Reliability at 400wrhp(310wrkw)

[Guest RedLineGTR]

just go to japan, go to a well know company tell em how much power ya want and they will do it for ya...nice and simple...but expensive...maybe??

[Sydneykid]

Hi Steve, you were right when you said "I know what Sydneykid will say about decompressing the engine with gasket, but its ALOT cheaper to fit a $300 gasket than fully build a bottom end or buy rb26 internals".

Firstly, tell me where I can get a stainless steel RB headgasket for $300? I can't get them for anywhere near that.

Secondly, you can size the combustion chambers for about the same price as a head gasket. Why wouldn't you do that? It has none of the side effects of sticking a 1.2 to 1.5 mm piece of stainless steel between an alloy cylinder head and a cast iron block. At least you will know that the combustion chambers are all the same volume, so the compression ratio is the same in all cylinders.

For the same cost you could probably have the head ported and the valve multi angle cut as well, for better performance and quicker boost.

Thick headgaskets are popular in Japan because any fool with tools can do it. Good head machinists are hard to find there and so charge like poison. That's simply not the case downunder, where our machinists were brought up on dinosaur engines that always needed head work.

Hope that clarifies my position

[dabigbolf]

would it be fare to say that if you are chasing 300 rwkw reliable the rb26 is the best option. (as it can handle the power, without opeing up the bottom end (thus cost would be less in the end, compared to rebuilding rb25)

and would it be fare to say the best option would to just get a hold of an r32 gtr, and just do the basic mods, of turbos, cams, exhaust, injectors, etc.

(would it work out cheaper, i am not sure)

Unless you like the idea of going through the conversion, and getting a fully rebuilt r25, or big single turbo rb26.

But it just seems a lot of money to throw at a motor, when chasing 300 rwkw.

And the price to put an rb26 would not see much change from around 15 k, if you did it properly. With changing over sumps, custom tailshafts, engine mounts, crossmember, fuel pumps, radiators, cooler piping, wiring it all up.

Just dont reckon the rb26 conversions are worth the money, when gtrs are getting cheaper these days. Cause the cost of labour is high, and getting a person who knows what they are doing can be hard.

just a thought, cause i know if i had a chance to turn back the clock, i would have just bought an r33.( i say that now though)

:bahaha:

[Guest Lord]

we cant buy skyline here

there is no RHD car allowed in canada either

[dabigbolf]

damn,

thats gotta suck.

300 rwkw in a s14 should be fun still, but remember you gotta stop aswell, brakes would be important. and also a twin plate clutch or something. starts to add up.

but go for it, if you got the cash.

i think i read you were going for street use, and if you can't have the rb26 as a twin turbo, then maybe it wont be the best for street use. Cause if you are after a big single turbo, then they may have a heap of LAg.

rb25 with say a gt30 (which i think Fuzz has on a video on another thread, on 17psi made 300 rwkw).

and that was on boost by 4500 rpm so not too bad.

i am not sure, will be good fun though.

[Guest Lord]

in fact, i am going to sell my wrx....for about $can29k, and spend 2k for an old diesel jetta, and rest in my 240sx project..i have already a s14a sitting in the garage.

i believe rb26det would fit in my budget...also all the chassis enforcement and suspension

i have no idea how lag its gonna be with single turbo rb26...but i am going to get an smallest turbo for my goal wrhp at safest boost lvl, which means keep engine alive (hope), in reason to reduce as much lag as possible

i am living with wrx's turbo lag, personally, normal driving in off boost, i kinda like it (max boost at 3,8k rpm)

yeah, Fuzz's setup is definitely in my mind too....

[dabigbolf]

well for 29 k (in the us currency thats what 58 k australian), you should have heaps and heaps of change left over.

as for lag, i was talking about the massive turbos t88 or whatever.

but you get that when you wanna make the big power i spose.

worth it when it comes on boost.

take pics, and post em up, always good for progress.

