So While The Head Is Off My R32 Rb20Det...

[BobbysCustoms]

Hi guys,

I have a 1992 R32 GTST, RB20DET. 130,XXX kms.

Short story is im about to refit the head, and am curious to the pros/cons of a cometic metal head gasket, what thickness gasket i should run (1.3,1.8mm etc), and benefits of arp studs as opposed to standard head bolts.

Bear with me as i give you more info than is possibly necessary -

Head is off due to a leak from cyl6 to water jacket - bought the car 9 days ago and I pulled the head off last night. Engine ran healthy compression across all cylinders (including 6, actually) which I was happy to see.
Still has cross hatching on bores, no lips or scoring etc and ive checked for taper and out of round. Super happy with the block. Head has all clean chambers, valves vac up fine, valves guides are tight enough and it measures straight down the cam tunnels and across the bottom face also. No corrosion. Gave it a clean and can find no cracks. Block deck is straight too. Piston height at TDC is equal across all cylinders. Im happy to simply refit the head.

I have an RB25 turbocharger to fit, and will possibly upgrade again in the future. I have a turbosmart dual stage boost controller. Car has a large FMIC and a cat back exhaust which ill upgrade to turbo-back system later.

I understand that it is sometimes good to have a weak point in the setup that is sacrificial in order to prevent damage to more expensive/difficult components to replace. Is that something I should be worrying about with such a mild setup? What thickness should i be running? Im happy to just keep standard but if a slight raise in compression is safe then i wouldnt mind doing that at the same time.

Is it worth spending the extra cash on ARP head studs? I only expect to run 13psi tops for T&T's and night runs (unless more is still safe) and standard boost pressure all other times.

[kitto]

OEM Nissan head gasket and factory head bolts.

No point in wasting your cash on ARP studs and a metal head gasket when your not pumping lots of boost into it or asking for a lot of power.

You also can't use a metal head gasket unless you face the head and ideally face the block.

Do you know what was causing the leak?

[BobbysCustoms]

OEM Nissan head gasket and factory head bolts.

No point in wasting your cash on ARP studs and a metal head gasket when your not pumping lots of boost into it or asking for a lot of power.

You also can't use a metal head gasket unless you face the head and ideally face the block.

Do you know what was causing the leak?

Thanks for the quick reply. The faces look fine and measure up but yes i was concerned about how a metal gasket would seal (even with the plastic coating) without them being perfectly machined surfaces.

Facing the head wouldnt be a huge issue but no way will i be pulling the block to have it decked.

Im not sure what caused the leak - visual inspection just shows a gasket failure. The metal sealing ring is corroded to the point where it has allowed the rest of the gasket to deteriorate until it reached the water jacket. Further than that im not sure.

Nothing indicates overheating really, tho it does have a replacement radiator so i wouldnt rule it out.

[GTSBoy]

With respect to how hard you could/should push the combo.....if you run an RB25 turbo to about 12 psi you'll be going close to the same operating points on the AFM and injectors as if you were maxing out the RB20 turbo....ie, pretty close to 100%. So you won't want to go much further unless you've got it on the dyno and can watch how these parameters are going.

You'd also be well advised to at least Nistune the ECU so you can tune it. It will use a lot less juice and make more power up top if you can dial out some of the excess fuel and add in some timing. And of course then it will be able to support any changes you might do later, like bigger injectors etc.

Also, make sure you check the fuel pressure when the engine is at max load. You don't want that to be a weak point that costs you what sounds like a quite good engine.

[Simon-S14]

i agree with kitto. Keep it stock and simple. the OEM rb20 gear is more then good enough to support large boost and power. just make sure you solve the leake issue first. spend the money and get the head pressure tested and hardness/crack tested. if its all good then refit and away you go

[BobbysCustoms]

Ok so I've got a set of bolts and a gasket on the way to get the thing back together once my head is ready to be picked up- just having it hot pressure tested.

GTSboy your of the opinion that the boost I want to run will start to max out the duty cycle of the injectors, fuel pressure, as well what the afm is capable of reading...?

I don't have the funds to throw it on a dyno- it's a bit of a budget toy. Tho if something needs upgrading as part of the typical modification process then happy to do it. Will later model injectors rectify the issue? And a Z32afm? Does this need to be calibrated?

Will an aftermarket fuel pressure reg help the pressure drop? Really want to avoid leaning it out and damaging it.

[GTSBoy]

No. Open that can of worms and you start the whole money spending thing.

A fuel pressure reg doesn't make pressure, it just sets it. If yoru fuel pump is not big enough (or has worn out some) to keep up with fuel demands then pressure drops (regardless of what reg is in place) and you get lean or lean right out, followed by smoke and steam.

If you put in bigger injectors and/or AFM, then you must tune the ECU. So that adds up to a couple of grand easy to do those three things together.

If you can't at least put a wideband onto it as you wind up the boost, then it is probably safer to stay at 11 or 12 psi until you can. Even 12 is getting up there on that combo.

[Roy]

If you speak to the likes of Toshi etc then that may help you out with the direction you should take some tight tweaks as I believe he has a few stc chipped plug and play tunes for people that are running 2530s, RB25 turbos with std fuel injectors and afm etc.

If you can get one of his chips that suit std injectos, afm and fuel reg...just with a nice fresh fuel pump pumping away ensuring sufficient flow. You could end up with a nice 180-190rwkws car for rather cheap (~$300 for one of his chipped ecus?)

[sneakey pete]

That's a good and cheap way to go, cost me about 600 bucks in ECU stuff to get my setup, which is the same (25 turbo and fuel ump), and that was with some nice second hand bargins and the like.

[SiR_RB]

Stock gasket with standard bolts

Metal gasket with arp bolts

[BobbysCustoms]

#@Roy This Toshi guy will have a tune to suit my sort of combo?
Rb20DET
RB26 Cams with adjustable cam gears (+2 in, -4 ex)
RB25 Turbocharger @11psi or so
FMIC & cat back exhaust.

Will be doing dump pipe, front pipe, highflow cat somewhere along the way, as well as a better fuel pump.

How can i get in touch to chat to him directly? He on here as a member?

Edited June 14, 2013 by BobbysCustoms

[GTSBoy]

Yes he's on here as a member. The cams might be an obstacle to him having a "typical" tune ready for you. But you never know.