Fat Thor

*****OPINIONS AND INPUT HIGHLY APPRICIATED******
******If you're in HOUSTON, TX and can offer eyes-on guidance (nothing dirty, just guidance), also much appreciated **********

I recently bought and am currently rebuilding an FM 2.0 stroker that sat in a non-running car for approximately 10yrs. It came with a story that I won't bore you with cuz 99% of the car parts stories are riddled with bullshit and so I'll stick to empirical facts as best I can.

Lets start with end so my questions are in context: 1990 Miata, rebuilt FM 2L, Kraken exh manifold (ceramic coated), G25-660 (hot side coated), 3" single exhaust. I'll be bringing over many of my associated parts during the final swap such as: SM reverse cooling, Skunk intake, LS coils, etc. I'll continue to run it on my MS3 Pro and tune boost per gear (I.e. 8# in 1st, 12# in 2nd, 16# in 3rd and 18-20# in 4th) producing maybe ~425+ whp (if its much more that this than I'd prob turn it down a smidge) running the beta kit TREMEC TKX 5-spd, and a Ford 8.8 conversion.

FM Stroker

I was highly suspicious of it and almost walked away but my cheapo Amazon bore-scope revealed clean, cross hatched cyl walls peeking thru the spark plug holes. No p2v signs, no foreign debris, etc. Fliped the motor over, removed the pan, to inspect the oil and lower bores. Once again, no "sparklies" in the oil, good cross hatch, and for the first time there was confirmation this was truly what the owner claimed because I could confirm the billet Moldex crank, billet caps, Carrillo rods and CP pistons, studded bottom and we had previously confirmed the studded head.

I started to tear it down by removing the intake, accessory brackets, etc. and that's where the questions started:

• This is an extremely well ported 90-95 head with casting number BP 05-6-1 and according to the build specs provided by FM, these came with +1 SS valves with chamber work to unshroud the "tight side". From my understanding, these were some of the most undesirable heads due to their valve train (shim over bucket), port angularity, and lack of VVT ( wasn't planning on running VVT anyways So no biggie there ). The valve train has been upgraded to shim under bucket so that leaves only the angularity issue.
• Can anyone confirm the cams FM used back then? If this where your project what would you run that takes advantage of midlevel torque? I was leaning towards using Mazda Speed cams but only cuz I don't know anything else....
• 2 more interesting finds: 1 - The intake manifold was gasket matched very-very well and recedes maybe 3-4" into each runner. Not a big deal but the quality of work here (especially on these small details) is very well executed. I'll replicate that on my Skunk along with port matching a Mustang TB. 2 - oil cooler sandwiched between the filter and block (stock or aftermarket?)

The plan is to replace-

• Cams (if we can't identify what I have)
• Springs to ensure continuity with build
• All gaskets, seals, etc. (given the motor has sat static for 10yrs)
• A really good cleaning since the exhausts ports are generously coated with 1/16" of oil yet the intake ports are pristine (???)
• Valve seals
• Rings ( gapped )
• Bearings (TBD upon inspection) - I know that sounds crazy but maybe the story is true and this thing only has 5k miles on it. I doubt it but we'll play this by ear.

I will do my best to keep this thread abreast of the project but I really need help with nuances, tricks, tips, etc. because the devil resides in those details. I'll do my best to include photos starting with my car and some of what I described above.

LeoNA

The head looks to be more gasket matched then ported. I personally would not build an engine that has $4k in rods and crank with a BP05 head. A BP4W head with stock cams and better valves, which are a necessity, will make more power than the BP05 head with cams. Do you have any pictures of the bottom end?

Fat Thor

ill take some tonight. Interesting you say that because I have a 2002 head (stock) at my disposal. I'd just need to disable the VVT.

I'll take more photos of the port work too because its pretty good handwork. I could always strip the BP05 and have it transferred to my more modern head huh?

technicalninja

A stock BP4W head will outflow a completely worked big valve BP05 head.
You will also need an intake to match the higher port location that is incorporated in the later heads.
The serious intakes are the Skunk and the euro "flat top". The 99-00 VICS manifold is usable, but the VICS diaphragms are all 20+ years old and expensive to purchase if you can find one.
The Skunk has multiple mount holes to "fit" on either early or late heads. This is one of the sketchy things regarding this manifold. No mount for the factory manifold brace is another IMO.

Now, this engine should have a fully worked BP4W head with Inconel valves, big cams, SUBs, and serous valve springs.
Read lots of threads regarding SS valves and bad wear. I personally will not use SuperTech SS valves due to the extreme wear I have witnessed.
I'm waiting for FM to have the Inconel +1 intakes back in stock.
I already have the exhausts.

