Miata NC3 Engine Swaped NC1 legal in CS?

[Brian Ernst]

I just learned that the Miata NC1 has a flaw with it's oil feed system. Running an NC1 engine in autocross is a guaranteed early death sentence. Supposedly NC2 and NC3 the flaw was solved. Seeing as I'm stuck with an NC1 for now, when the engine eventually goes, is it legal for me to swap in an NC3 engine into my NC1 and still run in the street class? I'm running in CS.

I'm miffed.

[Steve Ekstrand]

That's a no go on the engine swap to stay in CS.

I'm not so sure the stories of doom and gloom on the NC1 are so accurate. There was an improvement made, yes, but NC1's saw a lot of autocross laps nationwide.

[Brian Ernst]

My engine is dying around 72k miles (it's knocking anyway), and a bunch of people on the NC FB Group are corroborating that by 100k miles.

[Brian Ernst]

That's a no go on the engine swap to stay in CS.

Why's that? Is the no go on any engine swap, or just swapping outside of technical car generation? NC1 and NC3 are both CS; it's still the same [NC] generation, CS class engine to CS class car.

[Anthony P.]

That's a no go on the engine swap to stay in CS.

Why's that? Is the no go on any engine swap, or just swapping outside of technical car generation? NC1 and NC3 are both CS; it's still the same [NC] generation, CS class engine to CS class car.

Except for modifications authorized below, Street Category cars must be run as specified by the manufacturer with only standard equipment as defined by these Rules. This requirement refers not just to individual parts, but to combinations thereof which would have been ordered together on a specific car.

Alternate parts (parts that may fit due to common platforms) listed in a factory parts manual are not authorized unless their use is specifically referenced in the factory service manual or in a service bulletin for the specific model and/or option package.

If it doesn't say its allowed, its not.

[Reed Gibson]

The reason behind that (as I understand it) was to avoid people making Franken-stock cars that took the best bits of different model years. For example, an S2000 with the 2nd-gen engine (more displacement = more torques) plus the 1st-gen transmission (~6-7+ mph faster 2nd gear) would be an absolute monster in stock class.

So in the spirit of the SEB, time to go to Street Prepared!

[Anthony P.]

So in the spirit of the SEB, time to go to Street Prepared!

Well, at the time the rules were made there was no Street Touring. So,....

[Steve Ekstrand]

Street Touring wouldn't allow an SP style swap within the listing line.

In the case of the NC, the later motors had better internals, an oil cooler, and a 500 rpm higher rev limit. Did the NC3 put on pounds from the NC1 like most models do over time? Doesn't matter from a rules perspective. But makes it easy to understand the why?

[Mike Simanyi]

I'm not familiar with the distinctions between NC1, NC2 and NC3 engines, but there are two other key points to research before declaring this a Hard No:

• Is there either a Tech Bulletin from Mazda stating that replacement NC1 motors must incorporate the NC2 or NC3 components or configuration? If that exists, get a copy of it and follow those requirements.
• Alternatively, if the manufacturer parts list has superseded the NC1 with NC2 components, you can use those. (This likely receives a Tech Bulletin, so be cautious.)

In general though, no - Street doesn't allow swapping engines within a certain chassis family unless those engines are identical and have the same part numbers as your model-year originally received.