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Old 06-02-2009, 11:09 AM   #1
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Default Building Bottom end for FMII, seeking advice

Hi all,
I installed an FMII Hydra kit into my '94 last july. At the same time, I also installed a bunch of other FM parts onto the car, incl:
Supersize clutch kit
2.5" single exhaust
Hi-Flow Cat
Aluminum race radiator w/twin Spals

In addition, I did a NB head swap at the same time with a 2000 head, had an aluminum head shop go over the head before installing. They planed the surface, and worked a few of the valves to seal up right.

One week after I had everything installed on the car, I got an unwanted phone call. It was a one month notice that I was being deployed.

During the last month, I also installed a set of 225/45 RS2s on Nickel 15x8 6ULs

Since being deployed, the car has been sent from my home in Columbus, OH. to FMs Exhaust producer out in Lancaster, CA to help them fabricate their 3" NA turbo exhaust. I got a free 3" upgrade out of the deal with no "miata downtime" to me, and an excuse for a cross country road trip as soon as I finish this deployment!

The car runs great except for one exception: Heavy oil burn, especially under boost. Since being deployed, Ive been weighing the options in my mind, and as is my nature, I've been over-researching everything at the same time. Since the car is now at 120,000 miles, I've decided it's time for a full rebuild, and because I don't want to rebuild it twice, It's gotta be done right the first time.

My current power goal is 300hp at the rear wheels on 93 octane - whether I'll reach it or not is a different story, it is just a goal after all. I was never able to get the car on a dyno to see it's current power: My priorities changed quickly when i got the deployment phone call. The following is a list of expenses that ive put together:

Pistons(84.0 mm)/Rods - Belfab/Supertech 389+439= $830
Bearings/Gaskets - FM Engine Rebuild Kit -$600
Oil Pump - $40
Already has a farily new water pump - $0
M-Tuned Coolant Reroute - $300
Fuel Pump - Walbro 255 - $140
Shop Work, incl. cylinder boring / balance rotating assembly - 600???



Total - $2500 + incidentals

For the actual engine build, my questions are:

What compression ratio would suit me best? I see these pistons offered in 8.7, 9.0, and 9.5:1 I am currently leaning towards the 9.0:1 CR, but I am definitely not against 8.7:1 ratio, It is closer to stock on the 94 IIRC. I'm probably not dead set against the 9.5:1, but I think I would need some convincing to go that direction. Is there any reason to chose a piston such as FMs 9:1 Wisecos, +$200?

My selection of the super expensive FM rebuild kit is based on an unfounded fear of getting an incomplete kit, a kit with inferior components, or a kit that assumes I'm doing an OEM style rebuild. I am also not a fan of going the e-bay route for engine internals. It's a long discussion of sociology and economics that I won't get into with this post. Certainly, there are some of you who have rebuilt for hundreds less? What are your experiences with bearings/gaskets/kits?

I've read discussion on crank scrapers but can't seem to pull it up with a search lately. IIRC, it is a simple bolt-in upgrade found stock in later model Miatae. Does anyone have a part number? Valid points against?

Shop work: I've seen prices ranging between $200 - $1200 and higher. I will find something competitively priced and within my means, for the quality of work that I expect will be done. What I am more worried about is what shop work I'll need to have done that I can't do myself. Boring the cylinders, of course, and balancing the rotating assembly, are the two jobs that I plan to send to a shop. The shop I am looking at using is AIM Tuning out of Indy. Other work that I'll be trying to learn more about is knife-edging, and line boring.

Is the fuel pump necessary at 300rwhp? Im currently running the RC550 injectors.

I suspect I may have to add a WI system to safely reach the 300hp mark. Has anyone reached the 300hp mark at stock displacement w/o WI? Safely?

Do I install valve stem seals myself into the stock 99 head, and call it a day, or send it to a shop for a rebuild?

Extras: I fully expect to grenade the stock 5-speed transmission if I dont upgrade it at the same time. I expect to have one by the time the build is complete, and maybe even a 3.636 rear to go with it. I'll also be throwing on a FCM suspension as soon as I get home.

What are your thoughts/opinions? What have I forgotten, or what should I add to my list? Does anyone have shop recommendations? Should I start from scratch and build a street legal F1 style car?
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Old 06-02-2009, 03:08 PM   #2
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I suspect I may have to add a WI system to safely reach the 300hp mark. Has anyone reached the 300hp mark at stock displacement w/o WI? Safely?

