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damn i created a war.
300bhp/ton, from what i see your comparing alot of cars that have over 100hp/ltr that are V12's so thats not really a good comparison, sure they have 7 liters or 6 liters or even 5 liters. but they have also 2 or 4 more cylindars than the LS7.
I'm by no means nocking the OHC, its a good engine, but i just kinda wished gm stayed w/ OHV. bring back the Big Block
. who cares about gas savers.
300bhp/ton, from what i see your comparing alot of cars that have over 100hp/ltr that are V12's so thats not really a good comparison, sure they have 7 liters or 6 liters or even 5 liters. but they have also 2 or 4 more cylindars than the LS7.
I'm by no means nocking the OHC, its a good engine, but i just kinda wished gm stayed w/ OHV. bring back the Big Block
. who cares about gas savers.
02-24-2006, 04:04 AM
#68
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Originally Posted by slt200mph
4 vavle per cyl. engine make its horse power up on the top..they do not make comparable HP and TQ numbers in the low or mid range like OHV engines do.
If you had two engines of the same displacement and the same bore x stroke, but one was 2v (OHV or OHC it makes no odds) and one 4v DOHC (or clever OHV push rod setup).
The 4v unit will have a broader power band. And will be able to match and exceed the 2v in the high rpms and yet still have a better more tractable low end. Think about when you put a massive cam in an LS1, you maywell be able to get it rev to 7000rpm but it will have very little comparitivly below 3500rpm. A 4v unit would be able to rev to say 8000rpm but yet still be tractable from as low as say 2000rpm. I'll be honest the physics is a little beyond me to explain it so this is a better explanation:
Originally Posted by Bret @ Bauer Racing Engines
Anyways, what a 4 valve setup gives you is curtain area, lots of it.
FWIW Curtain area is valve diameter x Pi x lift. The more curtain area you have the more cubes and/or RPM you can run.
FWIW Curtain area is valve diameter x Pi x lift. The more curtain area you have the more cubes and/or RPM you can run.
Originally Posted by Old SStroker
Curtain area is the "window" or "door" through which the air flows. It is the circumference of the valve(s) x the lift. (dia. x PI x lift x number of valves)
Two 1.60 inch diameter intakes lifted .500 inch have the same curtain area as one 3.20 inch diameter valve lifted .500, or a 2.02 valve lifted about .790 inches. You can see that curtain area increases quicker with 2 valves than with one given the same lobe aggressiveness.
Smaller valves lifting less over the same duration are a lot easier to control that a heavier valve lifting farther. It should be easier to get high revs because of the "milder" lobes you can use and the less inertia loads the springs have to control.
Two 1.60 inch diameter intakes lifted .500 inch have the same curtain area as one 3.20 inch diameter valve lifted .500, or a 2.02 valve lifted about .790 inches. You can see that curtain area increases quicker with 2 valves than with one given the same lobe aggressiveness.
Smaller valves lifting less over the same duration are a lot easier to control that a heavier valve lifting farther. It should be easier to get high revs because of the "milder" lobes you can use and the less inertia loads the springs have to control.
Originally Posted by slt200mph
..before Pro Drive started using the A M they used the Ferarri and the Corvettes kicked their *** too..so bad they quit the ALMS series.
Originally Posted by slt200mph
STAY TUNED to the SPEED CHANNEL on the 18th of next month your going to get another dose of American OHV Iron kicking Euro DOHC ***.. 
02-24-2006, 04:09 AM
#69
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Originally Posted by JD_AMG
Oh yeah, and with one less gear the Corvette is getting better gas milage than the M5 as well.... Ouch...
Of course the Vette gets better gas milage infact I'b be VERY VERY VERY VERY worried if it didn't.
But it's not the engine, at least the engine is only a minor part.
The Corvette is a LIGHT weight sports car compared to over 4000lb 4 door saloon for the M5, this alone should cause a MASSIVE difference in MPG.
The Corvette is also a MANUAL which are always more economical. And employs 'tricks' such as CAGS to acheive the MPG figure.
The M5 has a sequential gearbox and is a totally different animal.
02-24-2006, 04:33 AM
#70
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Originally Posted by black_knight
No I don’t have a bunch of statistics to show the cost of OHV vs OHC. That knowledge is second-hand so feel free to prove me wrong. Do you have any proof?
I don't honestly know, and I'm not backing either side. But logically speaking if OHV is so great at everything why are MOST engines OHC/DOHC?
