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I think you have the right idea Nate.

It's a bit difficult to describe, but you want to deepen and widen the bowl
so there is a place for all the gasses to go as they leave the chamber.
You have to visualize three dimensionally and see a constant increase
in open cross-section as you move away from the valve.
It doesn't have to be round, but it has to be a smooth transition.
Since you can't remove the guide, you go around it.
You also remove a bit of the nose of the guide boss without actually exposing much more of the guide.
The guide can be shortened just a little bit too.

Jake is right about the intake side not needing to be opened up,
but the same idea of widening the port so gasses will go around
the guide applies.
The open cross-section should constantly change such
that the gasses follow the path of least resistance.
They don't mind being squeezed, but they don't like sharp corners
or obstructions.
You want the choke point to be as close to the valve as possible.

Nice work Nate! The best way to visualize where improvements need to be made is by getting in there where you can see what 's there, and what's not there. As they say, a picture is worth a thousand words. I believe your presentation SHOULD go a long way towards educating the forum members about the strengths and weaknesses of typeIV heads. One thing that is not apparent from your 1.7 ex. cutaway is just how close the studs get to the chamber (need to cut right through the middle of the boss for that.) That's why flycutting depth is limited to about 2mm's without welding modifications.

As for how much ex. boss to remove, for the street I machine the boss down 6mm and shorten the guide the same amount. This duplicates the 2.0l 914 specs. Before installing the guide I hand shape the port WORKING ONLY ON THE LONG SIDE. If you shorten the short side even more you kill your flow in a couple of different ways. First by decreasing the straight distance beneath valve, which pulls apart the flow cone before it has a chance to remerge into a consistent "slug". Second by creating turbulence in the port. A gas charge can not be forced to bend like plastic. When a tight turn must be made it is best to do it quick and get it over with. Since the flow can't follow an increased radius over that short of a distance it creates a sort of dead space. This sets up pressure gradients in the port that cause turbulence. The same is true of the in. port. While that nice rounded turn on the short side feels good when you run your finger over it, the reality is that you have now set up some serious negatives with these particular ports. If the turn beneath the valve was an inch or more up the port ( away from the valve) the effect would not be as dramatic because flow around the valve would not be affected, though it would still cause turbulence and decreased flow in both ports, as well as fuel fallout in the intake. MAINTAINING THE SHAPE OF THE FLOW CONE LEADING UP TO AND AFTER THE VALVE IS THE NUMBER ONE CONSIDERATION WHEN MODIFYING ANY CYLINDER HEAD! To achieve this there must be a minimum of .500" below the seat where the shape of the port is consistent. If this means the short side makes a sharp turn with virtually no radius, so be it.
Jake and I have been pumping up the volume with sq. port heads. We have a pair going on a 2321 that is absolutley going to kick ass. There is much potential with these heads, more than any of the production type IV heads.
And just FYI. The Q head with the split guide boss and fried ex. stud boss could have been saved. I machine out the old stud boss, weld it up and remachine. As for the guide boss, they get machined away for dual springs with no problems. I just fit the guide a tad tighter. At least it went for a good cause! Keep on looking for answers. There's more where that came from!
Len Hoffman
owner
HAMInc.

Len, Thanks for chiming in..

After seeing this guys work, I can say that there isn't anything he can't repair!

FYI, EVERY cylinder head that he has completed for me to date has made more power than its comparable head on the exact same engine otherwise!

Thats how I cranked out almost 180 ponies from a 10.3:1 2270 yesterday!

Nate, I have a 021-101-371J head laying around that broke an exhaust valve and bounced it around it's chamber, intested in another "victim" for comparison to the Q head?

Class 11 streeter wrote:Nate, I have a 021-101-371J head laying around that broke an exhaust valve and bounced it around it's chamber, intested in another "victim" for comparison to the Q head?

Sure. If you want to send it to me, I'll slice it and could send you back the slices. These pieces I cut up have made really nice desk-top paper weights/conversation pieces that we keep at the office of the VW shop I work at. P-mail me and I'll give you my address.

So besides enlarging the exhaust size, and possibly trimming the valve guide just a bit, what else can be done to make the heads flow better than stock, and yield more juice?