The guys at SuperMiata have really good advice when it comes to FI cams. You might want to check with them for their suggestions/prices/availability.
At one time they also listed "CNC" ported heads. I've worked on one. They are worth it unless you have been porting heads for decades. Very nice CNC work, Both ports and chambers- all of it!
As decent cores are getting rare they may have dropped this from their site.
I'd ask them "Can I send you a head and have the porting done?". They might still do that.

The fact that you understand "the devil is in the details" is 3/4 of the battle. You should do fine!

You found a Unicorn! The billet crank/main caps are super rare. Nice find!

This could be an "Uber" Miata engine...

technicalninja

Below 20 psi the VVT can help. Slight increase in torque in the lower RPM range.
Above that others have had trouble controlling this. Search forum member Ted75zcar for insight.

All the 1.8l head parts interchange easily

Fat Thor

hey Tech Sensei, I contacted Super Miata and they said they only sell parts now. Is there a head guy here in TX who you recommend? The guys I would use wouldn't know a Mazda head from Kia head........Now'n days, if it aint LsX or Coyote, the big boyz arent interested in discussing and they have back logs that span months.

I guess we'll continue to tear this motor down, saving whatever we can and reusing whatever is prudent. Its a shame to waste this nicely ported head but "it-is-what-it-be-like" and no use in bitch'n about it. With luck, the valves will be Gucci, the cams will be Mazda Speed types, and the lifters will be solid. Regarding Inconel; I'd upgrade the exhausts but my experience suggests the intake valves should be fine. The group consensus suggests the ST double spring seem to be the ticket so I can order those sooner than later. Is there a "super light lifter" solid lifter on the market?

I gotta buy a cam wheel tool to lock the front together as I continue to disassemble. FM has a new design that I guess I'll try. Any other "special tools" you think I need? Figure I'll order now since I wont be touching this motor as long as the Astros continue to kick ***!

Fat Thor

My strategy was to utilize the KISS method and deleting the VVT while opening the door to cam choices. Let the cam work from 2800-4800 and let the turbo do its thing beyond that given I have more turbo than I can use. doest mean I'm "right" means I'm practical and can always come back later if I second guess myself.

LeoNA

Cams are a poor value for turbo applications. As previously mentioned, you will need inconel valves on the intake and exhaust. You can run the VVT head without the control, because you will have a bit extra low end TQ from the increased stroke. The poor rod to stroke ratio is going to limit the max rpm to 7k, but it should be able to make over 400hp on E85. Service life is not going to be long and will depend on how well it's put together. I recommend buying core engines now.

Fat Thor

• A bit of low end TQ eh? This thing will fly!
• Rod Ratio will not limit my ability to spin it
• Its a G25-600; I "should" be able to make 400 on 91 dependent on tune and nothing else I've said. this combo is capable of 600hp with a very wide torque band
• I've owned multiple strokers such a FSB 345 and a 347 and a CBB 528 with Dyers 871 and the rod ratio myth about "RPM" as been long debunked. RPM capability has more to do with valve train control and weight of reciprocating parts. Now if the argument was time of dwell, then I'd listen but I'm using a lighter crank, rods, pistons and valve train, and I already said I'm interested in a mild cam to peak mid range torque, therefore Spinning this to 7800-8200 shouldn't be an issue assuming I'm still making power (of which I should)

As for Inconel on the intake side; I'm not familiar with that given the intake side typically runs cooler. As an example, I had buddies run Ti intake valves and SS exhaust valves because of heat on nitrous cars (granted, we're talking pro built motors running 500 shots in stages) but the logic should carry over.

Right now I'm bound by 2 questions:

#1. any more unique tools I should be investing in other than the cam gear lock up tool?
#2. any other racing shops in Texas anyone might recommend to full port and rebuild my BP4W head? (already contacted X-factor up near Dallas and contacted Keegan Engineering (CA) after Super Miata recommended them)

tblackey

So all of Supermiata motors I'm fairly sure were built by Keegan(From everything I've heard he does great work and takes forever.) . www.facebook.com/keeganengineering

I was running a 2.0L built VVT turbo motor 85.5mm bore / stock stroke - Just rebuilt with 84mm pistons/block, but the VVT can help a lot with low end torque if tuned right. I run low boost, but at 12psi I was making 315hp with an EvoX turbo.


https://www.miataturbo.net/engine-pe...-build-103415/

LeoNA

If you want to learn by trial and error that is up to you. These engines are an old design, were not designed to be FI and top out at about 300whp on 91. This engine design has intake valve issues. They tulip and wear the seat excessively when highly modified. The intake valve just runs hotter than average. Could be the chamber shape or the internal cooling passages around the seat. With a rod to stroke ratio of 1.494 (133mm/89mm) it will have a relatively high rod angle which will limit the max rpm. At 400+whp these engines may only have a service life of 20-30 full load hrs, maybe 10-15kmi on the street. It is not a FSB, BBC or a 4G63. Good luck.

