ok.so heres the story so far im building a a12 turbo suck through system ,,ive currently finished the head with port work k line guides crow cams valve springs ..ive got the turbo mounted and exhaust manifold side made... il be using the standard intake manifold with a small type of plenum,, not sure on this idea but stil tinkering with what to do in this area ....the only head ache i have is what pistons to use for this application ,,,,,,,,i relise that alot of things come into theories about piston relivance but what i need to know is on a turbo do i use a dome top flat top dished piston + gapless or gapped rings hmm.....where do i start..........

You cant go wrong with standard.

what piston you use will depend entirely on what CR you want to achieve and what head you are using.

cheapest way out is to mill some off the top of the standard A12 piston. This is not a problem as long as you are sensible about how much you get lopped off. Besides, the skirts will crack long before the crown ever fails!

as for the inlet manifold side of things, you could simply run the inlet pipe from the turbo straight into the standard manifold - I've done it before...

if the budget is a bit bigger, think about a 3mm overbore and E15T pistons. They have a 19mm pin, so you will have to use late A12 rods or maybe A14 rods - it can be done.

ok L18_B 110 thats sounds pretty good using the E15T pistons with a 3mm over bore would the a14 crank be an improvement to with the rods i have these items lying around at home anyother advice would be good.......... im not shy of spending a dollar when it comes to my datto im expecting good result and have good faith in my engine builder .....cheers....

there's an awful lot of work (and money) involved in getting the A14 crank to fit in the A12 block. Dodgeman is in the process of doing that, and has posted some photos.

If you want the A14 crank, just bolt the whole A14 engine in there - way cheaper and easier.

forget that A14 rod in an A12 block comment. They won't fit with any production piston option.

See, I bought an engine a while ago that was supposed to be an A12 block with 76mm A14 pistons, which I plan to use as a base for the turbo engine this year. I disassembled the engine yesterday and it had A14/15 rods.

Today I was investigating piston options for that motor, but my sums wouldn't add up. I couldn't work out how it was all supposed to fit in the A12 block. So back to the shed I went with a measuring stick, and I discovered that this block is actually at A14/15 deck height and has an A14 crank to boot. It's stamped A12, but is obviously a bit of a dodge job! Looks like I may have stumbled across an old rally engine

on the topic of pistons, this is what's out there in 76mm diametre with 19mm pins:

E15 comp ht: 32.10 dish: 22.2cc
E15T comp ht: 33.10 dish: 23.5cc
E16 comp ht: 32.10 dish 18.4cc
GA16DE comp ht: 29.10 dish 12.3cc

there were no stats on the dish for the A14 and A15 piston in the ACL catalogue...

btw, the A12 piston comp ht is 31.95. And your 120Y should have the late rods with 19mm pins already.

thanks heps this has cleared up alot of my worries and foes ....the piston specs are great iwas realy lost there now i have a bit of an idea on pistonns and cranks ...
cheers and thanks again...................

just do as i and a few others have done get ur engine builder to machine the dish in your pistons into a concentric cirle like below

What sort of hp and torque do u guys get from a good working A14/A15 turbocharged engine??

Quote: As far as i know, ALL engines that came with the 73mm bore size used the small wrist pin. This group would include the A10, A12 [1200] A12 [later design] & A13 [small bore]

All engines that used the 75 or 76mm bore size also used the larger wrist pin. This group includes the A12a, A13 [big bore], A14 & A15

I don't believe that any A12 engine came with the large wrist pin.