It would seem to be reverse logic. Take a 4 cylinder engine, the basic principles of combustion are the same as a V8. Yet ALL petrol 4 cylinder engines are OHC infact I can't even think of a mass produced OHV 4 cylinder engine in recent times (20 years??). But if OHV is cheaper and just as good on performance and smaller where have they gone and why?
Originally Posted by black_knight
Pardon my ignorance, but which motor exactly is the AJV8? What is its output and what does it weigh?
Originally Posted by Roger Bywater, ex Jaguar Cheif Engineer
Let us start by dispelling the belief still held by a few people that Jaguar just adapted a Ford designed V8 to create their new power unit. The truth is actually the reverse. Jaguar designed the engine in its entirety, it is manufactured in the UK, and a simplified variant is shipped over to the US where Lincoln install it in their LS model!
Jaguar's design team started with a clean sheet of paper for this new V8 engine. Nothing carried over from previous engines and the aim clearly was to produce a class leading power unit with few compromises. In most respects they achieved success and were able to devise remedies for the inevitable weaknesses that emerged with time.
So wide ranging was the research to determine the best engine format to carry Jaguar into the 21st century that the program included building and testing a number of advanced two-stroke engines. Most impressive was a 3.2 litre V6, lean burn, supercharged, two-stroke using the Orbital air-assisted injection process. It produced 350 b.h.p. but emissions and durability proved to be hurdles that were too difficult to overcome. Although a fairly conventional V8 was soon perceived as being the best solution, details like the number of valves to use were resolved in a series of single cylinder prototypes, echoing the V12 program 30 years or so before. Most modern engines use the four valve layout but as befits a project aiming for the best solution, Jaguar's engineers also considered alternative arrangements like the five valve configuration used so successfully by Yamaha on their high performance motor cycle engines. No real advantage could be found that way so progress continued with a more conventional four valve layout.
A very efficient and compact combustion chamber was achieved by closing up the angle between the valves from the 47 degrees of the AJ6 and AJ16 engines to a more ideal 28 degrees, accepting the slight drawback that the head bolts were situated right under the camshafts so the heads could not be totally pre-assembled. An incidental advantage of the narrower valve angle is that it helps to keep the cylinder heads compact, so minimising the weight and package size of the complete power unit.
Special attention was devoted to the valve train to keep masses as low as possible, valve stems for example being just 5 mm in diameter. This brings advantages in three respects: firstly, there is a measurable improvement in fuel economy due to reduced friction losses; secondly, it is easier to reduce mechanical noise thereby improving refinement; finally, the mechanical stresses in the valve train are reduced. The latter point is particularly relevant but to understand why a short digression is necessary.
Purpose designed four valve V8 racing engines use a single plane crankshaft (like an in-line four cylinder) to obtain evenly spaced firing impulses along each bank to allow for optimum exhaust tuning, the downside being that the engine shakes laterally because of unbalanced forces. Even with a regular firing order such engines are notorious for timing gear problems associated with severe instantaneous torque reversals, which at different times have caused much trouble in four valve V8s from such illustrious names as Coventry Climax, Repco, Cosworth and Ilmor.
Production V8 engines almost always use a two plane crankshaft (four crank throws disposed at 90 degree intervals) which provides good balance but an uneven firing order along each bank. Because of this a four cam production V8 inevitably has the cams asymmetrically phased around the axis of each camshaft as shown in the diagram. This gives rise to irregular loads on the drive between the crankshaft and the cams and between the two camshafts on each head.
It is perhaps then not surprising that on the Jaguar V8 the tensioners on the secondary camshaft chains in particular have developed a reputation for being troublesome. In fact it may not be that there is any weakness in the tensioners themselves, rather that at certain critical speeds heavy torque reversals on the chain can produce higher than expected stab loads, a condition which can probably be exacerbated by some usage patterns. It is perhaps interesting that the later 4.2 V8 uses more rugged morse internal tooth primary chains and that when BMW introduced a similar V8 (four valve, twin OHC, Nikasil bores, sintered fracture split con-rods) in 1992 they used duplex chains throughout. Whilst Jaguar's design team, in choosing a single link chain drive, did specify that it should be rated for heavy duty, one wonders if there have been any regrets that space wasn't made to use a duplex chain rather than relying on the lightweight valve gear to let them get away with the narrower option?
Of course, all engines have weaknesses that only become apparent with time and the engineering of the Jaguar V8 is not without many positive attributes. The combination of quite large valves and cam profiles of modest duration, allied, in the case of the naturally aspirated 4 litre, to a variable timing mechanism controlling the inlet cams, results in an engine with a particularly wide spread of torque.
