Changing the heads on standard V6

[kreel]

Quote:

Originally Posted by Tim_K While we're talking about power curves, I have another question. With its very short 2.99" stroke, how is it that the 3.0 makes so much bottom end torque and mid range power? My guess is the very short cam timing, keeping cylinder pressures fairly high at low-mid rpms.

Long intake runners are part of reason for our low-end torque as well.

[Ondonti]

wow turbo3.0 you REALLY dont know how to read and now you are making up stuff that I said.

Why dont you go back and QUOTE ME instead of BSing what I said.
Thanks. Bye.

Im glad Ed can read very well and make great posts.



Turbo3.0 you need to learn the difference between REALITY and THEORY.

The Fact is that sohc 12v's are currently the king of n/a 6g72 power......and there is a LOT more to get out of them.
Dohc 24v's could make 20-30whp more then the most maxed out 12v if you built them to make power @ 9000 rpms and have a 10k rpm limit. I dont think you have any idea how much work that would take.
That engine would not run very well from 1000-3000 rpms.
I know nelsons big cam'd dohc turbo 6g74 idles @ 1800 rpms.
But Im talking about facts. Im sure the sohc guy had lots of custom headwork done (like redoing the ports) but it was still a 2 valve head.



Im sorry your theory is based on....very little knowledge of the platform.

Do you know what it takes for a 6g72 dohc to rev to 10k???? I know you dont.


Since you live on the east coast why dont you ask someone who had an alky fed 1800hp 6g72 in a rwd tube frame dragster. And that guy was running sohc heads Someone now (Nelson Performance Pro) is building a 2000hp dohc 6g75 BUT that motor is a custom billet crank stroked to 4.9 liters AND the cylinder heads are custom pieces, not stock dohc heads
Just thought you should know that a stock 6g72 crank (stock forged not cast) sohc head motor has made 1800hp, competed out on the east coast but I believe he closed up shop. Call Nelson performance pro and maybe you can get some info about that guy as they are supposedly friends.
Like Ed said. you can make power with 2 valve heads, you just need to know what you are doing.
Anyone who knows how to build huge HP out of 2 valve heads knows you have to get the right port work for your powerband and the right valve sizes, and then run huge camshaft durations to make up for any inefficiencies in the sohc heads.
Thats why 600ci big blocks have .900" lift and 340+ duration.
When you get to that point with either 4 valve or 2 valve heads, your valvetrain wont last long.


And I dont want to hear ridiculous stories about f1 cars that run 18000 rpms with pneumatically controlled valves. those engines idle @ 6000 rpms and nowadays are running 22k+ rpms.
Those things are nothing like the motors being discussed.

[Ondonti]

Quote:

Originally Posted by Turbo3.0 You seem to be basing everything on one source and a lot of guessing that you claim as "reality". Your original claim was that no 24v 6g72 could ever come close to making the kind of power those 12v engines were making. What I'm saying is that with two identical engines, the one with the capability of flowing more air will have the higher power potential. This assumes identical flow characteristics of the ports, cam lift/duration, and scavenging through intake runners and exhaust tuning. Who's to say no one has built a 24v engine that revs to 8 or 9000? I dare you to go onto a Honda forum and tell them that they can't build an engine that makes power at 9000+ rpms and not be streetable. Get some new sources and maybe some comparison data with similar mods and I might start believing your bs. You might also want to consider reading a few of those books on engine theory "that I base everything on" and stop basing everything on a couple examples. Also, how does my drivetrain power loss statement make no sense?

This is a conversation about 6g72's here.

6g72's in the USDM so not have variable valve technology like hondas do.

I KNOW PEOPLE WITH DOHC MOTORS MAKING POWER @ 8000-10000 rpms BUT THEY ARE ALL TURBOCHARGED.
Those motors idle @ 1800 rpms.

I know what Im talking about. This is reality. This is not Theory.




Here is a list of 6g72 shops/vendors you can call.
Ask them if a Dohc N/A 6g72 with cams etc to make peak power at 9000 rpms will be a street friendly car.

