2v vs. 4v heads. By Gti (Read 2,669 times)

[Gti]

What are the advantages and or disadvantages for switching to a 4valve head? I considering the switch and I just want to make sure that a 2v performance head will not be just as or more effective.

[kz1000st]

The only knock I've heard about some 4V heads is that they don't sell pistons with them with 4 cutouts and there were clearance issues. The theoretical advantages are undeniable. More flow with lighter, smaller valves for higher redline and less stress on the springs. Look at the people using 4V in their street bikes. The Big Four, MV Augusta, Ducati, BMW, Aprilia, Victory. Look at the people using 2V-Harley Davidson. That alone should tell you which is more technologically advanced.

[fugaziiv]

Yes, but the GM LS7 also uses 2 valves per cyl, and that particular engine isn't a slouch. There is still a place for 2 valve heads, particularly if you need more torque. KZ is correct that the 4v heads tend to be substantially more up to date than a 2v head as far as flow dynamics are concerned, particularly with a high RPM engine.

I think there is an argument for both sometimes.

And then there is this: my Yamaha and many Ferraris have 5v heads, while many modern Ford V8s and Yamaha's newest small scooter engines use 3v heads.

It is all over the place about what is actually better in day to day use.

I know I didn't help any yet but I had to toss it out there, so I'll get to a point here... for some scooter riders, a 4v head can be a good option with the addition of other mods, as it typically allows for more efficient airflow than a 2v head. If you aren't planning on a bunch of of other mods, such as intake, exhaust, fueling and such, then it probably won't help much as you won't be able to take advantage of the extra flow capacity that it offers.

We actually use a 2v performance head on our QMB Drag Racing Scooter, and we only run that wide open with N02, no air filters, no exhaust. Just food for thought.

Matt

[Deleted]

I have always wanted to try out a 4 valve head just to see what difference it makes. But they are not cheap here in PR lol

[sprocket]

I agree with Matt.. you must open the intake and exhaust up or a 4 valve or large 2 valve head won't have a lot of impact on performance. It certainly will have some, but there is more to be had with a larger carb or EFI and a free flow exhaust...

[jct842]

This is a very expensive option that does not have much like other accessories to go along with it. Cams, pistons, in fact I imagine it would be hard to purchase any replacement parts for it. I imagine the valves and valve springs are different and finding them for a reasonable price would be hard. I believe the head on a gy6 is where a weak spot exists and a good solid head would help a lot of people here to keep an engine running with out constant adjustment. john

[sprocket]

There used to be a cast iron head for the GY6 but I haven't seen one in awhile.. but you know the early Hondas were terrible for valve regression too...

Perhaps Ruima, Hoco and other Taiwan heads are made of better materials...I don't know

[imnts2]

I stumbled on a 4 valve psistons on ebay. I'm certain they were BB for gy6 125/150. Did not take note of vender.

finally
cheers
lefty2