Advice needed for first engine build
 

I’ve decided that I want a built engine but I have no experience and would greatly appreciate any input on my plans so that I can hopefully avoid some mistakes.

The car:

1999 with a 2554R making 220 WHP currently. It has: Kraken manifold and full 3 inch exhaust, MS3 Basic, ID 725s, DW 100, LS coils, FM level 1 clutch, 5 (soon to be 6) speed trans, coolant reroute, FM crossflow radiator and stage 2 fans. It’s a street car that I daily. Rev limiter set to 7200 or less.

Motivations:

Reliability above all else. Obviously, the clear answer here would be to just take the turbo off and keep everything stock. But the turbo is just too much fun, so what’s the next best option?

When I chose my turbo parts, I never intended to build an engine. I listened to a lot of the good advice here and decided to stay under 220 HP/200 lb ft and enjoy my 5 speed transmission and unopened stock motor. I did, and things were great. Then my differential housing snapped. I was aware of that potential problem, but by most reports I wasn’t making nearly enough power for it to be a concern. It snapped anyway and that changed my thinking on failure points.

We have a lot of consensus guidelines about where parts start to fail. These are tremendously helpful but are still anecdotal. I fell into the trap of thinking “part X often fails at Y HP” was equivalent to “part X is perfectly good until Y HP.” I also assumed that the chance of failure increased linearly with HP/torque for most parts, but really there’s no reason that has to be the case. Adding a little more power than was originally designed for can greatly increase the chance of failure.

Now I just want the engine to be stupid overbuilt for 220 HP.

Constraints:

Car needs to be able to be revertible to stock and able to run on the factory ECU (turbo removed, factory injectors put back in, etc) for a few weeks every 2 years.

Semi-reasonable budget. I have no delusions about this being cheap, but if there are savings to be found without major compromises I would like to know. Here are my proposed parts:

94-Early 95 Block

I recall reading that the 01-05 blocks have thicker cylinder walls, but I need the oil feed port on the driver's side. Removing and replacing the tee at the pressure sender every couple years is a pain and this would be a huge quality of life improvement and reduce the chance of messing up the threads and developing a leak.

Supertech 9.0:1 pistons: The 99-00 engines are 9.5:1 from the factory, but from what I understand the stock ECU will be able to compensate for this minor difference in compression without issue, and it would give me a little more protection against detonation.

Wiseco XX rings

Manley rods

ARP Main studs

ACL main bearings

ACL rod bearings

OEM 94-00 head gasket

Supermiata blueprinted oil pump

ATI SuperDamper

Gates Racing Timing Belt

Gates water pump with cast impeller

OEM seals, gaskets, accessory belts



99-00 Head

As much as I would like to have VVT, it’s just not feasible.

FM +1 mm inconel exhaust valves (I am interested in these for the material rather than that they’re oversized. I can’t find any non-oversized inconel valves)

Supertech backcut stainless intake valves

OEM valve stem seals

Supertech manganese bronze valve guides

Volvo stiffer springs

Stock cams



Procurement

As convenient as it would be, I think the chances of finding a good condition 94 block and a 99-00 head for sale separately are low. I will keep an eye out as I do more research, but I’m thinking of buying a 99-00 full engine and selling what I don’t need. I could then buy a 94 bare block. From what I understand, I could use the crankshaft and main caps from the 99 engine. Is this a terrible idea? Should I just try to find a 94 block with a crankshaft and main caps included?


Anyway, thank you for reading all this. Let me know what I’m missing/could do better.

Don't try to put 99 main bearing caps on a different block. The only reason to deal with the headache of swapping main bearing caps would be to run billet ones. The block and main caps are a matched set, you can't swap them without line boring the mains.

Thanks, already glad I posted this! If I bought a bare 94 block with main caps, could I use the crankshaft from another engine? Or do the block, main caps and crankshaft all have to be a matched set?

As long as it's a good crank it is fine, only need to worry about bearing clearances. Only the block and main caps are matched.

Why would you have to remove the tee for the oil feed? You could just cap the line when the turbo is removed.

