chuntington101

so are you guys honnestly saying that you would favour a 2 vales per cyclinder LS7 to a 3 valve per cyclinder one, even if the packaging was only slightly bigger???

if so you seriously need your heads looking at (aprdon the pun! lol)!!!

more valves means more flow! you already have the cubes! now its time for some heads to let you use them all!!!

Chris.

MrDude_1

iTrader: (4)

I highlighted the flaw in your logic.

once you correct that part, you might change your way of thinking.

redfulcrum

What is this guy talking about? Those 2 VALVE HEADS already flow from the factory over 360cfm. How much more flow do you need? That's already enough flow for a 427 to make max power at 8700 RPM at 100% VE. How much higher do you want to rev that 7 liter with your 3 VALVE HEAD. The damn thing already revs to 7000, which is unheard of for OEM. No single profile cam without variable valve timing/lift is going to idle smooth and make power at 9000rpm. I suggest you stop and think, and study some automotive theory before you just blurt out bulldoodoo.

chuntington101

try this one then! merc 6.2ltr V8 with 4 valves per cyclinder makes more than the LS7 out the factory doors!

andother one. a 100% RACE ford pinto (2.0ltr 4 pot) will make 240bhp at the crank, a camed and throttle boddied 2.0ltr zetec can do that and run over 35mpg and be drivable!!!!!

im not going to argue with you guys cos i know im not going to get anywhere! all im saying is a multi valve setup WILL make more power than a 2 valve setup! infact i think ithe maths says you get about 10% more airflow through a 3 valve per cyclinder as you do a 2 vavle.

but then i guess me and the rest of the motoring world are wrong, right???? and i guess you guys will b!tch if GM dose go 3 valve????

brace the future guys, you will go faster than if you go against it!!!

Chris.

chuntington101

hahaha well im sorry for telling you the simple facts!!! and i never said the 2 valve heads where crap!

and the way things are going, 500bhp is going to be nothing in a 4 door soon! i mean the new Audi RS4 is making well over 400bhp and the new BMW M3 will probably be shotting for 450bhp, thats not a million miles off the big headline figure of 500bhp the LS7 makes form the factory!!

also look at merc, they are pushing out big saloons with more and more power!

all im saying is for GM to keep up they are going to need to do something in the power department, and going for more valves seams a viable way to KEEP UP with everything around them. and at the end of the day all GM wants to do is make money, and to do that they need to sell cars! and at the minute, power sells!!!!

thank you Chris.

PS. im not having a go just saying what i have seen happening over the past 7 years!!!

treyZ28

The M5 is a crazy screamer. A very impressive but very expensive engine. Its backed by gear and futhermore when you start running into high specific output NA engines, the powerband becomes very peaky.

GM is not ignorant to OHC technology, but why would you use it if it doesn't do you any good. While its "cool" to make the same power with less displacement- what is the actual benifit if its a less efficient, bigger, heavier, more expensive engine?

While everyone is scrapping for 1% fuel economy, why take a step back to OHC and increase parasytic losses and weight?

OHV is a compact, efficient, cheap way - the "right" way. OHC is kind of like bigger fuel injectors. Its only benificial if warranted. There is NOTHING wrong with displacement. If I could figure why people think displacement is a design flaw and OHC is a correction, I'd die happy.

treyZ28

yeah, power sells. Thats why the Mustang went out of production and GM cant build F-bodies fast enough.

treyZ28

Slighly bigger? have you ever seen a Mod motor? Compare the size of a 5.4L DOHC and an LS2 or LS7

WECIV

I realize some of you love OHC engine...but the fuel economy and torque numbers do not lie.

Look at the fuel economy of a M5, F430, RS4, M3, or anything of that calibre and compare it to what a Vette will do.

Then look at thow little torque those engines make...most of our LS engines make more.

I realize OHV is an old design, but if it works best use it.

