ohthisthreadagain.jpg

I'm so glad everyone is wrapped up in flow numbers because its obviously the only factor that should be looked at when comparing or selecting heads.

Oh wait...

 

As has been said getting the mixture into and out of the cylinder is what it is all about. The good ls heads and intake do this as well or better than the 4valve heads and the heads are 30lbs lighter(each) and way less moving parts. The mpg figures for the ls engines also hint at the efficiency of the design. BTW I have a 500rwhp cobra 4 valve and I only wish it had a lightweight ls engine up front so it would not be so nose heavy.

 

GM could make better use of their 4.6L Northstar powerplant, but for some reason, they don't... I think it's that the LS series has been so successful and the OHV can come in a smaller package. Besides, for "serious" OHC power, multi-valve engines are almost required unless an absolute monster engine is built. That means more money in design and in building an engine. That's the case regardless of size when compared to OHV designs in general.

Cadillac did what? I think Cadillac had positively nothing to do with pioneering OHC, and as far as I can tell, other companies were using it some 20yrs earlier.

 

The LS heads move less total volume (only exception being the factory CNC'd LS7s on a 4.125" bore) with lower velocity despite having the advantage of much larger bores. The 4Vs have more parts but actually have less moving mass, and the cylinder heads can be made more compact than the 4V Modulars with direct acting mechanical buckets.

It hints more at the total package moreso than the engine alone. I would love to compare brake specific fuel consumption of the two engines, which is what will tell you about engine efficiency...the sticker on the window is just a snapshot of the whole story.

Al block to Al block, the 4V Modular is within 20 lbs of the LS1.

 

Is that block for block or entire motor to entire motor? One has a supercharger on it.

 

Wow we got some modular nuthuggers in here. Simple fact, mod motors don't make horsepower without boost & head flow numbers don't tell the whole story. I'd bet a built 4.8L ls motor will make more HP than a built 4v modular 4.6... Similarly, I'd put money on a 5.3 over a 5.4. But I can't prove those, so back to discussing things I can prove.

You want to know why they don't move to OHC? Because manufacturers have to meet a LOT of criteria you don't even think about (a car has to run the same in Alaska in winter, and in Saudi Arabia in summer), and then they have to make money on the car afterwards. The LS motor is developed to an efficiency level other pushrod motors can't dream of reaching, and because of that it is cheaper for GM to continue putting their very efficient OHV motor in their cars than it is for them to develop a seperate OHC motor.

As a side note, the High Feature V6s are some of the most advanced OHC motors out today, GM does not eschew the development of OHC motors, they have simply developed OHV V8s to an artform. OEMs don't think like we do, it's not all about what is best and makes the most HP. It just has to be slightly better than the next guy, do everything the government wants it to do, and sell and make money. That's their criteria.


Long story short: if it's not broke, don't fix it.


Quoted for truth.

 

Simple fact? There are mod motors other than the 4.6L and several have made near or over 300hp without a power adder, as sold by Ford. Today, Ford offers the latest rendition, a 5.0L which makes over 400hp in stock form... To take from that, the idea that Mod motors can't make power without boost is to ignore reality. Since the Mustang no longer gets a 4.6L, and since the 4.6L offered from 2005 on was over 300hp, using that as your example is essentially a waste of time making an argument that no longer exists.

As for S/C's themselves... Well, they exist. So it wouldn't matter if one was "needed" to make power because the option is indeed available. In regards to cylinder head flow numbers... While they matter, you're surely correct that they aren't everything. Overall design can improve or hinder one engine vs another which has greater head flow numbers. It comes down to the overall package, certainly not just one aspect.

I think that's about right. I've been saying for ages, it's about SALES... Keep in mind though, GM has made very good use of OHC engines already, for the past 20 plus years. They don't need to develop one... They can expand the program they have... That costs money though, and I believe GM won't push that envelope until emissions standards require it. The way our government is involved, it's coming. Some of the best engines and even entire vehicles ever created essentially go nowhere due to lack of sales. If I put 10K into production, but only get 10K for a sale, I'm not going to continue that route.

This goes in line with what I said above... Clearly you see this as many others, including me. It's not the OHC's can't get it done, but rather, OHV's can too... short only on emissions levels, which, if our government has its way(and it always does), will be their undoing. Hopefully, brighter, more educated minds will take control in that area, and slow the process of breaking what is working... By raising a standard which simply doesn't realistically matter(emissions) in the least.

Enter US government... It's broken...

 

That's not the whole story. What about the weight of the heads? I imagine a complete 4v head weighs considerably more than a complete LS1 head.

