Yes, the cam bearing need the grooves. They are not normally replaced during an overhaul

Yes, those look fairly typical for used pistons. Brown or black oil heat marks are common

Valves not coming right out usually mean previous owner did not regularly adjust the valve lash, and the tips of the valves got hammered

Be sure to measure (and probably will need to replace) the valve guides, which is the #1 wear spot in the A-series engine

Water pump seizing could be caused by rust. The most tell-tale of overheating is if the head is warped. To check for overheating damage do this:


When my engine massively overheated the head was warped 0.020 inch -- 10x the standard! Coolant ran out of the spark plug holes

I agree with you. Will see what the machine shop says. Are the grooves in the Cam bearing ok? And is the yellowish color on the pistons normal? When I disassembled the motor, I noticed a couple of the coolant passageways in the H89 head were clogged with a white substance and the water pump was seized. This motor likely overheated and dont know the extent of any damage, if any. After removing the valve springs, I had to tap out several of the intake valves from the valve guides. All the others came out good and felt snug. Will replace all valve stem seals.

The wiki lists new bearing specs. The full service manual additionally lists service specs (maximum worn clearance which are still OK to run).

If yours are in the new bearing specs, why replace them? A lot of guys will say, for cheap insurance. But why fix what ain't broken?

Ok DD....you got me thinking about aftermarket bearings. I checked the tolerances for the main and rod bearings and they are all within specifications .038mm to .051mm which are the two closest measurements on the plastigage scale (Haynes manual has a maximum of .060mm for the rod clearance and tech wiki shows a maximum of 0.50mm ???). They all look in real good shape unless you see something out of the ordinary. No significant scratches that I can see. I dont mind spending money on a rebuild but if these bearings truly do last 500K miles and they are OEM Nissan parts, I may just put them back in the motor. I will have the machine shop polish them along with the crankshaft. The cam bearing closest to the timing chain has a couple grooves. Is this normal and some sort of oil passageway? this same bearing has a slight scratch which I hope can be polished out. Also all of the pistons has a slight yellowish color as pictured. Any concerns here? Everything goes to the machine shop tomorrow. Will have them mic the crankshaft and cylinder bores and get everything cleaned up including the GX and H89 head. And turn the flywheel. Will report back later.

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Want to make sure to get quality parts?
* Make sure the bearings are Datsun-spec F77 tri-metal and not cheap alumninum bearings
* Don't get fel-pro printoseal (ps) head gasket. Other Fel-Pro lines are top-notch

Your best bets are genuine Japanese brands, but american suppliers are usually good like Clevite 77 for bearings, Beck/Arnley is almost always packages Japan brands, Moog usually repackages Japanese parts ... in other words most stuff that RockAuto sells is OK, and the less expensive closeout parts are usually best. The cheap chinese stuff is becoming the new normal "regular stock"

The lower head looks ported

Yes, measure the head, as the manifold can be different sizes. When assembling have "port matching" done to even up the size difference between head and manifold. Or not (most folks don't), it's worth a little bit of HP.

58custom (Tom)...thanks for the explanation on the imported motors. And I did take your advice (pop off the valve covers) and got lucky with this H89 head. I have enough parts now to build two engines.

Tom...I have been thinking about building a race motor with the spare A12 I have. But will save that for another day. Have my hands full at the moment with the A15 conversion on the MG. Bearings look ok for the A15 but may go ahead with replacing all of them. There are kits on ebay that are fairly reasonable which includes rings and bearings. Is there another supplier that sells good rebuild kits? Rockauto seems to be popular. Want to make sure I get quality parts.

DD....oval ports for the H89 head pictured on the bottom in the photo. Measures approximately 35mmx29.25mm(+-), compared to the GX 39mmx30mm. I read Tech Wiki and it says 36mmx30mm for the GX head?? I dont think this one was modified. Used calipers on the manifold side to measure the oval ports. Should I be measuring on the inside of the port?

H89 head is closed chamber and is highly sought after by MG enthusiast for the nissan conversion. I got real lucky finding both in the North Texas area.

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I still have the GX motor that we got from one of the engine importers in 1991, it's my spare "race" motor. The A15 motor in the car now was an import as well. I don't know the ratio of cars with import engines but I have 3 oil caps like the one pictured that came off extra motors I ended with.

I am always reminded, when posts about checking clearences come up, that I am so not an engine builder. I have more than once simply measured the bearing thickness with a mic or caliper and if it was remotely close slapped it back in. All of the bearings in the A15 are new but on the A12GX I never even looked at the bearings, after 18 seasons of abuse the rings & bore finally wore out so I relented and changed the bearings. (Don't tell anyone I actually checked them properly)

Tom

Yes it's probably a "good used Japan motor" that they sent over by the container loads in the 1980s and 1990s.

* it might be a round-port H891
* Are there any signs it overheated? Rust scale & stuck bolts indicate that someone ran plain water in the engine. So flush it out well or have the block cleaned

G,
The Japan home market has a registration tax system that taxes cars progressively higher as they age. As a result, there is a large supply of decent used cars that are scrapped and the low mileage engines are imported into this country. I bought a couple of used import engines and transmissions for our Civic and Accord in the 90s. There were used Japanese engine & trans sellers in Houston so I am sure they were/are in your area as well. That's how the engine came to be in the car in the junkyard where I found my H89 head. That's the reason I tell everyone to look under the valve cover of any Datto A series when visiting the junk yard. Ya might get lucky.