[Steve]

Originally posted by Sydneykid

For the same cost you could probably have the head ported and the valve multi angle cut as well, for better performance and quicker boost.

you can find the gaskets here: http://www.greenline.jp/catalogue/bcpartli...ntake=FI#engine

Slight error on the price its $350 not $300 (my bad:)). But please lets compare costs here, cos I have done a bit of research.

Remove head $300

New Gasket $350

Postage < $40

ie under $700

I have been quoted for some head work. Clean, Mild port, triple seat vavles, assemble and dissasemble was all up $1295, then add the cost of fit and remove $300 plus a new headgasket. This was the cheapest I have found so far.

Over $1600.

I would love to know where I could get a head done for $350, as I am sure alot of people here would - even just a mild port for that price would be awesome, the best price I have been quoted for a mild port is $700 - thats supply bare head. Extrusion hone in SA costs $100 a cylinder - its just not economical. I do intend getting a mild port done when the head is off.

Bottom line in my reasoning is head gasket is quick easy and has proven results - what more do you need?

[Sydneykid]

Hi Steve, let's see........

The most expensive is ¥35,990, around $500 (HKS)

The cheapest is ¥27,489, around $382 (Tomei)

Using your freight of $40, plus 15% Import Duty and 10% GST

That's $533 and $633 respectively.

The people quoting you $1,600 in Adelaide for the head work are very expensive. PM me and I will give you the Sydney prices.

Lowering the compression ratio is pretty much out of date technology these days. It simply is not necessary in most cases. But if you have to do it, why have the side effects of using a thick headgasket? Especially when you can achieve it by resizing the combustion chamber with no side effects.

"What more do I need" No side effects, that's what more I need!

Let's compare apples with apples here....

Between $533 and $633 for a headgasket or $600 (Adelaide price) for a combustion chamber resize.

That's a fair comparison since remove and replace the cylinder head costs the same whichever way you do it.

I know which one I would pick, every time. But that's my choice, you are fully entitled to choose the other way if you wish. I am merely stating the alternatives.

Hope that clarifies my position.

[Steve]

Still not quite right 27489 yen = 352.88 aud, (current exhange rate is 77.9 yen : 1 aud) no duty no gst 'cos its a private import (customs seem to be kind) bought a fair bit of stuff, never been hit any additonal charges, this includes injectors and a new HKS turbo.

I havent acually priced having the chamber resized, only porting, valves seated, triple faced, extrusion honing, etc - added to the cost of fit and remove valves, cams, clean head - well it all adds up.

The $700 I was quoted for a port was for a bare head, no remove and replace furnishing which would be required - but not in the case of a head gasket.

Doesnt changing the shape and size of a combustion chamber have the possibility of creating hot spots - I was under the impression that most manufacturers spend alot of time and effort getting the combustion chamber design pretty close to perfect. How much can actually be removed before heading into dangerous territory?

Could you please explain the downsides of a headgasket approach to decompression - because so far the gasket appears to be tried and effective and cheap by comparison.

What is it exactly that I am missing?

PM on the way for those quotes - thanks

[maximumrpm]

try looking at a older hot4s magazine that had this conversion done in japan...it was a silver s14 and had a rb25 with a t88...it was a beast...its a really old issue i think in the second year...will have to find the magazine lying around the house

[Roy]

From memory it was an RB26, not an RB25... are you talking about the one with the fat rear guards, if so definitelt a full house RB26.

[Sydneykid]

Hi guys, I get asked a lot to give my personal reason for disliking thick headgaskets, so once again here goes ..........…………

Thick headgaskets are made from multiple layers of thin stainless steel. The thicker the gasket (lower compression ratio) the more layers. A normal thickness stainless steel headgasket will have 2 or 3 layers. A thick one can have 4, 5, 6 or even 7 layers.

These layers are very thin, almost knife edged, and sit at the junction of the cylinder head and the block. This makes them a perfect target for combustion chamber hot spots which cause detonation. The very device you are installing to decrease detonation (by lowering the compression ratio) actually adds to it. Pretty crazy, if you ask me.

The extreme number of layers makes them susceptible to slippage when the block moves in relation to the head. This of course occurs every time the engine warms up and every time it cools down, due to the differential expansion and contraction rates of the alloy cylinder head and the cast iron block.