3sx - ask for chris
IPS - ask for renner
Dyamic Racing - ask for matt
Nelson Performance pro - ask for whoever
Pampena Motorsports - ask for Ray
LSE - Ask for Josh (niterdyr)

And I think I could come up with a few more then those that came from the top of my head.
I can look up phone numbers for you if you really want to keep BSing about things you know nothing about.


BTW most I have ever seen a 6g72 dohc dyno is 210whp and that was with about 5000 dollars in mods according to the owner.

I know Ed can get 210 out of a sohc 12v with a lot less $$$ then that.
He could easily do the same or more with a DOHC but it has not been done, and that is what we call reality.

[Ondonti]

Quote:

Originally Posted by Tim_K Someone look up the specs on the 1/4 mile times and speeds for stock 24 valve cars, like Stealths and 3000GT's, and compare them to stock 12 valve cars. Then we can use an online dragstrip calculator to get some WHP numbers for comparison. My '93 Shadow ES ran mid 16's at 82 mph before I started doing some light mods on it. With 3100 pounds racing weight, that equals 136 HP. I went to google, typed in 'drag racing calculator', and used the Ray Hall one for my numbers. I've never understood why so many 4 valve per cylinder twin or 4 cam car engines have such low amounts of valve lift. It's ridiculous. They give you more valves and cams, and take away lift! And the answer "because they don't need more" isn't a good enough answer. If 0.300" lift gives you "X" power, then 0.400" or 0.450" lift should give you the ability for "X+" power, assuming everything is properly set up. Why not USE the flow capabilities of the multivalve heads if you have them?

One thing Ed didnt mention (i have already stated this too)

Valve lift is something you usually figure out based on valve size.

4 valve heads have very small valves.
2 valve heads hav every large valves in comparison.
I dont have the equation right here but there is a way to estimate the lift you would want to have to get good hp in the 7500 rpm hp area.

You have to lift the 2 valve setup more because he larger valve needs to get father away from the seat to open up equivilent space. Just imagine taking the small dohc valve and seat and making them expand into the size of a large valve in a 2 valve motor. WHen you do this the valve gets father from the seat (at least when you measure with a ruler...the ruler is not getting larger). Does that make sense?

We cant just lift every valve .450"
a 2.2" valve in a big v8 will want .600" lift of more to make high RPM power while a 1.2" valve in a dohc engine will only want .325" lift

[Ondonti]

Quote:

Originally Posted by kreel Long intake runners are part of reason for our low-end torque as well.

Even though some of Ed's dyno tests show greater torque increases by adding another inch onto the intake runners.... I think Tim is correct that most of the low RPM torque is caused by the tiny cams.
We know they are tiny, and thats what tiny cams do on 2 valve engines.

My short runner intake doesnt have a bottom end torque loss so i would say that our stock intake only accentuates the low end torque but probably doesnt cause any large differences (unless a few low rpm hp is large).

[Ondonti]

Sorry I had to edit some of my posts because i was being stupid and though this kid might be robert hassler (owner of prototype 3.0's) and I was shocked to read some of the BS but now i realise its just some kid.

He is spouting off because he dumped his 12v project for a 24v dohc motor which he doesnt know much about other then the hp numbers on the window stickers.
Too bad. Education helps. I know he is going to school so maybe he should study his car stuff too.

6g72 info is very plentiful if you look, especially for the dohc heads.

kid who blew up his sohc turbo because he was using an SAFC which doesnt work correctly on our ECU's
Another thing he should have known about.
Even a psychology major knew that.

[c2xejk]

Quote:

Originally Posted by phantomrt Just a hunch.

In order for that to be reasonably true, the 4-vavle/cyl setup would need valves about the same size as with the 2-valve/cyl setup. That is _not_ the case. The 2-v/cyl valves are much larger... Plus there is room to increase the size of the valves. (remember what I said about the bore size of the 3L...)

The one question that nobody has bothered to ask, "how much cfm is needed?" Not to mention "how important is quality vs quantity of flow?"

[87turbodance]

Quote:

Originally Posted by c2xejk The one question that nobody has bothered to ask, "how much cfm is needed?" Not to mention "how important is quality vs quantity of flow?"

