Driftnuttz

I am looking for specs, how big is the dome on the pistons (red and silver), how big is the combustion chamber of the red and silvertop heads, are the head gasgets the same thickness. things that I cant find on google, and would not be in the fsm. I know people say the bottom end is the same, but I am wondering if the pistons are the same and if the heads use the same cumbustion chaambers. I know the heads are not made from the same cast, so I am wondering what esle besides the intake runners are different. You cant just look at the CR of the redtop and silvertop and say it will get X CR. There is simply too many factors involved in getting X CR. Thanks for the response.

I am looking for the combustion chamber size. I also need to know if the eccs redtop and silvertop heads use the same cumbustion chamber setup. Lastly, are the pistons the same? I am trying to figure out the compression ratio that I will get just from the head swap, then if I can get any more out of it. I did do some searching.

you guys are mad.....lol I am still doing stuff, not done yet.I have decided to up the compresion to either 9.5-1 or 10-1. I have not figured out which one yet. That should help out all around.

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....

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........

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.

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.

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

Yeah they are a nice little upgrade over the stock rb20 turbo. Nice up in power and hardly any drop in response, and thats at 15psi. I would guess this turbo on a rb25 would be like the stock rb20 turbo on the rb20, kinda crapy....lol. I do see why you would hate them on the rb25.

Yes this may be true, on a rb25det. On a rb20det its not moving the same amount of air at 15psi. My last 240sx(s13) had an rb20 and rb25 turbo and it held 15psi strong till redline all day everyday. When I installed the manual boost control I had it set waaaay too high and it shot up to 18 at the blip of throttle. So if you have problems with yours holding 12 psi on a rb20, I would check to make sure something else is not wrong.

Why is everyone scared of these turbos on rb20s? I mean I see people saying on rb25dets they should stay below 12psi, why is it the same on a 25% smaller motor? I would think that you could push more boost on a smaller motor, as the reason they fail is because the heat makes the wheel weak and comes apart at higher shaft speeds. 12psi on the 20 would not need the same shaft speed as on the 25, plus the ex would not be as hot at 12psi. Add to that the fact that the head does not flow the same, so the more resistance in the system the less air the turbo needs to move to see 12psi. This means the wastegate is opened more and the ex wheel is seeing less ex gas helping even more to keep the heat off the wheel. Make sence to you?

You can make it flow more and still keep the air speeds up, like I said I am not just going to make the ports as big as I can. The good head builders here in the states do it all the time. Thats how you make the best power with a usable power band. I have never seen a motor here with lots of miles and failing rings look so good. Most of the time they are real faint if visable at all. Really though it doesnt matter as I was not planning on reringing it unless the cylynder walls were messes up. No scares or scraps and plenty of hone left. Arps and a oem gasket kit and I think I am golden. The big end looks good too. Anyone know if a oem gasket kit comes with a waterpump gasket? I have a new pump but no gasket with it.

Yeah maybe, but from what I have seen they would not look this good. I mean they really look as if the hone was just done. I moved the pistons side to side and there was little to no movement. The big end looks good too, so with a gasket kit and arp head studs it should be a nice motor.

I dont get it.....lol. I got the head off and the hone is still vary visable on all the walls, so this tels me its been rebuilt before. No way thats a 20+ year old hone job.

Yeah man its this one http://www.skylinesa...&attach_id=1595 I wonder how much boost would be safe on a rb20det? I had a older rb25 turbo on my last one and ran 15psi, I didnt drive around at full boost all the time. It would move when I floored it though...lol I take it they still used the crappy ex wheel, right?

Ok so the rear housing does say op6, but the front housing does not say 4v54. Any clue way this is? Think I could have gotten lucky and it is a jdm remanned unit? < I dont think this is the case, but I guess anything can happen. The guy I got it from really had no clue what was in it or on it, other then what he could see. He did claim a lot, but non was true. I am thinking that he bought this from an importer to swap into his car and ran into truble cause it was redtop rb20det.

I am keeping the block stock, I am just trying to get the head to flow better so it will be a better overall motor. I will gladly go in to the engine sales and make a ton of money with you.... Shipping will be a bitch though....

Rolls- Your not getting what I am saying. I AM NOT SPENDING A LOT ON THIS MOTOR. I will have less then 1000 usd in my motor when its done. No way in hell I get a rb25det setup for anything close to that here in the states. I guess it may be easier for you guys cause they sold cars there with them, but here every rb is imported and costs more. Here rb20det redtops run for around 800, silvertops 1500, rb25det s1/s2 about 2500, a neo 3000, a rb26 4000, and if you can find a rb30 block it will be 1500 by itself and then you still need to buy everything to bolt to it. So here in the states it wont be a waste of money to work a rb20.

