hi fellas just wondering if any one can tell me the standard bore size for a A15 last weekend i swopped a a12 running for a A15 running but a bit suspect i have stripped it and found that the crank has been reground has .025 shells in the mains n big ends the bore is 76 mm is that standard , also wots the max u can bore them to with out any water jacket probs .
would very much like to hear from anyone in the know since i have never played with the A series before allways done L series this motor is just for my parts runner but i still want it to be a good thing lol .

the stock bore is 76 mm,which you have.the motors can be bored to 78 mm without any problems,& some will go to 79 mm.

thanks b310gx now i know i will get it bore for sure

There are five diferent "A" series engines [A10, A12, A13, A14, & A15] but only two basic bore sizes.
The A10 & A12 are 73mm in size, while the seldom seen A13, along with it's more popular brothers, the A14 & A15 are all 76mm in size.

There are three readily available oversizes in half mill increments, so 77.5mm is the largest readily available replacement piston size. Larger sizes use pistons that are either made to order, or are derived from something else, but if you go for these options, be prepared to PAY.

While the pistons share common bore sizes, they are mostly diferent for the diferent engines, so if you have an A14, get A14 pistons. A15 will fit & are recomended if you want a compression ratio so low it will run on Kerosene.
You can probably go 3mm oversize without drama for street use, but available, affordable pistons are likely to be the limiting factor.

L series engines are nice & i run one myself, but the "A", now thats the jewel in the crown.
Chris

I've got an A14 bored to 79mm that was given to me. When it was running, it fouled the oil fairly quickly (like after 3- 8 lap races)
Comp ratio was about 10.5:1 and I suspect that the bores were flexing just enough for some blow by from the combustion chamber.
I've not had it tested ultrasonically, but I do know that some blocks are happy to run 79mm pistons. It depends whether the cores moved when the block was cast.
Another thing is that there does not seem to be enough metal to sleeve it.
78.5 mm might be that bit safer.

DodgeMan,
A correction... there are 6 different A series engines: A10, A12, A12A, A13, A14, and A15.
A10, A12, and A13 are 73 mm bore.
A12A is 75 mm bore.
And A14 and A15 are 76 mm bore.
There are 4 different crankshafts; A10 is all by it's self as it is a 3 main bearing engine.
The A12 and A12A use the same crankshaft.
The A13 and A14 use the same crankshaft.
And the A15 is all by it's self.
I hope this clears up some confussion.

I stand corrected about the A12a. You are right & i thank you for bringing it to our attention.

As for the A13, i stand by what i wrote on the basis of the dimentions of an A13 block that i have access to.
A 76mm bore with a 70mm stroke [1200 size] yeilds 1270cc & that is usually close enough for most manufacrurers. After all, the A12 is 1172cc

I have read the A13 specs from the Gregories manual & that info agrees with what you have writen, so i wonder if the A13 that we have is a fork lift one. It definately has a 76mm bore & is engine number frefixed A13

I'm not too sure what you mean when you write that the "A10 crankshaft is all by itself with 3 main bearings," then you write in the following line that the "A10 & A12a use the SAME crankshaft."

I did not go into crankshafts & their strokes as the subject was BORE SIZE.

A puzzling & perplexing problem.
Chris

A typo on my part, that has been corrected.
The A12 and the A12A share the same crankshaft.
As to the A13, it was used for 1 year that I know of, that being 1974, it was used in the B210 (120Y) here in the states. The bore diameter is the same as the A12 but the pistons do not interchange. That reason being that the pin diameters are different.

Interestingly, it has been my experience that the 73mm pistons used the small wrist pin & the 76mm pistons used the larger diameter one. We never saw the A12a engine, so i have no idea what size the wrist pin is, but i would dearly love to know as that info just might solve a problem for me.

The A13 that we have with the 76mm bore has the larger wrist pin in it's pistons, which ties in with my first sentence.

If you can confirm the A12a's wrist pin size, i would be most gratefull.
Chris

OK...........
I just looked it up, and I need to make a correction. Piston pin diameter for the A10, A12, and the A13 is 17.4 mm (0.685") and the pin diameter of the A12A, A14, and A15 is 19 mm (0.748"). Not a lot but enough to make a difference.
The other variable is the conecting rod lengths which are as follows, given center to center big to small ends:
A10 Don't have as it was not used in USA.
A12, A12A 121.5 mm (4.78")
A13,A14, A15 133 mm (5.24")
Source, Nissan Motor Sports.
Sorry for the earlier incorrect information.