Whats the differences between the A14(oval port) and the A15, in terms of rods, crank and pistons.
I would like to know if the rods are the same length.

Rob. :)

If I remember correctly, the rods are the same length and size, the pistons are much different, A15 has a bigger combustionchamber and it

The different pistons must explain the different compression ratios a14/15, I think the combustion chambers are the same(in the head) Is that correct? Which pistons are superior?

The combustion chamber in the cylinderhead are also different, the A14 head has bigger combustion chambers than the A15, so it

This may be the case , but which offers the better sqish thermodynamics, centre dish or offset dish?

Offset dish combined with A15 cylinderhead gives the best squish! But it

Quote:

A14 & A15 cylinder blocks are dimentionally interchangeable. The rods are the same length as each other, but the crank in the A15 has a longer stroke. The journal size is the same for all the 5 bearing A series cranks.

The A15 pistons have the wrist pin positioned higher, or closer to the crown than A14's to prevent the piston from coming out of the top of the bore at TDC. As for the piston crown, i believe that they have a larger bowl to control the compression ratio, as the longer stroke pushes more air into the combustion chamber than the A14 does.
No comment on the cylinder heads, because i simply don't know.
Pretty much everything else is interchangeable, but flywheel weights seem to increase with each increase in engine displacement.

I'm about to turbo my a15 and with 9.9:1 hope to get 4-6 p.s.i. , probably create some headaches but it should be worth it.
I dont like the idea of low compression off boost, I had a VL Calais and it was lame off boost.

sunny
I think that you are probably on the right track in keeping boost pressure down with a near 10 to 1 CR

This whole turbo / supercharger thing is a matter of balance. Low CR engines can handle more boost, & reap the benefit of that, but as you note, are a bit soggy untill boost comes on.
With higher CR, you get a more responsive engine than the low CR one while off boost, but the max boost pressure is more limited, & max output is also more limited.
It's all a matter of balance.