unusual71

I'm working on an H22 head and am unsure about what to do with the exhaust ports. They all curve towards the center slightly, with the port being slightly biased towards the valve nearest the center of the head.

I have not seen any examples of high end cylinder heads which have as much directionality and was just wondering what everyone's thoughts were on the subject? would it be better to straighten out the port or does the bias help with cylinder evacuation due to the location, size, characteristics etc, of the exhaust valves?

I welded up a bit of the exhaust port just because i was doing some other welding and wanted to hit it while the head was hot in case i did decide to straighten out the port.

My feeling is that the bias helps in the lower rpm range but as piston speed increases it becomes more of a hindrance. I would like some actual info on flow in a bias vs. non bias exhaust port if anybody has anything.

Combustion Contraption

On the H22 head, actually all the production honda heads ive seen, the EXH is where the most compromise is made due to packaging requirements. Power steering, EXH manifold packaging and overall cyl head height all play a big role. In a perfect world, the EXH port floor, from the valve seat short side, to the exit, would be one big tall smooth turn, but they obviously cant fit that. Any time you can make a port straighter its a good thing, but I wouldnt go ape-**** and spend alot of time straightening them out. There are quicker ways to pick up flow in the EXH port.

unusual71

lol "Adv." in the thread title is short for advanced in case that wasn't clear.

we all know there is much more to the exhaust port than just flow numbers. also a quick image search of high end engines will reveal the general shape of the port, ie. the single smooth turn from seat to exit along the short radius/floor. Im more interested in other details.

like what effect biasing the port more towards one valve has on scavenging. By the shape of the port there is more to it than simply packaging constraints.

The Ogre

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eDm cRxXx

Are you sure you have enough room to straighten out the port (without hitting any water canals)?

hondamark35

Could you elaborate a little on what you mean by "high end cylinder heads?" are you talking race spec. heads, Ferrari heads, sport bike heads?

unusual71

There is plenty of room to straighten out the port because it doesnt need to be very much larger, the furthest any wall would move would be maybe 1/8" or so.

also i was talking about heads were are purely for racing. most have tall, smoothly curving exhaust ports, that look a little bit like the letter " r "

vtechjunkie

iTrader: (2)

Good topic. Looking to do a bit of porting myself. In for some info.

MAX_CFM

here is my h22 side view of the ex ... The one nice thing on the h22 the ex ports dont bend much the K and the B there is Inner and outer ports
the h22 is the same port just transformed and mirrored

unusual71

nice pic, thanks for sharing it.

how much do you work the outside walls of the throat or not necessary in this head? I notice the stock casting has a nice curve into the merge but not sure if this is enough if you were to say, raise the peak output rpm considerably.

what is the widest point in the throat of the port you posted?