A guide so far not the best written so excuse me Im more and more short for time lately but will try my best with permission from the AB series owner:
This is for the Datsun community as always and for my enthusiasm/hobby so no
profit or gains are made as we are all enthusiasts tinkering away for fun.
I see the more peeps find the A series still a force to be reckoned with the better meaning more will be saved from scrap and stay on the road, track and sheds as they are fitted on all datsuns, austin sprites, mg midgets, Morris minors, Austin of all kinds, Speedway or circle track and many other cars I have not listed but exist eg. suzuki sierras, boats all over asia & more.

So here goes Datto folks......
drill and tap block to fill pushrod holes
drill and tap for screws to go on the oblong shaped oil drains
fill oblong with metal filler
block oil feed to head from block (another method is available)
run oil feed from side boss covered by brass seal or from the
rear by drill and tap then feed to head.

Bore to 77mm for HD daihatsu pistons or
Bore to 78mm for stock Mazda b6 pistons
19mm pin on A15 can be used
17.45 pins on A12 need bushing pistons

New method for using side water inlet for electric or
mechanical pump (a few options avail for Mech)
New method is ridiculously easy and trouble free
Keep block in camshaft for oil pump and fuel pump
if running carburettors, dizzie or modded sump
can be used to drain oil from the head

Head mods require some drill and tapping of oil drain
holes no big deal and easy redrilling and tapping to
suit brass fittings like on CA18de/t extra oil draining
Oil drain can also be made from head into the dizzie
cavity area using a simple plate with tubes or if running
efi you can also use the fuel pump cavity instead or
as well its your choice but Im using sump drilled and
tapped for brass fitting so requires no welding.

Run cam extra Mazda b6 camshaft pulley on original
A series block camshaft, the cam is sealed by a custom
cover that bolts on to the custom front plate, there is
also a crank snout cover for the front crankshaft seal.
The front plate seals up the sump as well with a semi
circular piece of alloy welded onto the front plate &
two taps on the sides to allow original sump fitment
and sealing. There are no leaks whatsoever and a very
clever way to avoid any sort of welding or heat being
applied to the original sump.

Headgasket is custom, some of the water galleries need
a little tweaking with a die grinder but otherwise its
a very just fit on the block and head in terms of all
holes been very compatible. Dowels can be matched to
suit the B6 head for alignment very easy again.

Cam belt no. already sorted and easy to get anywhere.

Some pics will follow and a better detailed guide
for those interested in doing such a conversion
with is possible to those with a little tinkering
ability nothing major, but essentially the front cover
and the headgasket are the main pieces of this build
sorted out while then the rest falls into place.

The rewards of this conversion are endless and the
camshaft cover choices are so many not yet counted
for but Mazda has 3 for the B6, one like shown in the
original conversion, 1 or 2 rounded types as on Mx5
of different s1 and s2, Ford Laser has 2 depending
on model s1/s2, Kia has several alloy and plastic
rocker covers Ive yet to count but so far 3 I could
see where distinctly different from model, years etc.

Then there is the choice of the 8v sohc and 16v sohc
which is what is been converted atm for another build.

Ignition is via megajolt jnr crank ignition to run carbs
or many sorts, eg. weber manifolds are available or use
bike carbs using pipes welded to original flange.

Mazda ecu can be used for crankfire ignition also but
to run ignition alone has been done on the miata USA
forums with no info at hand yet.

Otherwise Mazda efi can be used or aftermarket ecu
depending on the needs of the owner.

edit: here are some primary water & oil mods
for my AB16 and AB11 (a15 78mm & A10 76mm)
Although not necessary as the front cover
seals this area well and only needs the hole
made to pass through the block wall from the
side entry point to access but.... Im fussy.
A10 illustrated below for reference.

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  twin cam A series water mods.jpg (161.25 KB)


  datzda oil mods.jpg (183.55 KB)

Well D when and if you guys make up batches of parts let me know, as my A15 is on the engine stand at the moment.

Tom.

I wont be making any batches but will be buying front covers & headgasket which are the main pieces of this puzzle.
There are another 5-10 members also interested so Im in the same boat but helping out with the information online as he is a single index finger typist who would rather tinker in his shed than be online with us over-salivating datsun junkies.
They will be made by the man himself when he gets the time as there is a bit involved to get them spot on and although CNC would be the best way for now its laser of waterjet cut some plates up and combine them with drill, tapping, countersunk bolts, nuts, sanding and sealing for ready to use items.

