whoa, I didn't mean to insult your rods - I take it back, they're perfectly normal A series rods. albeit from the other side of the planet. All I was saying is that I was not sure what length rod you had used (but they had to be short), and I couldn't recall if you said they were A13 or A12a rods, I just knew they were out of one of those oddball A series engines.

As for this...Quote:
I don't know what I was thinking. Yes, simplicity itself! So easy in fact, I think I'll go do it tonight. Just pop it in me lathe... ah, hang on... will this here angle grinder do?
I seem to recall your mate did this for you in his home made lathe, but for 99.9% of us machining doesn't come cheap. You say it took 35 minutes to machine the crank. An engineer however, is going to charge for time spent measuring the block and crank, and double checking everything to make sure it actually fits after the operation, then there's the trial fitment, which will involve a dummy assembly of the bottom end (crank, rods and pistons), which I'm sure the engineer would also insist on so that he knows it's not going to come back. Conservatively, you'd be looking at 4hours, and at cheap charge-out rates that bill would come to arond $340. did I mention that's a real conservative estimate?

Then you have to balance the reciprocating assembly wether its just going to be a street motor or not. But that's probably simplicity itself and free too... For the rest of us, you'd be looking at another couple of hundred. This would be an optional extra if you were building a street A14.

OR, you could drop in the A14 engine. And then spend the five or six hundred dollars you saved yourself on stuff that will make it go faster. Anyone who owns a hacksaw and an electric drill can do the conversion - That is simplicity itself! Or if you want to get really fancy and make it look factory at first glance (that's all your A12 block will do anyway), just unpick the mounting brackets off the x-member and weld on some 120Y ones - that will invlove such exotic tools as an electric drill, cold chisel and a hammer. Then take it to someone to weld it up - might cost you a carton.

All this begs the question - why did the Datsun engineers go to the trouble of using a taller block and longer rods for the A14?

It's a pretty big assignment to explain how the rod to stroke ratio affects engine performance on a web forum. It has taken much more cleverer people than me chapters to explain this. I think if you go read the Racer Brown stuff Datsport has one thier website, you'll get a good broad grounding in this and other aspects of engine building.