fixbroke

Hello cat-acquirers of mt.net.

The car: NB1 donor Exocet, 120,000mi, second-hand and new-ish to me, **sees almost exclusively track time**
Winter plan: Rebuild engine, add eBay turbo for moderate power (200-250 hp), **restrain desire to throw a bales of cash into it**
Me: Intermediate/advanced driver and mechanic, mechanical engineer by trade, have rebuilt several motorcycle engines, never rebuilt a car engine or built an engine for FI

I was a few track days into Exocet ownership when the engine started sounding expensive. I had been losing oil rapidly, probably through the PCV and/or breather, and I had accidentally run the dipstick super-low at high revs once or twice. I'm now in the process of tearing the engine down, and I've definitely munched my rod bearings and distributed the flakes throughout the engine. The cam journals/caps/bearing surfaces got lightly scored. See pics below. It looks as though the crank got pretty plugged-up with flakes and restricted flow to #3 and #4 rods, but this might be a chicken-and-egg scenario. I haven't pulled the head yet to have a good look at the bores and pistons.

No biggie! I was planning an eBay turbo and MS3 build this winter anyway, so I may as well open up the engine and freshen things up a bit.

Having never rebuilt a car engine or built for FI before, I'm hoping the mt.net hive-mind can help me decide what I really need to do and what I probably should do (I did read the pinned engine build thread and it was super-helpful). For the condition of my engine, and my intended usage, is there anything I've missed in the list below? Which of the Maybe-Gonna-Do items should I plop into the Definitely-Gonna-Do list?


Recently done:

• Clutch/flywheel/PP/trans seals

Definitely gonna do:

• spray out oil passages with brake cleaner
• coolant reroute
• Manley forged rods
• OEM rod bearings
• OEM crank bearings
• OEM rings
• full set of gaskets (MLS where appropriate)
• water pump
• timing belt
• engine mounts (turns out that one was busted)
• ARP head bolts
• hand-polish cam/crank journals
• ball-hone cylinders
• valve seals and guides
• OEM valve springs
• valve shims
• oil pan turbo drain fitting

Maybe gonna do:

• machine shop hot-tank block/head/crank to clean out all the flakes
• machine shop hone
• machine shop crank/cam journal polish
• machine shop inspection/measurement
• new OEM or upgrade pistons
• upgrade/chromoly rings
• upgrade oil pump gears
• upgrade valve springs
• upgrade crank damper
• give up on this block/head and just build another used engine that isn't full of glitter

Pics:


#4 rod

#4 rod

#3 rod

#3 rod

#2 rod

#1 rod




main bearing caps

rod caps

glitter in my valve cover

Exhaust cam

Intake cam

technicalninja

Hit the easy button...
Another used engine that is in good shape. Your cam lobe damage is fatal (No ZDDP was added). The crank turning purple is not a good sign either. maybe it's just the light but your "core" does not look good to me.
Buy everything that MKTurbo sells, the whole critter is what you want here. It actually inexpensive and most of the problems are solved.
Check with him regarding the exhaust for your Exocet.

Going down the built engine rabbit hole is more difficult than a beginner ever expects.
Most of the "carnage" posts regard the start up of a newly built motor.
The stock BP appears to die "softly" from boost.
Lots of folks bend the rods, but seldom scatter a motor.
I WOULD NOT build a BP for less than 275 HP.
By the time I got into one I'd be shooting for less than 300lb/ft (6 speed life) and as much hp I could hit...
Somewhere above 350.
Below 250 is "good used engine" and run it till you bend a rod FIRST.

fixbroke

Thanks for the info! Though the prospect of junking my engine is not a welcome one.

• The blue color on the crank was definitely a trick of the light.
• Attached are some more pics of the cam lobes to confirm they're toast. I was actually more concerned about the journals and bearing surfaces than the lobes, so what you noticed is a surprise.
• With my 5-speed car, I am shooting for the 250hp number as I've read that's around the limit of track reliability with the stock drivetrain.
• I guess I'm aiming for a minimalist build (rods only?), but looking to maximize my (reliability*power):dollars ratio, and to hit all of the easier/cheaper "while the engine is out..." items, like rings and a hone.
• eBay turbo kit (with intercooler, manifold, downpipe, etc), MS3, and Innovate LC3 are already acquired, so the MKTurbo options don't seem like the right choice for me unless they sell individual components on request

technicalninja

The first picture you posted that shows the end of a camshaft has an obvious flat spot on one of the lobes.
The valve cover looks like it has tiny bits of metal embedded in it.
Many of you other pictures show bits of metal all over everything.
Clean that crap off before taking pictures...
The fact that that stuff looks to be on everything is not good either.
The cam journals look toasted, the cam bearings (built into the head, all I can see are the caps) don't look great either.
All the cam lobes appear to have serious wear. I'd have to clean them up to see it better but the single flat spot in the first picture damns the cam anyway.
You need a bunch of stuff to resurrect that motor.
The whole "do it when you are into it" is false.
"YOU DO, or YOU DON"T DO, THERE IS NO TRY" (Yoda!)
I wouldn't do it for your power goals and I have much experience. I could fix your motor as cheaply as anyone can and I would refuse too if you brought that into my shop.
We'd just get another "core" engine even if we were going to build it up...

