RB25DET head bend

[czeno]

It's been 10 years with my RS4 series 1. The head gasket had catastrophic failure when under boost a while back, went choo choo train emitting a large white cloud out the back. Temp quite normal, no recovery bottle warning signs leading up to event apart from developing rough idle a few days before. I pulled off to side of road and could see temp gauge sneaking up, switched off & assessed situation. Most telling thing was green coolant running from exhaust. That was a tow truck ride home.

It's been in the shed a while now as I go my glacial pace of sorting it out. I've got the head off & cleaned off gasket surfaces. I put a straight edge on & checked with feeler gauges to find I have a bend to deal with.

Odd really as it's been 5 years since I changed out it's previous dodgy radiator. In that time before it's temps would elevate but not to severity. Although there was this time pulling a trailer and all was OK until I switched off, recovery bottle started to blow steam & I restarted to get circulation going again and settle temp down. I suppose with a 0.9 bar rad cap it'd have seen about 120 degrees to make steam.  

Gasket failure was on the exhaust side of No 6 cyl. I see my bend on the head viewing it with deck facing up as the head is convex across it's length. The straight edge rocks end to end and contacts the middle of surface. Would be approx 0.1mm per end clearance.

The gasket failed on the steel compression ring and continued on to rupture water & oil gallery sealing.

My question is do these things tend to warp up on the ends of head (imaging it's still face down on block)?  Most head warps I've seen usually go up in the middle. What I'm seeing on the RB would seem to fit as it's known the end cylinder gets the most heat.

[GTSBoy]

11 minutes ago, czeno said:

My question is do these things tend to warp up on the ends of head (imaging it's still face down on block)?

That will depend on why it warped. If the head bolts loosened at that end....

[czeno]

I found the head bolts between 5 & 6 yielded easier than all the others when unbolting. No 5 cyl also showing signs of gasket distress towards those studs too. I imagine when it gets hotter than normal expansion occurs in head causing stud stretch & gasket compression.

Wondered what other peoples experience of RB head warp is.

[GTSBoy]

Usually they warp because they got soft because they got cooked. But there are obviously a bunch of ways this can happen.

[czeno]

New development, my straight edge was bad. Rechecked with a better grade one. Now within 0.05mm (0.002") and any of that is in the middle - the more conventional style warp. Good to go again and no trip to machinist required.

[Dose Pipe Sutututu]

Tomei head gasket, ARP head studs, 350kW+ time.

[czeno]

Oh I've got Nissan factory gasket and new studs. And new exhaust studs. Should be good for it's stock 180kw. This thing is standard right down to original wheels and the tape deck - which died a long time back.

Just the sweet sound of inline RB and the road.

[czeno]

Well that took a while, part time in weekends only when there was time.

Just a heads up, got this thing up & running, great, no leaks etc..

Come road test time and the dreaded blue/white cloud out exhaust came after about 2kms. told myself not to panic, probably just something burning off exhaust. Well it got worse and I turned for home at 4km, got a little better. Got to my gateway, hopped out & looked at exhaust, steaming and wet.

 

Refusing to accept I could get it that wrong, but evidence out exhaust looking bad. I figured it had to be the large muffler at the back sloshing with coolant all this time parked in shed.

 

luckily I was right, second run all systems normal, no steam. Glad I didn't tear it down again only to find nothing.