In my enthusiasm I have found the Z series heads are an update to the B6 series engine and in doing so we have a choice of a newer head design with nicely angled ports and narrow combustion chamber design similar all up to a bike engine but with much better exhaust ports.

The smaller cam pulleys will alleviate some reciprocating weight from the whole assembly and shorter then length of belt required. This will allow a more compact final setup even when using these pulleys on an older B series head and help with designing a front cover that fits with more ease.

just some samples of what these pulleys look like in front of an A series.

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  cam gears difference.jpg (62.60 KB)


  B series pulley front A12.jpg (97.97 KB)


  Z pulley front A12.jpg (109.04 KB)


  B series pulley on A12.jpg (112.25 KB)


  Z series pulley on A12.jpg (114.03 KB)


  Z series cam & crank timing pulley.jpg (115.63 KB)


  pulley weights 60gsm less.jpg (90.08 KB)

I'm abit of a parts collector
So might be interested when its all nutted out

Yellow circles indicate the pushrod holes and oblong oil drain cavities need to be tapped and plugged while the green shows the oil feed hole to the head that needs to be plugged and just on the side is a brass plug to the same oil feed passage which can be used with a cheap turbo oil feed line and brass fittings.

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  late A series block mods.jpg (81.44 KB)


  oil feed line for head.JPG (12.29 KB)

My A10 engine block is just getting the work done in above pics, The AB man is doing the front plates and head gaskets but Xmas is here so most places are tight for any new orders and work but progress is happening.

Some of the later heads have extra drain holes which will need to be plugged up, drilled and taped on the sides for brass 90 degree fittings then to a 4 into one T setup to drain into the side of the sump or dizzie hole.

The smaller pulley setup will require a shorter timing belt and tensioners moved in closer on the inlet side and one further downwards so if this is too much for peeps to try and work out you can wait till I sort it out then choose this head if thats what you would like or if you want smaller pulleys. However take note Im doing an A15 later after I finish the A10 overbore motor.

The Z6 head is the one Im attempting on the A10 and last pic shows the extra drain holes which can be Teed up and sit hidden by the inlet manifold and carbs

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  twin cam a series camshaft area front 2.jpg (54.70 KB)


  zm head gas.jpg (77.77 KB)

As this is the first version naturally little tweaks can be made and atm Im looking at using the smaller pulley narrower Z head which means I will have to adopt a mounting method on the opposite side like the BMW headed Mini engines do tensioning the longer belt side opposite the oil pump. The water outlet will no longer be on the block above the crank pulley but from the side as previously posted using a small hole within water pump cavity to the block like on second pic.

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  twin cam ab tensioner position.jpg (85.14 KB)


  twin cam ab tensioner position 2.jpg (89.78 KB)

Update
3 front covers will be ready soon, 2 new headgaskets will be available by the weeks end so far 2 kits will be available to guys who have been putting their hands up first (both american members) and one for myself for my big bore A10.

There is an easy off the shelve mechanical waterpump that can be used and looking at ebay there housings which are also necessary to use these waterpumps are still available from the USA and some other countries. Those who are buying the kit will be given every bit of information to facilitate a successful build.

Also update on the heads, the early 1300 and 1500 using 73mm bores have no clearance issues using the original pistons or daihatsu HD pistons but the 1600 heads have one inlet valve that touches the edge of the bore so the bore will need to be notched to clear this inlet valve when using these bigger valve heads however if going bigger than 76mm by using the mazda b6 twin cam head pistons of 78mm there wont be any notching to be made providing the bore walls match exactly the factory bore spacing of the 1600 heads. That would mean 2 and 3 bores will need offset boring inwards to suit which is also where there is most meat available on A series bores to help.

Im using the Z head for the A10 and since the Z head has more valve angle they might no clear as well but have noticed exhaust valves will have no problem just inlet valves are big so might need to small notches on deck/bore edge which is no big deal.

I dont have final costs of the headgasket and font cover kits but will do so in the next few weeks once the originators lathe is back up running to finish the front covers.

For those looking at doing this conversion take into account which head you want to use as the B series heads come in many different flavours and also the Z comes with 3 types to suit 4 different Z engines one with VVT which I dont recommend unless you run factory ecu.

I have 2 american members and myself interested for the first 3 atm Im getting another head gasket when I decide what head to use.

so the head i have located is the mazda 1.6 b6t out of 323 gtx awd turbo. this should work ok with this set up right?