This post will be a long one.
But anyways, started off by using my new thick walled impact socket to get the crank pulley off and remove the timing covers. This is so much easier with the engine out of the car. Also the thick wall sockets are amazing, took the pulley off instantly whereas my normal socket just rattled feebly.
I pulled the cams and was not happy with what I found. Very extreme wear for an engine with only 100k miles, my BMW engine with similar miles had a valvetrain that looked nearly brand new. The caps and journals were scratched up pretty badly and very unevenly, I've never seen anything like it.
A lot less wear on the heads, but still some.
In this photo you can see some of the miserable job the dealership tech did installing the cam caps. I have new SoS billet O-ring caps on the way.
After talking to a local machinist who specializes in cylinder head repair he recommended that I just plastigage to check clearances and reassemble if it's close, as there isn't much to be done that doesn't involve spending huge amounts of money at shops with special equipment that are a minimum of 3 hours away. I was delighted to find all of the cam journal clearances within the factory service limit.
I reinstalled the cams using factory plugs before ultimatedly deciding to go with SoS billet plugs so I wasted a bunch of time and ended up buying a bunch of new cam seals as well since my OCD self won't let me reuse them for fear of leaks since they way they get clamped into the heads deforms them slightly.
Replacing various vacuum tubes with new OEM tubing. The number of vacuum lines in this car is insane, might as well replace them before they can start leaking.
My replacement oil pan showed up so I put reflectagold tape on the bottom where the exhaust goes since my aftermarket headers don't have heat shields.
I removed the old oil pan and found this. The entire rear of the oil pan gasket was absolutely covered in sealant from when the dealership worked on the car. This is unbelievable, they didn't even need to touch any of this. I guess they pulled the whole rear seal plate instead of just popping the seal out and installing a new one and rather than do it right and drop the pan they just used a whole tube of Hondabond to seal it back up.
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And now we come to the root cause of the cylinder head wear, and really the root cause of every problem I've had with the car over the past year.
About 14 months ago, a rock fell off of a truck in front of me and it knocked my oil pan. I was on the way home from the machine shop after trying to get the BMW flywheel resurfaced. When I got home I inspected the underside of the car and the only damage I could find was a very minor dent in the bottom of the oil pan. People drive around Civics with oil pans that look like they got run over by a truck and banged back into shape with a sledgehammer, so I assumed the barely visible bend was nothing to worry about.
I was wrong, not worrying about the dent in the pan is arguably my worst automotive fuckup to date. That minor bend was in just the right place and just severe enough to push the bottom of the pan up into the oil pickup.
Apparently the oil pickup has 1/8-3/16 inch clearance with the bottom of the pan. I never connected the dots until now, but somewhere within a few weeks of that incident was when I first noticed the LMA ticking sound, and also when I noticed my factory oil pressure gauge reading a bit low. Both of those things were just plain old oil starvation as opposed to the rather common benign causes of each. The factory oil pressure spec in the service manual of 10psi at idle and 50psi at 3000rpm are blanket numbers used for pretty much every 90s Honda and not really based in reality, I was seeing 15psi at idle and 65psi at 3000rpm with an AEM electronic gauge so I just assumed the factory gauge was being crappy as they are known to be and didn't worry about it anymore. The valvetrain noise was probably due to lack of lubrication in the heads and not sticky LMAs since it did not go away after having them replaced at the dealership. I was tipped off about the oil pressure after a conversation with a fellow NSX owner who was seeing 20-25psi at idle and over 100psi high in the rev range, my car topped out at 80-85psi and that conversation was what ultimately led to me pulling the motor.
After finding this, I realized that I needed to pull the crank bearings for inspection now rather than wait for the motor to start knocking and likely ruin the crank in the process. In the process of tearing into the block I installed a new oil pump for good measure. Side note, the front seal was replaced by the dealer last year, it was installed noticeably crooked.
Then removed the engine from the subframe and separated it from the transmission.
This was one of the most miserable tasks I've done so far. It was brutally hot that day and the transmission just would not come off. The NSX uses a twin disk clutch so the input shaft is very long and binds very easily if the angles aren't just right, it took a friend and I an hour or two just to pull the thing off.
Afterwards though I pulled the rear main seal plate to redo it due to the huge mess of Hondabond mentioned earlier. With the transmission off it was even worse.
Globs of the stuff everywhere, even on the inside.
Taping up the crank and bearing so I don't contaminate them during the cleaning process.
Everything cleaned, new seal installed, sealed back to the block with an APPROPRIATE amount of Hondabond.
Engine stand plate bolted up. I like how Honda uses a small number of giant bolts instead of lots of small bolts like BMW, makes things easier. Honestly the way Honda engines go together is just so much nicer, things fit right, they don't leak all the time, etc.
Engine on the stand, so much nicer to work on this way. Getting it out of the subframe was a huge pain but everything will be easier this way especially since I need to tear into the bottom end.
Bottoms up, oil pan off. Pictures of the insides of a C30A are fairly hard to come by so doing this was kind of cool.
Crank girdle removed. I didn't know this before, but this engine uses 6 bolt mains.
Rod bearing cap removed, so far so good.
Cap bearing looks fine too.
Factory spec for rod bearing clearance dictates 0.04-0.06mm with a maximum allowable clearance of 0.06mm. Plastigage says right around 0.04mm, so nearly perfect results. You have no idea how much relief I felt after seeing this.
I checked one from each row all with the same results, clearances are all at the tight end of the allowable range. Perfect. Looks like the bottom end survived this ordeal.
I suppose it makes sense, looking at the oil flow diagram in the manual, 100% of oil from the pump goes straight to the main bearings, then everything else gets oil from the main bearing channels. Since the rod bearings are okay I'm not going to bother with the mains since they are extremely difficult to remove and should be fine if the rod bearings are okay. I can finally start putting things back together instead of taking them apart, right after I place a couple more orders for parts I didn't know I needed lul.