Machine the bores completely and make the a15 a wet sleeve with a step at the bottom like the renault 50psi turbo engine.
billet sleeves of 80mm diameter with 90mm stroke with main ends modded e16 crank to fit the a15 will make it a 1810cc.
Ive seen a the Renault 5gt without the sleeves at Alpine Affaire last week and if the a15 was machined as a wet sleeve they would be almost twins.
http://datsun1200.com/modules/newbb/viewtopic.php?topic_id=21170&forum=1#106331

Theres a bunch of varieties of 1.6L Mazda B6 MX5 / Miata pistons. Approx five of them. 8V, 16V, etc. The 1.8L's are no good because the bore became larger. There's also other Mazda pistons plus daewoo, opel, Izuzu pistons that I know of that can be made to fit. Assuming you are going to bore anyway, the pistons height, the bowl volume (if it has a bowl) and the pistons wrist pin (gudgeon pin) are the main concerns.

In addition to the above specs, A10's & A12's have a 17.5mm wrist pin. A12A's, A13's, A14's and A15's all have 19mm pins. When you compare these sizes to those selected by most other manufacturers, the Datsun sizes are uncommon. So, if you want to run MX5 pistons, you must increase the conrod little end from 19mm to 20mm in an A14/15. Other pistons will require different things.

Lets look at an A15 for example: Half the stroke + the conrod length + the piston height = 82/2 + 133 + 30 = 204mm. The block height is 204.1mm. This means the piston at its heighest point is 0.1mm below the deck (gasket). If you vary this figure, you will be changing the compression ratio. Likewise if the piston bowl volume changes. So do your homework first!

I was playing with a cc calculator on the net with different bore sizes and...

with a 77mm bore on an a15 you have
1527cc - 39cc more than standard

with a 78mm bore on an a15 you have
1567cc - 79cc more than standard

with a 79mm bore on an a15 you have
1608cc - 120cc more than standard

maybe a 77mm bore at 1527cc would be best in my opinion. its still 39cc more and has 4mm more between bores then the 79mm bore. Just some thoughts.
By the way:
A15
Bore: 76mm
Stroke: 82mm
Conrod: 133mm
Block Height: 204.1
Displacement: 1488cc
Power: approx 81hp

just for referenece

if you were looking for boost, you'd probably be better to leave the bores alone and o ring and plan on stuffing as much mix in there as you can without it blowing up.

maybe this should be a tech article with all the confirmed info it it isn't already.

The A14 block is dimentionally interchangeable with the A15, & both the A15 crank & rods are used, but from memory the pin sizes are different, so some work is needed there.
I also think that there are different versions of the piston, so check them all for the best one for your needs

I also believe that some Mishy-bishy [Sigma] pistons can be used with a little work.

The block in the picture is either 78.5, or 79mm in bore size.

Just understand that this is not my block, & I have never built a big bore A15, but the info is gleaned from a friends engine, so do your homework & procede carefully.

If running boost, then I recomend that you maximise the gap between bores by using a smaller bore size.

thanx

Will a A14 block also go the distance?
Is that a 1608cc bore ? ( the pic )

And with the Mazda Mx 5 pistons I would use a A15 crank and what conrods ?

Mazda MX5 pistons seem to be the go from what I can find out & at 79mm, it would be a good idea to offset the bores a whisker & 'O' ring the block if serious performance is what you have in mind.

A copper head gasket is not cheap, but there are those who would recomend it.

This is the real problem with big bore sizes. The gap is so small that it is not possible to individually 'O' rong the cylinders & this figure '8' pattern becomes necessary. This is also why a small offset when boring will help.

You gotta remember that the A series engine was originally designed around a 73mm bore size, not 79mm.

Hey Thanx Rallytwit.

I think alot of new-'B's wanted to know this.
So Dodgeman, i want to know will a Replica of the head gasket made of copper work (better) on the 1608cc A15 engine. I guess what i'm asking is will it hold ?

Wow I had no idea this topic would generate such a response.

OK who if anyone makes off the shelf pistons in 77MM and 79MM bores........remember I'm a low tech kinda guy who mixs and matches Datsun parts cause it's cheap that way!!

Tom

Quote:
Well, it's all down to money. With a 79mm bore in an A15 block, & you can find a way to keep the gasket from blowing between the end pairs of cylinders you would have 1608cc

Now if we offset grind the crank & just use 1mm undersize bearings, we can incrase the stroke out to 83mm. If dished pistons are used, we might just get away with a 1/2 mm skim off the rim & the total displacement would be 1627cc, but this would be pretty much pushing it unless special rods &/or pistons are used to allow a welded stroker, & even then, you start running into crankcase clearance problems.

So there you have it, 1608cc with just a boring bar &1627cc if the crank is stroked. I'd say that is probably very close to the practical/cost effective maximum in an A15.