foryorent

what are the advantages ( or disadvantages ) of a 32 valve head for LSx engines? There is a company that offers them for CSB's and I was wondering what the actual technical benifits of such a set up might provide.

http://www.araoengineering.com/Chevy/chevysmb.htm

this is by no means a solicitation. just wondering about the technical differences.

thanks,
dan

SStrokerAce

iTrader: (2)

These things are a piece of work... I have a set for a LT1 in the shop and the things that need to be corrected on them to make them work take a LOT to do.

Anyways, what a 4 valve setup gives you is curtain area, lots of it. The head that I have in the shop is good to 8000rpm on a 400 cube motor with .500" lift due to the 2 intake valves.

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.

Bret

TransAm12sec

http://thirdgen.org/techbb2/showthre...ighlight=valve

chuntington101

major benafits of 32vlaves would be curtain area (more equals higher peak flow numbers), vvt is also easier and you can swing the timing (with adjustable pullies) whenver you want (great for setting up a FI engine). there are more (like less spring stress thanks to less parts the spring moves), but there are the downsides!

the major ones are weight (a big one) and size (they can make a V8 HUGE). you cant really get around the first one, unless you go for new materials like BMW has done on its new (ish) strght 6's, but these add a lot of cost to the units. as for the second, well again very difficult to reduce. it normally means going a smaller V angle or reducing the deck hight a bit. you could maybe use the cams to close the valves (like Ducate do) but this add complexities to the thing, increaseing costs.

have a look at the new Mercades Benz 6.3 V8 and the Lex V8. both are veery good (drag guys reputed to be making 2300bhp from Lex on production blocks!!!!!).

thanks Chris.

PS. do a search on the subject it has come up a few times!!

rons 00z

iTrader: (10)

As much as I love these heads Russ is this most difficult person to work with. We used to carry his heads till he lost his priorities. I won't dicuss our buisness problems but if your interested send me a PM and well see what we can do.

But as a FYI there is a ls1 head in design. when will it come out? Your guess is as good as mine. Also, look for a SBC 408 with a set of stage 3's and two big *** turbos in a gbody. Should be a rocket ship

TurboZ28

So if they're are 2 intake valves would it be:
(Valve diameter1+Valve diameter2) x Pi x lift?

Valkyn

iTrader: (8)

It would be 2R^2 x Pi x Lift

THE_SUPRA

that valve train looks alot like a 4-valve hemi head...sweet!

chuntington101

neslon racing has a couple of vids of engines runing these heads. they do look very good!!!!!

Chris

Old SStroker

No offense, but that formula gives a volume, not an area. (in.^2 x in. = in.^3)

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. There's no free lunch, so the pushrod side needs to be VERY stiff because it's moving 2 valves and their associated bits. Remember, the pushrod is the second weakest spring in the valvetrain.

chuntington101

BINGO!!!!!! well put mate.

its just a shame that a four valve head has to be soooo big!!!

CHris.

Old SStroker

It's not all that big. You could probably stuff an AERO-headed SBC into a Gremlin if you were so inclined.

racer7088

The curtain are is a limit until a certain valve lift and then the ports cross sections come on line as a limit. The main advantage though is:

1. As Bret said the curtain area and thus lower lift flow ramps up FAST so shorter cams can be run and yet still breath very very well. This allows better street manners and more power so it's a win / win mostly.

2. Also the valves are smaller and lighter and this allows more valvetrain control and rpm etc. so that's also a win / win deal.

The downsides are hokey weird low volume castings and weird geometries when trying to still use pushrods along with weight and complexity and extra friction to open and close double the valves. Overall it's certainly a win though and that's what you see unrestricted race engines running as well of course.

At lower rpm the 2 valves aren't that far off though and allow bigger engine with much better packaging and like usual cubes are easy power. Look at the new LS7 and what it can do. It has no equal in the smaller CID multivalve NA world really and all it is basically is a big *** pushrod engine with big *** heads. Seems like that is a pretty proven approach!

chuntington101

your right! racer7088, but look at the BMW 5.0 ltr V10! thats what can be done with four valves per cylinder! it will match the power of the LS7 (ok not the torque) with 2ltrs less displacement! imagine what a 7.0ltr version would be like!

but as you said it would be hard to package! so it means it can only be used in a bigger (read heavier) car!

as for the complexiy, well i dont think there are any problems with them. most engines these days are OHC and most of them are DOHC! i know here in the UK 7ltr engines dont exsist because it would cost a fortune to run one! thats why deisels have something like 50% of the market now! you can rag the nuts off one and still get over 30mpg! wonder how much boost the new BMW 3series deisel can take.........

Chris.

DavidNJ

The BMW is rather unimpressive IMHO. We actually have quite a few engines in that power range. Ferraris F430 is only 5% shy of the BMW's power yet has 15% less displacement. Lamborghini has a similar 5 liter V-10, currently rated at 520hp. Mercedes also has a 500hp motor, trading revs for displacement, it is 6.2L and 512hp. And probably the smallest packaging and most docile performance of this group. In reality, it is in a lower or similar state of tune than a G35 or BMW's new 6.

The there is the LS7 and the Viper/Ram V-10. Dodge does it with displacement. Lots of it. GM does it with lots of little tricks: very light valve train, very sensitive MAF, two-mode exhaust. GM also wins the smallest packaging.

If someone said to pick from this group for the best engine for a 24-hour road race, I'd pick the MB. My guess is it also has the highest ultimate power capacity of this group if built as race engine (with the appropriate bottom end, cams, intake, and exhaust.

qqwqeqwrqwqtq

I like that. I have some high speed videos of valvespring testing. Are there any out there that show pushrod flex? I think it would be interesting to see just how out of shape they get.

blackz93

iTrader: (2)

I'd like to see that as well!

Deep Blue

But haven't the factory Corvettes been scoring a number of wins in class (and once overall at Daytona) at Daytona and Lemans for the last few years using pushrod engines?

DavidNJ

Racing rules allow more displacement or less weight for OHV.

spy2520

iTrader: (3)

dont all those motors keep up by using a whole shitload more gas??? i dont think any of the italian cars are near 16/26 mpg like a z06, how much hp would a ls7 make if it used as much fuel as a lamborghini motor?? or would it not be able to use a comparable amount of fuel due to breathing restrictions of the heads??? i doubt that last one is possible...