So the sleeves allow > 15 psi boost with the otherwise thin walls?

I take it too that they don't need to select a block for thick walls that don't punch the water jacket when bored to 85.5 mm like the 949 85.5 bore n/a build?

That's the idea. When you punch a BP to 85.5mm, the best you can do on wall clearance is ~0.110". That's borderline acceptable for an N/A build with an excellent radiator and oil cooler setup, but a FI setup really needs more wall thickness.

Yup, thought about it again with a clearer head and longer rods alone will just move the stroke higher up the cylinder. It does look like that it will increase compression but with stock pistons, at the risk of a collision.

what your saying is zero decking the motor by moving the stroke instead of decking the block. Like i said the most you might get is .010" more stroke, That would be if the pistons were .010" in the hole.

You could get away with elongating the rod by all of ~.015" before the squish becomes too tight. Decking the head is a much cheaper way to accomplish the same thing.

So the sleeving increases wall thickness by using space taken up by the water jacket?

That's a question for McCully, not me.

I have a receipt for my crank from Tennessee valley crank shop (I think that name is right). I think the crank work on a stock crank ran about 800 bucks. I'll try to pull the receipt and scan it tonight. They may be able to help you.

-Greer

What did you have done?

Bringing this back from the dead. Work was done by Crankshaft Specialist in Memphis TN, date was Feb '03.

Description on the work order is : 3.350 4CYL. Mazda, CK Out, Index, Lighten, STROKE 3MM. Work was 750. Shipping & handling was 33.00

I don't have an exact weight, but the below photo should give an idea.
https://www.miataturbo.net/attachmen...ine=1376274170

Work was good but they didn't turn the crank snout down to correct size. I ran my pulleys over to a machine shop and just enlarged the pulley the .00125 needed to make it all fit up right. I would have hit up the crank shop but this was 8 years after the fact (I'm the second owner of this setup).

-Greer

You run that crank yet? Curious how a regrind would work out for an n/a (no need for 800hp) build.

Am I reading this right? 3.35 liters? Would that still rev properly?

I am thinking that is the bore or stroke in inches.

And they added 3mm to the stroke by offset grinding the journals.

I would be interested in that sleeved block, longer rod, and shorter 85.5 pistons. I wonder if you could get a real 2.1 liter out of it? Might have to call Keith about those long rods for the stock crank.

your not going to get more than like 1970 cc with the 85.5 bore, so no more displacement without stroking too. I still don't like the idea of sleeving, look at how thin the webs between the cylinders are, now a normal sleeve is like .187 thick or so. that whole center web is made up of sleeve material.

They will machine out one bore and install the sleeve, then machine the adjacent bore and cut into the newly installed sleeve. I just don't trust it, to much to move and your reducing the coolant passages of the block. Maybe this would be fine to me if you were building a drag motor and filling the bottom of the block with hardblok and running methanol.

Oh if only we could get an aftermarket tall deck block with modified bores and water jackets, with room for a big swinging crank.

Now your talking, but if these k24 swaps take off I think the BP engine is a thing of the past.

The only reason I'd want to stick with a BP in a miata is in classes that require the stock block or block from the same make.

If the K swap kit isn't priced into the stratosphere than a K24a2 sounds like the best way to go.