W

MrDude_1

iTrader: (4)

you have completely missed the point.

door is to your left.

RussStang

OHC is just as old of a design, at look at some of the engines of the above cars you posted. They make high hp numbers for their displacement because they get revved so high. That is pretty obvious. However, look at their torque numbers. Pretty low compared to an LS7, right? Look at the torque they produce per cubic inch. Look at the LS7s. They are producing more torque per given displacement than an LS7 is. Torque is directly related to volumetric efficiency, correct? Volumetric efficiency is the ability to fill the cylinder with air as dense as atmospheric I believe. To do that, you need a good pathway for airflow. The multivalve engines are ultimatetly flowing more air than the 2 valve LS7 does to produce a better torque to displacement ratio.
I am very well aware of the benefits of a 2 valve OHV setup; I have seen a 4.6 Ford and an LS1 on engines stands almost right next to each other, and the 4.6 is not "just a little bigger." It is substantially bigger. I have also seen a Merc 4.3 v8 in person, and that "little engine" is also noticeably bigger than an LS1. I am just saying that a multivalve engine will likely produce more peak torque given an equal displacement value with a OHV engine, and when tuned for the same power delivery in the same rpm range using the two equal displacement engines in this comparison, my money is actually on the OHV engine being peakier.

treyZ28

OHC isn't exactly new either. They differ in age by like 5 years... out of like 130 that "old technology" bit is weak. You wont buy 130 year old technolgy but you'll embrace 125 year old technology?

Torque is from displacement, compression and engine technology level. Whether the valves open from a cam in the block or above the block is irrelivent. Even still, tq is irrelivent. Its all about the power number when you're comparing performance oriented engines like the Ls7 and M5. You saying "we have more torque" is like them saying "we have more rpm"
both are meaningless on their own.

marv

iTrader: (40)

In my opinion, regarding the pushrod VS. OHC debate, as my dad used to say "if it isn't broke, don't fix it".

If GM is experiencing success with the technology they have (well proven I might add) and are selling cars, I can't see why they would want to change it.

OHC, and DOHC definitely have their advantages, but I'll take my 2 valves/cylinder, old technology pushrod motor anyday...

Just my 0.02...

FieroZ34

iTrader: (1)

I vote to go back to carburetors. They aren't broken.

Big-DEN

The whole OHC OHV debate evolved into a power-emissions vs packaging and weight, with complexity also thrown in.

Some of the DOHC's nearing 5.0L where as wide and big and heavy as big blocks with alumimum heads.

Is why the LS1 was always good, was physically smaller than the 4.6L ford. One camshaft instead of 4 to change. Less moving parts, easier to work on. LIghter than the Ford 4.6L, can rev nearly as high ( 7500rpm on stock bottom ends done so many times ). And makes alot more power. Some of these are making competitive power as the 4.6L without any power adders.

Plus a 7.0L in LSx packaging is still the same size, barely any heaver as a stock LSx.

OHC have large heads, because cams are put there up over the valves.

Ari G

iTrader: (25)

You make more TQ by 4 vales then 2 by VE% increase and you spin it higher without pushrods,these 2 factors play the biggest part with variable valve timing(vamos),thatīs why you can both get good economy and power output

You have allso tuned runner length with invidia throttle bodys and less exhaust backpressure thatīs not in the LS6 design

joecar

A few comments:

- DOHC doesn't necessarily make more power at higher RPM; but it allows higher RPM by virtue of less valvetrain mass;
- it seems 2 big-assed valves will flow as good as, or better than, 3 or 4 tiny valves (tiny because you now got 4 of them);
- the DIY hates cost and complexity; a DOHC V8 would have 4 cam$ rather than just 1, not to mention the cost of 3V and 4V DOHC heads; tell us you don't have a budget...
- seems to me engine has more durability if it makes 400+HP at 5200RPM vs 6700RPM;
- GM went with pushrods in the LS1 in order to fit the C5's low hoodline; and a OHC setup will just not fit the F-body (...what was that about the spark plugs on #6 and #8...);
- adjusting valve lash on a DOHC setup is much more difficult than on pushrods.
- GM's target is to do it cheaply (for them, which then filters down to us);
- we can get 500+ reliable hp with pushrods for a reasonable cost, why spend more doing this with DOHC only to have doubtful results;
- do you know any bimmer owners who are DIY...?

