Bored and Sleeved 2.0 Miata Drop-in Miata Bottom Ends!

Are 1.8 liters not enough? Not sure you want a “stroked” 2.0 engine? Does $8000 or so sounds a little steep for a 2.0 stroked short block to you? How about  a bored and sleeved bottom end for half that price?

We’d like to introduce you to an alternative way to increase 1.8 liter Miata displacement to 2.0: by leaving the stock stroke alone and instead increasing the piston/bore diameter. “Stroked” 2.0 bottom ends and kits have been available for a while now around the web but never has a bored version been offered. We’ve set out to change that.


Introducing the MRM2.0:


Why is this better than a stroked 2.0?

It’s better because it’s more natural. Stroking an engine increases the length of each piston’s throw (thus the name) to create larger displacement. Increasing the throw creates greater reciprocal motion which in turn decreases “revability” of the finished engine. Our 2.0’s retain the original 1.8 stroke and thus retain the “pep” of the original while increasing the displacement 25% over that of a 1.6 liter. Also, stroking an engine requires replacement of the stock forged crank with an expensive “stroker” crank. By retaining the stock crank (which is actually quite a quality forged piece) the finished cost is much less.


How does MRM build a Bored 2.0?

First we take a good 1.8 block and crank. The block is blueprinted and then bored oversized to fit a proprietary steel sleeve which we have custom made just for MRM by Darton. After final honing, the bores fit an 85.5mm piston (total displacement is 1952 cc’s). We use Supertech pistons and can assemble the lower end with ether an 11:1 compression ratio for naturally aspirated applications or a lower 9:1 ratio for forced induction Miatas. To further beef up the rotating assembly we use can use forged H-beam rods (from ether Manley or Carrillo) although stock balanced rods are usually fine for naturally aspirated or low-boost applications. After thorough checking we reuse the stock forged crank (all Miata cranks are forged).


What do I get with this bottom end?

You get a completely assembled block with all new bearings. The crank, rods, pistons, and rings are all fully assembled and ready to go in the block. All you need do is pull out your old engine, remove the head , oilpan and accessories from it, bolt them on this bottom end and stick everything back in the car. All you technically need in addition to our bottom end is a new, large-bore head gasket which we can sell you.


Cool. How Much?

See the pricing table below. Note that currently we are only charging core charges for cranks, not whole bottom ends due to the number of good, yet crankless, donor blocks we have in stock. If that changes at some point we’ll drop the $250 crank core charge and replace it with a $400 bottom end core charge.


How do I order?

Send us an email or give us a call so we can discuss exactly what your needs are.

McCully Racing Motors

Allentown/Barto, PA

The block on the left has been bored and sleeved, the one on the right is a stock 1.8 block.

The custom MRM steel sleeve is fitted with such precision that only in this extreme close up can it be seen.

To Order email or call the following:




Phone: 267.254.6687






Who is MRM?



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McCully Racing Motors

Because there’s no replacement for displacement.



w/Head gasket

W/Core charge


Sleeved Block only

(with mains)





Complete bottom end

w/ stock rods





Complete bottom end

w/ Manley Rods





Complete bottom end

w/ Carrillo Rods