Z06Cam

There is a discussion on another forum regarding the merrits of a 3 valve head, such as the design many people think the LS7 will employ.

To me, a 3 valve head makes sense. You get more air into the the engine, without the problems you encounter in port velocity and smooth airflow when you use one big valve instead of two smaller ones.

However, someone on another forum seems convinced that a 3 valve head is inferior to a 2 valve head.

I'm no automotive engineer, but that doesn't make any sense to me. If I'm wrong and he's right, can someone explain why?

Let's discuss!

GMCtrk

iTrader: (23)

more air = more power

Z06Cam

That's more or less what I said to him, although I used a few more words to get my point across.

He also said:
WTF?

Z06Cam

Here's what the SAE thinks about the design:

Z06Cam

I think you're right on about VVT, but the technology isn't there yet, is it?

As for OHC technology, it's been around almost as long as pushrod technology. OHC motors are generally heavier and less efficient (specifically when it comes to fuel economy). I could go on, but I believe that arguement has already been beaten to death.
https://ls1tech.com/forums/showpost....2&postcount=24

3-valve heads a gimmick? Seems like A LOT of effort that will do nothing but **** everyone off in the end when they don't deliver. GM's made some dumb mistakes IMO, but I give them more credit than THAT.

pman

iTrader: (6)

We are doing the machine work for the 3 valve Vette heads and the V10 version going in the HDs. We have been told we'll get a ride in a car with one of the 3 valve setups in the next month or so. I'll let you know if its a gimmick

Z06Cam

Wow! Can I ask who you work for?

pman

iTrader: (6)

LSM Motorsports...we are going to be working on most of the valvetrain... cam and springs. Camshafts are our speciality but we are a full machine shop.

Z06Cam

Any ideas or comments on the sort of cam design you would use to take advantage of a 3 valve head?

pman

iTrader: (6)

I'm not a cam guru but i'll see what i can divulge tomorrow.

Z06Cam

Cool- that'd rock if you're allowed to say anything about this.

When I saw some of the data on the 6.4L GTO concept, it made me wonder if the motor it uses will be similar to the LS7 setup.

Here's what someone posted about it:

It was really those cam specs that caught my eye. Look at all that freakin exhaust duration!!!! Probably not a cam that you'll find in a production motor, but when you look at the intake duration relative to the exhaust duration, it's very tempting to think that cam was designed to take advantage of 3 valve heads. If nothing else, it's interesting to think about.

rons 00z

iTrader: (10)

i think ohc motors were out before pushrods motors.

and to piggyback on the 3 valve heads from a good source there should be a aftermarket 4 valve head out with in the next few years. but i dont want to realese any info untill that product is actually tested

rons 00z

iTrader: (10)

push rod motors or overhead cam motors? if you mean overhaed the lt-5 is a good canidate of it not sucking and well the pushrod motor is no slouch either.

PSM

iTrader: (2)

Typical of GM they are releaseing their plans in steps. The 3valve head is step one. What the valve positioning has allowed for, is the ability to place the fuel injector in the head giving the motors direct injection(more power and more efficient ). GM also plans on using two camshafts, 1 for intake and 1 for exhaust. This will also allow them to mimic variable valve timing through a cam phaser that varies the intake cam. So when you add up all three steps you get: a direct injected 3 valved pushrod w/ variable valve timing. Course by the time GM actually puts all three steps together Ford will have its camless motors

GoldenVelvet

If something is better then the other the weaker one dies. That why all cars use hydraulic brakes now instead of the mechanical friction type used on the original horseless carriages. If overhead cam was better then push rod, when GM spent millions design a new V8 it would have OHC. And let us not forget the nut less wonder that is the Ford 4.6. In its first incarnation it was much slower then the push rod 5.0 it replaced.
There are several advantage to multi valve heads, as well as disadvantages. Disadvantages are, cost and more precipitating mass. Causing parastetic loss. The advantages lager total valve size with less shrouding. (Ex. A single 2” valve vs. two 1” valves) and architecture. Allowing for placement of components that would not be possible on a two valve. There havent been any truly original designs on the automobile in fifty years just improvements on old ones

rons 00z

iTrader: (10)

gm spent millions on the lt-5 which is a dohc v-8 dont know why they didnt keep production but they had it and it's alot better motor than the ls-1 it's all about r&d those exotic european cars have ohc set ups and alot of them are fast as **** and run well at the same time.

Z06Cam

As cool as the LT5 was, as I remember it was pretty inconsistant in power output, expensive to produce, and difficult to work on.

granitemonkey

But alot of those exotic cars dont have anything down low, most of them rev very high. I would think the LS1 has got them on lower-end torque

JL ws-6

iTrader: (50)

My biggest ocncern with eh 3 valve head is that the entire thing looks fragile to me for racing purposes, that 2nd pushrod for the exhaust valve is a little scary, and the lifter for the 2 intake valves is gonna have to be really beefy to take the abuse of high rate springs, which makes for a heavier valvetrain. I thought that heavy valvetrain was the one downside of a pushrod motor, it looks like they are making the entire valvetrain even heavier than normal Has anyone else thought about this?

Z06Cam

The thought has crossed my mind. That setup looks like it'll need some tough lifters and hardened pushrods.

I would assume that the effects of having a heavier valvetrain are more than adequately compensated for by the additional airflow and more efficient combustion.