Ok so I have bought into and taken over another project and am looking for some insight into whats the best base engine to start with - heres what came with the car - which was going to be built as a 12.5:1 compression na screamer

1 x oem 1600cc engine - complete with everything but the exhaust manifold but in a lot of pieces however

1 x bpt 1800cc block with crank
1 x bpt head (with the funkychicken dog leg gurney tab on the intake port)
1 x bp head (na)
1 x set of oem bp pistons ceramic coated
1 x set of eagle rods for a honda - they 1.5mm longer than the mazda rods
1 x set of oem mazda rods for bp 1800 na motor
new bearings / gaskets / arp stud kit / mains bolts etc etc
1 x new sump and pickup for bp1800 for rwd
1 x intake manifold for bp1800 that points the right way

is it better to simply turbo the oem 1600cc ?
or what combo on the bp 1800 do i choose ?
or do i just go buy a complete bpt1800 motor ?
there is no engine in the car just a pile of bits and i have no idea if everything is useable - I would hate to get 90% of the way through the bpt build and find out the water pump / cam tensioner is useless or some obscure part is actually missing etc etc

the base car is a 1991 with a 1800 lsd swap / rebuilt gearbox
the goal would be 250whp, with intercooler / fuel pump / bigger injectors / ecu

 

the 1.8L x 99999999999999999999999999999999999999999999999999 999999999999999999999

preferably the VVT motor.


There's nothing good about the 1.6L despite the placebo effect of it "revving" better.

 

The 1.8 all the way. I was very pleased when I swapped all my 1.6 stuff for 1.8.

 

hmmm so 1800 gets the vote - neither of the heads i have are vvt heads - these 1800 engines here are labelled bp / bpt 1800 by the jap yards - i think they come out of the gtx 323 / familia they have the black tappet cover with ridges on them - does this change anything ?

 

I am not 100% sure if there is a difference between the 323 head and the 94 - 97 Miata head. I want to say the early 1.8 Miata head is better, and heads from 99 and up (US) are vastly superior. VVTs are the best if you do not plan to run a monster camshaft from what I have learned.

Edit: When I say 99 and up (US), I mean we do not have a 98 Model. Your 98 model (if you have one) may have the better flowing head. Can't remember how they did it overseas.