Ok i will give that a go

Sure, maybe a post in the Main forum with a title of "Brisbane -help requested to test my A12" or something like that. Buying lunch or refreshments sometimes helps.

Do u think i ask in Forum?

I recommend you buy or borrow a compression tester. They are only $25. Then you can test it yourself to know what you have. Otherwise you are always waiting on your mechanic.

Maybe one of our Brisbane brothers-in-Datsun can come by and take a look at what you got.

At this stage with the dollors i dont have i would have to say yes about the smoke.
But its a mater of geting the time when my mechanic is not bussy.
And if He has got any of the tools i need to test the compression Or check the sise of
the bore in the nmb4 of the A12 he said maby i could be oval shaped.
I asked if he had the machine tool 2 check it and he dident realy give a straight anser.
I thought if i pull apart all my A12 block,s maby i might find a better one.
Maby i could call u some time if u dont mind?

Do you want to fix it so it won't smoke anymore?

Or do you want to rebuild it, even if it doesn't need rebuilding?

Your choice.

Yes your right it is Bluish-White smoke.
I have Three A12 Block,s the one i removed from the car before the putting in A14 i
only did so Because The valve stem seals shot and it only had a problem in nmb4 piston.
I was pulling out the plugs every two week,s to clean. And only the 4th one was oily the rest whear ok just dirt brown maby carbin. I did try the hoter plugs on this engine dident do alot.It allso had a valve that had hole in on nmb four. But we fixed it before i put rego on the car. Anyway i think i would like to rebuild A A12 just because of petroll price,s and the A14 is allready in the car maby i should rebuild the A14 because i think the head is probley in better condition.
All so the A14 does seam to use any more fuel any way
Yes i do have a manual its a Gregorys 120y

Hi Dave, yes, if it is emitting bluish-white smoke and the compression is low, then it probably needs new rings. There are some other less common causes of bluish-white smoke, so a compression test is called for to confirm it.

To replace the rings, you need a "head set" gasket kit, new rings (I got mine from Repco), feeler gauges, and an oil pan gasket. If the cylinders have do discernable ridge, you don't even need a ridge reamer. The A-series is a good engine and usually rings is all that is needed. The feeler gauge is to measure the ring end-gap in the cylinder and side-gap in the piston. Be sure to follow the procedure in your repair manual (Gregory's, Haynes, Datsun Factory Service Manual, etc). Datsun does not call for honing or glaze-breaking, so keep it simple unless the cylinders are worn. If there is a discernable ridge near the top that you can feel with your fingernail, then it gets more complicated, and the bore dimensions should be checked with micrometers and boring may be required.

While you have the oil pan off, check the bearings with plastigage ($5). Chances are they will measure out fine if you don't hear any knocking now while it is running.

Bule smoke
I want to rebuild one before the cops tell me to take it of
the road

Depends on what kind it is. Black smoke coming out the tailpipe -- even if there is a lot -- is not fixed by rebuilding the engine.