E

Len, You know your stuff about heads! I've been reading quite a few articles by well know head porters and racers. http://www.theoldone.com/articles/
Talking Heads, and The Soft Head is really great articles.

All of them basically state that what Len is doing is the correct procedure. A lot of the time, people don't do it right-Even the big boys, and you end up with some Really pretty looking heads that flow for $hit.

Laminar air flow, fluid dynamics, a lot of factors can go into what will make a head flow.
Its not about volume of the port, its about velocity. Small straight ports, have high velocity. The large ports that get bottle-necked from the reletivly small valve seat suffer a lot of turbulance and reversion pulses.

Don't go too wide on the ports, mostly thin the boss a little, and try to keep it a straight shot if possible. However people have experiemented with humps, textures, bumps, etc and have found a lot of benefits.

Do you know why a golf ball has dimples? It so the ball will have less direct contact with the air in flight and can travel farther because there is less resistance on it. (the high parts of the ball is what has most contact, the dimples form pockets of air instead of having air rushing past the plastic directly). In Theroy.

This is why people put a textured (about 120 grit) buff on the intake ports. It keeps the fuel from condensing on the port walls and somehow reduces the friction on the air...this one I'm still trying to comprehend.

Take care,
-Bobby

Laminar flow... The best analogy I've read is that some air gets "stuck" on the rough texture, but then it forms a "bearing" or "lubricant" for the rest of the air, which then flows faster with less resistance. Hmm, actually the analogy as I recall specifically said "lots of little bearings", and implied that the air that is against the rough surface was actually moving around and around... Anyway, it's a decent way for a non-fluid-dynamics person to look at laminar flow.

--DD

Len really does know his heads!

Right now he has a prototype of mine ready for the flowbench!

He has taught me alot about heads in the past few months, and our R&D has really exploded since I added him to my network!

Dave,

You hit the nail on the head!! I'm at Work right now so my mind isn't up to snuff.

Jake,

You're an animal!! If I didn't have the 44 hour a week job, I'd LOVE to work with you guys.... Talk about work ethic!

Found this article a while back. He gets pretty deep into port design, as well as cautionary tales about what does - and doesn't - work.

[url]http://www.beautyofspeed.com/data/cylin ... ex.htm[url]

I'm impressed with how knowledgeable/inquisitive some of this forums members are. None of the theories I apply are new, so it's great to see that some enthusiast have been paying attention. Unless you were born before WWII, most cylinder head technology predates us all. (Overhead cam engines won EVERY Indy 500, starting in 1911, until 1994). Application of theory requires a serious dedication to developing machining & porting skills, as well as a never ending search for better materials and combinations of systems (ie. cams, inductions, exhaust, bore-stroke ratios, rod-stroke ratios, combustion chamber shapes and all that goes into that ie. piston shape, head shape, etc.) Because of all of the variables and constant material improvements, R&D can never be deemed complete, even though the theories in place are virtually unchanged over the last 70 years. Being armed with theory alone isn't enough, though it is the essential first step.
That's why I am so thrilled to be working with Jake. Over the years I've developed cylinder heads for a variety of applications and received feed- back from a huge list of customers, some knowledgeable, some not. Don't want to get all gushy on everybody, but with Jake I get consistent feedback that comes from very controlled test methods. I have seen Jakes shop and I'm very impressed with both his dedication and his methods. In the past four months, because of his feedback, I've been able to push my technology forward quite a bit. And trust me when I say that over the next year we will take some even bigger steps forward in both the aftermarket cylinder head area, as well as with modified production cylinder heads.
R&D takes time, and time is money (as we all know!) But for the customer who expects the state of the art in Type IV technology, I know of no one who is pushing the envelope like Jake. I'm very excited, and honored to be involved. Stay tuned!
Len Hoffman

Len, the envelope has just been opened!!!

Better be ready!

My one yar vacation from engine assembly for customers has just begun, wait till we do some back to back runs with the 3 liter and wear it out a bit!

MASSIVE TYPE IV wrote:Len, the envelope has just been opened!!!

Better be ready!

My one yar vacation from engine assembly for customers has just begun, wait till we do some back to back runs with the 3 liter and wear it out a bit!

no motors for a while? did I get in under the wire?

dr