there is a screen /mesh plate with two holes in it, the bottom of the block , my engine builder left it out he said he couldn't see what it was for so he toss it ,is it a purpose

Mesh in the block is the crankcase baffle. Put it back in there as it separates oil from vapor for your catch can or factory breather

Id be worried if an engine builder couldnt work that out

he use to building sprintcar motors first a/15

A-series are well known in sprint car
often many have converted A series to use
OHC and DOHC heads, in fact they are still
used by junior sprint series

Were they using DOHC / ET heads in mid 80s ?? Why did some run Alcohol ??

yeah I,am talking about 360/740hp-410/900hp very fussy engine builder my block has been freshen up with some new ideas from a different engine builder, etc, blue printed and now he,s building a new head ,the last one got to hot an cracked on the dino to lean on back two cylinders now putting in EGT in the exhaust to get all cylinders the right tune . I've always had trouble on the back two.

The 90s as far as I know when the pulsar head became more available
Rob that did the BAT (B series to A series twin cam) got the idea
from speedway guys who also ran mazda heads on A series blocks.
In the country out of the box thinking occurs more than in the big smoke.

Shane whats the build you have? I only suffered 1 and 2 cylinder cracking
from going 79mm then 79.25mm on an A15 never had issues with back cylinders.

it was the head that cracked, 78 mm bore and has a slight crack between 3/4 which was xray and ok.i run 28lb boost which doesn't help ca18 rods and ARP bolts all the way through the motor. I'am trying to bring the boost down for the same hp 270wheel I'll see what I get first with this new set up.

LOL 28lbs so you are the Yokozuna of the turbo A series guys!

What valve sizes are you running on this monster?
An A series supercharge freak in kiwi land ran 42mm inlets!