The early variable timing device was a two state system - either advanced or retarded over a range of 30 degrees (at the crankshaft). Retarding the inlet cam eliminated overlap so improving idle and drive quality at very low speeds and light loads. It also meant the inlet valve closed later thereby improving power at higher speeds. In the mid-speed, part to high load range, the cam was advanced giving early inlet closing to boost torque, the extra overlap then also providing a degree of 'internal EGR' to reduce NOx emissions. Later engines use a more advanced system that optimises the cam phasing within a much wider range of, incredibly, 48 degrees.
With the benefit of hindsight the decision to use Nikasil plated cylinder bores instead of conventional liners might be judged a bad mistake, but it is one that was understandable and which caught BMW off-guard as well. The Nikasil process had been used for years on motorcycle engines and is in common use for F1 and other racing engines so it is hardly unproven technology. At the time BMW's exceptionally tight control of oil on the bores was thought to be a factor in their troubles, which would not apply elsewhere. In truth, instances of failure of the Nikasil coating appear to have been induced by poor fuel quality in certain markets allied to short journey usage, and engines running on low sulphur fuel would be most unlikely to suffer the problem. Jaguar resolved service failures in an honourable fashion but eventually decided to abandon Nikasil and revert to conventional cast iron liners (from VIN 42776 XK8, 878718 XJ8). The advantages of light weight and close running clearances were sadly lost. Ironically the fuels which caused the problem have now virtually disappeared from the market.
The size increase to 4.2 litres was obtained by increasing the stroke - always a favoured approach at Jaguar - necessitating the crankpin journals to be reduced in diameter to maintain the same block height.
Jaguar's design team started with a clean sheet of paper for this new V8 engine. Nothing carried over from previous engines and the aim clearly was to produce a class leading power unit with few compromises. In most respects they achieved success and were able to devise remedies for the inevitable weaknesses that emerged with time.
So wide ranging was the research to determine the best engine format to carry Jaguar into the 21st century that the program included building and testing a number of advanced two-stroke engines. Most impressive was a 3.2 litre V6, lean burn, supercharged, two-stroke using the Orbital air-assisted injection process. It produced 350 b.h.p. but emissions and durability proved to be hurdles that were too difficult to overcome. Although a fairly conventional V8 was soon perceived as being the best solution, details like the number of valves to use were resolved in a series of single cylinder prototypes, echoing the V12 program 30 years or so before. Most modern engines use the four valve layout but as befits a project aiming for the best solution, Jaguar's engineers also considered alternative arrangements like the five valve configuration used so successfully by Yamaha on their high performance motor cycle engines. No real advantage could be found that way so progress continued with a more conventional four valve layout.
A very efficient and compact combustion chamber was achieved by closing up the angle between the valves from the 47 degrees of the AJ6 and AJ16 engines to a more ideal 28 degrees, accepting the slight drawback that the head bolts were situated right under the camshafts so the heads could not be totally pre-assembled. An incidental advantage of the narrower valve angle is that it helps to keep the cylinder heads compact, so minimising the weight and package size of the complete power unit.
Special attention was devoted to the valve train to keep masses as low as possible, valve stems for example being just 5 mm in diameter. This brings advantages in three respects: firstly, there is a measurable improvement in fuel economy due to reduced friction losses; secondly, it is easier to reduce mechanical noise thereby improving refinement; finally, the mechanical stresses in the valve train are reduced. The latter point is particularly relevant but to understand why a short digression is necessary.
Purpose designed four valve V8 racing engines use a single plane crankshaft (like an in-line four cylinder) to obtain evenly spaced firing impulses along each bank to allow for optimum exhaust tuning, the downside being that the engine shakes laterally because of unbalanced forces. Even with a regular firing order such engines are notorious for timing gear problems associated with severe instantaneous torque reversals, which at different times have caused much trouble in four valve V8s from such illustrious names as Coventry Climax, Repco, Cosworth and Ilmor.
Production V8 engines almost always use a two plane crankshaft (four crank throws disposed at 90 degree intervals) which provides good balance but an uneven firing order along each bank. Because of this a four cam production V8 inevitably has the cams asymmetrically phased around the axis of each camshaft as shown in the diagram. This gives rise to irregular loads on the drive between the crankshaft and the cams and between the two camshafts on each head.