LOL maybe, but I wont be doing a rb24 and wont be spending "heaps of money" on head and cams. I will be doing all the work myself. Here is what I am going to be running when mine is done. A redtop block with a silvertop head, port and polish work, ported and matched intake with front facing plenum, redtop cams (248in/240ex), rb25det turbo, arp heads studds, 10lb flywheel, front mount, 7mgte 440cc injectors, z32 maf, and 3inch turbo back with no cat. I am going with the redtop cams cause the intake is a 248 vs 240, the ex is the same. With a tune to run it all. I am looking for close to 300whp at around 15psi, if I get that then I will be happy. I will have less then 1000 bucks in this setup.

So the sr sucks too then? As last I checked they were 2.0l too. Its not the fact they are 2.0l its the fact that nobody wants to make the heads better. I have said it before ,and will post links to back me up, the head is what makes the power. So, if the head flows like crap, how can you make good power and a good power band? You cant. So, without head work your really holding yourself back and setting yourself up to fail. Making the head flow better will not automaticly make it more of a dog down low. I dont mean porting the hell out of the ports when I say make it flow better, cause that will do just what you say. The compression can be changed so thats really a moot point. If you get the head to flow better, and up the compression it will make the a world of difference in the lowend and spool time of the turbo. Now will it make the rb20 as good or better then the 25/26/30? No, as they are bigger and will be easier to make power with. It will however make the rb20 a lot better. I will keep you guys posted cause I will be doing head work and uping the compression.

I have noticed that nobody trys to much past bolt ons on the rb20. I am working on one and will be doing a bit of head work. I am not going to go crazy or anything. I will be cleaning up the ports and shaving the head down a little as well. I really think this will help the motor spool a bigger turbo faster then a standard rb20, as well as add power from a better flowing head. I do think people underrate the rb20det comapaired to the rb25/26/30. Now dont get me wrong, I do think, well know, the 25/26/30 are all better. Its just that the rb20, from what I have seen, has less r&d put into it. Nobody even trys to do work to the head to make it better, they just say trash it and go rb25/6/30. This lets the 20 down and is the main reason nobody makes much power with the 20. Think how lame it would be if every motor ever moded was treated the same way, after bolt ons put something bigger in. It would be real lame, there would be no monster rb30det builds no 500+whp rb25dets being daily driven and no 1000+whp supras. These all came from people stepping outside the box and doing stuff nobody esle had done. Its not "reinventing the wheel" its building motors. Some motors are easier to make powr out of then others, but this does not mean its a waste to build the others. Most of you that read this will probably think I am crazy, and thats cool as I could care less. I love the rb motors and untill I have the money for the rb20dets big brothers I am going to work with the rb20det. I do everything myself and am going to see what I can get out of the rb20det, and I am not starting with a big turbo like everyone else. I am starting with the head and will make it better. I am going to stop with this long winded post.

I will go look and see if it does say it. I have pics but I cant post them up. Here is the comp housing on my facebook, if someone doesnt mind can you post it for me. http://www.facebook.com/media/set/?set=a.160161667369856.51045.100001280722330#!/photo.php?fbid=190229841029705&set=a.160161667369856.51045.100001280722330&type=1&theater

Ok guys thanx for the imput. I was thinking that the seals would let oil through if there was oil just sitting in there. When I got this motor it was supposed to be a full swap readdy to go in the car. I was shocked to find that it was a full r31 rb20det redtop, and I have had to swap everything aside from the block over to silvertop parts. This has really pushed my budget way over what the wife and I talked about. I would love one of those high flowed units, but here in the states its not a real option. To do that to a turbo it costs almost the same as new greddy unit. I will be upgrading the turbo as soon as the money is there. I am just going to use this turbo to get the motor going. If any of you guys wants to help me out by sending me one of those hig flowed units feel free...lol I am 90% sure its from a neo. The comp housing has this on it "GARRETT A/R .60 M24 N (in a small raised box 6116) 1" When I googled these numbers they came back as a neo.

I am swapping an rb20det into a 240sx (in the USA). Well the motor came with a Rb25 turbo, I think its from a neo. I am pulling the head off to redo some stuff, and while the turbo was still on the motor I flipped the whole motor over on the engine stand. When I flipped it back up right I saw oil coming out of the turbo from both sides. Wen I removed the turbo it had a lot of oil in the exhaust housing. Do you guys think the turbo is junk? I have never seen the turbo in a car running, but it has little( I do mean little) shaft play and spins freely.

Doo It.....