I know paul has 300 whp on his internally stock 99 motor. Not sure if he has WI or not.
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Old 06-02-2009, 03:39 PM   #3
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My selection of the super expensive FM rebuild kit is based on an unfounded fear of getting an incomplete kit, a kit with inferior components, or a kit that assumes I'm doing an OEM style rebuild. I am also not a fan of going the e-bay route for engine internals. It's a long discussion of sociology and economics that I won't get into with this post. Certainly, there are some of you who have rebuilt for hundreds less? What are your experiences with bearings/gaskets/kits?




I wouldn't get my bearings out of a kit. I'd let my machinist size and reccomend the bearings. FYI, my crank needed signifigant turning and polishing.
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Old 06-02-2009, 03:48 PM   #4
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Changing out the valve stem seals is going to mean tearing down the head (pull cams, shims/buckets, springs), and rebuilding. This isn't hard to do w/ basic tools, a spring compressor, and a set of feeler gauges, but it's time consuming.
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Old 06-02-2009, 03:52 PM   #5
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I wouldn't get my bearings out of a kit. I'd let my machinist size and reccomend the bearings. FYI, my crank needed signifigant turning and polishing.
Miatas have nitrided cranks and should not be turned, iirc.

Edit: I believe that was Joe Perez that I heard that from...
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Old 06-02-2009, 04:00 PM   #6
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did you look here first. Racing Mazda b series engine. they have some good deals and build many fast miatas. the cost is not so bad.
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Old 06-02-2009, 04:23 PM   #7
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blablahblah some useless incorrect crap about RM
Don't listen to anything this person says. RM is a shitty shop.
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Old 06-02-2009, 04:36 PM   #8
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BenR, good advice. I suspect that a good shop is going to know their **** a hell of a lot better than I ever would.

Fluke, thanks. I know it's time consuming and a bitch to tear down a head. Before I found the 99 head, I took apart my 94 head, cleaned out all the HLAs, cleaned up the valves, and put it all back together. I think I spent an entire saturday working with that thing. After I got to about the 6th HLA, I was thinking "what the hell did I get myself into?" But it wasn't terrible overall. I just dont know how easy the seals are going to be to pull out and replace, what sort of accuracy/precision/tolerance will i need to get them in? I'm assuming you dont just set them in, and then hit them with the blunt end of a tool. But hey, if that's all it takes, then it should be an easy task!

Six, I'll definitely look into if there's any truth behind this.

locomonkey, i'll look into this shop

sav, sometimes I can't tell if you're being serious or sarcastic, but I know that you know your ****, and definitely value your input. TY
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Old 06-02-2009, 05:12 PM   #9
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Miatas have nitrided cranks and should not be turned, iirc.

Edit: I believe that was Joe Perez that I heard that from...


True about the nitriding, but the treating is pretty deep. The factory provides for some amount of turning. Mine was cut but, only to the next bearing size up, they did full hardness testing of the journal surfaces. I trust my machinist, they do this all day, and were building fast cars before I was born.
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Old 06-02-2009, 05:35 PM   #10
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Good info, I'm assuming i wouldnt need to worry about reduced bearing surface area. i.e. stock should be more than sufficient?
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Old 06-02-2009, 05:39 PM   #11
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Good info, I'm assuming i wouldnt need to worry about reduced bearing surface area. i.e. stock should be more than sufficient?




You never really know untill you see and measure it. You can guess and probably be ok. I don't like guessing with that.
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Old 06-02-2009, 05:39 PM   #12
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...I took apart my 94 head, cleaned out all the HLAs, cleaned up the valves, and put it all back together. I think I spent an entire saturday working with that thing. After I got to about the 6th HLA, I was thinking "what the hell did I get myself into?" But it wasn't terrible overall. I just dont know how easy the seals are going to be to pull out and replace, what sort of accuracy/precision/tolerance will i need to get them in? I'm assuming you dont just set them in, and then hit them with the blunt end of a tool. But hey, if that's all it takes, then it should be an easy task!
Well, no HLA's to deal w/ but you will have to check the clearances and possibly replace shims. Stem seals just pop off, new ones pop on; really easy.

After 170,000 km and valve lapping, I didn't have to replace a single shim in the head, springs were good too.

Assembly (after lapping) took ~ 3hrs, 1hr to check clearance. I spent about a day rebuilding the head with a good buzz on.

Do a full head check while you're at it (guide bushings, springs, etc...), get the engine rebuilding manual. I scanned mine and have that in PDF if you don't have it. Will the admins freak out about that?
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Old 06-02-2009, 05:55 PM   #13
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First off, where are you finding a $40 oil pump? IIRC, new OEM pumps run about $150.

