Faeflora

iTrader: (2)

Confuckinggratulations. You've never blown a motor because you push less air through your motor than some nat asp builds. You've succeded at not blowing your motor but you've failed at being a man. Then again you're probably one of those rogue target miata demographic 60+ year olds that dead ended here in a journey of unfortunate serendipity.

Also not explode motor is not that hard. Afr above 10.5 and below 12. closed loop knock trim cus ur map prob sux. nonsuicidal timing. Boost cutoff. Done.

For ***** sake. Is it really that hard? Next steps for you


Insert into sitz bath. Internalize.

Race a stock 4cyl mustang. Lose.

do a 1 wheel burnout, break ur 5spd at 7000rpm clutch sidestep, ,

part out, buy a cr-z :

give up on dream of finding a 40 year old mistress.

: die.

Ur oldest son gets the cr-z.

Sells it.

Buys a 4cyk mustang, keeps it stock.

PJnB

Now now. This is a place for love. We are mostly dudes probably that all drive or have driven miatas. No need to wreck the joy. I was just boozin after I checked the compressions with my boy toy so I wanted to document my impatience so that maybe someone reading would avoid this in the future.

My motor was totally my fault. Like the first or second post said, I got impatient. I just wanted to go to hyperspace too quickly. There were a couple of things I should have done prior to all of boosties that I even thought of at one point or another, but in the moment it just didn't happen. There is a SMALL chance that the build could have something to do with it, since I have had my reservations since the beginning about the motor since I did not oversee the process. But probably not.

I will definitely post up some pics of the piston when I get around to tearing the motor down or if the borescope can capture the carnage.

The big debate in my head now is: WHAT DO!?!? I am seriously considering just finding a long block that has low miles and throwing it in. That will make 3 miata engines in my garage, but damn, forged internals are a-spensive!!! I could also find some Stock NA 9:1 pistons that arent totally destroyed and try and piece together an engine with what I got. How much does a set of pistons run? Also, one thing that the last dude said about the pistons that I put a hole in is that the builder blended some of the sharp edges as to avoid hot spots, further avoiding the likelihood of knock. Is that a thing? It makes sense, but I just havent ever heard of it.

PJnB

Okie doke. The head has been removed. I am at a total loss. I have no idea what the issue is. The piston looks fine to me, granted I have never checked anything like this out before. Anyway. Here are pictars. I tried to get the best I could of the gaps between the sidewalls and pistons. I honestly suspect that the head is screwed. Like it got warped or something.

DNMakinson

iTrader: (3)

My point exactly.

Rest of your post I don't understand your points or motivation.

Braineack

iTrader: (62)

piston looks melted.

ryansmoneypit

iTrader: (6)

We need pics of more than one piston. All four please, and pictures of the cylinder bores of all 4 as well. Pictures of all four cylinder head combustion chambers. We can't diagnose your sickness, with a picture of 1/8th of your turd. We aren't Dr's god dammmit.

codrus

Notice how clean #1 is compared to #2 -- that often indicates that the head gasket has been leaking coolant into that cylinder. Look at the head gasket between the coolant passages and the cylinder, see if you can see a failure.

--Ian

Savington

iTrader: (31)

Yup. #1 piston is destroyed. You can see the top ring clearly even from a slightly oblique angle. Cylinder head shows signs of severe prolonged detonation too. IOW, motor is trashed and needs a full teardown+rebuild.

AlwaysBroken

Being able to see the top ring is a bad thing.

I'm curious how #1 detonation happened.

PJnB

More carnage pics since some wanted to see the whole motor. In order:

Cylinder 2
Cylinder 3
Cylinder 4
All Cylinders
Cylinder 1 and 2
Cylinder 3 and 4
Cylinder 1 Again
Whole Head
Valves 2
Valves 3
Valves 4

PJnB

Also, the whole decking and head machining and head gasket all look like total garbage. Nothing can be concluded from the gasket. It just looks like total trash. I have some pretty serious doubts about the last rebuild. I don't think the head gasket was leaking coolant though because I ran a pressure test on it and it held strong. I feel like everything on the long block is fine except for the pistons. (meaning I am hoping the rods, block, head, etc can be reused but not pistons) But I need to finish tearing it down.

ryansmoneypit

iTrader: (6)

Ya, that # 1 took a beating.

2ndGearRubber

Pistons/rings will obviously need replaced.


The big thing to check is that the damaged piston did not cause damage to the bore. You may be able to just hone, there's a chance not. The head itself looks to have some physical damage. That will need blended out.



FWIW: I'd be replacing the delicate stock rods if you still have them, and making sure the rods did not deform if you have.





Full valve job (checking the valve while they're out), smooth the chambers out. Machinist should inspect/measure all the bores. Pistons and a hone at minimum.


EDIT: How many miles/hours were on the motor, post rebuild until failure?

PJnB

There was about 1000 miles on the rebuild.

Savington

iTrader: (31)

Probably the same way it happened in #2, #3, and #4

Savington

iTrader: (31)

You're clearly looking for someone other than yourself to blame, which is pretty disheartening, since a failure to learn from this will just result in you blowing up the next engine you get your hands on too. You don't "see" anything regarding the quality of a decking/surfacing operation on a cylinder head after 1000 miles. You measure that quality with a machinist's straightedge and feeler gauge, and I doubt you've done that.

You blew up this engine. Any engine builder will look at the pistons and head surface and laugh you out of the shop if you expect to convince them that this was anything other than your own fault.

PJnB

Since this is the internet, it is going to sound like I am getting offended and defensive, but you are just going to trust that's not the case.

I have mentioned several times on this thread that everything that has happened has been my fault. To say that I will not learn from this experience is simply false. Will this ever happen again? Maybe. But there is a whole slew of things I will be doing on the next go-round in order to avoid this outcome.

I thought it was relatively clear from the very start that I am not disgruntled. I am not on a search to point fingers. I am just on this forum sharing my situation largely for fun. I like talking about engines and cars and I like working on them. This is my toy. It broke, and I will enjoy fixing it.

It is clear that the piston is toast, which was my doing. My whole thing about the machining and gasket was just information that I observed. I mean ****, I don't even know the guy who built this motor. So it's not like I am even trying to ruin anyone's name.

Correct me if I am wrong but I have always been under the impression that if you blow a head gasket, when you remove it, it is pretty obvious where the failure occurred. What I was saying about the machining and gasket was just that 1) You cannot denote a failure point and 2) The whole gasket and mating surface generally look terrible. I was also under the impression that a head gasket and head after 1000 miles and a fresh rebuild would generally still look pretty clean, which it clearly does not.

Anyway. I am appreciating everyone's responses. I don't mean to waste anyone's time, I am just enjoying the hobby.

Braineack

iTrader: (62)

What was the timing running at? can you post you last MSQ? and did you confirm the timing was in sync?

Joe Perez

iTrader: (8)

Might not be strictly relevant, but any idea what sort of foreign object was rattling around inside cyl 4?

codrus

Yeah, you might want to take a look at your throttle body and see if it's still got both of its screws.

The photos of the deck & head surface look pretty much like what I'd expect. I think the black coating on the MLS gasket starts coming apart the first time you get it nice and hot, so 1K miles isn't going to look all that different from 50K.

How badly was it running before you shut it down? Was it running-on-3-cylinders bad? If so, then perhaps the unburnt gasoline acted as a solvent to clean up #1? I dunno.

--Ian