k5egg

So, I ghetto-rebuilt my z6 about a month ago and ended up with a spun #3 rod bearing (no sign the bearing ever existed except for the gray goo in the oil), with quite a bit of bottom end damage. Here's what I've found I can get reasonably cheap/easy:

Y8 Crankshaft
Y7 (P2E) Pistons and rods

I was wondering if the valve depressions in the Y7 pistons would match the Z6 head properly and if the 0.3-ish compression ratio bump would throw everything out of tune? Should I go with a slightly taller head gasket to make up for it?

Also, will I have any "ohshits" with the Y8 crankshaft? Will my flywheel and harmonic balance work?

Also, do I need to pull the axles to remove the engine block? I've taken the pan off, and will have the head off before I pull..

Thanks guys. The way things are going with this car, I won't be a honda noob forever - its going to make me learn every single bit.

apexi_rsx

at least port your y8 or y7 oil pump ... valves on a z6 and y8 are the same so the clearances for valves should be ok. pulling the axles and transmission with the motor will be easier and less maneuvering if not ur gonna have to remove the drivers side mount from the block completely so u have enough clearance to pull it out. compression will be close to the same as a stock y8.

k5egg

Discovered I have more of a mess than I originally thought I did. I have metal filings *everywhere*. Apparently the bypass valve in the oil filter is defective (the filter material is not loaded with metal. Theres some metal filings present in the filter housing, but not enough on the filter material to make me think the filter "maxed out" and forced it into bypass.

Guess thats what I get for 'breaking in' with a supertech (walmart brand) oil filter. I won't make that mistake again!

94EG8

I don't think he's planning to run a Y8 pump. There's no real issue with running a Y8 crank other than they tend to spin rod bearings due to only having half the amount of oiling holes the Z6 crank has, they are otherwise the same crank.

k5egg

Yeah. I intend to keep the Z6 pan and get a new z6-style pump, if nothing else it 'looks right' when/if I go to sell the car.

I'm debating what I should do with the crankshaft situation - there's no doubt the Y7/Y8 cranks need modification to the rod oilers. Cross drilling isn't expensive, but my current engine is proof that having double the oilers isn't magically keeping the bearings from failing. I'm leaning toward retaining the single oiler, but getting a 'teardrop' shape cut into it, to help encourage the oil to 'layer out' evenly. Of course, this can be done *twice* on a Z6 (or a cross drilled Y8)... Decisions, decisions. Definitely one I'll have to go over with my machinist.

The #3 rod journal is WAY worn. from a quick check with cheap digital callipers it looks to be ovaled by about .035. I'd assume that disqualifies the crank from a regrind.

http://www.theoldone.com/articles/d_...building_tips/ was an interesting read. I'll be porting the oil pump and main bearing orifices for-sure.

Really what it comes down to at this point is "do I buy this 90k mile complete z6 bottom end off ebay for $210 shipped" or "do I get my hands on a clean crankshaft, some real rods, and new pistons (about $425 total, plus machine shop time for a balance job and the clip 'grooves' for the wrist pins)".

There's also the option of plucking an engine out of a junker at a pull-it-yourself lot for cheap. I've had mixed luck with junkyard parts on other vehicles, so I'm a bit leery of this option. I guess nothing stops me from tearing the oil pan off and checking out the rotating assembly before digging the engine out of the car...

Lots of variables to consider, and it all points back to money.

94EG8

I'd say there was probably more to yours, maybe something plugged up the holes, maybe the oil pump failed, or maybe that bearing wasn't installed properly. I do know that I hear way more spun bearing stories with Y8s than Z6s.

k5egg

Well, I broke every rule on that last "build" I did. #3 was spun, all the rest of the bearings were hammered (actually, flakes in the pan). I left the block and crank in the car, threw in the new bearings (and yes, I remembered the thrust bearing - that was my first panic when it failed), but one of the #3 rod bolts broke when tightening it back up. I ordered a set of ARPs for it, slapped them in, and prayed.

It even had a perfect sound for about 40 miles. Then I noticed the 'light throttle rattle' returned and then the car shuddered pretty violently, lost a lot of power, and started raising all sorts of hell.

Unluckily I was in the middle of nowhere at the time, I ended up driving for about 4 miles with it raising hell, to a place where cellphones work and people would have half a chance of finding me...

I made a video on that drive...
http://www.youtube.com/watch?v=fIAEEDrlv2Q

94EG8

I'd lay most, well pretty much all of the blame on that.

k5egg

Oh for sure. There's a pile of good reasons for it to have not worked.

I was thinking about it. The only reason why I really push the revs up on this engine is to make a 'little more power' - usually when passing or screwing around on the highway. I think instead of buying expensive rods and pistons, I should save my money and put it toward a turbo.

It may seem kind of backwards, but since my power requirements aren't that high the stock bottom end should be fine and I won't feel the urge to rev the **** out of it.

So, what I'm looking to do now is put together a stock bottom end, use good bearings, and check all the tolerances to make sure they're *right* - that part will be a lot easier when the engine is sitting in my living room, and not under a freezing-cold carport...

k5egg

Decided to go with modified LS rods (B18). My question is would I be better off using bushings to convert the rods to fit the smaller D wrist pins, or getting the D pistons bored to fit B wrist pins?