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

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

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

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

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

many thanks

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

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

Thanks DODGEMAN for all the info. Was your engine for racing or for daily driving?
You had an A12 running for 20 YEARS thats a great engine. WHO needs rotary or CA18DET (not that would fit in a 1000)

Thanks
PS Im sure ill start an argument with that

If you want to go to 1270 you can use A12a + .04 inch pistons and not have to deal with the making the A14 pistons fit your rods.

My question is are flat top pistons better and how much would they raise compression without cutting the deck?

What is the best source ( where can I find them) of A12a flat top pistons?


dog.

OK blokes, here's the good oil for the Datsun 1000.
I have had a 1200 engine in my '68 sedan for over 20 years.
Use the early 1200 engine & it will go straight into the chassis. I used the 1000 engine mount brackets & sump for a perfect conversion. Use the B10 [1000 model] altenator & bracket, including block mounting hardware for a true bolt in.

I bored mine to 76mm & drove it so much that i eventually wore it out. Use the A14 pistons & have the reconditioner bore the rods to accept the larger wrist pin that these 76mm pistons use. They might have a grizzle about that, but they should do it anyway.
This replicates the A13 engine that we never saw here, but i think that the US did.

Next i bored it out to the first oversize which brings it up to 76.5mm. The engine is still under 1300cc, but only just. I have worn it out again. For street use, you should be safe at 77mm which is the second oversize for the A14. We have one engine at this bore size running around here now without problems.
I will go for broke with mine & i will be installing "A" class sleves & run third oversize pistons of 77.5mm. The finished engine will end up at about 1453cc with a few extra tricks & a bit of money, but HEY, it's only a 1200. See, the engine number is prefixed A12. ALL of this will be achieved with STOCK Datsun parts, you just got to know WHICH parts.
This engine is going into my KB10 [1000] coupe. Please remember that the stock type carb & aircleaner will rub on the underside of the bonnet, so try to use sidedraught induction. My setup is 1200GX, which is what the whole engine is.

You will quickly find that you will need to install the 1200 diff center as the extra power will make it feel like you need an extra gear, & while you are at it, you may as well use the 1200 gearbox as well & your speedo will run truer than with the 1000 box. Get a ute box if you are going to use a 4 speed as these have a more satisfactory front bearing for the cluster, which may be important if you plan on "working it hard"
Chris
P.S.
The A13, the A14, & the A15 all used the 76mm bore size, but used 70mm, 77mm, & 82mm strokes to get their diferent capacities, & with each increase in stroke, the block was made taller, which is why the air cleaner rubs under the 1000 bonnet. The only exception was the A15 which was the same deck height as the A14, but used shorter pistons to accomodate the extra 5mm of stroke.
Happy Datsun 1000 driving. Its a great car, & with an "improved performance" 1200 engine, it's a great combo.