I just bought a kouki with a notchtop zenki s14 sr20det engine. The guy before me had it about 4 years with same setup and worked fine except was running T28, and a different radiator. Then his radiator blew and he told me it ran hot once when it blew but didn't get all the way to the H on the temp gauge; thats when he put the KA radiator in. It was tuned very rich ( poured black smoked at WOT. The tune was done at 17psi, and it gradually went down to 15.5 psi after about 3 seconds of boost and stabilized at 15.5. I have wideband and I never saw any problems, it would stay at about 10.8 at WOT. I have an ISIS RS3871 turbo, stock HG, nistune with daughterboard, 750CC injectors, BC stage 2 cams, and walbro 255. I was running a KA radiator with a crossover hose with no shroud for the clutch fan installed.
After about 2 weeks of owning the car, I decided to go to an autocross. This was a pretty fast course ( got up to 80-90mph ) and on the second run I miss shifted from 2nd into 5th. I worried this might have blown my head gasket from possible detonation. I didn't hear an knock or feel any missing though. Anyway, while in line for my 3rd run, my car started overheating. I parked, and noticed my silicone hose right at the turbo compressor had a large crack in it. This of course could have created catastrophic lean situation and maybe caused my pistons to melt, and then cause my head gasket to blow. Of course, my improper cooling setup without fan shroud could have also caused my head gasket to blow I suppose.
After that I patched the intake hose crack, refilled my coolant and tried to make it home. It overheated again 20min later. And I saw tons of white smoke/vapor in exhaust and suspected head gasket failure at that time. Also was low on coolant. Towed it home at that point.
I think took the head off and noticed coolant in #2 and #3 cylinders. #1 cylinder was melted the most. Take a look at the pics below. I also have pics of the head gasket and you can see some damaged parts near the piston holes for #2 and #3 piston on the head gasket.
I know I am going to of course buy new pistons, check the head out and have it resurfaced, check scoring of cylinder wall, buy ARP head studs, get Cosworth 1.1mm headgasket, new water pump, and thermostat.
Question 1: Why do you guys think this happened?
Question 2: Can I reuse this block? You can see the block melted a tiny bit near the cylinder wall but is that a big deal?
Question 3: Do you have any other recommendation that I need to buy, or check?
Video of the 2nd run I did that day at the autox showing temp gauge, and AFR: http://www.youtube.com/watch?v=u3IQgF38hyg
Pics of 2 slightly melted pistons and head gasket, and block.http://sdrv.ms/N5Cdrj