Forged Rb20

[N1 RB26]

yeah but surely with just a slight port and polish just taking the kinks out to make the air flow easier would increase volicty so you would still keep the response up..yes, no??

[Rolls]

I really doubt it will make any positive difference. Porting is usually for when you are making massive power and need the extra flow, you don't do it for low down response. For low down response you'd be better off making a custom intake manifold with massive long intake runners, or increasing the stroke, but as mentioned before once you spend any money this project becomes stupid and you should have just invested it into an rb25/30.

[Bl4cK32]

only way to be sure 100% is to go buy a ported head from lewis engines for $1150 and do back to back testing. Results come back that there is a tiny increase in flow or response, can you then justify it was really worth spending that $1150 on?

[Rolls]

and he wants to do it himself as well and not pay a pro, there is a reasonable chance you will go backwards, unless of course you are just smoothing the edges, in which case you probably won't go forwards or backwards.

[N1 RB26]

i'll only be assembling the engine myself all the head work and machining will be done by professionals some of dad's old mates from when he drag raced and i've got a couple of heads and yeah was gonna try with both and see what happens and how much of a difference it makes..

[Driftnuttz]

Guys I dont see why its sooo hard to understand there are many ways to port heads. One way is like everyone is talking about, just make the ports as big and open as you can, but this is not the best with every head and every setup. I have seen plenty of motors gain lots of power and response from head work, now when I say head work I dont mean every head had the same kind of work done, it depended on the setup and how the stock head looked and flowed. Some heads you can gain 20+ whp with just a small reshape, some need to have the ports opened up, some gain more by just a small clean up, It depends on the setup and how the ports are shaped. Looking at the stock rb20 ports I can tell you a SMALL amount of porting at the mouth, port matching to the manifold, and just smoothing the ports out should work wonders all over the power band. This will not drop air speeds, infact it should speed the air up a little. Add to this, making sure the head has the right cross sectional area for the size of the motor and the head will be a ton better then stock.... Just my .02

[N1 RB26]

driftnuttz how'd you go with your head what are going to do to it?

[Driftnuttz]

This is going to be my setup, stock redtop block (eccs), silvertop head, rb25 late neo turbo, front facing plenum on cleaned up runners silvertop runners, 440cc injectors, stock fuel rail, stock tb, rom tune, and an adjustable fuel pressure regulater.

I am thinking ( I have not used a micrometer yet) I will need to open the mouth of the intake side just a little, not enough to slow down the flow. Then I am going to clean up the ports and the port throught ( right where the port dumps into the cyl). On the exhaust, I think the best way to go for my setup will be just a good clean up and polish. I will port match both sides (in/ex), and may take a small amount out of the exhaust side. I cant take much out of the ex side, but the easier it is to get the gases out the better at high speeds the better. I really think the stock head is super restictive, and has lots of room for improvment. I will know more when I can get a micrometer and figure out the stock cross sectional area of the ports, this will help me figure out how much I need to open the intake ports to keep the motor from choking itself. This is what most people forget when they port heads, but cross sectional area is most importent.

Hope this helps understand what I plan on doing, and maybe gives you an idea about how to do yours.

[N1 RB26]

yeah cheers keep us posted how it works out for you...love to know what kind of response before and after

[Driftnuttz]

I will not be doing a before test, but I am sure there are plenty of stock rb20s running around with the other bits I will have. So we can use them as a basline....lol.

[The Mafia]

I'm surprised his thread is still alive. I look forward to all the porting and pulling over this head you do.

Instead of going quiet about it when you do realize it was a complete waste of time, money, and your life, please cone back and admit it.

$1100 and you could probably find a GTR head. $50 more and you have a rb30 block.

But you'd still spend or waste so much time on a rb20 and say it's better or different. Lol.

[Rolls]

I will not be doing a before test, but I am sure there are plenty of stock rb20s running around with the other bits I will have. So we can use them as a basline....lol.

It costs $40 to run it up on a local dyno before hand, we all want to see the before/after results!

[Driftnuttz]

It costs $40 to run it up on a local dyno before hand, we all want to see the before/after results!

Mafia I am not in Aus so your prices are void for me. It would cost about 4-5k to buld a 30, and thats just the motor and turbo stuff. I then have to buy something to tell it what to do and have it tuned. Bringing the build up to about 5-6k depending on the cost of the motor, tune, and ecu. I just dont have that kind of money.....

Only reason I am not doing a before/after is cause the motor is not in my car, nor has it been in my car before. I would have ran it on the dyno for a baseline, had the motor been running in my car. I mean the only reason its getting a bit a head work is cause I have to change the valves. I mean why not clean up the ports a bit if your there in first place? Its not like I am going to spend 2k on this....lol.... My head work is going to be free, well as free as my time is anyway. I am not going to keep saying the same stuff over and over, so I will ust wait to update when I have started porting........

[DVS JEZ]

Awesome. Let us know how it goes

[r33_racer]

You should pick up some decent gains if you clean up the bowl and throat area. A good 5 or 6 angle valve seat job will help a buttload. Actually anything will be a help over the std 3 angle.

I wouldnt port match your exhaust side. Just do the inlet side. You want the exhaust manifold to be larger then the port exit. You need something to help reduce exhaust reversion, having that step left where the manifold meets the head, Thats about as much as you can do. So match your manifold to the gasket and thats all you need.

But for $50-$100 bux you can pick up a porting kit with the cartridge rolls and stones and then go yourself. Just cleaning up, removing casting lines and machine overlap everywhere, blend it all in so there are smooth transitions and no sharp edges. Should be good. Thats all I did to my rb25 head and ive got the flow figures. But i need to get a stock head flowed to see what improvement ive made. I picked up about 5-10cfm throughout the range just from the better valve seat job over standard 3 angle. That was suprising. Just a few more transitions and suddenly air flows easier out the valve.

[Driftnuttz]

You should pick up some decent gains if you clean up the bowl and throat area. A good 5 or 6 angle valve seat job will help a buttload. Actually anything will be a help over the std 3 angle.

I wouldnt port match your exhaust side. Just do the inlet side. You want the exhaust manifold to be larger then the port exit. You need something to help reduce exhaust reversion, having that step left where the manifold meets the head, Thats about as much as you can do. So match your manifold to the gasket and thats all you need.

But for $50-$100 bux you can pick up a porting kit with the cartridge rolls and stones and then go yourself. Just cleaning up, removing casting lines and machine overlap everywhere, blend it all in so there are smooth transitions and no sharp edges. Should be good. Thats all I did to my rb25 head and ive got the flow figures. But i need to get a stock head flowed to see what improvement ive made. I picked up about 5-10cfm throughout the range just from the better valve seat job over standard 3 angle. That was suprising. Just a few more transitions and suddenly air flows easier out the valve.

Thanks for the constructive input.

I really didnt plan on doing much to the exhaust beyound a clean up. I am still thinking on the valve job, we will have to see how much the shop here wants to charge....

[N1 RB26]

so how'd you go what did you get up to??

[Rolls]

so how'd you go what did you get up to??

lol you still stuck on your silly idea of your built 20?

[N1 RB26]

haha yeah ... lol but gonna do 24 as a side thing so not fussed just interested in if the work made a difference

[Rolls]

Hey I've got a great idea, you should stroke an L24 up to a 2.8L using a diesel crank, it'll be sick because no one else has ever done it in a skyline, it will also sound mad.