Very thick headgaskets should require the use of longer head bolts. These are hard to get (expensive) and no one seems to do it. Every engine I have pulled apart with thick headgaskets has at least 1 or 2 stripped threads in the head. This causes all sorts of problems with warpage and eventual gasket sealing failure.

When you have this large a number of thin layers the head really should be retensioned, but, because of the reputation of thin stainless steel headgaskets for not requiring retensioning, people don’t do it for the thick ones. This is added expense, as anyone who has retensioned an RB head will tell you, it is not a 5 minute job.

The real reason thick headgaskets were made in Japan was because of the expense of the other methods of lower compression ratios ie; properly designed pistons and/or combustion chamber relief. With labour being so expensive in Japan (where a good cylinder head machinist earns as much as a Doctor) a cheaper solution had to be found. Thick headgaskets were the result.

Now downunder, being brought up on a diet of dinosaur engines that always required porting and cylinder head work to produce power, we are blessed with a cheap supply of very experienced labour. So it is simply not necessary to cheapen the engine work by using a thick headgasket when a machinist can do it without the side effects.

The small amount of chamber resizing required would have no effect on the integrity of the original design of the combustion chamber, in fact they benefit from the volume matching and polishing process. This removes any points or lumps, which can become hot spots and cause detonation. It’s a win / win. You get the lower compression ratio with no side effects and a better combustion chamber all at the same time.

Hope that explains my stance.

[Sydneykid]

Hi Steve, following are two quotes from greenline website...

HKS Head Gasket

(Gaskets) ¥32,201

Stopper Type. 1.2 mm. 88 mm bore. 9.0 compression ratio.

TOMEI Head Gasket

(Gaskets) ¥27,489

1.2 mm. 88.0 mm bore. 8.6 compression ratio.

It always worries me when a 1.2mm thick head gastket (88mm) gives a 9.0 to 1 compression ratio when you buy it from HKS, but a 1.2mm thick head gastket (88mm) from Tomei gives a 8.6 to 1 compression ratio...

I thick I would much rather trust my cylinder head machinist

[Steve]

I checked on this and was told that its because the HKS gaskets compress more that a TOMEI? Also, they have a stainless insert around the bore that is one piece, not multiple plates - perhaps I have been mislead.

How long ago have you seen these headgaskets that you are talking about - is it possible that the technology has caught up with the problems that were encountered a few years ago? Or are these companies lying to us?

[Guest mmdb]

i was lookin' for the same thing "son of rajab." There's some guys on the nico.net forum that're doing the rb26dett swap.

I also hear that the rb25det is good for close to 500??? I'm sure the austrilia guy sknow more since they actually drive the cars.

Just to clarify things: 400hp in a rb25det with stock internals, a bigger turbo, an upgraded fuel system and stand alone engine management will suffice as being reliably? I'm hopin' for those goals when I put in the rb25det in my s14a.

[hippy]

mmdb ... 400hp in a rb25det with stock internals, a bigger turbo, an upgraded fuel system and stand alone engine management will suffice as being reliably? I'm hopin' for those goals when I put in the rb25det in my s14a.

ask whatisname .. he had a similar setup .. engine died soon after ... cant' remember what the problem was .. go to the SA section ...

[Guest mmdb]

e-gad... that's not good.

[Steve]

merli has 280rwkw, and I believe he puts his car on the track. this is with stock internals. I think alot of the problem is detonation, which is harder to keep at bay with the 9:1 CR, but with a really good tune - perhaps drop merli a pm too?

[Guest drift_me_silly]

i'm looking at a 2200cc RB20 with a 25/30, i hope to be able to run 9:1 comp, 1.5-1.7 bar of boost and a 9000rpm redline...with appropriate strengthening procedures i don't see why i shouldn't be abel to accomplish this (with a high quality tune)

my aim is 250rwkw, everyday all day.

-new r33 gtr crank

-custom je forged pistons

-carillo rods

-nizpro crank girdle

-electric w/pump

-cryo treatment of internals/block & head

etc etc etc.

no idea of cams yet...