$0.02

redfulcrum

See, Joecar understands. Pushrod gets more power for your money, fits in a smaller package, weighs less, more durable, and probably has less parasitic losses.

You're right about revving a pushrod high, but that would take solid lifters and wouldn't idle very well for an OEM product. That was the idea behind variable valve timing, to have both worlds of idling and high revving. Some motors with VVT don't even go past 6500, I guess it's just used to boost low end torque and increase VE during lower rpms to help reduce pumping losses.

It really doesn't matter if a motor is OHV or OHC, or how many liters it has, CFM is CFM regardless. So with that being said, now compare the costs and you will clearly see that OHV is the winner.

redfulcrum

Another point I want to make is not many people are going to buy your MERC 6.2 or 6.3 and modify it. GM knows that if people want more performance out of it, people will modify it. That's why you have brands like World, edelbrock, etc.. It's kind of like paintball. No paintball gun comes with truly nice barrel, because they know everyone will buy an aftermarket barrel. So why go all out and overengineer just to make a few people happy when most people just want decent power for their money.

Presitgous cars have to make more power, people are paying top dollar for them. They can't make less power than a NORMAL car and expect people to pay more money.

Exotic cars make 600hp+, people still buy 400hp corvettes. Last time I checked, most people in this country aren't celebrities. I would say most people buy cars under $40,000. So, I don't think GM have to try to reach those astronomical levels of 600hp, at least not in volume.

I hope you don't become CEO of any corporation, Chuttington.

redfulcrum

Ari G, by the way, more liters with 2 valves(if the valves are proportionately sized) will make more TORQUE than going 4 valves and less liters. That's why most of those high rpm 4V engines have a torque/power ratio of about 2/3, and the ground pounding 6000rpm 2V have a ratio of about 1.

Small liters, high output motor just feels soggy. When I first got into cars, I was into the import scene, i had a supra and a rx-7. I thought they were fast, back in the 90's. I loved those cars, they seemed more technological and superior at the time. After the wankel blew up for the 2nd time, i decided to look into a v8 swap. That was an awakening. The LS1 matched with a RX-7 chassis was no joke. I fell in love with it. The throttle response, the USABLE POWERBAND, the simplicity of pushrods, and the best part, there was only one vaccumm hose, JUST ONE! If you're familiar with the 13B-REW you would understand the RAT'S NEST of vaccuum hoses and solenoid valves everywhere. An engine that was so small, so light, so simple, was the CURE for the RX-7. Highly recommened swap for those with time and money. The fuel economy was phenomenal. Torque was everywhere, no lag at all. I beat up on all my cars and I love the LS1, it just takes it. Rotary vs V8, no comparison. RPMs don't make up for less liters in my book. The rotaries don't even have valves, so they should in theory make lots of power. How come mazda call it a 1.3L and reference it to 360deg, when the standard is 720Deg. That would make my 5.7 a 2.85 liter at 360deg. For the same CFM it makes less power than a conventional engine.

With displacement on demand technology available, GM should be increasing their displacement, now that they can decrease pumpling losses by shutting valves down. When they need more torque or more power, turn the valves back on. That's an AWESOME idea. It's almost like VTEC, instead of increasing rpm ability, it increases displacement ability, which brings in MORE TORQUE and MORE POWER, instead of just a little more power and a wee tiny bit of more torque, and you're not putting crazy high rpm loads that requires exotic materials. It still gets better fuel economy than a regular V8, which isn't really bad for the gen III+ motors.