BrknSmkinSpokes

I normally find myself working on vintage motorcycles. Nothing really much like this but occasionally people come to me with...things. Being a sucker for a challenge I just can't say no.
TLDR - Basically took apart an engine that had 250psi on 1-2-4, and only 30psi on 3. I found 77mm bores in a 1983 Civic Hatch and need help Identifying them. How and where do I find if this is a 1.8L block. What head is this? Is this why the 3 good cylinders had that much compression?

So I have a little story, and a host of problems / questions.

A man recently brought me a 1983 Civic Hatch that apparently contained the 1.5L engine. The car sounded like it had a miss, had terrible blow-by and a catch can to contain it. At first glance it looked like a 1500 and it had a Weber carb attached to the intake, basic stuff. Pulling plug wires 1 by 1 I could tell cylinder #3 was definitely the weakest. With the blow-by and misfire I assumed the worse. I went ahead with my checks anyway. I found Cylinders 1-2-4 to have 250psi of compression which I thought was surprisingly high. Our friend Cylinder #3 checked out at 30psi even after a bit of oil was added. So still assuming the worse I checked that the valves weren't stuck open, they were fine. Leakdown test it was confirming 100% blow-by on #3.

I told the man his options, and what my thoughts were.... We can pull it apart and easiest case, we're honing it and putting some rings in...not so easiest case we're taking it to the machine shop. Or keep runnin' it and wait till it goes boom, because he was driving it at the time haha.

Still assuming this is just a untouched 1.5L 1983 Civic Hatchback with a 5spd manual gearbox. He wanted me to proceed.

Off comes some bits, including the oil pan. I found the problem in there. It was filled with pieces of the rings and ringlands.
So off comes the head, all the bores were in surprisingly great shape, including #3's.

This is where things start get interesting. I believe the 83' Civic 1.5L engine would be referred to as the EM1 and should have 74mm bores? This block has 77mm bores. A little searching around and I find Honda has made a few other engines around this time that also have 77mm bores, including 1.8L engines that came in Honda Accords. A little more searching, and I see people doing what we all love to do...mix matching Heads and Blocks and all other sorts of fun...

Taking a peek at the headgasket that was used, it has a Fel-Pro part number of 8736PT. Hmm, that part number checks out to a 1979-1981 Honda Accord with a 1.8L engine. Was this used because this block was sleeved to 77mm? or is this actually a 1.8L block? Is it possible to bore a 1.5L to 77mm? I don't think so huh lol? Trying to figure out what we have here.

The head does have the auxiliary valves, and the spark plug tips covered inside the domes. They are not exposed like I believe a Non-CVCC head would look? Also, it clearly uses the valve cover gasket for the 1.5L not the 1.8L...So it must not be a 1.6L head like I've discovered people use?

Really I would love to be able to just throw some rings and pistons back in and call it good but can't even figure out what I need at this point haha...Quick measure with a cheap caliper the pistons all come out to almost exactly 77.17mm =/...Nothing precise yet.

Could having 250psi per cylinder and running old / or bad / low octane fuel cause ringland failure? Help me I beg you! haha Thanks!

UPDATE-
I found the stamp on the block that says EK1 - XXXXXXXX, so this must be the 1.8L Block...Now how do I identify the head?