Diy Head Port And Polish

[marksuxass]

Just wanna know who has attacked this themselves,

Whats the best abbrasives you found?

Whats the best buff you used for the polishing?

Basically im gonna have a crack at it myself, 80 grit and clean all the dags on the inlet ports and manifold match. Clean the cut and castiings out the inlet bowls. Remove exhaust bumps and mirror polish exhaust ports, and mirror polish combustion chambers.

[snozzle]

although you might not find the answer to your questions in that threadyou should give it a gander, shows a guy from HKS doing abit of porting, the guy who made the thread took excellent pictures

http://www.skylinesaustralia.com/forums/topic/246240-hks-japan-28-engine-build/

[Dobz]

There's no point polishing your intake ports unless you're taking a lot of material out beczuse you're making so much power your ports need the flow.

For a street car it's best to keep the cast surface in the intake ports for better fuel economy. The cast surface will hold and spread excess fuel out in the port allowing the air to mix with better before it reaches the cylinder where as a polished port will let any raw fuel puddle and get dragged straight into the cylinder.

It's a good idea to clean up and polish the exhaust ports because the easier the exhasut gas can get out the better.

[REMANIS]

I did my LS1 mate just got a heap of flapper wheels in different grits bought new gaskets put them in place scribed the inside of the gasket the used the flappers to take it out to the scribbing I stuffed the first set up as I hadn't taken very consistent amounts out of each port.

I did pick up some power thought in the top end but this is on a built hi comp engine so I'm not sure if it would go the same for your example.

[James_03]

I did my LS1 mate just got a heap of flapper wheels in different grits bought new gaskets put them in place scribed the inside of the gasket the used the flappers to take it out to the scribbing I stuffed the first set up as I hadn't taken very consistent amounts out of each port.

I did pick up some power thought in the top end but this is on a built hi comp engine so I'm not sure if it would go the same for your example.

Sounds errrr.

If I was going to have it done it would be CNC, and by a pro, that or nothing. I don't think it's one of those things you can do yourself in the back shed, not well anyway.

[marksuxass]

There's no point polishing your intake ports unless you're taking a lot of material out beczuse you're making so much power your ports need the flow.

For a street car it's best to keep the cast surface in the intake ports for better fuel economy. The cast surface will hold and spread excess fuel out in the port allowing the air to mix with better before it reaches the cylinder where as a polished port will let any raw fuel puddle and get dragged straight into the cylinder.

It's a good idea to clean up and polish the exhaust ports because the easier the exhasut gas can get out the better.

Never said i was gonna polish the inlet sides. 80 grit should be rough enought to aid in fuel atomisation, plus while taking out the rough edge that has been cut away from factory in the inlet bowl, i might aswell do the whole port

Sounds errrr.

If I was going to have it done it would be CNC, and by a pro, that or nothing. I don't think it's one of those things you can do yourself in the back shed, not well anyway.

Have been told by my tunner that you can get a much better finish doin this by hand (unless removing the quench pads). He also says that a mild port like that can be done on my own with the right abrassives and buffs. All headwork will be carried out in a credited workshop by myself

[T04GTR]

IN THIS COUNTRY its abit of a black art and those who know dont tell.

from my own and some other local hi power track gtr's ive seen the heads of the common thing to do is..

short side radius on inlet and more importantly exhaust.

you dont have to touch the port entry at all. most of the material needs to be removed from the short radius and smoothing of the bowl area where the factory has bored for the valve seats. sharp edges are left from the factory tooling.

once youve blended them all nicely i go over the whole port with a flapper wheel just to smoth out the carbide bit marks.

the exhaust side is where alot of gains can be had. there is a really big step on the short side radius and the bowl area is quite square shaped. so blending all that nicly takes a really small bit and lots of time. the hump in the port opening can be removed with no down sides. without going into alot of details

it is alot easier to do it with the guides removed.

the combustion chamber doesnt need much. i prefer to leave the squish pads there but generaly just unshroud the valves. so the chamber will have the squish pads partialy removed around the valves. and the edges rounded. then once you have cc'd them to the same go nuts with the polishing.

really rough up the inlet port and polish the exhaust and chamber.

a flex shaft tool is a must. or a long die grinder that can take 1/4 and 1/8 shanks.

it takes easily 2 hours a port if you take your time. ages!! but thats with the guides installed. they get in the way especialy the exhaust.

i would cnc in future. because it long and hard work.

but for a quick garenteed gain id just open up the short radius on the exhaust and leave it at that. thats all i did on my gf engine. (rb25) no changes except for valve springs and exhaust for mod went from 270kw to 305kw on first pull. no tune changes same boost..

hope that helps

[marksuxass]

IN THIS COUNTRY its abit of a black art and those who know dont tell.

from my own and some other local hi power track gtr's ive seen the heads of the common thing to do is..

short side radius on inlet and more importantly exhaust.

