Rb30Det, Head Gasket Blown Between Cylinders?

[nicksamaniac]

Has anyone seen this on an rb before?

Mine has randomly let go between cylinders 3-4, oil is clean and pressure is spot on, not running hot at all, coolant is clean.

It just started running All of a sudden really rough, and after a comp test, cyl 3 and 4 have nothing, sooty plugs and that's it, every thing else seems fine.

[Simon-S14]

Could be several things.

Head not flat

Deck not flat

Head bolt not torqued correctly

Detonation

[533 RYC]

Anythings possible. how much boost does it put up with?

My wifes Cube decided to not start one morning. popped between 1 & 2. Both cylinders were a perfect 82psi.

[battery]

Pulled down my old rb20 the other day for a look. I had milkshake coolant from this though.

[GTRPSI]

Sounds like the seal between 3 and 4 is compromised, there will be no water or oil mixing issues, simply no compression if dead on right between the cylinders.

Good way to check is pull a spark plug out of one of the 2 failed cylinders, leave the other one in the other failed cylinder, turn over the engine by hand, when the cylinder that failed with the sparkplug fitted is in the compression stroke you will hear a hissing into the cylinder without the spark plug.

Same will happen if you swap the sparkplugs the other way around, whichever cylinder is going into compression with the spark plug fitted will leak out into the failed cylinder next to it without the spark plug.

Edited January 2, 2014 by GTRPSI

[nicksamaniac]

Only runs up to 8psi, standard r33 tune. Standard timing, it is an rb30/25 running the stock 370cc injectors and ecu, afr's are spot on at 14.7 @ cruise and up to 11.7 @ full boost,

Components look flat under a straight edge but may have to look closer with feeler gauges, maybe get some bits milled/surfaced.

Might be an excuse to build a full angry engine!

Edited January 2, 2014 by nicksamaniac

[luke gtr]

youre running the 2.5 tune on a 3l?

[nicksamaniac]

Sure am, even had it on the Dyno to check it! The afm goes over 5v at around 11psi boost, it's at 4.89v at 8psi, so that's as hard as I can run it.

I have a set of sard 700cc injectors but am waiting/saving for a power fc.

People say it can't be done but if you think about it it's the same as winding up boost on a stock 25.

Its only 500cc or 500ml capacity Extra.

[discopotato03]

Best to start with flat square machined surfaces to give the fire rings the best chance of sealing . I reckon an OE or better spec gasket too and if the head and block are down maybe studs and nuts instead of bolts ?

A .

[Simon-S14]

Lol that's the craziest thing I've heard. just Because it runs Ok at 8psi on the dyno doesn't mean that in the real world it might not boost spike and max your afm out and cause detonation. Which is exactly what's happened.

500cc more is a biy more then winding the boost up. The comp ratio has changed. The airflow characteristics have changed all throughout the load and rev range. It's never going to work safely on a stock 33 ecu. Do yourself a favor and get the head checked. Gasket replaced and put a tunable ecu in it

[75coupe]

School holidays surely

[nicksamaniac]

Boost spike? With a 4 psi spring in a 50mm gate, bleeding off to get a MAX of 8 psi, with the boost controller at full bleed.

Funny how I've been driving on this setup for 22000km.

I actually have an answer now, head is not flat, out of spec over the length, explains why it went between 3-4.

[GTSBoy]

Lol that's the craziest thing I've heard. just Because it runs Ok at 8psi on the dyno doesn't mean that in the real world it might not boost spike and max your afm out and cause detonation. Which is exactly what's happened.

500cc more is a biy more then winding the boost up. The comp ratio has changed. The airflow characteristics have changed all throughout the load and rev range. It's never going to work safely on a stock 33 ecu. Do yourself a favor and get the head checked. Gasket replaced and put a tunable ecu in it

Actually, it's not all as silly as it sounds. The load is measured by the AFM, so the fuelling will be correct at pretty much all points, and where it is wrong, it will be richer than the original fuelling in the 25, so safer (if more wrong!). The timing will probably stil be OK, as the RB25/30 doesn't usually end up with more compression.

I'm not saying it's a great idea, but the ECU at least is able to do it. If it was an olde schoole MAP sensored ECU, then you'd have good reason to call foul.

[533 RYC]

^ +1. The capacity increase VS the amount of boost these engines can put up with COULD allow it to run safely. The fact that the afr's have been checked should confirm the state of tune is sufficient to support the load/demand of the setup.

[Ben C34]

A bit unlucky it let go. Good on ya for chucking it together and having a go.

To many people spend too long thinking about stuff and not enough time doing it and seeing what happens.

[nicksamaniac]

Thanks for the positive reply, most forums only dish out negative stuff and false tech info.

At least I'm doing my own r&d (so to speak) if it doesn't work, at least it's only made/built from spare/leftover parts around the shed and hasn't cost $thousands in the first place.

[StevenCJR31]

What you need to find out now is WHY the head is no longer flat?

What caused it to do that?

Detonation?

Overheating?

[nicksamaniac]

Probably was always out of spec, it was just removed from a stock n/a rb25 (r32/cefiro) and bolted straight onto an untouched r31 rb30 bottom end. Using a cheap fiber head gasket.

Probably was a good thing I had a nasty gasket as aposed to a mls-r, it probably would of done head/block damage in the long run instead of chewing out the gasket.

I'll get it milled, fit some better valve springs (bin the non turbo ones)

and screw it down with a good gasket.

Edited January 4, 2014 by nicksamaniac

[533 RYC]

got any pics of the gasket &/or head where the leak occurred?

I build large stationary turbo engines - I see quite a few failures - mechanical mayhem is a big favourite of mine!

[Griffin]

Don't listen to the knockers. I fitted a turbo to an efi patrol. AFRs were fine up to 6 psi. Like has been said let the AFM do the work for u. Horses for courses....