patsmx5

iTrader: (16)

So I'm wondering is the head from a 94+ 1.8 Protege the same as the 94-97 miata? Are the cams different and if so, is that the only difference? Are the bare heads themselves identical?

Reason I'm asking is I can find 1.8 Protege head locally but can't find them from a 1.8 miata. I'm thinking of buying one and porting it in my spare time and selling it to some turbo natzi that wants more spoolage. I'm sure a select few would be interested in good headwork. (oh ****, this thread de-rails from here...). Anyways if anyone can confirm or deny or link me to a miata.net thread with hand holdage that would be fan-*******-tastical.

neogenesis2004

iTrader: (12)

I don't thin the proteges use a cas, my bet would be that the cams are not compatible with it.

patsmx5

iTrader: (16)

Yeah protege's have a distributor I do believe, but it does snap in the same spot as a CAS on a miata. Hell if the bare unassembled head is the same that's all I really need.

The_Pipefather

iTrader: (5)

why not just get the head from a escort GT or a Kia sephia? Or even a 99-02 suzuki esteem?

patsmx5

iTrader: (16)

Um, so your insinuating that basically all BP 1.8's have the same head? I know I've seen some kia's with 1.8's. Just saying the protege's are more popular then a miata in a salvage yard around here.

cjernigan

iTrader: (13)

People swap the kia motor over once in a while. It's fairly entailed but doable.

The_Pipefather

iTrader: (5)

more or less. i'm inclined to believe that the Kia head would have been milder in terms of cam selection since it went into a bread and butter sedan where a flat torque curve and fuel economy are more important, thus automatically rendering it more suitable to a boosted application.

reddroptop

iTrader: (4)

That was disproven over on GRM IIRC that 1.8L esteems are BP's.

They are NOT BP's.

Pitlab77

iTrader: (3)

try checking www.solomiata.com
http://members.aol.com/solomiata/MX5Engine.html

photoeye0

The 1st gen pro head is the same!... I'm using a miata cas in my pro right now.
And as far as I know the Kia BP is the same too.

patsmx5

iTrader: (16)

Well, I found a 96 Kia Sephia with a 1.8 BP engine today. I'm going back tomorrow to get it. It has 81K miles on it and looks perfect. The head has BP05 cast on the back of it. From my research this motor has the MBSP the 01+ miata's had, 9.0:1 compression, forged crank, and forged rods. My motor's fine but I'm getting this one to have a good spare or possibly to build a motor.

chance91

iTrader: (3)

are you sure it has a forged crank and forged rods? that sounds a little out there to me, no offense. If that's true, I feel kinda funny knowing a kia has better internals than my MSM... we didn't get forged rods.

patsmx5

iTrader: (16)

All 94+ miata's have forged rods IIRC. They suck, but they are forged. Crank is forged too. Main difference between a miata motor and the Kia on I got is the kia motor has the BP05 head, but has the MBSP bottom end. And I believe it's 9:1 compression. So put a 99 head on this, and I have a 9:1 motor, 99 head, and MBSP. Basically collecting all the mazda goodness into one motor.

photoeye0

The Protege BP's have a MBSP too, but the Escort's don't...

chance91

iTrader: (3)

Not trying to start a fight, but I just want clarification, but also am pretty sure the stock rods aren't forged in any 90-05 miata. Reason being the cars at most ever made 178 hp from the factory, and really is not enough to justify forging the rods vs. casting. In order to forge the rods more time and money would be involved, and I would assume mazda went the cheaper way out with cast rods, just because the stock motor would be fine with them. They even used these same style stock rods in the msm motor.
Motors where you may find stock rods being forged would be something like the older audi 5cyls, vw 16valve motors, etc. made a bit of power NA, or were lightly boosted stock, and older technology didn't allow as precise construction. I'm going too far with this, anyway. sorry. I think the kia will be a good base block, especially with the nice 9.0 comp and the MBSP if it does have it. Enjoy the build man!

Arkmage

iTrader: (3)

The heads are not identical... the mounting bosses on the back of the head are different with the fwd application. If someone can post pictures of each side of a miata head (can't get to the back of mine right now) I'll post pics of the escort head I have for comparison. If I recall the differences won't matter unless you are trying to use the stock coils.