Anyway, some '94s had 8.8:1 CR and '94.5+ had 9:1 CR. Honestly, never really been able to tell a difference when driving either in OEM form. With my own build I went 9:1. It's responsive out of boost and in boost.

You can find the Walbro pumps all day long for $100/shipped on eBay, there's one seller that regularly lists them for our cars, has 100% feedback, etc. I know someone on here posted his UserID on here at one point in time, but I can't find it. Anyway, you want the 190 lb/h HP because the 255 is known for overloading the FPR on 90-97 Miatas.

Main Bearing Support Plates were offered on later Miatas, however, scrapers were not OEM to my knowledge. MiataRoadster.com offers the scrapers and I believe the site hints on what's required for the installation.
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Old 06-02-2009, 07:56 PM   #14
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I wouldn't get my bearings out of a kit. I'd let my machinist size and reccomend the bearings. FYI, my crank needed signifigant turning and polishing.
If you buy your rebuild kit from a good supplier, they'll ask you what size bearings you want You really should measure the crank to know if it's going to need machining. Most don't, but...
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Old 06-02-2009, 08:04 PM   #15
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I thought I recalled seeing an oil pump for $39 on one of the vendor sites - just the gears. But cant seem to pull it up. Never had the oil pump out so didnt know what it entailed. After a quick check, your numbers are more inline with reality at about $150.

Regarding the FPR, I had an AFPR in my list some time ago, it must have slipped off somewhere.

Thats probably why I couldn't find the "crank scraper" anywhere. Indeed, you're right. It was the MBSP that I recall being a "bolt on" upgrade!

Thanks Keith, I know you've got different bearing options in your kits at FM, but the numbers never really made sense to me. It's all starting to come together now...
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Old 06-02-2009, 10:09 PM   #16
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If you buy your rebuild kit from a good supplier, they'll ask you what size bearings you want You really should measure the crank to know if it's going to need machining. Most don't, but...
yes, let the builder decide which bearings you need.
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Old 06-02-2009, 10:53 PM   #17
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I thought I recalled seeing an oil pump for $39 on one of the vendor sites - just the gears. But cant seem to pull it up. Never had the oil pump out so didnt know what it entailed. After a quick check, your numbers are more inline with reality at about $150.

Regarding the FPR, I had an AFPR in my list some time ago, it must have slipped off somewhere.

Thats probably why I couldn't find the "crank scraper" anywhere. Indeed, you're right. It was the MBSP that I recall being a "bolt on" upgrade!
Ah. I was interested to know because I was about to be mad that I got ripped on mine. lol Definitely get a new pump though, it's not worth it to get everything in and then have it fail. Ask me and ZX-Tex how we know. Having a stupid $0.50 plunger and spring fail (relief valve) is not cool after a long build.

I gotcha, you might still want to consider the 190 though, it is able to outflow the 255 at higher pressures. (Read the Turbo DIY FAQ on here if you haven't yet, it will start sparking ideas while you're considering your list.)

You may also want to consider a set of ARP head and main studs as well.
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Old 06-03-2009, 12:40 AM   #18
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I think you should go with the low compression. At 15psi I hit MBT well before detonation. I made 252wtq at 27* advance, with over 30* on the dyno with no detonation. I also recommend a bigger compressor housing although this forum doesn't agree. I've opened up the exhaust a bit since and added cops. I have no doubt that I'm over 300whp on a dynojet, probably around 290whp and 285+wtq on a dynodynamics (man's dyno). John Day built my motor with a reasonably "loose" bore and it has zero blow-by problems, its not loud, and the motor is incredibly strong at 6k miles and 2-hours of track time.

I showed up with pistons/rings/pins, rods, ARP mains, and ARP headstuds. I handed over $1200 and he did a bore, blueprint/balance on the rotating, cleaned-up the castings and port matched the 99 head, and assembled it too. That guy has put together a ton of FI miata motors and everyone I've spoken to is happy with him in the miata world and outside. I searched for a long time before I selected my machinist, I recommend you do the same.
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Old 06-03-2009, 04:30 AM   #19
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hustler, are you running that power on WI, or without?

your builder sourced all the bearings/gaskets/etc himself?
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Old 06-03-2009, 04:37 AM   #20
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rotornut, after looking at the FAQ again, I think I've been convinced to go the 190 HP route. Thanks!
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