bimmerboy

Putting together a parts list and goals for a 1.8 VVT rebuild. It will remain NA. 100% track only HPDE.

Why?... for the fun of it! To put it in a chassis that I will try my best to not add aero. So I can drive a "normal" Miata on track with "normal" Miata friends and enjoy the chase. Also like the inherent "money-shift" resistance this motor has proven to possess. MS3 Pro with 7300 rev limit.

But which internal parts? I know stock parts for stock rebuild but new OEM parts are getting harder to find and for a little more, you get better parts. Here's what I'm thinking:

Goals:
93 octane pump gas tune
Years (not 1 season) of reliable HPDE tracking
7400 rpm redline
Maintain money-shift resistance

Parts:
Manley Rods
Supertech pistons/ Wideco rings - but which diameter and which CR? 9.5:1 with .020" off head to maintain 10:1 CR?
Supertech valve springs - to maintain/increase over rev protection
ACL bearings throughout
OEM Mazda head gasket and shaft seals
ARP head bolts
BE oil pump
Square top manifold - because I already have one


All of the other bolt on parts already on the car.

Stealth97

iTrader: (5)

Stick with OEM pistons unless you want boost.

and you don’t need valve springs either unless one of yours is broken.

bimmerboy

Source for oversized 10:1 OEM VVT pistons? That’s the difficulty. Found some oversized 9:1 OEM pistons but they cost over $600 for the set with rings. Wouldn’t going with 9.5:1 Supertechs be the better buy… or am I missing something here?

SpartanSV

Why do you think you need oversize pistons?

technicalninja

Everything depends on the state of the core engine you are starting with.
Normal bore wear on a 200K engine will often allow you to just hone the cylinders and run the stockers. The extra clearance P-W clearance can actually help in a motor that will see extended high RPM use.
No way in hell I'd pay $600 for stockers that were oversize. I'd buy forged every time.
For a buget build I'd re-use all of the stock rotating mass including the stock rods.
I'd use "street" bearings, probably would still be ACL, just not the expensive ones.
Wouldn't waste money on head studs either. I scored a set of Mahle head bolts at RA for $27 recently. I would not use for a FI build but NA they would be fine.
I would use the BE oil pump or just the gears if I was being super-cheap.
I'd use the flat top. A decent header and free flow exhaust is a requirement as well
20 year old valve springs should be changed due to age. The ST sets are nice (I love the titanium retainers) but the Volvo set would probably get installed.

I'd add to your list
Fluid damper
Skunk t-body (screws can come out of stockers).

"Machine shop" work I'd do myself:
Ceramic coating on chamber/valves/piston crown, Moly on skirts.
Head/manifold port profiling. The pocket area is critical on these heads.
Balance pistons and rods. Replace rod bolts with ARP (or replace rods)

Things I'd pay a machine shop to do
Power hone on a real honing machine
Decking the block to minimum quench (<.040 total, will raise compression more than milling head)
Milling the head. The finish on both the head and the block is more important than head bolts and this increases compression.
Have crank micro-polished - Balance rotating assembly. (crank/flywheel/pressure plate).

The rod bolts themselves are expensive enough to keep your eyes open for a good deal on a cheap set of h-beams. I scored a new set of no-names from another forum member with ACL rod bearing for $125 a while back.
Any of the H-beams will work fine for a 7300 RPM NA build. The stock rods will work fine as well.

I have a set of 9.5 83.5 Super Techs that I do not like. The deck height varies over .008 for the set. Normal Mazda pistons vary less than .001. I cannot recommend this brand due to this.
I prefer the alloy they are made from over the normal 2618 that everyone else uses but their tolerances are too wide IMO.
I'd go Wiseco, JE, CP for forged pistons...
I'm leaning towards the Flyin Miata Wisecos for my MSM.

der_vierte

Put an aftermarket throttle body on your list

bimmerboy

Thanks for the details and I agree. Maybe 4-5 years ago there were more parts for BP's out there, but in post Covid 2022, options are more limited. This is my first Miata motor but not my first motor.

Pistons - will evaluate as suggested once torn down but your experience with ST pistons has me thinking twice @technicalninja. And no, I do not want to use 2618 alloy.
Rings - if stock pistons are re-used what rings?
Rods -after balancing and adding ARP bolts, might as well go with H beams
ARP head suds - because race car!
Valve springs - anyone got link to the Volvo ones?
Coatings - Calico CT-2 piston top coating is around $40 ea
Decking - Noted. I have used and have access to a prolifometer (RA surface measurement thingy).

bimmerboy

And even if I re-use the stock pistons, I will not be using Mazda OEM rings at $100 per piston or $400 just for rings. This goes back to my original thought of just going new Supertech/Wiseco for under $600.

In any case, any rings to avoid? Mahle OE for $56 for the entire set of Enginetech for $31 are what I've found so far.

