i want to assemble together e12 2.0 cylinder block with e30 1.8i head. which pistons will be best choise for such engine? flat-top or other? as i know the pistons have to be choisen by head type. it is true? if yes, then which type i have? 121 or e12?

Pistons are pretty much dictated by your cylinder/head and compression/ratio, my engine is similar to what you mentioned 79' 2.0l block, 84' 318 1.8l head I chose this setup because the 84'-85' 318 head flows the most air out of all the cyl. heads for the m10, and it doesn't have any injector holes to plug-up making it ideal for a carb. setup or custom fuel injection with a fuel-rail ie. turbo. My pistons were custom, matched to my cylinder head and the desired CR. I wanted which was 10:1, also which was custom about them was the pivot-point, the pivot-point was moved up further on the piston enableing me to use M3 s14 rods which more or less creates a stroker-motor without changeing the crank, instead the longer rods have a further throw up into the cylinders with the changed pivot-point on the piston and it all works together. Prior to haveing my engine built, even before I bought internals for it my engine builder was headed in this direction and I was not about to second guess him, but very soon after I called VAC. and explained this type of rod and piston combo. and word for word they knew this setup, and have done this setup before so I knew I was headed in the right direction. My block was bored out to 89.5mm the actual piston size was 89.37mm and I actually one/up'ed the rods with Arrow M3 s14 rods, the pistons are CP pistons and are dome'd to match the exact shape of the combustion chamber on the 318 1.8l head with pockets cut out for valve clearance. I hope this info. helps ya' a little bit, I still have yet to fire up this bad-boy but the engine is in my car, and I'm working on fuel and cooling right now so pretty so it'll run, good luck to ya' I'll check back later, peace out.:buttrock

thanks a lot. next question is which size of pistons rings you are using?

And did you put together your bottom end, or did the machine shop? I wanna know when you fire it up...all the gory details, what you did play by play, where/how you drove it, etc. I will be there myself in a few months..

waferman

My pistons were custom, matched to my cylinder head and the desired CR. I wanted which was 10:1, also which was custom about them was the pivot-point, the pivot-point was moved up further on the piston enableing me to use M3 s14 rods which more or less creates a stroker-motor without changeing the crank, instead the longer rods have a further throw up into the cylinders with the changed pivot-point on the piston and it all works together.


Changing the rod ratio is a well documented, and often bantied about subject. It doesn't do anything like "creating a stroker motor without changing the crank" though. The piston stroke hasn't changed in the least - you may understand that but from your post it seems misleading and someone not fully understanding could be misled.