cjprelude

Hey guys, so I hope I'm not offending anyone by posting about my 1990 Honda Prelude SR 4WS. If it helps, I appreciate the crap out of civics.

So before the long story, long story short I rebuilt my stock B21A1 engine and after 120 km on it, it was blown. I've now since confirmed my assembly and clearances were 100% correct, so now I need to figure out what happened, because I'm rebuilding again and I can't afford a 3rd time.

Long story.

My B21a that I "rebuilt" in highschool finally threw a rod bearing. So I decided to rebuild it turbo ready so that when I could afford my turbo set up, it'd be good to go. (rather than stock rebuild or higher comp). Here's my build.

B21a1 head - B18a1 intake cam, B21a1 exhaust

ARP head studs and cometic head gasket

B20a5 block (no FRM sleeves) bored to 83mm to replicate the B21a1 block.

Wiseco Forged Pistons and rings

H23 connecting rods

B20a5 crank polished

everything was machined/polished or cleaned up.

So I'll start from the top.

I had starting issues. Finally once I figured that out and was able to prime the engine, I was able to start it. Instantly it started revving to 3500 rpm, so I shut it off. After messing with vacuum lines and started the car and shutting it off multiple times (yikes?) I figured out the problem and it idled. But I couldn't get the timing right. After much again turning on and shutting off, I figured out the Acura Vigor Throttle body I'd put on wasn't allowing me to get proper timing. swapping back the original B21a1 TB fixed my timing issue, although I can't seem to get a low enough idle and the idle screw is in all the way :/ .

throughout all this it was smoking a little. But I thought hey, that's normal for a new engine right? It'll go away once I can actually drive it and break it in....right?

So finally I took it for a drive. First off? Felt like ****. I remember my old engine, and it was running bad, but it had WAY more reponse and power than what I was experiencing. Hesitation, slight bogging and no power. But this was/is my first real rebuild, so....it was because the engine wasn't broken in yet......right? it was smoking a little bit more than before but I was hopeful. Went on the highway and did some pulls and letting go of the throttle, I followed a procedure for my engine. Got home, parked it, did an oil change and let it cool down. When I started it again, my heart was shattered. Literally, so much grey oil smoke came pouring out I'm surprised my neighbours didn't phone the police. Obviously didn't let it run for long. But that was the tough indication that I had to take it apart again. So I did.

head off, instantly notice the glazed cylinders. since found out the wear is so bad, I need to go from 83 to 83.5mm on my bore. Know what that means? my custom made Wiseco's are now ornaments.


and THEN found this?!?! No one thus far internet and real life knows what caused this. It was one of the rod bearings. like....what?? This is irrelevant to my main problem but I stumbled upon it when I took everything apart. there was no moisture near the bearings upon installation and they were well lubricated. could it have been a bad bearing? some weird chemical reaction with oil additives? Or something? with the zinc? No idea.
one side

two side


Back to the main problem. I don't have pictrures but on removal, my pistons were very sad. Super bad discolouration, and intense scuffing on the sides. #2 piston was garbaged, while the other 3 while showing wear, could have been re-used if I didn't have to go larger on my bore.

So, discolouration, insane cylinder wear as well as piston wear. From my knowledge, discolouration is a result of overheating in the combustion chamber. Over heating in the chamber would also result in over expansion of the rings, causing them to bite into the cylinder walls and wear them down. As for the scuffing, my machinist's first response was there must have been a foreign matter inside the engine, something like a couple grains of sand. I was very careful and can't see how crap could have gotten in there, but I'm not going to eliminate that possibility.

With the worn cylinder, upon cold start up the blow by would be insane, and easily explains the smoke. But what caused my chamber overheating? (To any unfamiliar, your temp gauge can read perfectly fine while overheating in the chamber is occurring). All I can think of is a lean burn. And I remember having an EGR code but I ignored it because of my ignorance of what a bad egr can cause. I checked out my egr and it LOOKS fine. the diaphragm moves in out out when air is applied, and the valve feels very tight and springy when I press it in with a finger. But I'll be cleaning the crap out of it.
What else would cause a lean burn? O2 sensor? a going fuel pump? Thoughts??

Any input on what anyone thinks caused the destruction of my beautiful engine would be greatly appreciated. If you read this far, Thanks.

- Cory

ezone

Were the cylinders able to pass the white glove test prior to assembly? Any material remaining from the boring and honing processes can eat rings (and bearings) in short order.

Same goes for 3-M Scotchbrite and bristle discs, and any other abrasives commonly used for gasket removal and cleanup. I've seen more than one engine ruined by those discs.

Were the rings correctly sized for the bore?
What were the ring end gaps prior to installation?
Were the gaps staggered correctly upon installation?
Were any rings installed upside down or in the wrong grooves?
Pistons and rods all pointing the correct directions?

Flow test and match injectors?



/Random thoughts.....

cjprelude

I did NOT do the white glove test, and I'm glad you also mentioned that because the guy at my parts store also said the same thing. I'll definitely be doing it this time.

rings were custom made for 83mm bore along with pistons (for B21a1)
Ring end gap was perfect
gaps were staggered
rigns were installed correctly
as for direction, the pistons can only go one way (valve indents are different sizes for intake/exhaust) so that was 100%, the rods are non-directional.

I had previously had the injectors rebuilt. I take back what I said about it running like **** before, that was a straight up lie. It had a knock and burned a ton of oil, but besides that it ran amazing, as weird as that sounds.

ezone

Clean it with hot soapy water, rinse, repeat--- until the cylinders pass the white glove test.
Rod knock or piston slap knock? Measure skirt/bore clearances? IDK. Probably too late to figure out what went wrong with the bad one. (Wrist pin/rod/piston bound up, not free?)

Oil consumption--if it wasn't caused by the PCV or valve stem seals, would almost have to be a ring problem (oil smoke diagnosis to determine most likely cause)....Did any of the plugs show oil?

When you are doing all custom stuff, there are a lot of chances for something to go wrong. It's a lot more involved than just slapping a matched set of pistons and rings that Honda sent as a kit, into a stock block.

sdaidoji

iTrader: (1)

for the sake of order in the forums, thread have been moved to the general automotive discussion, since this is not a civic 7th gen.

other than that, feel free to ask for help in this place. g'lucky!