Quality of flow is very important. Low valve lift numbers are very important as well. Valves spend more time at lower lift then they to at their maximum lift. I have always read that 24V motors benefit from better low lift flow because they have 2 smaller valves which increases velocity through these valve are creates very good low lift flow numbers. I also know that GM has done extensive work with their 2 valve heads. Some of GM beats flowing GM heads are 2 valve heads. I think of the Corvette as an example. GM went to through a ton of trouble back in the early 90's to have Lotus make a set of 24V heads for their ZR1 Corvette. These heads added huge costs to the car and GMs latest 2V heads make more power then the 32V heads on the ZR1. GM put 24V heads on the 3.4 in a very car for a few years but they ended ditching the 24V heads after a few years and going back to the 2V heads.

This makes me wonder if the 24V heads really worth the effort. I have thought about the 24V heads because if you compare the 24v heads to the 12V heads (all SOHC) them the 24V ones do flow better out of the box IMO. They are a newer designed head and should flow better just because advances in technology alone. For someone who doesn't have a flowbench or any prior porting knowledge they might be better off with a "bolt on" head that flows better out of the box. We can argue until we're blue in the face about which makes more power and overrated this and underrated that but until we make a direct comparison who really knows. I would never dream of installing the DOHC heads on one of our motors but the SOHC looks like it could be done providing a few thing fall in place. If someone intends to build their own exhaust manifolds or header anyway and intends on going stand alone regardless of what heads are used then why not give the SOHC 24V heads a try - without touching the heads the 24V ones will flow better (in theory ). If you intend to have the heads flow benched and you go all out then perhaps the 12V are a better choice. I intend to grab some cam gears from the wreckers soon and compare the SOHC 24V ones to the 12V ones and hopefully they wont be too different.

I really wan to try the SOHC 24V heads myself but I'm too cash strapped at the moment to buy a pair of heads let alone and tig welding for a set of headers. So who wants to be guinea pig?

Ryan

[kreel]

Quote:

Originally Posted by Ondonti Even though some of Ed's dyno tests show greater torque increases by adding another inch onto the intake runners.... I think Tim is correct that most of the low RPM torque is caused by the tiny cams. We know they are tiny, and thats what tiny cams do on 2 valve engines. My short runner intake doesnt have a bottom end torque loss so i would say that our stock intake only accentuates the low end torque but probably doesnt cause any large differences (unless a few low rpm hp is large).

Ok, but in theory our long, curvy intake runners should result in low end torque versus a short, straight runner which would help high rpm hp, right? Have you or anyone else done dyno runs comparing the 2 styles of intake runners on our engines? I'm just curious about what *should* work and what *does* work on our engines.

I agree that the cams are the biggest cause of low-end torque...I'm just saying that our intake runner (in theory) should help it too .

[87turbodance]

I imagine our intake runner do a good job of killing top end performance but create a nice big torque spike at the RPM they're tuned for. I imagine a short runner intake would make for a flatter torque curve (I'm assuming our curve is peaky due to the long runners but I've never seen a 3.0 dyno graph) but with a lower peak number and more HP up top

[87turbodance]

I posted some stuff then realized it was for a damn 4G64

[RoadWarrior222]

I'm thinking what's the point of a bigger cam, then going to a smaller valve to keep flow up. That's gonna suck for low lift flow.

Though I'm thinking crazy again now, pondering going for stupid high static compression and enough camshaft retard to put it close to atkinson cycle.

Edit: retard retard.

[c2xejk]

Quote:

Originally Posted by 87turbodance Quality of flow is very important. Low valve lift numbers are very important as well. Valves spend more time at lower lift then they to at their maximum lift. I have always read that 24V motors benefit from better low lift flow because they have 2 smaller valves which increases velocity through these valve are creates very good low lift flow number

Sort of. When you talk "low", "mid" and "high" lift, you need to consider valve diameter. High lift for our 43mm (~1.69") valve is much lower than say for a 2.25" valve...

