9 replies to this topic

[Pauly]

Hi guys,

Is there any marking on 1275 pistons to say which way they go? Theres no marking saying "front" on them, but there is a "A" which seem to point to the front of the engine?

Thanks.

Paul.

[Sprocket]

Doesnt matter, but any decent engine builder will fit the pistons to thr rods so that the markings that are on the pistons read the right way up when they are in the engine and the engine is in the car

[Pauly]

The pistons are still on the rods because im re-using them, its to know which way the con rods go round really.

Paul.

[GreaseMonkey]

Have a look in the haynes manual in the engine rebuild part, theres a pic showing which way each conrod goes so it all fits

Edited by GreaseMonkey, 08 November 2009 - 07:45 PM.

[GreaseMonkey]

Did you find it?

If not I can scan it in for you

[bmcecosse]

They should go back in the bores they came out of! Don't swop them about between bores!

[Pauly]

The pistons are in bore order, its just the orientation in the actual bore im worried about.

Thanks.

Edited by Pauly, 09 November 2009 - 09:11 AM.

[Guess-Works.com]

They will only go in one way as the bigend is offset..

Older pistons use to have a mark on the top ( an A ) to indicate the "trust" side which should be towards the rear of the block ( in transverse configuration ) basically as the crank rotates the conrod thrusts the piston up the bore, as the rotation of the mini crank is clockwise when looking front end on from no1 piston, where the radiator is, the piston is thrust up towards the rhs of the bore, ie the back

If a piston has no thrust marking then it can be fitted either way round, but it's a good idea to arrange the rings so that the gaps are not on the thrust face.

[Pauly]

So that would explain why the "A" is to the left side of the piston (looking in front) pointing towards the front.

Thanks guys.

Paul.

[Sprocket]

No, the A is to denote the bore tollerence when the engine was built at the factory. There will also be an 'A' stamped on the top of the block if it has not been skimmed. There are also pistons and blocks stammped B. This is much the same as how the mark up the sizing of the main bearings. You will notice on the bottom face of the block by yht center main bearing three letters, any combination of 'G' 'Y' 'R' These letters denote the tollerencies of the main bearing journals.