Bare minimum needed when getting in to replace rings
 

Hey all,

I am wishful thinking that I blew a head gasket but the head gasket doesn't look mangled. I plan on swapping in a cometic headgasket when it arrives, putting everything back together and compression testing again. If things looks bleak I don't want to do the whole "While I am in there" thing because I don't have a few grand to through at an engine. The engine overall looks healthy and only has 90k miles. I put a turbo on it recently and have been running around 13 pounds of boost. Back to my question at hand though. If I am going in to replace the rings, would I need to do bearings as well? Is that required? I feel that the answer is no but I wanted to make sure.

All of my compression testing was done on a Pittsburgh compression tester so I take the original numbers with a grain of salt.

Cylinder 1: 60PSI
Cylinder 2: 90PSI
Cylinder 3: 120PSI This tested the same as last week.
Cylinder 4: 130PSI This tested the same as last week.

PS, I have no issue getting back into my engine later if I have to. I love this stuff as much as I love driving the car.
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Thanks all

A ball hone and rings are all you need. That's like, oh shit we have 6 hours before our next pass and need to stop blowing so much smoke so lets rip it out and throw rings at it. But stock bearings are ~$20-25 per main/rod set from a number of companies, so it'd be a little foolish not to replace them.

For a 1.6, grab a thick cometic MLS head gasket. If you go standard thickness, your pistons will kiss the head, ask me how I know.

How do you know the heads good? Take the cams out, flip it upside down, spray soapy water in the bowls, and shoot compressed air in each port. My guess is your head isn't in great shape, but most miata engines could always use a set of rings.

I feel like your pistons are telling me something about your injectors or tune, but I'm not sure what yet.

I know I have been running rich while self tuning to be safe but that was until I could get the car professionally tuned. maybe low 11s in high boost. when you say thick cometic, I ordered a .040 thick cometic on fab9. they had a .060 option. Should I get that one instead? It looks like .0.4 is what every other site was selling so it's what I went with.

Thanks for the fast response too! I really appreciate it!

This is just me talking into the wind, but if I was going to go through the effort of taking a recently-turbocharged engine with 90k down far enough to get the pistons out, I can't imagine not also replacing the rod bearings, water pump, timing belt, crank and cam seals, the o-ring on that water pipe, etc.

And if you have to take the pistons out to slap on rings, why not some maxpeepeerods, since the rods are the weakest link?

Rods are on my mind, know that! lol Theoretically on a shortnose 1.6. As long as the key isn't having issues and I replace it correctly I could have the same power and reliability as a long nose? With upgraded rods where does the power limit come to? I have an act 1.8 clutch happy meal good for 245trq so that is a soft limit. If I invest in rods could I expect 300+ at the wheels? My problem with spending the money is I am in the middle of a career changing certification that I have to front money for. That comes first but I would like to at least have a drive able Miata in the foreseeable future as well.

Thanks everyone, I really appreciate the relaxed conversation of this and not shaming me for wanting the bare minimum at this time. I love blowing money on my car when I have it to blow!

Take block apart, dingle hone and new rings. Pay machine shop to hot tank and clean out all the oil galleys. New rings, new bearings and max speeding rods w/ stock pistons on the slightly looser side of the ring spec.

Thats how i built my first 1.6 and it was great until it ate a compressor wheel and bent a valve.

Short nose will be fine if you use a new crank gear bolt each time and torque it to spec.

Honestly. The cost to machine and assemble my entire short block was 550 bucks with a 1.5mm overbore (so a bit extra). It'll probably cost you more to dinglehone your own block than it would to just have them do it, clean it, paint it, and assemble it.

So I Pulled it apart and found that 3 of my 4 pistons were cracked by the rings. (I know it was more than likely my bad guys.) I like to learn the hard way in life I guess. lol Anyway. I am having a machine shop bore and cleanup the block in the next few months. Is there anything else I should be aware of or ask them? I plan to upgrade rods, pistons, rings, bearings and add an ATI Damper. The head will stay as is for now but I do have plans for it later. Is there anything specific I should ask the machine shop? I am mostly worried about bearing clearance. I want to return to the power I was making prior to blowing my engine (~200whp) then add more power later when I can afford a new rear end, fatter tires and a bigger clutch (I am on the ACT 245tq happymeal right now).

Thanks for everyone's help!

How does your math work? I think I paid $35 for my ball hone.

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My math kind works like this... Most of these engines are high mileage now which means the bores aren't true due to wear, dingleballing the cylinder will work on the cheap, but your rings are still going to fail faster in a cylinder that's not true. Thus having to do it again, sooner than you should. 👌 It's that common core math. Also I think they charged me well under $100 to hot tank and hone three last engine I brought to my shop.

does ATI even make a short nose damper? I wouldn't bother for your purposes. You can get oversized pistons for $80/piston, cheaper than wiseco/ST. But with the cost of a 1.6, at least in my area (100-200), I'd look into that for spare pistons or use the entire long block (long nose maybe?) or a 1.8 first, then refresh.

Slightly off topic, but I'd shoot for no richer than 11.5 AFR. Somewhere around 11.5-11.8 is the sweet spot depending on the motor. You get maximum cooling with minimum torque loss at 11.5 AFR on pump gas, that target changes if you run signifi9can % ethanol...but ethanol burns cooler anyway.