The throat on area on a valve can simplistically be defined by A= pi*r^2. The curtain area is determined by C*valve lift. C=2*pi*r. So as the valve grows in diameter, the throat area is growing by a square, while the curtain area is only growing linearly (with respect to vavle diameter...) To compensate, the valve must be lifted higher...

The rule of thumb is you need to lift the valve ~.25*diameter for the throat area and curtain area to be equal... For us that is about 0.43", well under the stock lift...

Quote:

I also know that GM has done extensive work with their 2 valve heads. Some of GM beats flowing GM heads are 2 valve heads. I think of the Corvette as an example. GM went to through a ton of trouble back in the early 90's to have Lotus make a set of 24V heads for their ZR1 Corvette. These heads added huge costs to the car and GMs latest 2V heads make more power then the 32V heads on the ZR1. GM put 24V heads on the 3.4 in a very car for a few years but they ended ditching the 24V heads after a few years and going back to the 2V heads.

Not just GM. Look at what the Viper engine is doing too... They just added an adjustable exhaust lobe to it for even more power and streetability.

As for the 3.4L, that was just a plain messed up, cobbled together design... High warrenty costs did it in... It was a fun engine to drive, but a nightmare to work on...

Since the early 90's there has been some radical improvements in port design. 2v/cyl Corevette engine came with some legacy ports. Since then engineers have gone back and redesigned the ports and made them much more efficient. Same size valve, but now with a lot more CFM...

4-v/cyl can has a distinct advantage when the bore is small and the stroke is long. Or when RPMs are very high... I suspect many 4-v/cy had an advantage because they were for the time a "fresh" design. The port was designed with all the latest knowledge of flow efficiency...

Thus it was largely an "apples vs oranges" comparison. Now, much port design knowledge is being put to use in 2v/cyl heads and they are making dramatic gains.

Quote:

This makes me wonder if the 24V heads really worth the effort. I have thought about the 24V heads because if you compare the 24v heads to the 12V heads (all SOHC) them the 24V ones do flow better out of the box IMO. They are a never designed head and should flow better just because advances in technology alone. For someone who doesn't have a flowbench or any prior porting knowledge they might be better off with a "bolt on" head that flows better out of the box.

The problem is 24v is not exactly "bolt-on"....

On the other hand, there are people like myself that can do the 12v porting and the price is not outragous. If you still want to tinker, trust me there are issues like providing enough fuel that need to be taken care of.

Quote:

We can argue until we're blue in the face about which makes more power and overrated this and underrated that but until we make a direct comparison who really knows. I would never dream of installing the DOHC heads on one of our motors but the SOHC looks like it could be done providing a few thing fall in place. If someone intends to build their own exhaust manifolds or header anyway and intends on going stand alone regardless of what heads are used then why not give the SOHC 24V heads a try - without touching the heads the 24V ones will flow better (in theory ).

The problem can be size of the project scope and creep of scope... Projects tend to get larger, not smaller. The old addage "the first 90% of project uses 90% of the budget. The last 10% uses 90% of the budget..." applies to time and money... Been there...

Quote:

If you intend to have the heads flow benched and you go all out then perhaps the 12V are a better choice. I intend to grab some cam gears from the wreckers soon and compare the SOHC 24V ones to the 12V ones and hopefully they wont be too different. I really wan to try the SOHC 24V heads myself but I'm too cash strapped at the moment to buy a pair of heads let alone and tig welding for a set of headers. So who wants to be guinea pig?

If you are cash strapped, you might consider going with a MIG welder. Or paying somebody to do the welding.... Another alternative, some community colleges have nice welding equipment. I have heard of people taking a welding class just so they could have access to the equipment...

[87turbodance]

Well, right now I'm just setting my self up to start a 11 month long welding class. The cost is 15,000 but in the end I will be a licensed welder and I will learn MIG, arc, TIG, Pipe and some other interesting thing. Once I finish the assigned projects in the class I'm free to weld whatever I want... Hello stainless log manifolds and turbo flange, custom intake.... and whatever else I can think of. I have my Megasquirt almost complete and an A543 ready and waiting. As for myself, I'm 90% sure I'll be running a 12V head with with custom cams and a 50trim. I'm really interested in trying a 24V head though.