Pistons for my NA engine...
 

I just called and found out the pistons for a 2001 Miata are priced at $62.92 a piece. I'm going to buy them seeing as they have a 10.5:1 CR.

I have a question though. I have a shaved head. Would I have problems with the valve heads having enough clearance?
I'm wondering if the pistons will smack the valves. They are just domed more than the stock pistons I have now. I guess I should be fine, but I would like to get a second opinion from one of the more experienced mods on the board.

As per a conversation I had with one of the mods, I'm concerned about making additional hp from the 12hp billet cams I have. Because the early 1st Pros had 8.8:1 CR pistons in the engine, I'm really not going to see that much improvement with the cams on. Having a shaved head and putting in the 10.5:1 CR pistons in, I would see the maximum gains out of the cams. Would I be correct in assuming this?


Thanks in advance for any input/advice.
:shift:

a few thoughts...
 

do you know what kind of shape the cylinders/walls are in yet?
MAYBE you'll need to bore them...if so, obviously those miata pistons won't work.

also, i wonder what kind of compression you'll get with a shaved head AND 10.5:1 pistons... might be 'too much'???!

No. They aren't different in size. Goto http://members.aol.com/solomiata/MX5Engine.html. The pistons are completely interchangeable between years.
Oh. I thought they were 10.5:1 when they are actually 10:1. With the shaved head, it would prolly be up to 10.5:1, which is fine.
Well, I'll figure out if I need to deck the block or what not when I rebuild the engine and put one of the pistons in and compare it to the one next to it. I'm pretty sure it'll match up fine. Just wanted to see if anyone was out there that have tried this yet. I think I'll shoot off an email to a couple of lists and see if I get any replies from there. I know the EGT crowd does a bit more tinkering, and I might have better luck at a response from there.


Later on.

they are interchangeable...but...
 

i was coming from the idea that you MAY have to bore/clean up your cylinders a little bit; and if that's the case, i didn't think the miata pistons would work as your cylinders would be larger.....

bty, some of the guys haven't been on the board the past day or 2, so i'm sure you'll get some more input :)

AFAIK, there is no reason to bore this block out that I have. I know I'll prolly have someone hone the cylinders, or do it myself, but that's all. Unless of course there are deep scratches. In which case, I'll prolly be SOL. :)

Yeah, I might check back Monday or Tuesday and see if I get any replies. A lot of people are busy this weekend. I know my legs are tired as hell from being at a parts yard all day. All I want to do is freakin' go get something to eat, come back, grub, and fall the hell to sleep. :bt: heh

Actually, now that I think about it, the friend that I got the engine from, said that the third piston needs new rings, so that one may be f'd. I hope it's not so bad that it needs to be bored. That would suck fucking ass. Then I wouldn't be able to use the 10:1 CR pistons. Grrr. I guess I'll have to search around for diff pistons. Bleh. I'm too tired to think about it and how depressing it would be... Uhm. Yeah. Anyways. :)


Later on.

I have no number on how much it is shaved (bought from a third party). I guess I could call Gude and see how much they usually shave.
Thanks for the info regarding two overbore sizes. That's real useful. At least I know I can have the thing bored and not worry about pistons not fitting. :bt: