Time for a new motor.
 

Well, looks like my motor wasn't as healthy as I thought.
Compression:
1: 151
2: 136
3: 108
4: 92

Starting out at 135k beat-on miles and boosting 12-13psi w/bandaids for 15k miles might have done it. I was gonna run 14-15psi sooner or later, so I guess it's good I found out pulling out of the driveway:bigtu:

SO, where to go now?
The $$ factor is important here as I've gotta tell the wife I blew up the car. The actual work of SWAPPING the motor isn't a big deal (gonna do the clutch at the same time). I've got a hoist, tools, and lotsa space...

My goal w/MS has always been 220whp @12psi. I don't think I need anything that you would apply the word "built" to.

I honestly know very little about the costs comparison of stock parts vs. upgraded parts or what all I'll need to buy.

So, let's say for example that I need to keep the whole thing under $1000. The ACT XT is $344 from PSO, so that leaves me $660 for a new motor, or parts, a build, or whatever.
What exactly do I need?
Do I just need a shortblock? What all parts does that entail? Rods/Pistons/Rings???
How much is OEM stuff?
How much is (one step above OEM) aftermarket stuff?
Can I do an engne rebuild of the caliber we're discussing here in my garage with a GOOD set of tools?

Basically I need to know your suggestions on what you would do (on a budget) to get this car back on the road @12psi for at least 50k miles. Start at $660 and work it from there.

Let me hear it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I vote for just a 94-97 short block, or complete engine-swap and drive it.

Then take your original block and build that one up.

P.S. I don't remember what year your car, obviously a 94-97 short block would be a tough fit on a 90-93

We did have a professor at school that blew the motor in his K car. He took the block down to the machine shop, bored out the one bad cylinder and slapped back together (not sure where He got one oversized piston though) (this was back in the late 80's)

Or how about just finding a donor 1990 mustang? might as well put in a 'bigger' motor...

well with a $660 budget you're looking at pretty much a stock rebuild or pick up a used motor.

everyone says the rings are the weakest link, i wonder if you just got some really nice rings and left the rest stock, but still at 220whp you shouldn't have much of a problem

If you haven't tried http://www.car-part.com it's a database of the inventory of a large number of junkyards, searchable by distance from your location. You might score a lead that way.

From what I understand, the rings leaking is the problem, but the cause is the ring landings on the piston fail. Stock ring landings are not that beefy, and the stock pistons are not forged. If there is any detonation, or a cylinder is running hotter than normal, that ring landing is what's taking a beating.

If it were me on a budget, I would get a set of forged pistons and rebuild the bottom end. Look into new rodbolts as I've heard they are the first thing that fails on a stock rod. Make sure whoever does the machining is one sharp individual that really understands how to build motors and has a reputation for building excellent motors.

Cheapest/easiest option is to pick up a complete junkyard motor with good compression. With a good tune and good starting compression a stock motor should hold up fine to 220hp/12psi without needing to upgrade anything. Recoup some costs if they leave any accessories attached that you already have (i.e. starter, alternator, CAS, coils, valve cover). Do all the routine maintence with the engine out of the car (seals, TB, WB, etc...). You can always separate the head/shortblock and clean things out a bit as well if you don't mind springing for a new HG and clean all the other stuff as well.

I got lucky and found a local engine with about 70-80k and good compression for $300. I sold off a bunch of parts I already had for almost the complete $300. Spent another $300 or so in all the maintenence stuff (including MS engine mounts, seals, pulleys, TB, water pump, gaskets, 323 PVC, etc..) Cleaned out the chambers and head before putting it together. So spent just over $300 for a "refreshened" engine. Most likely, you can find a low milage engine for ~$500 so it'd put you in the $600 total ballpark.

Sam, I'm sorry man. :mad:

To keep costs down, stick with the 1.6--otherwise you gotta get all the conversion hardware and tweak your charge pipes, plus at minimum a new exhaust mani, if not also a new downpipe. I'd also just get a new clutch disk instead of dropping nearly $400 on a whole clutch assembly. That should free up some funds to get into the motor a bit. I know you said you don't "need" to build it, but you could get into a very minor build: forged rods (our friend Jim Belfab has them on ebay for $300 right now), and if your pistons aren't broken get them ceramic coated (if they are, you can pick up used pistons for nearly nothing), get new rings and have them moly coated, new bearings, head gasket, and oil pump, and the basic machine work. You'll come in at budget, and have a stronger than stock motor that's probably safe for 7500 rpm and 300 hp. Overkill for 220, I know, but my thinking is that odds are you won't be able to break it (really bad tuning aside, of course), and then you'll have the ability to get into more power if you ever want to. And eventually you probably will.

