2v TF heads or 4v power these days?

[D3VST8R96GT]

3v?!?!

The D3V

 

[Burninrock24]

Ok burninrock24...a little quiz for you. What is known by the use of 2 intake valves in a cylinder? Your answer can not be or related to "more flow". Im not trying to be a smarty pants but i am offering the readers a challenge.

Alrighty then! With twice the amount of valves you need twice the amount of camshafts, twice the amount of springs, twice the amount of essentially everything in the cylinder head. Which leads to more friction and that leads to more heat. You could argue that with two intake valves you run into an issue of valve shrouding on both ends. At low RPMs having two intake ports does hurt air velocity and doesn't promote mixing as much. You could also say that the CC design of a 4v head doesn't promote mixing as much.

BUT

Every real world example of this in calculations and actual testing show that a 4v valvetrain is superior in the bottom line given everything else equal. With less valve travel needed, there is less valvetrain inertia leading to less valve spring float. And with high HP applications, 2vs need longer duration and overlap cams than 4vs do, so whatever low-end torque gained by being a 2v design is largely nullified by aggressive high RPM cams.

Sure, you can say that there are 2vs that make tons of power like the LS powerplants, and plenty of people on here. But they make that power because of displacement, not as much the valve train design. All the highest HP/liter cars on the market right now are 4v designs, and you'd be hard pressed to find a 2v V8 being made anymore outside of the LS series.

That's just about all I know regarding the topic.

Quick weblinks: http://www.forgecycle.com/FF/2v4.htm

http://www.billzilla.org/2v4v.htm

http://www.motortecmagazine.net/article.asp?AID=1&AP=5 some info regarding both sides of the coin. Written by our buddy David Vizard and he likes the 2v valvetrain.

 

[97stanger]

^ good info there

 

[JerZeyStangz]

Ok...I just got word about a guy in the next town over, Frankfort ky. He swapped on top of his stock short block a set of tfs heads with cams and a typhoon intake and netted out 404rwhp tuned at Blankenship. Im investigating the mystery and will report my findings.

please report, thats one of the highest rwhp numbers i've heard with that combination.

TF heads have a high enough vale placement that you don't need the pistons fly cut?

From the description from trickflow the heads are drop in heads with no modifications.

^ good info there

This thread is great.

 

[miss.mod.50]

From the description from trickflow the heads are drop in heads with no modifications.

No modifications when using factory internals and factory cams, correct?

 

[MustangChris]

The Mustang I went to look at was junk. :0/ I shouldn't really be looking right now anyway but if something nice falls in my lap, I'll lug it across the country when we move again.

where you movin' to?

 

[NERD]

Back to Michigan to be closer to my wifes family. Virginia is a gorgeous state but they practically charge you to breathe. The main reason though is to have the wife and little one around the family.

 

[JerZeyStangz]

No modifications when using factory internals and factory cams, correct?

yup, I do not know why we would use factory cams but they sure will work with the heads.

 

[96blak54]

You da man burninrock24!! Good info but let me challenge you more....?

 

[Burninrock24]

You da man burninrock24!! Good info but let me challenge you more....?

Haha go for it! I can only try my best.

 

[96blak54]

I know why mr. Vizard likes the 2v and I think you should know too, but to give you the answer I was looking for about "whats known" with 2 intake valves. Tumble is guaranteed by using 2intake valves, regardless of port shape, valve angle, or intake length and this is known by all manufacturers in pursuit of simple hp and efficiency. Yes 2valves offer more flow potential in a tiny cylinder were one large valve would suffer, but the "tumble" is more sought after over flow. The flow of 2valves is a very positive by product that cant be utilized by manufacturers keeping the vehicle street drivable. Pm your email and ill send you a few very insightful links.

All the info you stated is correct and far more beneficial than a 2valve train. Not to mention the hp potential with the stock equipment!!!!

 

[Burninrock24]

I know why mr. Vizard likes the 2v and I think you should know too, but to give you the answer I was looking for about "whats known" with 2 intake valves. Tumble is guaranteed by using 2intake valves, regardless of port shape, valve angle, or intake length and this is known by all manufacturers in pursuit of simple hp and efficiency. Yes 2valves offer more flow potential in a tiny cylinder were one large valve would suffer, but the "tumble" is more sought after over flow. The flow of 2valves is a very positive by product that cant be utilized by manufacturers keeping the vehicle street drivable. Pm your email and ill send you a few very insightful links.

All the info you stated is correct and far more beneficial than a 2valve train. Not to mention the hp potential with the stock equipment!!!!

Very cool. I will stand behind people when they say that the big drawback to DOHC is the cost. You literally do have twice the top end motor to worry about upgrading/failing. So when 2v vs 4v threads come up its always a case of "Do you already have a motor or not." Because it's usually more cost effective to mod the 2v than it is to swap to a 4v and now have the upgrade potential be lessened by cost factor.

Now if only we could have SOHC 4v like my Honda has!

 

[Carnage281]

So what do you guys think of these blower cams with some tfs heads? Think they will make some decent power n/a? http://www.lunatipower.com/Product.aspx?id=2568&gid=289

 

[NERD]

CMS or MPH for 2v cams.

 

[Burninrock24]

So what do you guys think of these blower cams with some tfs heads? Think they will make some decent power n/a? http://www.lunatipower.com/Product.aspx?id=2568&gid=289

Why do you want blower cams specifically? Blower cams are going to have less overlap so that less fuel atomized air gets forced out of the combustion chamber without even burning. Because where NA engines are sucking air in, FI engines create a lot more pressure by forcing air into the chamber. And that pressure can evacuate new air straight out of the combustion chamber.

NA cams have a longer overlap to take advantage of the negative pressure generated by escaping exhaust gases and help to scavenge the already combusted mixture out of the chamber. Also promoting mixture of the incoming fuel atomized air.

So unless you have a blower, I'd buy NA cams is what I'm saying lol.

 

[96blak54]

Blower cams do have overlap, just not like a n/a cam would. The blower cams intake valve stays open longer utilizing the incoming rush well past abdc. These guys are stuck on using some sort of forced induction to improve power. Nothing wrong with that, but cost goes straight up and in my opinion, ...its a copout for power....lol...

 

[Burninrock24]

I'll have to look into it again, but that's what I've always understood about the main difference between blower cams and NA cams.

 

[Burninrock24]

Turns out we're both right: http://www.badasscars.com/index.cfm...ct_id=120/category_id=13/mode=prod/prd120.htm

Feel free to provide your own sources too. For the record I never said blower cams don't have overlap, just not to the same extent that NA cams do.

 

[Carnage281]

I didn't start considering blower cams until it was mentioned earlier in the thread that blower cams make somewhat similar power to n/a cams. Instead of getting another set of cams for my blower (when I get it) I'll already have them.

 

[97stanger]

If you guys read, he plans on going blower in the near future...so it doesnt make sense to do twice the work and spend twice the money when gains will be similar even with blower cams while he is n/a...that was the point of the n/a vs blower cam topic