4 Valve heads - does Honda know what they are doing?

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David Vizard
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4 Valve heads - does Honda know what they are doing?

Post by David Vizard »

Sorry about the delay in making this post. I was going to do it right after my 10-day porting seminar which went down in grand style mostly due to the all-encompassing quality of the attendees. This full attendee class was about the most intense I have ever had the pleasure of having along to one of my head porting seminars. Class is supposed to be from 8:30 am to 5:00 pm with a one-hour lunch break. By day two it was clear that they all were ready to go by 7:45 So I had to drag my sorry butt out of bed an hour earlier. As for finishing time --- well Marvin and I had to throw them out at sometimes as late as 10 pm. Now if this sounds like I am complaining then you would be wrong. My problem was keeping up with the enthusiasm and passion these guys had for their chosen professions. The class was full at 5 attendees for this 10-day course. Only one was a non-professional. The other 4 were guys who were close to the top of their profession and were more than willing to share some of their knowledge. This meant I had the opportunity to learn as well as teach. Thanks guys - that was a fun 10 days and well worth getting worn out for.

One of my attendees was a motorcycle racer and campaigned a Honda CB 600. I had no experience with this engine as an entity or the 4-valve head used on it. Working with Tom the CB 600 owner, we did a flow bench analysis of the head to see just how well it compared to the last of the NA F1 heads. I was also able to get some useful input from a very successful student of mine from way back in the 80's. His CB 600 race engines have been very successful and the last one he built turned in some 135 hp @ 14,100 rpm with a shift point at about 14,800 to 15,000 RPM. That is 225 hp per litre or almost 3.7 hp per cube.

To analyze the head I used IOP. That's the flow program that Stan and I developed.

Here is what these tests revealed: -

• An intake port that, according to IOP, was right on middle limit for area with respect to the intake valve sizes.
• Same as above for the exhaust port.
• Intake port velocity was right in the middle of the IOP recommended range.
• Discharge coefficients were high and only a few % short of what I have seen on F1 heads.
• Port energy density, which is a measure of overall port efficiency, was better than many F1 heads but shy of the best.


Hats off to Honda. This is one of the best production 4 valve heads I have tested though I must say all the 4 valvers other than this have been for cars not M/cycles.

It turns out that Toms engine is very competitive but unless luck is with him a win is a rarity. The cylinder head is his starting point on a quest for more power from his already race modified engine.

Well we already are competing with Honda’s proven know-how so what are we facing here?

Answer – a major challenge!

With some diligent flow testing and port probing Tom and I managed to increase flow by an average of about 5%. We did this without any loss of port velocity. We added some swirl and increased the port energy. The project is still ongoing at Tom’s home shop. In near future we plan to PolyQuad the head.

Without revealing and compromising Tom’s efforts here I will see if I can keep you posted with the results.

Another small piece of news – finally got Dreadnought going. Just shy of 1000 cfm and 110 inches at low lifts even on BBC with a 2.45 intake valve. In the shot below attendee Scott (left) gets the first shot on the bench with his TFS SBF heads. Here we see Marvin and Scott setting the head up for a smoke trace test which subsequently proved very revealing.

Our seminar program is currently working with Performance Trends to further augment to data that can be gleaned from flow tests but more on that down the road.

David Vizard
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David Vizard Small Group Performance Seminars - held about every 2 months. My shop or yours. Contact for seminar deails - davidvizardseminar@gmail.com for details.
LotusElise
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Re: 4 Valve heads - does Honda know what they are doing?

Post by LotusElise »

I don't see an answer here. So let's find it out.

An engine is much more than it's port, but these are the bottleneck finally, and need therefore some attention. So how well did Honda their job? Very well. The K-series Honda engines I've tuned are just with a mix of OEM parts, a aftermarket header and and nicely designed induction able to push the VE well over 115 %, some even touched the 118 %.

Why does the K-series 4V-engine of Honda achieve that level just with OEM parts?
- First these engines have on intake side a cam phasing mechanism, which greatly optimizes two point: scavenging and pressure keeping at EVC (ramming).
- Second point is their revving capability. The piston acceleration and speed are well high enough to give the air column a nice punch. Where other engines have their redline, these engines turn in second gear ;).
- third point, as mentioned as 2nd gear, and one of their unique selling points is, VTEC. Not enough to phase valve timing, enough is when valve lift and duration is also flexible. But this is no VANOS complication, this is a simple and shift-able two cam lobe system - the 2nd gear
- fourth point, the rigidity and durability of the block and head is amazing. Over 700 hp at flywheel on the stock longblock out of 2 Liter on boost, or well over 250 flwhp on a stock NA longblock. Able to run at least one hour on the track at full load at piston mean speeds well over 22 m/s.
- fifth point, their valve seat and port design just impressive: 316 cfma@0.6" (28" WC) out of a 47 mm ID at flange and two 35 mm valves. While other OEM's played still with 30-45-60, Honda knew already air need more care after the throat with 30-45-67.5-80 degree at inlet. For those who think of typical Yamaha heads with steep intake ports, low inclined valve angles, don't get this wrong. This is a 51° inclined valve angle with an 15° port, just mass production and clearance driven interfaces. So we still have a 50° turn in into the chamber and a nice short turn challenge.
- sixth point is their flexibility, there are more then 10 different engine setups, more then 5 different head designs, more then 6 different IM and as well a bunch of different cams available. Mixing those parts and retune it can lead to NA levels well above 250 flwhp.

Honda knows what to do and they did it! Unfortunately they jumped into the downsizing with the K20C1. These ports are like those of a VAG engine, designed on budget and cost restrictions, emission driven and of a lower passion in the fabrication. Times changes, seems not only Honda does not leave the show with a buuuuuum, rather then with a puuuups. But hey, there are still so many K20A and K20Z engines available on the market for a good basis. What can we do with it?

I used a simple K20 engine longblock, throw forged parts in the block, modified the head a bit, swapped aftermarket cams in it and designed the alternation of load path new. I am still on the way to tune it, but I saw already 101 ftlb/liter at the flywheel at 5250 rpm (at 5500 rpm the gearbox broke). Which NA engine is capable of 101 ftlb/liter? These are measured 130 % in VE or 202 ftlb of torque. The simulated VE peak should be reached at 7500 rpm. Will be back on the engine dyno this year.

Anyway, I will do a K-series head port comparison, a few series heads against some aftermarket heads on our flow bench. Keeping you guys updated about the question (I altered it a bit), what Honda knew and did.

Markus
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DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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