Polishing the intake

[gassergrant]

Hi all I've been thinking for a while now to give my ec 300 just that bit more tuning, I would like to polish the inlet system to help with throttle response. Has any one done this that would be able to give me some tips etc.

Many thanks

 

[Harry]

I have my cases apart at the moment and was suprised to see how rough the castings are around the reed block, I too am interested in the effects polishing may have?

 

[Brian VT]

I've never messed with porting/polishing, but I'm under the impression that a rough intake is fine or even desirable ? I think the exhaust is better when smooth ?

 

[Jakobi]

I've never messed with porting/polishing, but I'm under the impression that a rough intake is fine or even desirable ? I think the exhaust is better when smooth ?

Thats correct. You want the intakes to have some texture to help create some turbulance to keep the fuel suspended in the air (I think thats the theory). The polish is for the exhaust to stop the spooge and carbon build up which essentially reduces the port size over time.

In saying this though there are definate gains to be made by cleaning up and large rough areas caused while casting and matching the intakes between the reeds (cases) and cylinder.

Basically you want everything to fit together well, no burs or jagged edges, no casting slop, but not mirror finished.

 

[gassergrant]

I had this done in my lancia and got a a big bhp increase, my friend who got the work done for me said use wet and dry to take the worst of the roughness away and not polish to a mirror finish, the proting side of things i would not touch as i believe it changes the power band ie like adding race cams to a car.

i will see how i get on and let you guys no well if im brave enough

 

[stainlesscycle]

the biggest simple porting performance increases are:
match reed to case
match cylinder transfer ports to case
radius edge transfer split in cylinder
polish exhaust port/match exhaust flange
clean up flash on cases in transfers, reed etc.
don't forget to size gaskets for new hole sizes

you won't change the powerband unless you change port area/location on the cylinder. as long as port timing stays the same, powerband will stay the same. you just get more flow. if you increase flow, it might feel like you've narrowed the powerband slightly, because you're zinging through the revs quicker... be reasonable though, you're not taking a bunch of material off, just minor cleanups. the transfer split 'edge' is pretty square to start with, so you will narrow the split pretty dramatically (maybe 1mm) to make it radiused (kinda like knife edge, but don't make it sharp, just make it so mix will flow smooth, instead of square-edged like it is stock)

here's a pic of a radius'd transfer split. i have pics of the last one i did, i just can't find them now.

here's a another pic of a radiused transfer. this is wider than ours is stock..

none of these will increase performance like proper squish will though...

 

[gassergrant]

thanks for the info guys. going get the engine out and have a good look.
i will take pics of the job so anyone can see what the end result will be.

thanks grant