I'm well aware that the most of the valve train is contained in the heads of the 4v, but I think the OHV setup would still weigh less even if you add in the weight of the lifters, pushrods, cam, timing chain and the like.

Maybe having the weight of the DOHC setup being higher up lends itself to a more "nose heavy" feel when it slightly raises the center of gravity.

 

http://www.coatesengine.com/csrv.html

done.

this is the only thing i would take over a simple 2 valve setup, bc the limit is non existent. the heads in the link posted, dont take any coolant, or oil. completely dry motor from the deck up. rpms would no longer be dependant on valve springs etc. they would only be limited by the bottom end. the noise reduction would be amazing too

 

http://www.youtube.com/watch?v=pDsRa4eT7co

 

this head design was created to lower emmissions. but other benefits include:

reduces emmissions
does not burn oil
eliminates cams
can use higher compression ration
more volumetric efficiency
reduces fuel consumption
lower hydrocarbons
less oil changes
engines with these type of heads have had oil tested at 50k miles, and was like the typical 3k mile oil change
doesnt require any modifications to block
no hot exhaust valve to cause detonation in high compression apps.
fully open ports, no valve to be in the way of flow
no horse power wasted to turn cams, pushrods, compress springs ect.
no valve float
no pcv system needed

 

i could see a problem there.

if the head is completely dry ( no coolant and no oil) the cylinder head will warp in a very short period of time

 

Seems they've been available for at least 10yrs now. Apparently it's a 2piece design and that may help prevent warping, or make it worse.

Way back, seemingly in about 1997/8, I remember reading about them in several magazines and thinking it would be nice to have 5K to toss at my cylinder heads. Back then, I just couldn't see it, but I sure wanted to give it a run.

One magazine(or more) showed them on an otherwise stock(save their parts) 5.0L Mustang engine and I could swear they advertised 500hp... Then again, they also waste little time claiming the engine could theoretically reach over 14,000rpm as well, and we all know basically any V8, and certainly a 5.0L of old, would blast apart well before then. I can't imagine 10K, let alone 14 in any old style V8.

The idea though... outstanding!

 

they were really gonna bring back the LT5? any more info on this?

also that rotary valve set up looks pretty tit! wonder who will be the first major automaker to adopt it?

 

You'd lose both of those bets. Built 4.6 4Vs (.030 over, stock stroke) are making over 500 rwhp N/A in Pure Street, and there are built stock displacement 5.4 4Vs making over 600 rwhp N/A.

And stock for stock, both the new 5.0L and the Boss 315 (which uses Mach 1 heads) put more to the wheels than the LS3s in the Camaro SS and HSV GTS.

 

they have a test motor in a ford car that has over 150k miles on it.

 

one thing i just now realized, the rotary valve sytem would have 1 major benefit, more important than any other, no ptv clearance issues, you could have "full lift" or "full flow" at tdc!!! that would be amazing, instead of having to wait for the piston to drop to open a valve. you could have 350+ cfm(just a guess) for the entire intake stroke!

 

Only problem i can see with this is sealing thing tight enough. how are you going to seal the "valves"? Also it looks like there would need to be some bearing material on that shaft,or they would need to be oil in the head.......

An alternative might be tyo develop something like what Ducati use. The cams actually drive the valves on both down and upstrokes. The negates the need for valves springs totaly. however it dose add some complexity to the top end of the engine.

F1 cars and GP bike use pneumatic springs insted of coils. these are MUCH faster reacting and can be pushed to MUCH higher RPM.

 

From the looks of the Coates head, the "valve" and "cam" is essentially the same part. There's no real valve train and the system is sealed. Sealed bearings certainly aren't new, and sealed ball bearings have proven to be a pretty solid idea.

This technology isn't new though. If it didn't work, they'd know by now. The drawback for most seems to be initial cost. Over time, we find out what's best for the wallet and many people simply haven't seen this design at work, so they don't even consider using it themselves.

Pneumatic springs are another idea I've read about recently, but that's been around awhile. Sounds like a great idea for certain applications, just as the Coates head does... Which it's best for, or not... Well that's where people get concerned. And we don't like change as a rule, individually, which both of these ideas/designs are.

 

Yeah the new 5.0 motors are killer but I still am happy with pushrods..

As for comparing Pure Street, Hot Street, Factory Stock, or any other NMRA mod motor.....Really???? How much time and money are in those motors??

Here is what I will bring to the table, stock blocked - stock headed - cam only ls1's going how fast?? Sure the Ls motor has more cubes but the Mod motor has how many more valves and cams? There is a trade off with everything

Like I have said before I prefer pushrods, has nothing to do with Ford or Chevy. I would just rather have pushrods. You prefer mod motors that is cool.