Chapmans disease is also a common builder ultralight pilot condition!
What I thought was my original A12GX bottom end was even lighter than another stock front
dizzie A12 bottom end I had. I gave both away to another 1000 enthusiast and kindly called
me to see if I wanted it back as it had a knife edged crankshaft, 124mm H rods and custom
flat top pistons (27mm comp height). Never clicked it was way lighter than another stock A12.

The A14 bottom end felt almost 60% heavier in comparison and was a 2 person job versus
this worked A12 bottom end which was an easy 1 person lift.
Come to think of it the bores at 77mm removes like 4 x 3mm thick steel pipes as well
but still the difference was night and day in weight with the stock a12.

I have one of those front dizzy A12 blocks in my shop as well. It is easy to maneuver around. Rallytwit mentioned he has one of those A12A engines which is a bored out A12 fitted to the later model 210 car. Is it as light as the stock A12?

The later A12 engines seem heavier than the early dizzie units but
Im not sure on the a12a but which confuses me as Ive read early blocks
are supposed to have more casting material than later?
Cost cutting measures are definitely there on A15 blocks as they
seem to develop corrosion on the walls that affect overbores.
Ive seen A12 engines go to 78mm with no issues at 10k rpm
but A15 engines going to 5mm overbore dont seem to last
without developing pin holes on their bores.

there is no early vs late A12A -- it was only made 1978-1982. It's a totally different casting than the 1978-1982 A12 -- some say the cylinder walls are larger (so not bored out from the A12 size, but actually cast larger)

56-series 4-speed is 28 lbs lighter than 60-series 5-speed. Engine-wise, A12 is about 13 lbs lighter than A15. The main difference is 15mm taller block, otherwise exterior dimensions are the same

Colin was right of course

There is also 2 different A13 engine blocks one tall one short
maybe the tall ones are A14/15 ones with extra wall thickness?
I still dont know why datsun would do those 2 models.

Quote:For the upcoming 1974 B210 introduction in USA -- with its heavy features (400 lbs heavier than B110 and 120Y) -- Nissan needed more grunt than the A12. So they created the A13, a stroked engine with longer crank throws than the A12. It was the first tall block, and immediately was upgraded to A14 for 1975

Now come 1977 and again more than A12 was needed, this time for the Japan market base B310. So a new A13 was created with +2mm bore size but still using the standard A12 stroke. I haven't seen an official reason for the change, so maybe it was one of the usual:
* To keep pace with competition (e.g. Corolla specs: E55 already had 1.3 engine and base E70 would start at 1.3)
OR
* Power/emissions changes (e.g. to meet the Showa 53 (1978) "H" level emissions)

The last part of your article is more likely to be the main reason as a lot of the heads were cast with H on them but not the GX heads

Ah interesting. H emissions came into effect 1978, while H series AMC came out 1969 (H code numbers refer to the later Sunny cars)

Some castings use the AMC numbers, some don't. Now you got me thinking that the GX head casting may have started as a works project, and maybe that's why it wasn't cast using a production code?

AMC
H01 1969 B10
H03 1969 KB10
H10 1970 B110
H18 1970 KB110
H23 B110 GX
H50 120Y
H85 B310 1200/1300 Sedan/Coupe
H89 B310 1400/1500 Sedan/Coupe

Dave when I mentioned th 28lb weight saving it was 16lbs difference for the transmission and the 12lbs between the A12 & A15. Granted I weighed them with a bathroom scale but I have the 60 series 5 speed at 54lbs and the 63 series at 65lbs give or take.

The 14lb lightened flywheel will drop another 6lbs, so you can get a whooping 34lbs. If you use an early A12 starter that's 1.8lbs lighter, one of the alternators is also slightly lighter by 1-2lbs (I'd have to look at the spread sheet) additionally the crank pulley with triangle holes is 200grams lighter that the one with round holes. So hold,on to your socks you can cut 38lbs.

I know I've mentioned it before but with GX valve springs I was spinning the A12 to over 8000 rpm.

On the A12A one could use Honda D15 or D16 pistons (75mm with close to a 30 pin height) in conjunction with A14 crank and the only machining needed would be putting the pistons on the rods. That would take the motor out to 1360cc and with GX head compression would be 10.8 thereabouts. In my case with the 27cc milled head I have it brings it up to 11.5

In my case the the rules allow for a for huge displacement increase, so 1360 is well within that.