Jump to content
SAU Community

Recommended Posts

Hey guys,

Thinking of running these shortly:

http://www.rhdjapan.com/naprec-forged-big-valves-set-rb26dett.html

Trying to get info on what I will need to order parts wise to run them.

I know they are 6mm exhaust guides instead of the 7mm, was just going to pick these up with the valves:

http://www.ebay.com/itm/Supertech-6mm-Exhaust-Valve-Guide-24-pcs-Nissan-GT-R-RB26-RB26DETT-/301266390742

Anything else I am missing?

Link to comment
https://www.sau.com.au/forums/topic/462789-naprec-15-os-big-valves/
Share on other sites

Yeh I did read about supertech doing parts for Tomei. I read a post by fitzpatrick speedworks about the trumpet angle on the Ferrea valves being a lot better then standard 16 degrees vs 20 on Ferrea.

I'm just trying to justify if it's even worth doing the valves when I have the head off. It made 620hp @ all 4 on 25psi on e85 last time it was tuned (26/30). This time going back I am chasing 30-35. The head currently has grex 272 cams (10 lift intake, 10.5 exhaust) and HKS step 2 springs I believe, and some unknown porting from Japan on both in and ex.

I was going to change over to supertech dual valve springs, as I am unsure if the single HKS step 2 springs are up to the task of that much boost, and I thought I would look at valves while I am at it. I have searched up and down the forums to try and see what standard valves are good for in terms of HP. From what I head read on other forums, the port job has a lot to do with the end result also, according to a post on Peformance Forums. What's your opinion bigmikespec?

I was quoted roughly 2k in labour and parts to fit the larger valves, which is quite an outlay given I don't really know if it's justified.

Should I look at doing valves, or just springs, or neither? I was also considering running a larger duration/lift cam on the ex side too.

What's everyone's thoughts?

Cheers.

Yeh I did read about supertech doing parts for Tomei. I read a post by fitzpatrick speedworks about the trumpet angle on the Ferrea valves being a lot better then standard 16 degrees vs 20 on Ferrea.

I'm just trying to justify if it's even worth doing the valves when I have the head off. It made 620hp @ all 4 on 25psi on e85 last time it was tuned (26/30). This time going back I am chasing 30-35. The head currently has grex 272 cams (10 lift intake, 10.5 exhaust) and HKS step 2 springs I believe, and some unknown porting from Japan on both in and ex.

I was going to change over to supertech dual valve springs, as I am unsure if the single HKS step 2 springs are up to the task of that much boost, and I thought I would look at valves while I am at it. I have searched up and down the forums to try and see what standard valves are good for in terms of HP. From what I head read on other forums, the port job has a lot to do with the end result also, according to a post on Peformance Forums. What's your opinion bigmikespec?

I was quoted roughly 2k in labour and parts to fit the larger valves, which is quite an outlay given I don't really know if it's justified.

Should I look at doing valves, or just springs, or neither? I was also considering running a larger duration/lift cam on the ex side too.

What's everyone's thoughts?

Cheers.

Rightio,

I have had the full effort NAPREC "RB26 drag kit" + the "RB26 drag combustion chamber kit" done to my head which was ported by HKS Japan. I chose to only take out the intake squish pad.

Whats in the head is listed below;

- NAPREC Big valve

- combination valve guide https://translate.googleusercontent.com/translate_c?depth=1&hl=en&prev=search&rurl=translate.google.com.au&sl=ja&u=http://www.naprec.co.jp/product/p004&usg=ALkJrhhLdKu4fyLlk8pZTewN2weuv0jj9A

- heat-resistant sintered sheet ring

- the cam cap stud bolt ,

- valve guide replacement

- sheet ring replacement

- the race for the seat cut (protruding alignment)

- water jacket air vent hole processing

- oversize jacket plug-in processing

- 1.0 surface Labs until mm

A custom set of cams were made using an Alfa Romeo Naturally Aspirated lobe of all things that measured 260 @ 10.85 mm with a very agro ramp rate. The HKS step 2 springs valve floated with anything more than 19 psi/5500 RPM from memory. They got ripped out and replaced with supertech single springs. Not an issue so far.

Below is the final result using a 2.8L/-5/E85/9.0:1 comp combo.

