DYI Head Porting

[slatroni]

huuu?

[Jonny Hotnuts]

Changing the profile of the port, enlarging and removing physical obstructions (as caused by valve guides protruding into the port, and misaligned valve seats, ect. ) is where the HP is made. Much of the profile changes that improve HP are a closely guarded secret between head porters and is why one head makes more HP then another.

A nice shiny port flows worse then a slightly rough one. This is due to the boundary layer formed along the walls of the port and a rough (*within reason) keeps the boundary layer from being 'lazy' and results in better flow.

A nice shiny port sells port jobs but doesnt help performance.

-also....

A proper valve job and the angles used on the seat can make a significant difference in HP. True a better flowing profile on the seat wont last 100K miles but will make more HP.


http://www.motorcycleproject.com/motorcycle/text/cows-porting.html

Good lucki

~JH

[magus]

I had heard it is best to leave the intake side a bit ruff for better fuel air mixture.    I know the kws head on the gixxer I had was ruff on both ends.


   so is the school of thought that a basic clean up job is pretty worthless?  with or with out polishing after?

[slatroni]

I am planning on doing a "scotch bright" finish on the intake side and a polish on the exhaust. I am not and expert on this, but it would seem to me it would be better than stock. Please give me your feedback.
 Thanks

[tyboogie]

Changing the profile of the port, enlarging and removing physical obstructions (as caused by valve guides protruding into the port, and misaligned valve seats, ect. ) is where the HP is made. Much of the profile changes that improve HP are a closely guarded secret between head porters and is why one head makes more HP then another.

A nice shiny port flows worse then a slightly rough one. This is due to the boundary layer formed along the walls of the port and a rough (*within reason) keeps the boundary layer from being 'lazy' and results in better flow.

A nice shiny port sells port jobs but doesnt help performance.

-also....

A proper valve job and the angles used on the seat can make a significant difference in HP. True a better flowing profile on the seat wont last 100K miles but will make more HP.


http://www.motorcycleproject.com/motorcycle/text/cows-porting.html

Good lucki

~JH

I heard it is best to have a "turbulant" airflow that is what happens when you leave the intake side rough.

[slatroni]

I heard it is best to have a "turbulant" airflow that is what happens when you leave the intake side rough.

 This makes sense when you think about it. I don't want the air/fuel sticking to the walls of the intake port. But rough, how rough? is a scotch bright finish rough enough, or should I leave the 120grit finish?  In the old days we would polish the exhaust side, but the exhaust is still on the wet side. So would the effect be the same on the exhaust side?

[tyboogie]

I heard it is best to have a "turbulant" airflow that is what happens when you leave the intake side rough.

 This makes sense when you think about it. I don't want the air/fuel sticking to the walls of the intake port. But rough, how rough? is a scotch bright finish rough enough, or should I leave the 120grit finish?  In the old days we would polish the exhaust side, but the exhaust is still on the wet side. So would the effect be the same on the exhaust side?

Hell if I know that's just what I've heard

[slatroni]

HA! I am in the same boat! I learn everything the hard way, but I learn good!

[Jonny Hotnuts]

Also welding up your PAIR valve ports help HP. I have never seen any data on this but its a good sized hole in the top of the exhaust port and will hurt exhaust velocity.

Also look at the way I profiled my valve seats to flow with the port on my first posted pic and this (*the other side)

(Before on left, after profiling on R)


You may be able to use these pics to help grind some excess material off your ports. Just make damn sure they are all the same.

Here is a really nasty transition between the OEM valve seat and the port. Its hard to tell how bad it is from the pic but its almost 2.25mm deep. This can all be blended out.



As far as doing your own port job I still say get a ported head from good head porter and copy the profile on your head.
It really is not hard and takes the worry out of going too far and you KNOW you will be making HP.

I will say that I didnt find anywhere on my example head that wasnt enlarged at least 1mm on all surfaces in the port over OEM. (So mesuring from side to side would be 2mm larger diameter).

 

~JH

[slatroni]

Thanks again Jonny! I figured I would do just that with the seats. Is that your finished porting job? That has more texture than I had planned to leave.  I wish I could get my hands on a ported head to see where they ground out. I have seen lots of HD heads but no Busa heads. One of my friends builds HiPower Harley motors and he wants to look at my head. He is on his way over now.

[dave393]

80 grit is the smoothest you should go. Anymore and you lose low end power. I have ported hundreds of Harley heads over 30 years. Low speed tuning is more difficult.

[piratediverjefff]

I heard it is best to have a "turbulant" airflow that is what happens when you leave the intake side rough.

 This makes sense when you think about it. I don't want the air/fuel sticking to the walls of the intake port. But rough, how rough? is a scotch bright finish rough enough, or should I leave the 120grit finish?  In the old days we would polish the exhaust side, but the exhaust is still on the wet side. So would the effect be the same on the exhaust side?

Hell if I know that's just what I've heard

 

[Nosgsx1300]

someone should buy my HMP Ported head and copy it

[Chet]

My electric die grinder and porting kit is on its way!  What kind of HP can I expect from a " clean-up and polish" port job? I am going to send out some cams for a .368 regrind also.

I suspect you will loose 2-3HP.

~JH

Unfortunately what "looks good" to the human eye may not work well at all.
Strongly suggest you perform only very minor changes unless you have a proven design to work from.

Chet

[ras31]

My electric die grinder and porting kit is on its way!  What kind of HP can I expect from a " clean-up and polish" port job? I am going to send out some cams for a .368 regrind also.

I suspect you will loose 2-3HP.

~JH

Unfortunately what "looks good" to the human eye may not work well at all.
Strongly suggest you perform only very minor changes unless you have a proven design to work from.

Chet

I agree with that

[slatroni]

Thanks again for all the imput! I have finished the porting and bench shimmed the valves. I will be putting the head on in the next week or two along with cams and a 40 shot and s2000 injectors. I will give you the #'s after the dyno pull. I am going to tune with my wego.
 Thanks again
 Steve

[Competition CNC]

The most important areas are the ports minimum cross sectional area, the short turn radius the valve seat profile and seat choke %.  These are all determined by the size of the engine and at what rpm you want peak hp at.  Intake cam duration is also a factor on determining the ports MCSA.

Any visual surface treatments on a fuel injected modern high velocity port is purely aesthetic and have very little effect on flow or performance. 

It is true that carburetor street engines will like a rougher port wall to help keep the a/f mixture in suspension.  with injectors its not so important.