a couple of questions.

can the A12 block be bored out to 76mm?

will the A14 piston fit the A12 conrod.

thanks
chris

By early A12, do you mean the Datsun 1200 engine, the one with the front distributor? To separate it from the later A12's It's probably better to refer to this as the datsun 1200 engine [or block]

In the main, you can bore these to 76mm without drama. Mine is currently at 76.5mm & has been that size for about 20 years or so. There are probably some dud blocks around, but generally, 76mm is fine.
Pistons of this size & larger were offered through the Datsun competition department & others back in the 70's, so it's a factory approved bore size

A14 pistons use a 19mm wrist pin while the 1200 & other A12 rods have a 17.5mm hole

Three fixes
1. Bore the original rod to 19mm. This is what I did & have had no problems.

2. Find a set of late A12 rods. There seems to have been a change in the later rods & these forgings look like they are the ones that were used for the A12A & A13 engines. [more on this later]
These rods have more 'meat' around the pin hole & would be stronger than a 1200 rod after the pin hole was bored to 19mm.

3, Find a set of A12A or A13 rods as these have the right length & the right wrist pin hole for the A14 pins.

Some background
A series pistons for engines that used the 73mm bore size [A10, 1200, A12 & 1974 A13] used the 17,5mm pin.

A series pistons for engines that used the 75mm bore size [A12A - USA only] & the 76mm bore size [1979-'81 A13 [Asia only], A14 & A15] used the 19mm pin

A12A & 1979-'81 A13's were just bored out A12's, so they had the shorter 1200/A12 length rods, but with the bigger pin size.
My '79-'81 A13 came as a bare block only so I sourced some A12A rods from the USA & I will run the A14 pistons.

There you go, now you're a blinkin expert on the subject.

thank you dodgeman. just what i wanted to hear!

lets say i reem the conrods out of the A12.

should i machine a bronze bush or maybe just scrape the hole so some lube can sit between the pin and the conrod?

or is that not worth it
chris

Taking 1.5mm from a Datsun con rod with a reamer is a task you will very quickly regret as the rods are made from a very high grade of steel, so it will take a while

The pins are a press fit into the rods & bloody tight fit at that, so a machine shop that can bore the rods exactly parallel with the big end bore would be a good idea as the finished hole needs to be a precision finished size.

Using a bush, or just a scrapeing the hole bigger means that nothing is holding the pin in place since the pistons do not have, or need, any method of retaining the pins. Unless you use some method of securing them, the floating pins will contact the cylinder wall & quickly turn your engine into scrap.

lol no i'ld drill it out to 18.5 first. but i guess there isnt that much movement between the pin and the conrod.

well i have iginiton problems i have to tend to before i give it more boogie

thanks for your time dodgeman

If you do this, then get the rod finish bored as the final size is pretty much critical & a reamer does not leave a truly round hole.

No problemo & good fortune to you with the project.