Vvt na engine build question
 

Hi, I'm thinking about building my vvt engine for n/a 93 octane setup and I have a few questions before starting to buy stuff.
I have a few different plans in mind.
First off, I will run a BE oil pump and Manley rods.
1) Valve springs: volvo, supertech singles or st light doubles?
2) Mill the head around .030"-.040" and keep stock pistons, get 10.5 jdm pistons from Mazda Comp for $45 each or go with Supertech 11.1?
3) should I keep the stock valves or go with +1 on intake side or both sides? Would the ST 11.1 pistons and the +1 valves make contact?
4) can I get away with new mazda main studs or should I get arp and modify the windage tray?

I'm trying to build a lasting motor with a little more power and keep it very reliable. My goal is track days.

Thanks

All you need to know
https://www.miataturbo.net/engine-pe...g-ideas-83443/

This is just my .02 based on the research I have done while collecting parts for my current NA motor build, which is nearing completion (finally).

I went with light doubles based on the amount of NA builds that seem to use them. I am also running running the baby Tomeis, which probably want a stiffer spring. Are you staying with stock cams?

Supertech 11:1 is going to give you better squish IMO, but the stock pistons may provide better longevity. If you are going all out track performance I vote ST, street/track might be worth staying factory.

I went ST with a coating. Consider 85.5mm if planning to stay NA.

From what I have seen the +1 valves are going to add torque. A buddy is running an 12:1 Bp4W on E85 with ported head and +1 valves on both sides with almost 160tq. I would think I VVT may even improve on that some.

I bought some for my motor and my engine builder said that unless your planning to run billet caps or something fancy like that, we probably won't need them. That being said it seems like most of the very reputable builders like 949 and TSE run them.

I decided against them, but opinions vary on this quite a bit it seems.

Good luck!:party:

Thanks for your ideas. I plan on taking the engine apart this weekend and if the cylinders and pistons look good may just put new rings on it, but the 85.5mm pistons sound good too. The thing that worries new about going with that size is that I would need a new engine block if I need to rebuild it.
What gasket do you recommend using with that size? I want a 94-00 head gasket since I have a coolant reroute.

Sounds like I will go with the double light springs, not sure about the valve size yet. I am staying with the stock cams. How high can a vvt motor be reved with the light double springs?

With 85.5s you'll need either a broached factory HG, or a vendor like 949 or TSE can probably set you up with one. I think Chikara/maruha sell one too.

I ended up staying with an 84mm ST and less compression so that I can still add a FI/rotrex later if I decide I want more. If staying NA, I would have gone 85.5 for sure.

IIRC the light doubles are good until you are planning sustained 8k plus/enormous cams. So well within the RPM range of a stock came VVT motor.

ARP main studs are required above 250whp or 8000rpm. I lost a perfectly good bottom end at ~300whp to a broken stock main bolt. Run without them at your own peril.

Any information about valve interference using +1mm valves and 11:1 ST pistons? What about +1 valves, stock pistons and .030" head shave?
Thanks

ST have relief pockets large enough for +1mm valves.

But you need to check your own clearance anyway, don't trust a mix of suppliers specs, or internet "facts".

I was debating which pistons to use on my eventual VVT build as well, and think I'll go with the JDM 10.5 stock sized pistons which previously I was unaware of. Only $32 each on MazdaComp! I figure I'll get them top and skirt coated and call it good enough. Funny though coating will cost me most then actual pistons.

Thanks for the idea of MazdaComp for the JDM pistons!

Would there be any value in +1 valves with the 10.5 JDM pistons? From what I read probably not is my guess.

I think I made a decision, I am trying for my wife not to get too pissed off for spending $ so here is my build idea.

Stock pistons/hone and rering- $125 + $100 hone
Shave head .030"
back cut valves- $300
BE street strip pump- $400
King bearings- $160ish
Arp head studs- $110
engine gasket kit for 2001 plus 94-00 head gasket ~ $280
ST light double valve springs- $330
Valve seals - $12
Gates timing belt - $60
Skunk 2 TB - $260

Total $2137

Maybe ill buy a low mileage engine at the junkyard for $1000 and build this one over the year.

What engine gasket kit are you ordering? That seems way expensive for them all. I know I recently picked up all the rubber gaskets needed to rebuild my motor for less then $100 from Rosenthal. I picked up both front and rear oil pan gaskets, oil pick up tube gasket, rear main, front main, cam seals, thermostat, oil pump o-ring. The only main one I did not get was VC. For the head gasket you can get those for about $25 shipped on eBay. The 1.8 MLS are exactly the same as OEM so you can save a bit there.

Well, I got a 66000 mile 2004 engine for $800 today from the junkyard. I'll build the other one slowly. Next year is all about track time. But I will still build it.
The gasket kit I'm talking about is the one from mazda competititon. Basically it's every single gasket and oring on the whole engine. I'll look around before buying.

This is awesome to hear, after just finishing my build. Why did I only hear the complete opposite answer from this? Glad I saved the hundred bucks on my 8k build. Shit. Now I'm paranoid.