Fat Thor

Leo, that's the whole game of backyard engineering right? I mean, how fast do you want to go is directly relational to "was not meant to do this" as if on a **** Around / Find Out Graph. I think most of us recognize that the Windsor 5.0 block was never meant to make 500+hp no more than the Chrysler 440 was meant to make 800+ yet we do it all day / every day. I will make 425-ish hp from this combo and no i dont expect it to last 250,000 miles as a stock trimmed may. This is my toy and it will clock 12k or less miles per year on the street. If I goto the Tail of the Dragon, The Texas Mile, and or any open road rallys such as the Silver State Classic, she'll be trailered back and forth.

You may be right that I need Inconel intakes as well; thank you and I'll look into it.

Regarding rod ratio and their ability to spin, its direct effect on torque, effect on dwell and how that could actually be of benefit, I decided to pull up some geeky videos if you want to watch:

• You Tube
• You Tube

LeoNA

I understand the effect of the rod to stroke ratio. A 425hp 2L engine is equivalent to a 1500+hp big block. Mean piston speed, thrust side piston bearing stress and rod angulation are the limiting factor. The thrust component of the bmep is increased with the rod angle. Hot rodding, backyard modding and DIY are great. There is also nothing wrong with doing research and learning from others experience.

technicalninja

I have a machinist here in Granbury that I use but my best advice for you down in Houston..
Is to seek advice on machine shops down there from PatsMX5 who lives there.
He should know the good from bad machine shops local to you.


He's building a super serious BP currently.
He's doing many of the things you're contemplating right now, and his advice is golden.
Search threads started by him for some serious A-Team type action.
Moving condenser for AC to trunk...
Running twin sequential turbos...
Using Bugatti Veyron fuel pumps...
You will like Pat.
Pat's Ebay Turbo Compound Boost Build - Page 95 - Miata Turbo Forum - Boost cars, acquire cats.

Fat Thor

thanks brutha.....I'll look him up!

off to the TX Miata Round Up in College Station this morning. talk to yall on Monday.

GO STROS!

emilio700

iTrader: (3)

While the NB heads (BP4W/BP6D) flow significantly better than the BP05, cams flow even more besterer. If you already have a good BP05 head, turbo and feel like doing cams. I'd say go. The cost analysis is building an new BP4W head from scratch (including core) vs the cost of BP05 cams.
Another generic rule with any engine but particularly with low rod ratio motors like the BP is that revs cost exponentially. If you can meet your power/fun goals on lower revs it's save many dollars. The FM stroker kit roughly replicates the rod ratio of stock but with a far more robust rotating assembly. Lots of builds with that kit running 8500rpm.

Our tech guides here: https://949racing.com/supermiata/tech-info/

Short version, go for short duration, max lift. Turbos like slightly different lobe centers than N/A. If it doesn't already have adjustable cam gears, invest on those and plan on some dyno time with an experienced tuner. Longer duration will give you more top end but gut the low end. Fine for a road race or drag car but no fun on street, auto-x or road course. Soft low end power places a high priority on optimizing gearing and ratios. Big low end power doesn't care what your gearing is.

concealer404

iTrader: (3)

BP05 has more meat for porting. If all you care about is raw CFM, it will outflow a 4W/6D head. Velocity gets kinda blah, but matters way less in the context of big turbo power. I don't know where this bizarre rhetoric came about regarding "a completely stock 4W will outflow a completely worked 05 head" but it's completely wrong. As is the arbitrary crap regarding a relationship between VVT and manifold pressure.

Car looks cool. Congrats on the buy.

LeoNA

That is not what was claimed. A ported bp4w will out perform a ported bp05 head. My recommendation was to build a ported 4w instead of buying cams for the 05. The 4w will have a larger area under the power curve. Cams present many issues besides the cost. For a turbo application it is better to go with more valve area and a better port geometry. Everyone has an opinion and that is mine.

msmola2002

Is absolutely what was claimed.

concealer404

iTrader: (3)