you dont have to touch the port entry at all. most of the material needs to be removed from the short radius and smoothing of the bowl area where the factory has bored for the valve seats. sharp edges are left from the factory tooling.

once youve blended them all nicely i go over the whole port with a flapper wheel just to smoth out the carbide bit marks.

the exhaust side is where alot of gains can be had. there is a really big step on the short side radius and the bowl area is quite square shaped. so blending all that nicly takes a really small bit and lots of time. the hump in the port opening can be removed with no down sides. without going into alot of details

it is alot easier to do it with the guides removed.

the combustion chamber doesnt need much. i prefer to leave the squish pads there but generaly just unshroud the valves. so the chamber will have the squish pads partialy removed around the valves. and the edges rounded. then once you have cc'd them to the same go nuts with the polishing.

really rough up the inlet port and polish the exhaust and chamber.

a flex shaft tool is a must. or a long die grinder that can take 1/4 and 1/8 shanks.

it takes easily 2 hours a port if you take your time. ages!! but thats with the guides installed. they get in the way especialy the exhaust.

i would cnc in future. because it long and hard work.

but for a quick garenteed gain id just open up the short radius on the exhaust and leave it at that. thats all i did on my gf engine. (rb25) no changes except for valve springs and exhaust for mod went from 270kw to 305kw on first pull. no tune changes same boost..

hope that helps

Thanks for that

Just purchased a long nosed 1/4 inch die grinder. Have also been recommended to grind down and knife edge the inlet port spliter?

Think i might give that step a miss hahah

[STATUS]

why bother run another 2pounds....

i have had lots of 3000 dollar head build and port jobs on the dyno and at the end of the day they make no more power than many of the std ones.... for most setups we see throught the door port and polish is a waste of cash and time. If it is a bigger setup then gains may well be worth it.

[waxracing]

Interesting every one loves the cnc ported cylinder heads.

But the cnc porting is only as good as the person who programed it. Its not the be all and end all

[Beer Baron]

yeah the CNC just allows you to get was originally a $3000 porting job for $1500 and it's repeatable over and over again but if the original head they used for the program was no good then as you say yours wont be either. and I would generally take the finish on a hard ported head over a CNC milled head.

[r33_racer]

There are reasons why the cnc finish is how it is. Its not the machines limitations by any means.

[T04GTR]

most cnc jobs ive seen either are a really raw machined finish but as far as im aware you can ask for a smooth/polished surface.

[T04GTR]

why bother run another 2pounds....

i have had lots of 3000 dollar head build and port jobs on the dyno and at the end of the day they make no more power than many of the std ones.... for most setups we see throught the door port and polish is a waste of cash and time. If it is a bigger setup then gains may well be worth it.

ok. with pon cams and the small exhaust porting my engine went from 305 to 376awkw @25psi.. i doubt the cams were the only power adder???

[tm_r33]

There are reasons why the cnc finish is how it is. Its not the machines limitations by any means.

not at all arguing with you mate but out of interest, what are the reasons the finish on a cnc milled head may be poor if its not the machines limitations?

i dont know a lot about cnc but it interests me a bit recently it sounds as if you may know a bit about it?

[STATUS]

ok. with pon cams and the small exhaust porting my engine went from 305 to 376awkw @25psi.. i doubt the cams were the only power adder???

yours falls under the bigger category... i get asked about porting and polishing on std rebuilds and 250-odd rwkw setups... WOC.

[r33_racer]

Basically as T04GTR stated. You can get whatever finish you want with it, it just costs more to get it as it equals more machine time. You can go from super rough to mirror finish if desired.

Alot of people who see the finish on the ports think that it isnt any good and sometimes get the extra time spent to smooth it out and rough it up by hand or leave it smooth, but in fact its just right as is. The machined lines left are actually beneficial in helping increase air speed through the ports. As the air passes over the these lines, the ridges create mini vortices which help give the air direction and a small amount of turbulence which helps keep fuel atomised and in suspension. Now the increase in air speed comes about by the breaking up of the boundary layer that exists between the outer most layer of air and the actual port surface. Because air is viscous, when it makes contact with the port walls the friction generated actually slows it down. Essentially, air, as it enters the port is fastest through the centre and it slows down as the layers get closer and closer to the port walls. Does that make sense?

I believe this trick was actually disovered accidentally but its now quite common on cnc'd heads. But everyone has different ideas on these things, some people think its good while others still believe in the more original port finishes.

So the finish some people think to be poor and possibly because of the machines limitations really cant be further from the truth.

[marksuxass]

Have started the port, cleaned up the combustion chambers and got rid of 1 exhasut bump (3 flap wheels later). Would like more of a mirror finish on these items, What should i use?

[waxracing]

When I do a head I port it to the shape I want then polish it mirror finish.

From there I sandblast it to create a uniform and rough finish

[marksuxass]

When I do a head I port it to the shape I want then polish it mirror finish.

From there I sandblast it to create a uniform and rough finish

What do you use to "mirror finish" the exhaust ports and combustion chamber?