joe morreale

I'm no machinist, but looking at the cam journals, I'm sure the head is wasted. By the time you buy a head, recondition it and rebuild the motor, you'll have invested a bucket full of money into it. I personally would source a lower mileage motor, maybe vvt and call it a day. You'd be limited to 220 whp or so. That should be a lot of fun on your chassis. Even if you want more power, a rods only build on a used motor is better than what you're starting with. BTW I have the MK kit on my car. It works great, tuned to 200 whp, for three years and over 20k.

curly

iTrader: (25)

With enough money, everything can be saved by a machinist, except the oil pump and cooler. You could have them remove the galley plugs in the crank, tap for NPT, and grind down the mains and rods, the NPT plugs will allow you to properly clean all the galleys before reinstallation. Removing all the pressed in plugs and hot tanking the block, along with a lot of compressed air and careful inspection should clean that up, and you can mill off a few thousands from the cam caps (making them oval) and have them line bored to restore their surface, then remove all the head galley plugs and have it hot tanked, blown out, and carefully inspected. After this you'll still need a new oil pump, they're ~$100-150 new from Mazda, or $300-400 from BE, and after all the necessary gaskets, you'll have a rebuilt engine for around $2000, depending on your local shop's rates, and you'd still be at risk of damaging the rebuild with foreign contaminants. Hence why we're suggesting a new donor. You might save a few hundred by doing rods at the same time, but I still don't think it's worth it.

fixbroke

All right, all right! The dark reality has set in. I'm on the hunt for a donor engine.

I'm still of a mind to lightly upgrade and refresh the new motor, though, and I'd love some guidance on the revised list below:

Definitely gonna do:

• coolant reroute
• Manley/Eagle forged rods
• full set of gaskets (MLS where appropriate)
• water pump
• timing belt
• engine mounts
• check valve clearance/re-shim
• oil pan turbo drain fitting

Maybe gonna do:

• new OEM rod bearings
• new OEM crank bearings
• new OEM rings
• upgrade/chromoly rings
• ball-hone cylinders
• valve seals and guides
• new OEM valve springs
• ARP head bolts

technicalninja

Install a used motor without opening it.
Spend money on:
coolant re-route
Upgrade flywheel and clutch. (includes all bearings and clutch hydraulics)
All the PMs (preventative maintenance) This includes cam and crank seals (4) Valve adjustment. cooling system
Upgrade motor mounts (Mazda comp) (maybe different for exocet)
Remove pan for inspection and drilling, re-seal. Find a "real" cap for the turbo drain for now
Clean it up and make it look nice.
Upgrade your radiator if not done yet. Do minor upgrade for 250HP level.
Install engine into car. Since it is still basically stock run it on the original ECU with the original injectors.
Verify it runs properly. Put a few miles on it. At least 50...
Do a hot compression test and a leak down and post results.
Once you have proven you have a runner...
Install just the MS3 and the injectors.
Learn how to tune the critter while running NA.
Put more miles on it. For a street car I'd suggest at least 1K miles during initial tuning education.
Then add turbo system.
By the time you get into boost you will be able to tune it without breaking it.
Continue to tune it for higher boost in small increments. HAVE FUN!
By the time you ACTUALLY bend a rod it will already be wicked fast and you will have MUCH experience.

IF YOU HAVEN"T BUILT MOTORS BEFORE LEARNING THIS STUFF ON A 350 HP BUILD IS AN EXTREMELY SHARP LEARNING CURVE AND THE CURBS YOU WILL HIT ALONG THE WAY WILL BE EXPENSIVE.

The fact that you thought you stuff was savable directly reflects on your lack of experience in this arena.
My advice is "Bend a rod with boost BEFORE building an engine for boost"
Most of the time they just bend 1 rod a small amount.
Your bent rod motor can still be the "core" for the motor build at a later date.
Do it this way and have a running car for a couple of years before you need internals.
Have fun, get it running sooner and spend $1000s less this way initially.

fixbroke

I appreciate the advice. It's a solid plan.

