As many of you know, my 1991 NSX suffered a head gasket failure at the 2012 NSXPO during the track event. You can read about my experience here. Well after a long discussion and much negotiating, I am very pleased to report Mile High Acura stepped up to the plate and agreed to repair the damage. They got rid of the guy who messed up my engine and hired a new tech, Michael M., who builds import race engines as a hobby and is a super competent tech. They even let me interview him before letting him touch my engine and he definitely knows his stuff. Since there are almost no threads like this on Prime, I thought I would chronicle the repair so other folks with questions might find a few answers here.
Day1: The engine is out! We made sure to use the 1997 service manual procedure, as the original 1991 manual calls for separating the ball joints, which is bad juju on the NSX. Also, my car has 1998 3.2 manifolds on it, so the 1997 procedure for removing the heads also applies.
Day 2: Lots of parts are here from Honda. Replacement main hoses, oil cooler hose, plus a few extra bits I've been meaning to replace. New battery ground, new ignition switch to replace my spliced one (from aftermarket alarm). Also, new A/C idle pulley, since my 23-year old one is getting noisy. Also, new PCV hose for dressup appeal. Note, the head gasket kits which have part no. 06110-PR7-020 are actually packaged by Stone Gasket (Ishino), who is the OEM manufacturer for the NA1 gaskets. Interesting that the new intake manifold gaskets are white now instead of the original green. The kit has everything you need for one complete cylinder head, including new valve seals! So, you should buy two of these kits to do the engine.
Also have new parts for the intake manifold overhaul, which I am doing myself to save cost. I will have a separate thread on that.
Day 3: Top of the rear head ready for removal. This head was heavily varnished from old oil last year when I re-did the valve covers. Amazing what a year of daily driving with Mobil 1 can do to clean it- much better!
Front head- still varnished, but vastly better than a year ago. Michael tells me the head with the PCV valve always is more dirty on all Hondas, not just the NSX. Makes sense. Also, you can see my new updated LMA's from Science of Speed, installed last December.
First sign of trouble. I should have gotten a better angle, but you can see some corrosion at the seam on both heads. This is evidence of the head lifting and leaking coolant.
Rear head is off. Incredibly, no sign of any coolant leak anywhere on the deck. Strange. Pistons look good for 90,000 miles and we could still see the cross-hatching in all the cylinder walls. #1 and #3 do look like they were running a little rich at some point in their life.
Rear head gasket. Again, no sign of blow through or damage (the tearing is from removal).
Front head is off. Again, no signs of damage on the deck and the head gasket was intact.
Rear head on the bench. Now, we start to get the picture. These pockets of corrosion on #1 are a clear sign of head lift. Coolant was seeping in and getting trapped here and corroding the aluminum. Front head had the same corrosion.
And finally, the smoking gun (no pun intended). All 16 of the head bolts had these rings of corrosion around them. This is clear evidence of the heads lifting completely off the block and letting coolant into the bolt sleeves, which rusted the bolts in this pattern. Think of the steam pressure in a boiler and immense force it can exert. Same thing here overcame the clamping load of 8 heavy bolts. Please make sure to check your coolant and make sure there is no air in your system or it can do this! When we compared these bolts to the new ones, several were at least 1 mm longer.
Never thought I'd see my NSX like this.
But, it is car porn for sure! 
More to follow later...
Day1: The engine is out! We made sure to use the 1997 service manual procedure, as the original 1991 manual calls for separating the ball joints, which is bad juju on the NSX. Also, my car has 1998 3.2 manifolds on it, so the 1997 procedure for removing the heads also applies.
Day 2: Lots of parts are here from Honda. Replacement main hoses, oil cooler hose, plus a few extra bits I've been meaning to replace. New battery ground, new ignition switch to replace my spliced one (from aftermarket alarm). Also, new A/C idle pulley, since my 23-year old one is getting noisy. Also, new PCV hose for dressup appeal. Note, the head gasket kits which have part no. 06110-PR7-020 are actually packaged by Stone Gasket (Ishino), who is the OEM manufacturer for the NA1 gaskets. Interesting that the new intake manifold gaskets are white now instead of the original green. The kit has everything you need for one complete cylinder head, including new valve seals! So, you should buy two of these kits to do the engine.
Also have new parts for the intake manifold overhaul, which I am doing myself to save cost. I will have a separate thread on that.
Day 3: Top of the rear head ready for removal. This head was heavily varnished from old oil last year when I re-did the valve covers. Amazing what a year of daily driving with Mobil 1 can do to clean it- much better!
Front head- still varnished, but vastly better than a year ago. Michael tells me the head with the PCV valve always is more dirty on all Hondas, not just the NSX. Makes sense. Also, you can see my new updated LMA's from Science of Speed, installed last December.
First sign of trouble. I should have gotten a better angle, but you can see some corrosion at the seam on both heads. This is evidence of the head lifting and leaking coolant.
Rear head is off. Incredibly, no sign of any coolant leak anywhere on the deck. Strange. Pistons look good for 90,000 miles and we could still see the cross-hatching in all the cylinder walls. #1 and #3 do look like they were running a little rich at some point in their life.
Rear head gasket. Again, no sign of blow through or damage (the tearing is from removal).
Front head is off. Again, no signs of damage on the deck and the head gasket was intact.
Rear head on the bench. Now, we start to get the picture. These pockets of corrosion on #1 are a clear sign of head lift. Coolant was seeping in and getting trapped here and corroding the aluminum. Front head had the same corrosion.
And finally, the smoking gun (no pun intended). All 16 of the head bolts had these rings of corrosion around them. This is clear evidence of the heads lifting completely off the block and letting coolant into the bolt sleeves, which rusted the bolts in this pattern. Think of the steam pressure in a boiler and immense force it can exert. Same thing here overcame the clamping load of 8 heavy bolts. Please make sure to check your coolant and make sure there is no air in your system or it can do this! When we compared these bolts to the new ones, several were at least 1 mm longer.
Never thought I'd see my NSX like this.
But, it is car porn for sure!
More to follow later...
