Valve Angle and Port and Polishing on B Series

[atari]

Hey Ozhonda peepz.
I've tried to search forums for question on valve jobs and port and polish information but haven't really found anything that is really useful.
I'm upgrading my b18cr valvetrain and would like to get more information about the types of valve jobs and the what to and not to do's when port and polishing. Car will be street driven with the occasional track day.
Eg. 3 angle, 5 angle, radius valve job, what size to port the intake or exhaust??

[dougie_504]

I've been led to believe that you just match the intake ports and exhaust manifold ports to the manifold gasket, and then the intake manifold ports and exhaust ports are supposed to be slightly smaller for anti-reversion purposes. Then of course you sharpen up the inside of your intake ports where they split off towards the combustion chambers.

Valves NFI, just leave them IMO lol.

[senna]

Stock valves for stock displacement IMO

As Dougie mentioned porting can be done to match the headers and intake - swirl can also be introduced to improve fuel mixing for more efficient combustion

[atari]

I've been led to believe that you just match the intake ports and exhaust manifold ports to the manifold gasket, and then the intake manifold ports and exhaust ports are supposed to be slightly smaller for anti-reversion purposes. Then of course you sharpen up the inside of your intake ports where they split off towards the combustion chambers.

Valves NFI, just leave them IMO lol.

I thought port matching the intake/exhaust manifolds with the head is the way to go. But you have suggested having one smaller than the other for anti-reversion which also makes sense.. I'm a bit confused now lol
Anyone care to share some light??

Stock valves for stock displacement IMO

As Dougie mentioned porting can be done to match the headers and intake - swirl can also be introduced to improve fuel mixing for more efficient combustion

Is the swirl created by leaving the surface kinda rough so the air is more turbulent?

[dougie_504]

I thought port matching the intake/exhaust manifolds with the head is the way to go. But you have suggested having one smaller than the other for anti-reversion which also makes sense.. I'm a bit confused now lol

Anyone care to share some light??

Anti-reversion is when you enlarge the intake manifold ports and exhaust ports but keep them smaller than the intake ports and exhaust manifold ports so that less intake/exhaust molecules flow backwards due to the reduced space/higher pressure. It can help keep intake/exhaust speeds up.

As for the 'rough surface' this is the intake ports. They are kept rough to encourage atomisation (the joining of the oxygen and petrol) by providing a rough surface on which these molecules can break apart from their initial structures. The exhaust ports are polished to encourage higher exit speeds.

Swirling is related to shape, not surface texture.

[Rayle]

Then of course you sharpen up the inside of your intake ports where they split off towards the combustion chambers.

Actually, from the reading I've been doing, it's not a great idea to sharpen the divider. If the flow is perfectly aligned with the divider this isn't a huge issue, but when the flow angle is off like the majority of engines, the fluid has a tendency to shear, which effectively reduces the cross sectional area available for flow.

In addition, there can be a tendency for fuel to cling to sharp dividers.

http://www.theoldone.com/articles/b16a_head/index2.html

Have a look half-way down the page at the intake port of an Endyn-ported head and you'll see that blunted dividers are the way to go.

You actually don't want turbulent flow in the intake port, only in the combustion chamber. Since turbulent flow means that the particles do not travel in a straight line, it effectively reduces the velocity of the charge.

There's more reading at http://www.thumpertalk.com/topic/786...h/page__st__40 and http://webcache.googleusercontent.co...&ct=clnk&gl=au if you're interested.

[senna]

Yes, swirl is more to do with the inlet ports "twisting" so the air and fuel is mixed on the combustion chamber more efficiently. Not as essential for performance...

[dougie_504]

Actually, from the reading I've been doing, it's not a great idea to sharpen the divider. If the flow is perfectly aligned with the divider this isn't a huge issue, but when the flow angle is off like the majority of engines, the fluid has a tendency to shear, which effectively reduces the cross sectional area available for flow.

In addition, there can be a tendency for fuel to cling to sharp dividers.

http://www.theoldone.com/articles/b16a_head/index2.html

Have a look half-way down the page at the intake port of an Endyn-ported head and you'll see that blunted dividers are the way to go.

You actually don't want turbulent flow in the intake port, only in the combustion chamber. Since turbulent flow means that the particles do not travel in a straight line, it effectively reduces the velocity of the charge.

There's more reading at http://www.thumpertalk.com/topic/786...h/page__st__40 and http://webcache.googleusercontent.co...&ct=clnk&gl=au if you're interested.

Thanks, nice article. I've read most of their D-series stuff but none of the B.

Those valve seats look ridiculous, with two angles blending into the radius lol. No way I could ever replicate that. Pity to hear that they believe the actual manifold/head ports do the least work given that they'd be the easiest to play with for a noob.

[atari]

Thanks guys. Lots of good info

I might add this link as well cos I thought it was a interesting read

http://www.importtuner.com/tech/0703...s/viewall.html