However, if the engine is on a stand already with the oil pan off, why not add rods at that time instead of bending them later on? The cost is reasonable for Eagle/Manley, the extra labor isn't significant, and seems like good insurance against the carnage that could potentially occur with connecting rod failure.

emilio700

iTrader: (3)

I think you should heed technicalninja's and curly's advice. They're right and have lots of direct personal experience on the subject. Your choice is to knowingly embark down an unknown path of discovery that is guaranteed to involve expensive mistakes or..take the boring route by listening and learning from the mistake of others. The latter choice is legit, we have all done it. Just know it takes longer, costs more and is a greater adventure. For some people, that's the whole point.

my .02

technicalninja

Read the childrens book "If you give a mouse a cookie" It will explain the issue.
Short and sweet. If a mouse shows up and wants a cookie you should squash that critter FLAT.

I believe if you take the internals apart on an engine (Head off, crank out) and don't do the whole shebang you are shooting yourself in the foot...
You're HALF ASSING it.
The ONLY reason to short change one is if you are in a competition that REQUIRES you to short change it.
You are NOT...
It is EASY to achieve your initial goals with a stock motor in good shape.
A 250 hp exocet will be wicked fast. It's really all that chassis needs.
You should be able to chase down serious Porsches and maybe pass them.
You will be running with the big dogs on the track and you will have less money in your whole car than they have in a set of wheels...

A "built motor" for boost in my book will include.
Stock un-cut crank in good shape, micro-polished
Rods/pistons
ARP head bolts
Valve springs
Fancy oil pump
Minor port profiling including both intake manifold and exhaust.
No exotic cam ****.
No exotic valves.
Really pretty simple...

This set up should be targeted for 400 hp. Commonly people hit just below this with a similar set up.
You will NOT make this level of power with an EBay turbo set up. You will have to be MKTurbo, Kraken, TSE, EFR at this point.
The 400 hp set up will require more mods to the car. Big Fuel, E85(or heavy fuel), A real harmonic damper, a good flywheel, better motor mounts.
Past 300lb/ft of torque the toughest Mazda drivetrains will start to show weakness. 6 speeds pull the gears apart (no fixing this **** for any money), rear ends start having issues.
Lots of mods on this forum to get by theses hurdles but in my book...
By the time you start hurting a Mazda 6 speed you should junk the entire drive train and start with a more capable set up.
A good one is K series Honda, Boosted this requires a BMW transmission and a GM rear end.
A better one IMO is LFX GM. You can easily use GM stuff for all pieces. A stock one is bad-assed. a boosted one can be insane...
Then you can hit the "BIG DOG" LS series V8. This is WAY TOO much for a Miata IMO.

Most of the carnage threads on this forum involve tuning mistakes or a "build". Running too lean breaks stuff badly, or initial start ups on a freshly built engine where the builder didn't have enough experience.
The guys who do it right just bend the rods a tiny little bit. I believe they should keep that bent rod as a "trophy", a rite of passage...
I would keep the rod LONG after the car was gone.

And here's the thing that every single newbie doesn't understand.
A built motor for non boosted application is 3 times as critical to build than a boosted engine...
The boosted build is EASY and I still see MASSIVE mistakes on this forum.

You need experience more than any other single thing.
You need to learn how to tune FIRST (or find a GOOD tuner that you pay)
You need experience driving a 8/1 car before you make it a 5/1 car.
This is the way...
Your choices are stay cheap, crappy EBay turbo, stock motor, have a running car much sooner and you don't have a shitload of money in.
Use this for your "experience".
Or build a decent motor, throw the EBay crap in the trash, get Kraken, MKTurbo stuff, increase your build time by a factor of three and the cost by a factor of four.
If you have a hic-up with the cheap stuff it's no big deal. You can toss it in the trash without killing yourself.
Have a hic-up with the "correct" way and it can KILL your enthusiasm for the whole process.

And, it is far more fun to trounce a GT3 with a 10K car than a 20K car....

I've also seen multiple time "I wish I had kept the car at the 225hp level, the 325hp level makes me work on it all the time and I cannot enjoy it like I did when it was simple".

Either stay simple or go "***** to the wall".
You will have more fun starting simple.

technicalninja

And the WOLF speaks...
I'm a big dog, I have serious experience but...
Emillio is a full blown thermonuclear WOLF.
He recently sold a couple of "BUILT" motors on this forum that were a "wet dream" in my book.
The first one was a 10K motor that went for 5-6. stock cams and crank
The second one was a "shoot the moon" motor, billet crank, big cams, everything...
He himself said it was good for 600+ HP BAD ASSED!
I just don't know what he could have bolted it up to that would live...

technicalninja

Suggested reading:
Andy's boost your 220k NB and then build a motor thread - Miata Turbo Forum - Boost cars, acquire cats.

Fireindc's attempt to build a decent miata. (the search for more torque). - Miata Turbo Forum - Boost cars, acquire cats.

I cannot find Son of the hills thread but it is a good one to show the power of a MKTurbo basic system.
Son tests the CRAP out of his car at the drag strip. I'm guessing he has more than 500 time slips.
Most of them have been on a tired used motor.
And "all season" radials! OLD ONES!
It looks like he has had an absolute blast doing this...