972FDE76-81E2-40D4-9009-FED29B987CB8-174

Turbo's are well and truly finished. What is interesting was at 19 psi (where the gates were set) it went 441 KW.

How much of that was down to the valve size itself, who knows.

The -5's are coming off and a single 8374/1.05 is taking its place.

I hope this helps.

Some good info there Piggaz appreciate it, especially about the valve springs. Not too sure how I didn't see float before 25psi if that's the case.

I bought the head from Japan already ported, so yeh it has in and ex already ported. I had a guy look over it at a cylinder head place, and he seemed to believe that whoever did it, did a pretty good job of it.

Had bronze guides in it when I got it, all the guides on ex side where flogged out. I put this down to the standard exhaust valves absorbing more heat through the valve stem itself over other aftermarket valves. This was another reasons I was thinking of going valves/new bronze guides. The replacement guides that they fitted where non bronze type, just some they had made up to fit.

Go for it then, replace the guides with bronze ones (I got Nitto ones) and replace the valves with +1.0mm oversize, at least they can recut the seats so it is all perfect again. Maybe try the Nitto valves.

Talking to RAMS cylinder heads last year, anything over 1.0 mm OS, you need to replace the seats for larger ones. 1.0 mm you can recur the factory ones.

That's interesting, as the majority of the cost to go the Naprec valves was due to having to replace the seats when I spoke to my cylinder head guys. Where did you source the Nitto valves from Bigmikespec? I can't seem to find them for sale anywhere online.

Definitely going to go 1mm OS now, just tossing up between Nitto or Supertech. Can't really afford the Ferrea kit, it's nice, but it's a little too much of a stretch once I factor in labour costs as well.

Thanks to Piggaz and Bigmikespec for the input, appreciate it.

Edited by James_03

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Hi. A little bit of an update. It maybe(hope not) looks like i would need a new tranny(it would be "maybe" a cheaper or better option anyway) So i need some info. I know i need a different propshaft(i can make custom one) LSD is not a problem cuz the engine will be still(for now) N/A RB20. So if i buy RB25DET NEO tranny...is there something else i need? I read something about push/pull type but i do not know if i need to "change" something or i can just plug n play onto my engine a go? Thanks for the advice  
    • Good morning all, Bit of a random question but figured I’d finally throw it out after wondering for a long while. Before I start, I'm hoping to do this purely out of personal preference. I think it would look better at night, and don't mind at all spending a few hours and dollars to get it done. I've copied this from a non-Skyline specific forum, so I apologize for the explanation of our headlight switch setup that we all know. Here we go: Zero lights (switch off) Parking lights (switch position 1) being a rectangular marker on the outside of the housing, my low beam being the projector in the centre (position 2), and a high beam triggered by my turn signal stalk. Most North American cars I’ve owned of this era have power to the amber corner (turning indicator) light as part of the first switch (parking lights). I’d love to have these amber corners receive power when the headlights and parking lights are on (headlight switch), yet still blink when using the turn signal which is of course a separate switch. Hopefully I’ve explained my question correctly. Is anyone aware of a way in which I might be able to achieve this? Thanks in advance
    • My heads are cathedral port! It's likely possible, but I don't want to add any extra moving parts (I know they don't move) between the heads, manifolds, etc. It will also affect how injectors/fuel rails etc sit and I don't really know if it would change how the FAST manifold goes/sits/fits. I have the LS6 steam pipes already as I have a very late LS1 block so it should be fine. I couldn't find anyone who had ever actually used one for this purpose, it seems 100% of people grind the water pump. The thermal spacers are 12mm and are half way to the cost of the newer water pump anyhow... so if it comes to that I suppose I'd rather buy a new pump. The bearing in the pump I do have is a little.. clunky, but it hasn't done that much time and I never noticed it when the car was together in the past few years, so..
    • The bushing has failed, not all that uncommon for a car of this age.  Any mechanic should be able to push in a new bushing for you, or you can probably buy the entire lower control arm, complete with bushes.
    • Could you not use "thermal" spacers to give the clearance, like the ones I used between the blower and head? That raised the manifold height by around 10-15mm Albeit the ones I used were for cathedral ports, but I assume they have similar for rectangular ports????
×
×
  • Create New...