99 CRV B20z has been burning oil at a rate of 1qt/4k miles. 212k miles. About 7k miles ago it lost coolant out the petcock which had vibrated loose and overheated to the point it shut itself off while coming to a stop (my wife's dd and she thought the temp gauge didn't work). Decided to do a leakdown test(and been needing a good reason to buy a good leakdown test kit anyway!).

Engine was warm. I tested with pressure regulated at 100psi, numbers below reflect psi each cylinder is holding. Tested at TDC of course. I removed the VC and blocked all but one oil return passage.

1: 93psi. Leaking into crankcase, intake manifold.
2: 74psi. Leaking into crankcase, exhaust, cylinder3
3: 75psi. Leaking into crankcase, exhaust, intake, cylinder2
4: 79psi. Leaking into exhaust, intake, and interestingly cylinder1 (weird but air was blowing through #1 sparkplug hole with #4 pressurized....rings??)

So besides the obvious blown headgasket between 2&3, it looks like #4 has burnt valves and #2&3 might also have burnt valves. It seems like the rings are probably also worn in all 4. Another note is that the timing belt has significant slack between the two pulleys but has not jumped teeth. I have been planning to change the tb this Christmas when we have a couple weeks off work but I didn't know it was this loose....and when I check the tb about 15k miles ago it was tight.

SO, please correct me if my diagnosis is incorrect. I'm an Accord guy so I don't know a whole lot about the b series' weaknesses. I have some questions:

1. IN GENERAL, if performing an oem b20 rebuild is merely honing the cylinders sufficient? If it looks like I'll only need to hone the cylinders can it be correctly done with the block IN the vehicle? I've heard this can be done on some engines although I'm not sure how one would get the perfect degree hone job...
2. IF the pistons are still in good shape is it wise to reuse them or get new ones?
3. I've heard b20 rods are a weak point, any reason to upgrade/replace if doing an oem rebuild?
4. Is the b20, b18a, b18b heads all the same? If so I could grab one from the salvage yard and have it rebuilt/refreshed to reduce down time correct?
5. Anything special about the b20 I should pay close attention to during rebuild (outside of a normal rebuild)

My other "potential" option is to have the block bored to 85.5mm and buy RS machine or YCP pistons with Brian Crower stg2 cams and a mild head port job to get a nice performance increase from the b20.....if I went this route (with a tune of course) is it necessary to upgrade the valve springs? I doubt it'll be revving past 7k even with these upgrades.


REALLY appreciate any feedback!

 

Blown HG for sure, may also be a warped head and deck. 94