And for main and rod bearings, may as well stick with the Mahle theme for my application.

technicalninja

Mahle=yes
Enginetech, DNJ=no

LeoNA

I agree with Mahle being the better brand, but DNJ will sell any available product including Mahle's subsidiaries. OE 01-05 VVT pistons cost $500 per set. At that price I would run the ST piston kit which consists of Mahle 4032 alloy forged pistons with NPR nitrided steel rings. I would not rebuild a Mazda engine that had over 100kmile without boring and would not re-use cast pistons. Cast pistons usually have more wear on the ring lands then skirts. Be careful when porting the bowl area on an NA build. They are very sensitive to the throat to valve area ratio. My preference would be larger valves over bigger cams.

DNMakinson

iTrader: (3)

What brand(s) of Ceramic Coatings are available for DIY?

DNM

bimmerboy

I think by doing it yourself he means put them in a box and mail to Calico Coatings. New or used they will coat. CT-2 is thermal coating for the top at $33 ea and CT-3 is anti friction on skirts for $50 ea. Just got the quote today. Another pro for new pistons from JE or Weisco already have the anti friction. But they are 2618 alloy and id don’t want to deal with the piston slap and/or skirt collapse when you run a too hot with tighter p-w clearances… been there before.

technicalninja

V-136 PISTON COAT (Oven Cure) | Cerakote Ceramic Coatings

These folks have multiple options. For decades the process has included baking at a specific temperature for a specific time.
Their newest stuff is air cured. I'm not sold on the air cured stuff.
I'm hunting for a used 36" wide oven for both ceramic coatings and small powder coating projects.
There are other vendors for this stuff besides Cerakote.
The $35 test bottle (4oz) should be enough to do 8 pistons.
The oven is "cooked" after the first set and should not be used for food production again.
Don't do this to your Wife's oven!

For cost no object I'd lean towards these people but I'd do more research first...
Piston Domes – Swain Tech Coatings | Industrial Coatings | High Performance Racing Coatings

Just sending them off is safest.
The pistons have to be "as new" in the clean department.
I'd finish the cleaning with alcohol. Not even germs on surface and I'd have cooked them multiple times between cleanings...
Manually clean piston, soak in B12 overnight, dry off and cook for 30 min at 300-350, Lather, rinse, repeat.
Far easier to start with new pistons but could be done to used on a buget.

Stealth97

iTrader: (5)

I got oversized OE 10:1 pistons from bill Wilner with or rings for about $500, but that was 15 years ago when I built my motor. Still runs great after 40k miles and two cars.

I’d avoid the super tech garbage. Lots of people use them, lots of failures. I couldn’t tell you why people buy them.

bimmerboy

I've updated my K24Z3 swap spreadsheet with another tab that tracks the BP6D "rebuild" to hopefully help others contemplating what to do with their powerplant. At this point I'm really hoping that the current used pistons are in good enough shape to re-use. Also hoping that bore taper is negligible so I can just use a dingleberry hone.

https://1drv.ms/x/s!AgVXBXahR9kktByZ...RU7qE?e=s4BmUw

bimmerboy

@accordionfolder @Boosted Falcon

Guess who wants a new motor?

LeoNA

SwainTech is one of the leader's in engine coatings and one of the oldest.

technicalninja

I use a set of sprung stones to check for bore out of round.
Spin them for 20 seconds and check patterns. This will show low spots better than any other inexpensive checking method.
If the bores look concentric, I might use a dingleberry hone to finish. I seldom find concentric bores.
A dial bore gauge will not catch the small low spots that this method does.

Normally I find enough variation that I give up and just take it to a machine shop that has a real honing machine.
These use stones that are fixed to a micrometer style holding jig and the stones are not "spring loaded".

A real honing machine tends to straighten out slightly OOR or tapered bores. It cannot straighten .001 or better but it can clean up .0005 deviations.

Back 30 years ago the rings were both softer and double the thickness they are now. The blocks were softer as well. Having a ridge at the top was normal.
Now days I commonly see almost no bore wear (no ridge at top of bore) and the bores are in much better shape.

The skinny *** rings are much harder now and require a finer and more concentric hole to bed into.

Dingle berry hones are a band aid IMO.
Cost to power hone a 4 cylinder are usually under 100 and vastly improve the bed in process.


Block Boring and Honing Machines | Jamison Equipment

Honing machine is different than a boring machine and a good machine shop will have both.
The first tool is like what I use to check for OOR. My tool is really old and has gone through 10 stones sets now...
Back in the day I would use this to correct small deviations before using a dingleberry to finish.
Now-days I just use it to determine if a trip to the machine shop in necessary.

Edit: Usually I see inconsistencies (low spots) at the top of the ring travel where sealing is the most critical.

bimmerboy

I was under the impression that big machine shop hones remove at least .001” of material… which I don’t want if re-using the pistons. If that’s the case, it’s a no brainer.

LeoNA

One thing to consider is that .001" in diameter is only .0005" per surface. Typically, I leave .004-.005" after boring, then use roughing stones to remove .002"-.003, then semi finishing (525) stone to size and a swish with a (625) for a plateau finish. I'm not sure what others use or do, but with the Sunnen CV616 hone that I use, you can control taper roundness very well. Usually within .0002"-.0003". There are diamond stones that work well, but I think their better for more production work. Ball/flex hones should not be used. I can't think of an application other than maybe field work or re-ring after a very short use.