Changing positions on A12 Engin

[LUIS COLCHETE]

Hi!

 

Im rebuilding a Datsun A12 Engine with some new parts (main bearings and rod bearings, piston rings, water and fuel pump, chain, tensiometer all gaskets) and  some used parts but in great conditions:

flat top pistons (i think are unmarked 

conecting rods. (i think are unmarked?)

 

I want to know if i can change  the positions on motor. Change the position of conecting rods and pistons on Engine.  1st with 2nd, 3rd with 4th and etc.

 

I think i can change the position of piston because i will put in it new rings as wll the conecting rods.

 

What do you think?

I counting with your experiences.

 

 

Many thanks on advance.

 

 

Luis

 

PS

In my mind the only thiing i cant change is the main bearing caps.  It is correct what i said?

[datsunaholic]

Why?

 

Always best to put parts back where they came from.  Bores aren't perfect, so pistons are sometimes matched to each cylinder based on the +/- imperfections.  And weight balanced for the rod/piston combo.  The rods will be marked unless aftermarket.

[Mattndew76]

Mark them as you take the engine down. 

 

Same with the push rods for the valves.

[LUIS COLCHETE]

Hi!

 

I know.... the marks are important... but..

[KELMO]

I second the motion to put them back where they came out of, IE, pistons, rods, push rods.

[LUIS COLCHETE]

Hi!

 

My car has an original engine that i want disamble..... I want build one... with some performance parts that i bought... Better intake, twin carbs, exhahust, better cam  but my problem is:

 

I have used flat top pistons and conecting rods with few kms to put in a diferent block engine in excelent conditions.... I dont know which is the first piston or second? As well the conecting rods.....

 

The clearences are perfect....... I dont what are the sequences of 1, 2 , 3 or 4

 

 

Thanks

 

Luis 

[datzenmike]

Datsun cranks are balanced separately. All the individual pistons and rods with caps also. You should be able to run any rod in any position but only if the rod is matched with the proper rod cap. 1/1, 2/2, 3/3 or 4/4.

 

I'm building an LZ engine and have access to a scientific balance. It's so sensitive that a breeze blowing in the window disturbs the readings. The KA pistons were all withing a few grams... I found the lightest and removed metal to make the others all within 1/10 gram. The individual rods and caps are close to the same weight within 4-5 grams BUT caps and rods are different individually and only weigh close to the same when matched 1/1 2/2 and so on.  I suggest keeping them together as sets. Replacement pistons and rods are available and nowhere does it say to balance them so you should be able to replace a broken one with confidence that the balance is not upset.

[LUIS COLCHETE]

Hi

 

 

Many thanks

 

 

The only thing i cant change is the main bearing caps....

 

 

My block has the main bearing caps in the correct sequence

 

[LUIS COLCHETE]

Hi!

 

 

As i sayng im pretending to mount used but in good shape:

conecting rods with respective caps and pistons (I know i have to install pistons in cylinders with stamped number of piston to head toward front of engine) in a diferent but in a good A12 Block with a difrent crankshaft.

 

It is a cocktail....... 

 

What do you think?

 

My block has the main bearing caps in the correct sequence (i think is the most important, without them is garbage)??????

 

 

Luis

[datzenmike]

The caps should be kept in sequence, yes. The factory bolts them down and align bores them so they are straight and line up with the crank.

[LUIS COLCHETE]

Many Thanks

 

King Rat