You could use the gaskets - that will help to confirm that the bolt holes will line up correctly - but there is no need. Just use ultra black gasket maker glue. thats all im using

I kept the plate design exact to your dimensions, and that left enough to do a the water passage. I am setting up the mill tonight and tomorrow morning to start the proto plate. I will need to get a factory timing cover gasket to see if that will seal up well.

I think I have enough time to knock this out before having to start on some 1600 parts.

nice work.
So you will have the alternator and the water pump sitting down to the bottom on the exhaust side.
Sounds like a winner. if you want air-con with your setup then matt (not a biggie for most) then you will need to move the aircon pump to the other side - the top on the intake side would prob be the easiest.

still - im keen to see how the modified plate fits up in the two part system and water gallery in the back you have devised - that is very cool.
On that, have you changed the thickness of the plate from the original design to accommodate that, or have you just milled out with the existing thickness of the plate.
My plate - of which the original drawing you have comes from is obviously already done. If i am to modify that, I hope I have enough meat for that.

The water pump and alternator can be on the same side with the early A12. The alt mount is already low enough to allow the pump to slide out over the top position and still keep an adequate belt triangle for belt engagement.

Yep timing wont be the use with front or mid dizzie A12 just
worried about front dizzie having no provision for the WP
you have in mind Matt. Easily fixed though with a later A12.

The other reason for an A12 apart from availability is
they are much lighter and rod stroke ratio will be the
same as a suzuki g13b from the famous swift/culturs Gti.
The gti makes 125hp and has incredible torque from low down.
Quite a departure from past DOHC 16v designs, suzuki went
for low rod stroke ratios like Honda adopted later on.

Timing done cheap using original mazda ecu.
https://www.flyinmiata.com/arp-main-cap-studs.html

The mazda nuts all use a 36/1 toothed timing wheel over the std CAS for better spark control in worked motors.
https://www.mx5performance.com.au/prod ... -trigger-wheel-mazda-mx-5


I want to use the Mazda CAS - just cause its easier at this stage, but I may need to move to the toothed timing wheel to get it to talk to a computer.

D, If you are unsure about the alternator position and thus the water pump location, yeah, the alternator position is different between the two, bottom right for early a10/12 front dizzy type or top left for late model/mid dizzy type blocks.

Even if it was the front dizzy A12. A crank timing setup can be adapted to this plate as easy as HRC taking Russian money.

good to know it is missing a piece of the puzzle
its reduced slightly the puzzling brain fog.
So you are saying Matt the mid dizzie a12 not the
earlier front dizzie A12 right?

I can get an a12 easier than a15 atm so was thinking
of A12 sleeved for 81.25mm 4age pistons, A14 crank,
A12A rods or H beams for 1597cc.

Being Pmd by Miata freak that the earlier and later
B6 heads are easier for cams from ebay chinese units.
SO will aim for this in my first build but really
want the Z head to maximize weight and performance.
He informed me the Mazda B6 head almost mirrors the
Toy 4age and the Maz Z the Toy 4afe which a good site
like Billzilla.org lists a full works 4afe making 248hp
with less head work than what TRD and Yamaha perform to
get a formula atlantic 4age to make the same hp.

Really love how Jap engines swiped the cosworth and lotus
designs then made them avail to bottom feeding enthusiasts.

Water Pump bracket hasn't been designed yet but it will occupy space where the alternator is on the
A12.

Call me a dunce but I still cant picture the original steel plate
with the waterpump somewhere in there. its eating me up inside