To L. M. 68 W. 1k
Racing? RACING??
How can you enjoy your Datsun to the full if you can't drive it anytime you want, to almost any place that you want to.

No, i wore my engine out at a little over 100,000 miles [thats miles, not those wimpy kyloe meeters] on each occasion.

Sadly, my sedan has passed it's "use by" date. Happily, the coupe will take it's place.
To maximise the fun, think about an option one five speed. Mine needs a "freshening up" overhaul, but it will go back behind the 1200 & into the KB10. Fun to the max 24 / 7. Try that with a "race only" car.

I only hope i was of some help
Chris

Dog
I must confess that i do not know just exactly what an A12a actually is, but if it is the B210 [120Y] version of the 1200 engine then it too has a 73mm bore as standard. The second oversize for these would then be 74mm & not 73mm + .040" even though there is not much in the diference.

With this bore size & a 70mm stroke, which is the standard 1200 dimention, the capacity is 1204.235296 cc [approx] Thats a long way short of 1270cc

To get 1270cc with the standard 70mm stroke requires a 76mm bore size [1270.208742 cc] which is where the stock A14 pistons come in. Boring the rods is no big deal, just a "few dollars more" Remember that phrase while making choices about your car & engine improvements. Believe me, they do add up.
The A14 piston is the right deck height & is a standard Datsun part, as well as being available from Repco etc.

Flat top pistons "can" raise compression from Half to a full point, depending on bore size, stroke & combustion chamber size, as well as the size of the original bowl, but be prepared to live with premium fuel at premium prices if you drive a lot.

Question.
Apart from custom forgings, where do you get flat top 76mm bore pistons? If you are using a 73mm bore [stock 1200 size] then use the Repco ones for the 1000 [A10] These are made on the shorter 1200 piston blank, but with flat tops. I used them in my wife's 1000 two door with A12 installed. Not a huge diference, but since the A10 & A12 pistons were the same price at the time, i figured the extra compression was for free.

Please tell me about the A12a engine as i am in the dark about this one.
Thanks........ Chris

do you use your stock 1200 sleeves or do you put 1400 sleeves in?

many thanks

An A12a is 1237cc and has a bore of 75mm
It came in the USA Datsun 210 (310 every where else I believe) 79-82 years.

Everything else is similiar to the A12 with a strroke of 70 mm

I just read the rest of you post

I'm using an A12 in a Lotus 7A replica (Locost 7) that I'm building. I'll do no more that 3,000 miles a year, I train into NYC for work. So the cost of premium fuel won't be a factor. But here in the states we are currently paying $2.05 a US gallion (about 4 liters) for premiom and $1.85 for 89 octane.
That is why there are a lot of Big cars here in the US that get 8-11 miles a gallon.

I saw A12 flat tops on the net some where so I assumed I should be able to get A12a flat tops, and since they would be replacement pistons I thought they may make them a little oversized. I saw on e-bay stock A12a pistons + .02 inch just a day or so ago, tha twould make arround 1250 cc.

I just purchased a New Old Stock A12 a few days ago and am awaiting its' delivery.

Dog

Nicholas
There are no sleves in the Datsun A series engines. The cylinders are bored direct into the cylinder block casting.

Sleves are used in this type of engine as a repair process. The "A" class sleve is thin & is used where the bore is thin or perhaps cracked, but will still provide support. "B" class sleves are thicker & would be used in the case of a bore with a hole through the side, or with serious core shift. These sleves are more self supporting with regard to resistance to bulging during combustion.

Both types can be used to restore a block that is worn beyond the maximum available oversize back to standard size.
Using 76mm pistons in a 1200 block means boring it out to that size.
Chris

Dog
Thanks for your reply.

I thought that i was fairly familiar with the "A" series engine & as far as i knew, they used only 73 & 76mm bore sizes, but with a 75mm bore, you are right, it yields 1237cc. This is a size not sold in Australian models & if one were to bore for the 75mm piston, one might as well go on out a little more & use the 76mm piston from the A14. At least it is an available size for us.

As you pointed out, the boring out of the little end of the rod is a pain, but not a big one & any competent reconditioner should be able to do it. After all, it's only "a few dollars more"

Repco [REplacement Parts Co] is an Australian supplier & manufacturer of [surprise surprise] replacement parts. To cut costs, they cast one piston for the A12 & machined it with a dish for the 1200 models, & machined it flat for the A10. Same "replacement" piston, two compressions, but only in 73mm sizes.
Chris
PS With a 76.5mm bore [first oversize] & a 70mm stroke you get 1287cc, so thats still comfortably under 1300cc for competition use