Anyone tried 4 valve heads?

[Half_crazy]

http://araoengineering.com/barley.htm

http://www.bikerrogue.com/Articles/T...alve_power.htm

http://thekneeslider.com/archives/20...-twin-engines/

http://www.cyrilhuzeblog.com/2007/07...v-twin-engine/

[2wheelrider]

I don't think that the second link , that they are still around. I tried to call the number at the end of the article and the number was disconnected. I would love to get a set of the areo Eng 4 valve heads. You could run a .550 lift cam and get big numbers with a low lift. I wonder what the combined spring pressure would be? Compressing 2 valves at a time.

[Half_crazy]

Originally Posted by 2wheelrider

I would love to get a set of the areo Eng 4 valve heads. You could run a .550 lift cam and get big numbers with a low lift. I wonder what the combined spring pressure would be? Compressing 2 valves at a time.

Lighter valves = lighter springs, right? I assume that high seat pressure would not be necessary. If the rocker arm system geometry can be worked out well, shouldn't be a problem. Yamaha uses 4 valve heads and pushrod operation on their 113" engine and that seems to work fine for them.

[JohnC FXDX]

4 valves like more rpm's in order to start showing their benefit. Harleys are not high rpm engines by nature. You would have to be building a HP engine for these to be worth while.

[Half_crazy]

Originally Posted by JohnC FXDX

4 valves like more rpm's in order to start showing their benefit. Harleys are not high rpm engines by nature. You would have to be building a HP engine for these to be worth while.

I disagree. The benefit of 4 valves can be seen across the entire range of engine RPM. Additionally, you can achieve the same or better horsepower with less radical camshafts which is also beneficial to low end torque.

Again, to use Yamaha as an example, the 4-valve 113 is limited to 5200 RPM. That motor is a monster on the bottom and makes .8 HP/CI in stock form. They don't seem to need high RPM to make the 4-valve heads efficient.

[CowboyTutt]

Half Crazy, I can relate. I really used to believe in 4 valve heads after having many different Japanese (including a beloved 99 'Busa), German (BMW) and American bikes with them (Buell 1125CR). After a good pipe, velocity stack and race ECM was installed on the Buell to correct the excessively lean stock ECM tune, it ran beautifully but boy! Did it hog fuel when yanking the throttle!!! I think that from a mass production standpoint a 4 valve head will flow better yes. But a good CNC or hand cut 2 valve head can do, IMO, darn close! If the 4 valve heads for Harley's worked so well, I suspect they would still be around. -Tutt

[Sledge Hammer]

I had a '99 Yamaha Road Star 98" 1600cc and my buddy's stock '00 Dyna would blow it in the weeds.

[TXCHOP]

Intake port shows one port dividing into 2 valves.
Port flow @ 28” test pressure:
LIFT FLOW
. 100” 122 cfm
. 200” 226 cfm
. 300” 286 cfm
. 400” 308 cfm
. 500” 312 cfm
. 600” 317 cfm
those are posted on the site....My heads outflow them by a ton everywhere but .100 lift.. Whats' the benefit?

[CowboyTutt]

TXChop, I think you just proved my point as well. Can you tell us more about the flow numbers on your heads and what type of head they are in this thread? I would be very happy to have flow numbers as posted with the 4 valve heads much less something better! -Tutt

[Half_crazy]

Originally Posted by Sledge Hammer

I had a '99 Yamaha Road Star 98" 1600cc and my buddy's stock '00 Dyna would blow it in the weeds.

The Road Star is a different story. 4200 RPM rev limit and wouldn't break 100 mph on it's best day. It was designed to be torquey, but that's all.

[Half_crazy]

Several years ago I saw the Quantum heads but never see bikes with 4-valve heads in magazines or on the web. I wanted to see if the horsepower junkies that frequent this site had any experience with this. I thought maybe some of you might have them or know someone that does. It would be interesting to see how they work in the real world, because the manufacturer can claim anything they want on a website, ya know?

It seems some are against the idea.

[CowboyTutt]

I don't think anyone is really against it par se, just dubious about the benefits. I agree it would be neat if someone had a set of heads on their bike to compare, but they were a pretty rare item I think. Also, the TC valve train angles are already less than optimal so perhaps there were engineering challenges with the 4 valve conversion. Your Vic makes outstanding numbers but can't remember what they were. But its valve train with SOHC is a completely different animal. -Tutt

[JohnC FXDX]

Originally Posted by Half_crazy

I disagree. The benefit of 4 valves can be seen across the entire range of engine RPM. Additionally, you can achieve the same or better horsepower with less radical camshafts which is also beneficial to low end torque.

Again, to use Yamaha as an example, the 4-valve 113 is limited to 5200 RPM. That motor is a monster on the bottom and makes .8 HP/CI in stock form. They don't seem to need high RPM to make the 4-valve heads efficient.

Since there isn't a lot to go on to directly compare a similar motorcycle like a Harley, you could go to a car. Ford switched to 4 valve head on its Mustang Cobra. That engine is actually an under square engine which is more prone to torque. Their standard 289( about the same size) engine built similarly will make way more torque down low. The 4 valve needs about another 1,000-1,500 rpm's to make the same torque. Ultimately this design needed more rpm's to make the power and they had to increase the bore and shorten the stroke to get it there. Now they have an engine, the new 5.0 that makes over 400 hp at 7300 rpm's vs an equally built 302 that can do that at 6,000. What happens is that they usually provide too much air at the lower rpm and they don't provide the velocity needed. That is why they need the rrpm's to really shine. Remember that it is not about peak numbers, but the averages and at what rpm the peaks occur. You can look at any 4 valve engine vs. a 2 valve and you will see where their torque peaks occur.

[Half_crazy]

Remember that it is not about peak numbers, but the averages and at what rpm the peaks occur. You can look at any 4 valve engine vs. a 2 valve and you will see where their torque peaks occur.

That would be totally dependent on how well-matched the port sizes are to the engine's displacement, rod ratio, etc.

I don't think anyone is really against it per se, just dubious about the benefits.

I was avoiding the comparison to Victory because it always veers off on a bad path and people take it as a put down or bragging... but... I make someplace between 133 and 136 horse, and someplace between 136 and 142 ft-lbs depending on what dyno the bike is on (SAE). Heads, valves, intakes, throttle bodies (45mm) are all stock. Cams are .484" lift. 100 TQ by 2300 rpm and 120 by 3000. Runs out of breath at 6200-ish.

I'd say that's a pretty good case for 4 valve cylinder heads being efficient. I know that people will say the OHC is the cause... and if we were talking about 7500+ RPM I would agree... but pushrods work fine below 6200 rpm, as you know.

[qtrracer]

Originally Posted by Half_crazy

That would be totally dependent on how well-matched the port sizes are to the engine's displacement, rod ratio, etc.





I was avoiding the comparison to Victory because it always veers off on a bad path and people take it as a put down or bragging... but... I make someplace between 133 and 136 horse, and someplace between 136 and 142 ft-lbs depending on what dyno the bike is on (SAE). Heads, valves, intakes, throttle bodies (45mm) are all stock. Cams are .484" lift. 100 TQ by 2300 rpm and 120 by 3000. Runs out of breath at 6200-ish.

I'd say that's a pretty good case for 4 valve cylinder heads being efficient. I know that people will say the OHC is the cause... and if we were talking about 7500+ RPM I would agree... but pushrods work fine below 6200 rpm, as you know.

Those pushrods/ rocker arms are the limiting factor in the arao/feuling 4 valve head. Do more research you'll find what I found.