It is perhaps then not surprising that on the Jaguar V8 the tensioners on the secondary camshaft chains in particular have developed a reputation for being troublesome. In fact it may not be that there is any weakness in the tensioners themselves, rather that at certain critical speeds heavy torque reversals on the chain can produce higher than expected stab loads, a condition which can probably be exacerbated by some usage patterns. It is perhaps interesting that the later 4.2 V8 uses more rugged morse internal tooth primary chains and that when BMW introduced a similar V8 (four valve, twin OHC, Nikasil bores, sintered fracture split con-rods) in 1992 they used duplex chains throughout. Whilst Jaguar's design team, in choosing a single link chain drive, did specify that it should be rated for heavy duty, one wonders if there have been any regrets that space wasn't made to use a duplex chain rather than relying on the lightweight valve gear to let them get away with the narrower option?
Of course, all engines have weaknesses that only become apparent with time and the engineering of the Jaguar V8 is not without many positive attributes. The combination of quite large valves and cam profiles of modest duration, allied, in the case of the naturally aspirated 4 litre, to a variable timing mechanism controlling the inlet cams, results in an engine with a particularly wide spread of torque.
The early variable timing device was a two state system - either advanced or retarded over a range of 30 degrees (at the crankshaft). Retarding the inlet cam eliminated overlap so improving idle and drive quality at very low speeds and light loads. It also meant the inlet valve closed later thereby improving power at higher speeds. In the mid-speed, part to high load range, the cam was advanced giving early inlet closing to boost torque, the extra overlap then also providing a degree of 'internal EGR' to reduce NOx emissions. Later engines use a more advanced system that optimises the cam phasing within a much wider range of, incredibly, 48 degrees.
With the benefit of hindsight the decision to use Nikasil plated cylinder bores instead of conventional liners might be judged a bad mistake, but it is one that was understandable and which caught BMW off-guard as well. The Nikasil process had been used for years on motorcycle engines and is in common use for F1 and other racing engines so it is hardly unproven technology. At the time BMW's exceptionally tight control of oil on the bores was thought to be a factor in their troubles, which would not apply elsewhere. In truth, instances of failure of the Nikasil coating appear to have been induced by poor fuel quality in certain markets allied to short journey usage, and engines running on low sulphur fuel would be most unlikely to suffer the problem. Jaguar resolved service failures in an honourable fashion but eventually decided to abandon Nikasil and revert to conventional cast iron liners (from VIN 42776 XK8, 878718 XJ8). The advantages of light weight and close running clearances were sadly lost. Ironically the fuels which caused the problem have now virtually disappeared from the market.
The size increase to 4.2 litres was obtained by increasing the stroke - always a favoured approach at Jaguar - necessitating the crankpin journals to be reduced in diameter to maintain the same block height.
Originally Posted by black_knight
Aston V12And it’s… HOW heavy and HOW expensive?
Cost - Sadly can't be compared. As at present all of the engines are handbuilt and only used for Aston Martin in small numbers. But the engine is not overly complex as it is essentially just two Ford Mondeo V6's. These are Duratec or Zeetec engines and are Fords main powerplant in Europe and outside the US. If the engine was put into proper production it really would be no more dificult to build than a V6, It would just have a slightly bigger casting for the block and longer camshafts.
02-24-2006, 07:08 AM
#71
TECH Addict
Originally Posted by chuntington101
how would you guys react if the next vette ran a V10 or V12???
i know the new ford Shelby GR1 runs a v10 plant. i imagine this is a big step away form the norm for ford.
Chris.
i know the new ford Shelby GR1 runs a v10 plant. i imagine this is a big step away form the norm for ford.
Chris.
It was shall we say a mixed response, most said it sounded cool and liked the idea. However there's always a few "speical" people who just decided to insult the other people and stating stupid things about how awful it would be.
EDIT:How did my post get above yours
I only clicked on the QUOTE button 
02-24-2006, 10:32 AM
#73
TECH Senior Member
Originally Posted by 300bhp/ton
I really hate to complain BUT listen to that sentance.
Of course the Vette gets better gas milage infact I'b be VERY VERY VERY VERY worried if it didn't.
But it's not the engine, at least the engine is only a minor part.
The Corvette is a LIGHT weight sports car compared to over 4000lb 4 door saloon for the M5, this alone should cause a MASSIVE difference in MPG.
The Corvette is also a MANUAL which are always more economical. And employs 'tricks' such as CAGS to acheive the MPG figure.
The M5 has a sequential gearbox and is a totally different animal.
Of course the Vette gets better gas milage infact I'b be VERY VERY VERY VERY worried if it didn't.
But it's not the engine, at least the engine is only a minor part.
