hustler

iTrader: (6)

Aparently there's a California company making sleeved miata blocks now. I don't know who though.

sn95

iTrader: (2)

Yeah, it would be nice to know who is doing it. MRM website says they are developing a 85.5mm/3.366" big bore kit for the Miata 1.8L block. I just checked Darton's website and they don't have any dry sleeves listed in that size but there is a 3.330" bore Honda sleeve in a 5.520" length. The Miata block isn't listed as a standard sleeve install either on Darton's site. I wonder if MRM is boring an existing Darton sleeve (like the Honda F22) or having a custom sleeve made by Darton or another mfg.

DOHCPanther

I found this on Solomiata. I wonder if there are any cheaper Japanese parts available.

"UPDATE 9/21/98 As reported in the August 1998 issue of the MCA magazine, Mazdaspeed makes a 3mm stroker crank for the 1.8 'B' motor. This crank is used in the Japanese only market 2.0 liter C-Spec Miata (85x88). It is part number 9E3A-11-300 and costs $2,258.66 USD. It is basically a forged racing prepped unit and that is why it costs so much. It is available for import from Mazda Competition at 800-435-2508."

I was a long time Ford fan before the Miata and have seen many crankshafts go in engines they weren’t designed for. It was done with a whole lot of homework and some simple machine work. Depending on how much material is available on the BP crank some stroke could be gained with offsetting the rod journal.

Hustler, any idea what to search for about the sleeved BP

sn95

iTrader: (2)

Offset grinding to increase stroke works well if the parent crank has large rod journals and longer rods with smaller rod journals are readily available at a reasonable price. Ergo, the popularity of the 514 BBF stroker which uses an offset ground 460 crank and cheap aftermarket BBC rods which have a smaller rod journal diameter than the stock BBF 429/460. You can scour the vendor parts catalogs and try to find a strong, cheap and longer than stock Miata rod with a smaller than stock Miata rod journal diameter to support an offset stroker 1.8L crank; let us know when you find a viable option.

Check out the McCullys's website (McCully Racing Motors- There's no Replacement for Displacement.) if you want to see an infomercial on the 2.0 big bore Miata. As I noted earlier, it's still unclear which supplier is furnishing the dry sleeve for the big bore and what the actual specs of the sleeve are.

magnamx-5

iTrader: (7)

didnt motorworx bore his 1.6 to 85 mm without a sleave is the 1.8 that much thinner?
http://forum.miata.net/vb/showthread...highlight=bore ok 81.5 still impressive

sn95

iTrader: (2)

Hmmm, what did I miss in the thread you posted?

"Arias 81.5 mm pistons for Toyota 4AG"? How do 81.5mm pistons relate to a 85.5m big bore debate???????????????

emilio700

iTrader: (3)

No info on the OGK motor as it hasn't been built yet. We just stuck the old (nearly stock) OGK motor into out track rental for a customer to use this weekend.

Plenty of shops that can properly lighten and bull nose the stock crank, nothing special there. 85.5 pistons are on our site. Fine for a low boost motor but unknpwn with 18psi from a GT3071. I don't think you'll need 2.0L to reach 350whp with a GT3071 though. Savington here is getting 320whp from his GT2871 with a POS stock intake manifold, stock cams and nearly stock head at 1884cc I think. That was with a MS PnP with wasted spark and batch fuel, CAS. I think he'll find another 20whp just from the crank trigger, sequential fuel and spark his new AEM will allow. Fully built head, cams and custom intake manifold, I think the GT3071 at 18psi will be well over 400whp on race gas.

I don't feel a burning desire to drop $3500 for that extra 100cc

sn95

iTrader: (2)

Emilio,

Thanks for your input on this. Please help clarify the following:

1. 85.5mm pistons in a stock block 1.8L. Boring block, sleeving block and what "warranty" for each. Are you using sleeves? Which mfg???

