Ok I did some searches and couldn't find this and know it's been discussed:

Can you put an A15 crank in an A14 block? (thought the blocks were the same)

Also could you simply use Nissan Comp A14 pistons in an A15?

What is driving this is I have a chance to pick up a stock A15 and a prepped A14 racing short block. If parts interchange then it seems like a good idea to go for the extra 100cc's of displacement. I do seem to recall the pistons being differant between A14 and A15.......I would think they'd have to be.
Oh and I would likely use my A12GX head or do folks simply bolt the GX manifold on the A15 head (provided it's oval port of course).
After 17 years I've finally broken down and decided the 85HP wonder needs a replacement..............Spec Miatas blow past down the straights



Tom

I believe the extra cubes in the a15 comes from the stroke so the crank would be different...? also are the pistons different height, coz i know they are the same diameter....

Same block, same rod, different crank, and different pin height in the pistons.

and standard A15 pistons have an offset dish as part of thier lower compression ratio specs

So which engine from stock is better to do head work to??

I have an A14 engine w/a15 head and a12gx manifold. What a combo!!

I would like to know whether I would get more out of the a15 bottom end or the a14 because of the more compression???

Cheers

So if i had a standard a14 block i was wanting to turbo would putting a 15 pistons in it lower the comp ratio? what is it normally at?

The Blocks are different. There are larger clearances in the A15 block (around the oil pan flange) and the oil pan is different as well to match.

A15 blocks have "A15" cast into the side if I recall correctly.

Normal comp ratio for US is 8:5:1 if I recall correctly.

I knew they stamped the blocks , obviously just didn't know if any meaningfull changes were made to A15 (Yamaha RD's of differant sizes uses same case even though the were marked differant)

Well regardless looks like I'll go with the A14 as it has been built up. As note the A15's were waaay undertuned in the USA, so bring that up to spec would cost way more than the already prepped A14...................might end up with a mid close 4 speed as well.

Tom

When you speak of A15's being undertuned, are you speaking of the ones I've seen equipped witht the round port head? I hope all of them in the US aren't like that - I've been hoping to find one with the h89 oval port head, but no luck in any junkyard from San Jose to Fairfield. I have seen the round ports though on several b310's, both the a14's and a15's had them.

It seems to be a crap shoot , I used to have an old B210 that should have been round port but was Oval port and then had the opposite on a 210 I stripped. If I get a line on an A15 I'll post....won't know for about another 6-8 weeks.

Tom