First build ever

teazer

Active Member
DTT BOTM WINNER
How do you know if you changed velocity? Larger ports tend to reduce velocity and will reduce flow as well if they are the wrong shape. A.G.Bell has a nice section in his book on 4 stroke performance that explains the different parts of a part and their relative shapes/sizes.

On the fuel side, you are almost right but slightly back to front. Fuel is mixed with air in a carb and the fuel is changed from fluid in the float bowl to small droplets as it emerges from the needle jet. By mixing air with the fuel in the so called "emulsion tube" the droplet sizes are reduced. Those droplets are not vaporized by a rough surface, but will separate out of the flow in a polished port. Fuel injection as the advantage of pressure. Where a carb relies on atmosphere./gravity/pressure differential to get the fuel moving, FI can operate at much higher pressure and potentially through small orifices all of which encourages smaller droplets which burn faster.

In the combustion chamber a polished surface will reduce heat transfer and the mixture temperature will potentially be higher leading to detonation in a worse case scenario. There are those who argue that a thin layer of carbon protects the heads even though it will raise the head temperature and reduce combustion temperature slightly. You could conduct your own experiments to see which variable has the greatest effect in your particular situation.

"More air only means more power" only when gas velocity is high and flow into the head is higher. With the same size valves and cams, porting is only useful to the degree to which flow is restricted. If a head already flows more than the motor needs, any further flow increase just results in lower velocity, less turbulence and slower combustion. The most critical area of a port is the 1/2 inch to an inch just before the seat.

One thing to avoid is directing the flow at the valve stem, the gas has to go around the valve to fill the combustion chamber and the easy thing to do is to open it's mouth behind the seat and that hurts flow.

Grab a copy of Bell and read all you can by Vizard and ignore most of what you read on the internet. :)
 

onefromexile

New Member
Yes yes I did
Go off vizards theories
In his book
I was unable to find a direct match for porting a 360engine
So I applied what I learned t o my build and
I mostly just got rid of casting impurities and port matched and cleaner path
Hard to explain exactly how much was changed
But I will say only time will tell
I'm confident in the info I've received from all my great friends on dtt
My own knowledge and skill
And the way I did it I think will be benificial
I'll be sure to let everyone know my results






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onefromexile

New Member



Sent from my iPhone using DO THE TONsome pics showing removing the casting marks and how much material and where it was re moved from
I'm thinking my air flow is better and before the ports directed air strait at valve stem
Now it directs more towards back of mouth of the valve seat and swirls around like a vortex
Theoretically of course!!!
 

onefromexile

New Member
Ok new update
In talking to another DTT member my work will continue on the head I am going to work on the exhaust port
Will post pictures as its finished


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teazer

Active Member
DTT BOTM WINNER
Doesn't look too bad. The exhaust is where you will probably make most gains. Too long since I looked at a 360 head but most Honda twins of the era were exhaust restricted and respond well to clean ups. The floor really needs to be raised but that requires a lot of cutting and welding, and not really worth it.

Crazy PJ is a guy that really knows those motors. So do a couple of the other guys on DTT.
 

Tune-A-Fish

BOTM LOSER Proudly Deplorable
Ok I confess... I know naaaaada about the porting of a honduh 360 head, I know some CRF 250 and 450 from racing days and yeah Mitch Payton is an inspiration.

https://youtu.be/5BfVF0wPli4
 

teazer

Active Member
DTT BOTM WINNER
Why are the cylinder liners out of the barrels? That can't be a good sign.

Small Hondas often have liners that come loose with very little heat, so they have to be refitted with a suitable grade of loctite and clamp them while they set. If not they cannot be bored or honed and even if they could they will overheat in a running motor.

Liners have to be an interference fit so that they transfer heat to the cylinder and fins.

BTW, on those ports, just clean up the inlets and don't open them up and on the exhausts raise the roof and try to avoid dropping the floor.
 

onefromexile

New Member
I left alone intake except rough clean up of casting marks exhaust however I opened up bowl below mouth of valve to port and ported the top half
So on its side a d shape


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