Hi guys
OK, I need really confident answers here.
I am in the process of getting a stock A14 crank that I want to use in my early A12GX engine to get it to 1300cc.
I don't like the idea but unfortunately I apparently have to enlarge the small end of the A12 conrods to fit A14 pistons.
Is there no other posibility that someone can mention except A12a rods?
Will A12 oversize pistons not work?

If I really have to bore the small end, is the hole going to be 1mm larger in diameter? (If you measure it from the center of the hole is it going to be 0.5mm larger on each side?)

I am planning on going 7000rpm but don't want to worry if I occasionally go 7500rpm. Those who have raced with this and no con rod failures, please reply as I don't want a con rod flying through the bonnet.

OK, I ran rebored rods for years [& years] without problems.

A12 oversize pistons will work a treat in a 1200 engine. As far as I know, they come in 0.5mm, 1mm & 1.5mm oversize from the factory & most 'replacement' piston suppliers.
Of course these will only work with a stock stroke 70mm stroke crank.

If you are going to use the A14 crank, then I have no idea why you would use the A14 pistons as they are the same height as the A12 pistons. You would need A15 pistons, which are shorter, & you will still need to machine some off the top.
This will, of course give you almost 1400cc, not the 1300 that you mentioned as the engine will now have the A14 stroke & bore size.

If you want 1300cc, then forget the A14 crank & simply use A14 pistons.
You will need to bore the engine to the 76mm bore size of the A14 & this should not be a problem, but of course, the rods will be.

Several sollutions present themselves.
1. Use A13 or A12A rods.
Hell, I got 2 sets of A12A rods from the US, so they are not THAT difficult to source.

2. Use the rods from a later model A12 engine.
It is my belief that the later engines [about 1980 or so] used the A12A/A13 rod forging with more meat around the wrist pin to allow boring to the larger 19mm size. They were then bored to either 17.5mm for A12's or 19mm for A12A's & A13's
These can then be bored to the right size.

3. Use the H beam rods from B Pro, if they are still available.
I had mine bored to 19mm in Japan before they sent them over.

4. Use the big bore pistons that were made for the 1200 engine.
These have a nominal 76mm bore size but with the smaller 17.5mm pin. I have no idea if they are still available but it might be worth an ask.

5. Bore out the standard rods.

This would seem to be the least appealing alternative, however I not only used these rods with my own A14 pistons, but I drove it so much that I wore it out & rebored the engine to 76.5mm [A14, first oversize] I drove this for many many miles too & I never had any problems.

I am trying to understand why you would want a street engine that screams its little head off at 7,500 rpm. My 1300cc engine rarely saw 6,500 rpm & it performed wonderfully. That extra 1,000 rpm capability may cost you more than you want to pay in terms of modification costs, driveability, fuel consumption, reliability & engine life.

Worth a thought.

see Dodgeman is wealth of knowledge that is always missed, good to see him back for a little bit.. :)

Thanks for the reply Dodgeman. I was actually bargaining on your reply. I got confused between the different combos giving what cc's.

How much did the A12a rods cost you? The thing is our South African rand is very poor in value and it is possibly going to cost me a bit too much. But on the other hand, maybe I must pay that little extra to have better reliability. There is a local engine import shop that has a bunch of late A12's lying around. It's the one's with the distributor in a different location than my GX. I presume they will have the meatier conrods.
The other thing is if I bore the engine, will there still be enough meat between the bores for the gasket to seal reliably?
It is not that I am definately going to use 7500rpm, it is just to know if I go there I can go there with confidence.

It's for a long time now not a daily anymore. It is a weekender. I am planning some upgrades like extractors, head work, 276 cam, and as mentioned a little cc upgrade, lightweight flywheel and if money later permits ditch the hitachi SU's and go fuel injection.

I bet when Dodgeman reads that he'll turn over in his grave, and he's not even dead yet...

GX carbs and the GX exhaust manifold are awesome...

I must agree!

With the original GX stuff already under the hood I also have the following spares in my cabinet:
Eat your hearts out!
1. Complete GX intake system.From the intake manifold, Hitachi SU's to the airbox.
2. GX exhaust manifold.
3. GX cylinder head still stock standard without even 1 skim in it's life. Just needs a deck to clean it up when I one day need to use it.Which I don't because I have one under the hood.

When I upgrade the engine with some go fast bits, I intend to store the GX stuff away to collect dust.

greedy bugger,
I have a very secure shed, I think you should send your parts here for me to look after for you...

I have thought about selling some of the double stuff to fund the A12 upgrades as the wife doesn't want me to spend salary money on the car.

Send the head to me, I'll open that ports up nicely.