Spei

I've been running on my stock 94 block and recently cracked the head. While I'm figuring that out, I've been planning a built motor for the eventual day my stock block goes boom, or if I get tired of the weaksauce. I've been doing a lotta reading (hopefully a good amount) on what internals and stuff to get for the build. I've come up with this.

My buddy has a 2002 BP6D that he pulled from a wrecked NB so I'm planning on using that, it ran before they pulled it. I was toying with the idea of using a 1994 block and the 2002 head for cleaner oil lines, but I don't have a 1994 block laying around to build that isn't the one in the car right now, and Emilio at Supermiata recently posted saying that the NB2 blocks have more cylinder thickness (anyone know anything about that?). Any other reason to go with a 94 block? The plan for this car is just to have a streetcar that I can rip and visit the track in the future. I like the idea of keeping the BP and hopefully able to keep the 6 speed with it, but I know this range of power is a grey area. Tranny swaps are kinda out of the question but if I blow a 6 speed I'll start considering one. Ideally, I want the bottom end to be bulletproof, and the headwork is kinda up in the air. The head parts are just kinda thrown in there, not much thought. I'll at least refresh the head. Turbo is undecided at the moment. I've already got a Kraken T25 manifold so my turbo will be limited to that flange style unless I want to go bigger but I know T2s can make the power I want. Maybe EFR? GT28XX? As for pistons I'm leaning towards 8.6, I can find 91 regularly here in Cali, but I got an E85 station 10 minutes from my house. Obviously this list isn't complete, but I hope it looks relatively textbook, I'm not trying to be a pioneer, I just wanna do it right and know that it'll work if built correctly.

For machine work and tolerances (Rough idea):
Planning on boring out to 84mm, I want that 1.9L clout
Ring gap, I'd assume I'd run the Wiseco specs? Around 0.014" and 0.018" for the "high street performance"? Not sure if it'd be street-moderate turbo or the high street performance.
Piston to cylinder wall, whatever Supertech recommends.
Rest of the clearances just be based on the OEM specs?



TLDR: I wanna build a 300+hp VVT motor and swap it into my NA cause I want to, how does this look?

matrussell122

iTrader: (1)

Skip the built head. Just do springs and injectors. Or if you really want a built head there is a guy on here psyber that is selling on . I'll try to find you the link later toda .

curly

iTrader: (25)

I think everyone who mentions a horsepower goal needs to mention an RPM goal. You're kind of building for high RPM without the head/cam work to make it worth it. I'd personally save a lot of money on that list and stay at the stock 7000rpm.

I'd skip the ATI damper, motor mounts, valves, valve keepers, and budget more money for the turbo, and you'll want to include manifolds, both exhaust and intake.

Spei

Are built heads really not worth it in a FI build? I might want to rev a little higher or have a little more overrev protection. If the valves and stuff aren't really needed though I'll just omit those.

I'm kind of thinking about revving a little higher... maybe like 7800? It probably wouldn't really be worth it cause of the lack of cams/head work as you said. I thought it was a good idea to change out the damper past like 250whp? Same with mounts? I understand that I'll be using the boundary pump, I'll probably throw on the ati just for extra safety. I'll probably leave out the vales and keepers though.

matrussell122

iTrader: (1)

Kinda sorta. For your goals you dont need a built head. However the head does become a limiting factor.

https://www.miataturbo.net/miata-par...sequel-100110/

https://www.miataturbo.net/miata-par...t-head-102323/

Spei

Thanks for the links, that ported head looks amazing. At what point does the head become a limiting factor? Does it just come down to how much boost you want to run vs the efficiency of throwing more at it?

Iamwill

This piece of advice is paramount. Going crazy with head work makes sense if your intention is to raise your RPM above what is OEM. If you simply want 300 HP It is obtainable on a lot less than you'd think. I just finished my build and got it on the dyno. Finalized @ 318 HP and 261 lbs/ft TQ on a '97 1.8L that i did a full OEM Mazda rebuild on with the addition of forged rods and ARP headstuds. Reconditioned the stock pistons and put new OEM rings on them. China turbo, 1000cc injectors, 340 lp fuel pump, stock ignition, and completely stock head with new valve stem seals as a precautionary measure. E85 will put me in the 330+ hp range im told by the tuners.

Spei

Yeah I get that I can get the 300 mark without going too deep into the block, I kind of want to overbuild for safety and I might end up wanting more power down the line. I'll probably leave the head stock as you did though, seems like building it isn't needed.

matrussell122

iTrader: (1)

How much power do you see yourself wanting in the long term. 350 can be safe. 400 and more turns into a time bomb on the BP. If you want more than 400 i would look at a K swap and forced induction. You also start to kill parts down the line at those power levels like the transmission.

sixshooter

iTrader: (12)

Supertech light double springs are cheap insurance.

Spei

Probably not past 400, I feel like beyond that would be excessive.

Good to know, I'll go with those.

sixshooter

iTrader: (12)

The forged rods and pistons and the supertech doubles keep things from exploding when you miss a shift. Stock rods and pistons can come apart with a serious overrev, and the valves can float open. No bueno.