The Corvette is a LIGHT weight sports car compared to over 4000lb 4 door saloon for the M5, this alone should cause a MASSIVE difference in MPG.
The Corvette is also a MANUAL which are always more economical. And employs 'tricks' such as CAGS to acheive the MPG figure.
The M5 has a sequential gearbox and is a totally different animal.
02-24-2006, 11:17 AM
#74
TECH Addict
Originally Posted by JD_AMG
Yes this is true, althought the BMW is a 7 speed. The main thing I was targeting was hwy gas milage, in which the vette doesnt use any cags to get.
In Europe we have urban and extra urban fuel test where each vehicle drives a set virtual route under the same conditions. This allows comparable results, but they all involve speeding up and slowing down.
And I really do agree with how good the LSx engines are on fuel, I rag my Z28 every journey (it's a toy not a DD
) and usually on short journeys as well, yet with the auto it still returns an overall average of 21-24mpg.Almost as good as my borthers 1.8 MGF (28-30mpg).
EDIT:
Ok here's why:
Corvette C6 Z06
Gear Type Tremec 6 Speed Manual
Final Drive 3.42:1
1st Gear Ratio 2.66:1
2nd Gear Ratio 1.78:1
3rd Gear Ratio 1.30:1
4th Gear Ratio 1.00:1
5th Gear Ratio 0.74:1
6th Gear Ratio 0.50:1
BMW M5
Sequential Manual Gearbox
Final Drive 3.62:1
1st Gear 3.99
2nd Gear 2.65
3rd Gear 1.81 :1
4th Gear 1.39
5th Gear 1.16
6th Gear 1.00 :1
7th Gear 0.83
The Corvette's 5th gear is almost as tall as the BMW's 7th. So 6th in the Vette allows for MUCH lower rpms/mph.
See also the 1:1 is 4th on the Vette which is common for regular manuals, but on the BMW the equiverlent gear is 6th.
The gearbox having closly stacked ratios and a sequential shift is a large reason why the M5 can accelarate as fast as it does. Chuck a regular 5 speed box on it and it'll still be fast, but IMO not quite so.
02-24-2006, 11:43 AM
#75
Originally Posted by 300bhp/ton
More cylinders don't mean more power. It just allows a lower rotaing mass per cylinder. So a shorter stroke is often common which allows higher rpms. But short stroke engines typically produce less torque low in the rpms. This is true for 4,8 10, 12, 16 cylinder engines.
More cubes and a longer stroke engine are not so high rpm friendly as a rule but will make more low end grunt.
More cubes and a longer stroke engine are not so high rpm friendly as a rule but will make more low end grunt.
02-24-2006, 11:51 AM
#76
Originally Posted by 300bhp/ton
But that's my point. If no ones REALLY knows how can they claim it to be true?
I don't honestly know, and I'm not backing either side. But logically speaking if OHV is so great at everything why are MOST engines OHC/DOHC?
It would seem to be reverse logic. Take a 4 cylinder engine, the basic principles of combustion are the same as a V8. Yet ALL petrol 4 cylinder engines are OHC infact I can't even think of a mass produced OHV 4 cylinder engine in recent times (20 years??). But if OHV is cheaper and just as good on performance and smaller where have they gone and why?
It would seem to be reverse logic. Take a 4 cylinder engine, the basic principles of combustion are the same as a V8. Yet ALL petrol 4 cylinder engines are OHC infact I can't even think of a mass produced OHV 4 cylinder engine in recent times (20 years??). But if OHV is cheaper and just as good on performance and smaller where have they gone and why?
I'll try and find the weight out. Performance is not the main goal, acceptable performance and REFINEMENT where the intended targets. The engine in both n/a and supercharged form run very MILD setups in terms of tune and cam profiles (this is a real shame from a hot rodders point of view).
Weight - I don't know probably similar or slightly less than a big block V8 as my Jaguar V12 wieghed in at less than a Chevy 454.
02-24-2006, 11:53 AM
#77
Originally Posted by chuntington101
how would you guys react if the next vette ran a V10 or V12???
i know the new ford Shelby GR1 runs a v10 plant. i imagine this is a big step away form the norm for ford.
Chris.
i know the new ford Shelby GR1 runs a v10 plant. i imagine this is a big step away form the norm for ford.
Chris.
If it was heavier and more expensive I'd be against it.
02-24-2006, 12:37 PM
#78
Originally Posted by black_knight
If it was lighter, cheaper, and made more power then I'd be for it.
If it was heavier and more expensive I'd be against it.