Of course, it's a slippery slope while you have the block apart...

QFMFT
Quoted for mother fucking TRUTH!!!!!!1111oneoneeleven

that's insane, i dont see how a few quick pulls hitting the boost cut would kill it......

do what i did and swap the short block if you can. I only spent about $300 getting mine back togther. $250 block/head, $30 HG/timing belt, $40 milling.

I've actually got a spare hg I could mail you if you wanted to do that.

PS. scott didn't buy a new hg, I sent him my other spare with his head.

Where'd you get a decent HG/TB for $30? I think my last timing belt alone was ~$45.

edit:
Oh, I see how it is ;)

ahem http://www.rpmmachine.com/engine-reb...ts-mazda.shtml 326 $ For the major engine kit and it comes with everything or, you can get some belfab stuff etc, for a little more. In either case it sucks to hear that you are having problems GL man.

I totally love the idea of just getting a used low-mileage engine. I can part out as much of my current engine as possible to recover some costs. But when I hear "low-mileage", I'm thinking like 30-40k miles... not 80k. Sure, 80k in a '90 is low mileage, but not to me when the intention is boost. It looks like I'm on the hunt (you guys let me know if something pops up in your travels).

I also really like the idea of a mild "build" with some upgraded rods and coated pistons/rings like Ben suggested.

Can I, in my garage, disassemble and re-assemble an engine with new parts? I'm pretty savvy mechanically, and I do have all the tools. I understand that I'll need the piston walls worked on... but can I do the rest? I've never done any major engine work, but I'd never installed a turbo or changed a clutch before this car either.

Sam, the miata block is pretty simple. You should be able to do everything except the machine work. After reading your other write-ups, I bet you'd absolutely love the ability to scrub and refinish/repaint everything. The only tool you probably don't have is the piston ring compressor you'll need if you install new rings.
Does your base of a hobby shop for you guys?

Put it together in the kitchen like me, its much cleaner there. I also have a ring compressor you can borrow if you decide this path.

Of course this is a little premature. Aside from low compression, what other symptoms are presenting? Did you try a leak down?

It would be a hoot if this was just a HG like scot had go bad.
I think you are very qualified to do the work so long as you just pay attention.

Look no further! It's almost like destiny!

https://www.miataturbo.net/miata-parts-sale-trade-5/fs-built-head-built-1-6-block-tilton-clutch-setup-6spd-tranny-14362/

I'll take 10% :)

HAHA, not even I linked that shit. I figured it was beyond the scope of what he wanted. I'd love to see him convince his wife.

sam even #1 looked low, which is odd.....i don't see how it let go so fast, how were the AFRs while driving around this week?

I would almost say its the hg because 3 and 4 are both off by about the same amount. You need to do a leakdown and see if air leaks out of 3 when you are testing 4.

All right, I figured somebody would recommend a leakdown test. Other than the blue smoke and the compression numbers, it seemed to drive OK. I pulled the intake to verify there was no blow-by through the valve-cover breather tube, pulled the coupler at the throttle-body... no oil so I assume the turbo is good.

On the last run of the night, I blew the dipstick out and coated the back half of the engine bay. I drove it home right after that, and this morning when I started to drive to work, I noticed the smoke out the exhaust, brought it straight home and drove the truck.

AFR's were in the 12 range everytime I looked down at the laptop under boost. I never got the chance to do some datalogging, but I think it was just a tired motor waiting for a little extra push to send it over the edge.

However, I think a little more investigation is in order. I will do a leakdown test. What's the most efficient way of doing it? And I will go for a decent drive this weekend to see if there's just some residual oil somewhere that's burning.

And thanks for the link Jay, but swinging $1k out of her is in the realm of possibility... $2k takes us that much further away from a new set of tits and I can't put that on the back burner for a motor.

sorry to hear that, and just got your ebc workin too :cry: I'd say find a clunker to swap in quick and save up to fix the one you have.

That is one hell of an upgrade. My ex-g/f got implants like 2 weeks after we broke up. They ended up looking like shit so no big deal. Went from an A to a D.

HAHA, nothing like motors and tits!

sam what was your proceedure for the test? cold? try wet? oil on plugs? throttle open?

I'm keeping my fingers crossed for you that it is just a HG or something, but if you do decide to go the used engine route, there is a place in northern NJ (I know it's a hike) that sells low milage <50k engines from Japan (JDM yo!) with most of the accessories attached for around $550-600. I told olderguy about them for his friend who was looking for an engine so he might be able to give more input. I found the place when looking for an engine myself and negotiated them down to $500 for pickup. Ebay the valve cover, CAS, coils, starter, alternator, throttle body/IM, injectors/rail, etc... and you'd be at a decent price point. If you want the info, PM me as I'll have to dig it up as it's been awhile.