2. What is "lightened" weight of a 1.8L crank vs. the stock weight? Is the rotating assembly still "neutral balanced"?

Mitch

Savington

iTrader: (31)

'94s had sequential injection, but my head was 100% factory, no port cleanup or anything. I think an intake manifold alone would be worth 40whp on my car - that's 360whp. Add some headwork, better ignition control, and a set of cams and 400whp is easy - and that's with a 2871R.

magnamx-5

iTrader: (7)

OK man i can see you cant see what i am getting at here. So it will simplify it
the stock 1.6 is a 78 mm bore so if he can add 3.5 mm and still beat the **** out of the motor with 0 sleeves etc. If and this is the real question here the 1.8's have the same beef on the block theoretically you could do the same overbore making our 83 mm bore into potentialy a 86.5 mm bore. Granted this is going on abot of faith that mazda left just as much room to play on both motors. If they did we dont need sleeves then and the **** just got alot simpler.

gospeed81

iTrader: (51)

See now....Andrew's just dumb....because this is EXACTLY what I got out of your first post.

sn95

iTrader: (2)

Got it, had the beer googles on last night and it seemed foggy! There are engineering standards for how much cylinder thickness one needs to be "safe" for both NA and boosted applications. You can get a block sonic checked for cylinder thickness and use that information to determine the maximum safe overbore for a NA or boosted application. Check this article out on Sonic testing Mopar blocks and making statistical predictions based on a relatively small number of blocks tested:
Sonic Checking the Mopar Big Block

This has got me thinking that it might be worthwhile to compare a few 1.8L Mazda blocks to a few 1.8L Escort blocks. They are cast in different foundries, so one may have consistently thicker cylinder walls than the other.

magnamx-5

iTrader: (7)

exactly a 100 dollar bore and hone seems more wallet freindly to me than a 3k dollar crank,

TurboTim

iTrader: (9)

You'll have to ask McCully.

DOHCPanther

I knew you guys would come through. This is good information. I didn't want to spend 3500 on a crank if my turbo didnt support it but if I can get more displacement at this price it dosent look bad.

85.5mm pistons from 949, 86mm head gasket from Chikara, will get 1952cc. Tis is some good displacement for the money. The larger bore would reduce valve shrouding allowing better flow. Sonic checking the block will let me know how much material I will have.

Anyone care to figure the displacement of 85.5 bore and (FM stroker crank) 89 stroke. Got to go my boss need the computer.

Savington

iTrader: (31)

The 70cc or so you gain by doing 85.5mm pistons over 84mm pistons isn't worth it. The 85.5 motor is going to run hotter.

When I was building my first motor I looked at 85.5mm pistons - the only HG I could find was the Maruha HG at 4-5x the cost of the stock gasket. No thanks.

gospeed81

iTrader: (51)

that's 2.04L

DOHCPanther

Ok, back on again.

Yea, I see that now. They have a warning about thin cylinder walls. I see why FM offers what they do. They already did the homework.

I got the turbine info back grom Jeremy. "On this T25 footprint unit, it uses a 56.5mm w/ 84 trim wheel & a 0.64 a/r housing" Comparing this turbo to the others on the Garrett site it looks a little small for the power I am shooting for. Maybe I have set my goals too high for the parts I already have. I dont want to resize my turbo. Also SN95 sent me a PM and reminded me what displacement does to cam specs. It would make the cam would feel smaller.

Hummmmm...... Stroker or not? I am beginning to think it isnt necessary for my goals. Tonight I will compare the pro and cons and post tomorrow. Thanks for the input everyone.

Savington

iTrader: (31)

FM Stroker will make more torque everywhere, spool the turbo earlier, makes the motor a bit nicer to drive on the street.

You can hit your goals with a ~1880cc motor - you have to decide if a bit more torque and a bit better spool is worth $3500 to you.

sn95

iTrader: (2)

Well put. I find it amusing that FM has never bothered to have custom cams spec'd for their 2.0L stroker kits; $3,500 is lot for another 100cc that provides a nominal torque increase and shifts the tq and rpm curves down about 500 RPM. The added displacement and the longer piston dwell time at TDC/BDC call for an entirely different cam than stock but they never address this on their website. I'm not sure what the limitations are on grinding new cams/regrinding stock cams w/reduced basecircle are for reasonably priced Miata cams but I'm hard pressed to believe that there isn't 20-50hp left on the table using stock VVT cams in a 1.8-2.0L motor @ 18psi.