I thought it would be too difficult to hide. I suppose I could cap it the line, cover it with wire loom and run it along the PPF. But the tee itself is still quite visible. If you mean capping the tee, it's annoying to get a plug threaded in and out with the limited access.

Why would the line itself be a problem? Does California not allow things like aftermarket oil pressure sensors?

Those are legal, but I'd prefer not to have anything that would suggest the car has been modified. It could result in more scrutiny during the visual inspection. Would it be fine? Maybe. But if I can avoid taking the chance, that would be ideal. It's been my experience that most places are very strict given how hard the state has cracked down in the past.

Are you in an area that requires a dyno smog test?

Yes, it’s a 1999 so unfortunately in CA that means it has to go on the rollers in addition to the visual inspection and OBD2 checks.

Yep! Don't mind these guys, they will never understand our "reasons." I painted my feed and return caps flat black.

I know, I’m in CA as well. I’m in the central coast and we only have the regular hc & co sniffer test. The reason I asked is because if you have the nox/roller test you probably can’t pass with a legal kit with an eo.

I just built a vvt block with a bp4w head. The later engines are poorly machined. The benefit of the vvt block is the larger thrust bearing and thicker cylinder cores. It is probably not worth it for less then a 300hp build.

You need a good block and it does not matter if it has the oiling on the driver side. It’s easy to cap the T or the later blocks can be drilled and tapped. All of the blocks have the boss on the drivers side.

There is no special wiseco ring pack for this application. All of the pistons kits, CP,JE,ST and wiseco use the same npr rings.

First I've heard of the VVT blocks having thicker cylinders. Do you have a source for the info?

​​​​​​The wiseco rings probably are made by NPR but the wiseco XX rings are higher tension. It's posted by Emilio somewhere in this thread.
https://forum.miata.net/vb/archive/i.../t-526890.html

That's a good idea. I'll definitely paint my return fitting and cap.

My car is one of the god-forsaken 2 cat CA-spec cars, so there's no legal turbo kit available. If FM had a CARB legal option I probably would've bought it honestly instead of going DIY. I didn't think about drilling/tapping that boss, thank you. Having just removed/reinstalled the tee, it would be a huge plus if I could get a good 94 block or have that driver's side oil feed opened up on a later block. I've made things as convenient as possible for myself with connectors to quickly swap my GM IAT back to stock, having 2 fuel injector harnesses with 1 pinned for the LS coils and the other for stock coilpack, AN fitting in the oil pain for easy disconnect and capping, AN fittings for the turbo water lines that I can just use a coupler with then tuck out of the way and not replace any hoses, etc.

It was also Emilio that posted about the cylinder wall differences here:
https://www.miataturbo.net/engine-pe...2/#post1563666

I didn't think the wall thickness difference mattered in this case but obviously I may be mistaken.

I have spent quite abit of time researching this and I know what SPM/Emillio has posted, but it is not currently correct. I have actually spoke with two different tech people at NPR America. There are only two ring packs that are available in this size. The standard ring set NPR PN# 21-GNH-0mm00, mm equals the bore size, and the XC3307LG. The GNH ring is the nitrided steel upper and the XC is a chrome steel ring. The XC is too soft for this application. The XC oil control rings tension is slightly lower (29.42N) then the GNH (31.75N) so there is no fact to it be being better for the street.

Even if you went with the FM1 kit or used their EO you would not pass the test. I have smogged many cars including turbo miatas. They can run clean but not clean enough to pass the 3 gas test.

I definitely wouldn't put an aftermarket damper on it if you were trying to fly under the radar. And it would be a pain in the ass to swap back.

I have one on mine and the ati is fairly subtle once the sticker is removed.

I don't want to run the ATI damper honestly, but from what I've read it seemed like it was mandatory for reliability. Plan was to paint it black, but if the sticker comes off that's even easier. I purchased a fresh OEM damper about 3 years ago when mine started to separate. If I could reuse that instead, it would be great. Cost me about $200.

Maybe also replace the 12 point screws with black buttonheads.

https://cimg9.ibsrv.net/gimg/www.mia...e0341ded20.jpg
https://cimg0.ibsrv.net/gimg/www.mia...5c643becd8.jpg