93sspcoupe

ah ok. i thought we were refering to stock size dohc lol. either way its good info

BOBthe4dH8r

iTrader: (1)

i cant think of one good reason why GM should make the transition to OHC motors. ive worked on 4.6's in rustangs b4 and it makes me wonder "WHY THE HELL" people buy them! like the saying goes- ''if it aint broke, dont fix it''-. GMs pushrod v8's punk on almost everything out there, so there's really nothin much to gain from goin to a ohc/dohc v8,imo. especially since vvt came out on LS's.

plus its fun to say "you just got beat by 60 yr old technology"


+1 = pushrods

= 10 ft timing chains

Fbodyfan

GM did have an DOHC V-8. The LT5 in the 90's era ZR1 was a dual overhead cam engine.

elias_799

iTrader: (8)

you can have 4 valves per cylinder with a pushrod motor

brian.moritz

I didn't know the new LS's had VVT. I have that in my DD. Do you know if it works the same? The VVT in my daily driver when you hit a specific RPM a pin locks the rocker to a middle rocker and that rides on a different cam lobe. The hole concept is cool.

Also, talking about 'future' some day we'll be talking about how many watts our electric motor is not HP. I'd say 15 years maybe.

brian.moritz

and a little googling...

Variable Valve Timing - The Next Phase
http://www.hotrod.com/techarticles/e...s_engines.html

Paint_It_Black

iTrader: (1)

The only reason DOHC engines make more power (from the factory) than pushrod engines is the 4V/cyl. The combustion chamber doesn't care if the engine is DOHC or OHV. The 4V head is not what we call in the industry "valve limited." Once you open up a set of 2V heads to flow what a 4V head will, the gap is closed. It's all about air in and air out.

VVT and VTEC and all that other mumbo jumbo is there for one thing and one thing only: low end power and cruising MPG. It has no advantage in a race over a car with a single cam specced for top end power. It is akin to running 2 cams in one engine because there are optimal valve events for cruising around town and optimal valve events for a wide open throttle drag race. It just does both, it doesn't do one or the other better than a single cam specced to do one of those things.

RaggedRides

iTrader: (8)

Word. Ford built plenty 32 valve Clevelands back before Windsors began gaining popularity. Excellent heads for antique, oem pieces.

SparkyJJO

iTrader: (11)

Why? What's the facination with DOHC?

Use a chain. But also they are more expensive, harder to work on, costs more to mod.

Not necessarily. They can be more complicated actually, my gearhead friend commented on how much of a pain it is to adjust the rockers and measure for the shims and all that on a DOHC, while on a pushrod with hydraulic lifters it is much easier to adjust properly.

Nah. GM is very good at making efficient, strong pushrod engines. Don't want them to screw it up by attempting a DOHC version. They've got the pushrod down pat. Leave the DOHC to those who "know" how to make them. I don't want one.

slow

iTrader: (7)

When an OEM makes an engine, they have the following priorities to worry about (there are a lot more, but this answers the question)

Packaging size
Power output
Emission
Weight
Cost

Lets compare the 5.0 mustang motor to the LS3

LS3 is smaller
LS3 makes more power
LS3 is lighter
LS3 is cheaper (parts are used on all ls series of motors to get quanities of scale vs a single application)

The last time I was having a beer with some GM employees at a Ford event, this question came up.

Ryan

06 6.0 GTO

Lot of misconception here. OHV motors came out AFTER OHC motors, but thats irrelevant as this was "NEW technology" in the early 1900s.

RPM WS6

iTrader: (3)

Doubtful. An industry wide shift from currently building 99.9% gas or gas + electric cars to 100% electric-only cars in just 15 years is highly unlikely, especially for the performance based platforms. I expect to see new gasoline/hybrid engines still being built well past 15 years from now.

Agreed.

I also agree completely with this:

Things like VVT are a concession for better MPG while still delivering higher peak power under WOT conditions. If you remove emissions and MPG concerns (like many/most of us do when modding), all that variable valve crap does no good and only serves to complicate the engine.

brian.moritz

Guess it really depends on gas prices. When they get back up to $4, $5, even $6/gal there would be a lot of motivation to switch. Whoever cracks the hydrogen nut will be one well off dude. Hybrid cars are a waste of time IMO.

Performance cars might be the some of the first places you see all electric. 13.2 sec 1/4 in a tesla all electric car is pretty respectable. Take out 900lbs of batteries and replace them with a hydrogen fuel cell. That could be one fun kick in the ***!

Also want to say that I have no hard on for OHC. Just from the little that I knew the concept seems good. My first car was an Eagle Talon with a 2.0 DOHC and that was an impressive motor. Once you make it a V motor things get exponentially more complicated. I didn't know or realize that and that was the hole point of me starting this thread.

WSsick

iTrader: (13)

1. it would no long be an LS motor if its OHC, considering LSx architecture is all OHV based.

2. as others have proved, OHC vs OHV isnt where the power is made. an engine is an air pump, air in & air out. more is better.

3. why fix what aint broke? especially considering the r&d $$ behind building a new series of engines with GMs current situation. they have been kicking *** with OHV for years with big power, great torque curves (big design goal for the LSx engines), lightweight, small in physical size, etc.

shaun

i dont think a dohc motor would of even fit in the f-body platform.
i dont think the make more power it took ford to put a sc on the gt500 to make 500hp and the z06 does it na

06 6.0 GTO

The Z06 has 7 litres and revs higher.

In the end its tough to beat displacement.

SOMbitch

iTrader: (8)

So what it is still smaller and lighter..........

RPM WS6

iTrader: (3)

I know this is all opinion based, unless someone here has the ability to see the future. But I really don't see a complete switch happening in 15 years no matter what. The economy will still take years to fully recover, and if there was a sudden spike to $5-6 gas right now (or in the very near future), it'd send the economy further into the ******* and demand would drop, thus prices would follow (like what happend last time gas prices super-spiked). Point being, I don't think gas prices will stay that high long enough (in the near future) to force a complete industry shift in such a short time.

Whatever may replace gasoline, the technology will be more costly for quite a while, further prolonging a complete shift in consumer buying habits. Even if they started rolling out 1-2 new 100% electric car and truck models from every major OEM today, I still doubt that gasoline engines would be totally off the order sheet within 15 years. It will take a long time to get all the consumers on board, and for prices to equalize between the two.

But, I think hybrids are a better idea currently than 100% electric cars.

Arc00TA

iTrader: (17)

Yep. As a matter of fact you CANT beat displacement. FI is only artificial displacement in the end, just more mass of air into a smaller volume.

RedVertTA

iTrader: (9)

There are 4 valve aftermarket lsx heads available. They use a forked rocker to push 2 valves open at once. Great heads, flow over 400cfm I heard. Based on the pics I saw I had trouble picturing those heads fitting in my TA and not having clearance issues with the wheel well.

I'm completely sick of hearing people measure an engines worth by power to displacement. A much better standard would be power to engine weight.