If it was heavier and more expensive I'd be against it.
how about, more power, about the same wait, but a little more exspencive (bigger castings and lighter materials as thats what you wanted lol)????
Chris.
02-24-2006, 01:13 PM
#79
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I would love to see the corvette get a dohc it would be great to rev a 6.0 to about 8000.I however think they could make it push 600 hp na it wouldent be a gas saver but it would blow the doors off any thing on the road and shut the asians up about hp per liter. Some sort of electronic valve timming would be nice too.Dohc is better than ohv because there is less friction without the push rods. Its the same consept as a rotory motor less moving parts less loss of power to friction.
02-24-2006, 01:58 PM
#80
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I still think it is ridiculous to compare a production OHV engine with a production OHC engine in terms of efficiency for displacement. Pushrod engines are built around their cheaper cost advantage (which I am looking to provide hard information for), and are rarely built full out from the factory that the OHC engine is. I am pretty sure I remember reading that a 2L f20c s2000 motor cost more to produce than a freakin 5.7L LS1. Hopefully I can get more info on this a little later. OHC engines, as has been stated, are typically built lower displacement and more taxed out, where pushrod engines are built more to make lazy horsepower. This does not mean that these characteristics are necessarily the inherent nature of the engine design, but rather the sum of the design philosphies of the company that put these engines into production.
The only fair comparison to make in my eyes it to pit full out race motor against race motor, where cost has little factor in the engine's design. In this environment, one will notice that the typical OHC setup is still making more specific output for its displacement, but pushrod engines have closed the gap cosiderably over their production counterparts.
In no way do I think the OHV engine is the superior design, but I feel that it is far from obsolete, as many people seem to suggest constantly. With metallurgy where it is today, I don't feel the pushrod itself is much of a limiting factor anymore in today's race engines (with the exceptions being engines like F1's that turn stupid high revs), but rather that there has not been a good consistent 4v head design for an SBC type engine pretty much ever, whereas pretty much every DOHC engine (and some SOHCs) support 4v heads. 4 valves will always flow better than 2 valve.
I have seen alot of OHV engines on stands, and OHC engines on stands, and I will say this about size; OHV engines are almost always considerably smaller. I remember seeing an older 4.3L Mercedes v8 one morning on a stand, than seeing a 454 big block Chevy later that day on the dyno, and I found the two engines eerily comparible in size. I know there are smaller OHC engines out there , Ferrari's v8s for example), but I have found them to be an exception to the rule.
One last thing. I remember recently there was a discussion on these boards about the c5r, and what that engine was capable of. In ALMS trim, the engine boasts in the 590hp area (correct me if I am wrong), turning at a lazy 6500rpm or something like that. This, of course, is with the engine also breathing through 2 half dollar size restrictors. I remember the Katech representative, when questioned about the engine's potential minus the restrictors, remarked that the engine could possibly be built for almost double the normal c5r ALMS output. Pretty remarkable for such a "dead" technology.
The only fair comparison to make in my eyes it to pit full out race motor against race motor, where cost has little factor in the engine's design. In this environment, one will notice that the typical OHC setup is still making more specific output for its displacement, but pushrod engines have closed the gap cosiderably over their production counterparts.
In no way do I think the OHV engine is the superior design, but I feel that it is far from obsolete, as many people seem to suggest constantly. With metallurgy where it is today, I don't feel the pushrod itself is much of a limiting factor anymore in today's race engines (with the exceptions being engines like F1's that turn stupid high revs), but rather that there has not been a good consistent 4v head design for an SBC type engine pretty much ever, whereas pretty much every DOHC engine (and some SOHCs) support 4v heads. 4 valves will always flow better than 2 valve.
I have seen alot of OHV engines on stands, and OHC engines on stands, and I will say this about size; OHV engines are almost always considerably smaller. I remember seeing an older 4.3L Mercedes v8 one morning on a stand, than seeing a 454 big block Chevy later that day on the dyno, and I found the two engines eerily comparible in size. I know there are smaller OHC engines out there , Ferrari's v8s for example), but I have found them to be an exception to the rule.
One last thing. I remember recently there was a discussion on these boards about the c5r, and what that engine was capable of. In ALMS trim, the engine boasts in the 590hp area (correct me if I am wrong), turning at a lazy 6500rpm or something like that. This, of course, is with the engine also breathing through 2 half dollar size restrictors. I remember the Katech representative, when questioned about the engine's potential minus the restrictors, remarked that the engine could possibly be built for almost double the normal c5r ALMS output. Pretty remarkable for such a "dead" technology.