Of the two JDM Yo engines I've seen, both of them had trouble. One of the "50k" motors need rings. The other had so much crap in the cooling system that it ruined a rad and a heater core. They both came from the same importer, so this might not be typical.

If the Miata isn't your daily why not tear down the motor you have and rebuild it. At least that way you'll know for sure you've got a good motor.

^Good points, that's the info I need to hear to make a good decision. I'm not decided by any means, so keep the options coming.

As for my compression test:
Cold motor.
Unplugged MS
Un-grounded fuel pump.
No throttle application.
Started at 1 and worked back, replacing the plugs as I went.
Each cylinder needed 6-7cranks to get to full pressure.

The plugs were dry, and looking at the plugs, I'd say #1 was running a tad leaner than the rest...but I'd only been MS'd for about 2hrs total run time.

Redo the compression test with the engine warmed up and throttle wide open during testing.

I only got $300 or $350 for the 1.6 motor that I sold, it took a month to move, and it was complete from oil pan to cam cover with all sensors except the thermoswitch (because I needed it on the other car). And it was a good longnose with compression 200 +/-5 on all holes. So I wouldn't spend $600 on some unkown "JDM" motor. Plus, if you got into a build, you'd have more effort involved but a pretty similar financial outlay, and at the end you'd get to replace the weakest link in the block: the rods.

+10x9

warm engine, pull all the plugs, unplug MS, start at #1, WOT, crank until it doesn't make anymore compression

redo with a 1/2 teaspoon of oil in each cylinder.

Hopefully it's not that bad- like a head gasket. You might even check the torque on the head bolts. I retorqued a head on KL v6 and manage to seal up the head gasket around the cylinder. Regained all the compression and ran that way for another two years.

If it's worse, pull the head, figure out what's wrong first. If it is the rings, and the bores are round, you can just re-ring with a cylinder hone.

Typically, I pull all the plugs to do the test. And 6-7 cranks to full pressure seems pretty normal. Also, the last time I did a compression test (this past Monday after I found the oil on the valve cover) I did an experiment where I tested one cylinder twice, with the throttle open, then closed. It actually didn't seem to make much of a difference. Maybe 10 PSI tops, and took slightly longer to get there.

As to a leakdown test- the cheapest tool I know of (apart from the one you borrow from a friend) is here: http://www.harborfreight.com/cpi/cta...emnumber=94190

Actualy on my nissan i saw numbers of 110 or so with throtle closed and numbers of 170-180 with the throttle closed. So yeah it makes a big dif there joe at least for me it has.

No shit? Wonder if it has something to do with the design of the idle valve or the PCV system or something... Like I said, it took a bit longer to build up compression, but it did finally get there (or nearly so). I'm pretty sure I don't have that big of an intake leak. :D

i get 110 across with the throttle closed and 190 open.....its the mere fact that the butterfly valve isn't open and theres not enough air pulled in to make high compression, i suspect if you crank it at least 20 pulses it would build.

Ok, moral of story: open throttle plate when cranking. :bigtu:

^It'll be the first thing I do when I get home..

Theoretically, what it the difficulty scale of replacing a head-gasket with the engine still in the car?

Not too bad to replace the HG, as long as neither the block nor head is warped. Overheat is the leading cause of HG failure.

simple.

On larger engines such as V8's and such, they hae more volume between the TB and the intake valves of all the cylinders, and running a compression test closed TB dosn't skew the results 'as much'. Still, I would always do it TB open. Most recomend putting the battery on a charger while doing it so when you get to the last cylinders to check, your motor is turning over just as fast as it did on the first cylinders you tested. I always do this when testing V8's, cause by the time I get to the last cylinders, the battery is usually half dead.

For any that care, I have not had any time over the last 2 days to do work on the car. I'm headed to Texas for 5 days on Wed, so hopefully I can knock out another compression test and do a leakdown test prior to leaving... I'll kick off a new thread when I know more.

-Sam

If you're gonna be in that E-2, I'll keep an eye open to see if you fly overhead into Kelly Field...the approach path is right over the building in which I work...F-16s are cool, C-5s are too freakin' noisy!

If you do pull the head or swap rods, spend a few bucks to ensure your torque wrench is in spec. If it's good enough for the the A&P mechanic torquing the propellors on your plane, it's good enough for your car. I was unpleasantly surprised when I discovered my 1/2" drive torque wrench was 15% out of spec *low*. Instead of 80 lb-ft, I was only getting 68 lb-ft of torque.

FWIW,
Barry

funny, i was considering sending my wrench in the be speced since it's not in use over the winter....I hear you should do it once a year, and a HG that fails within 20 miles says a lot.