15 replies to this topic

[SolarB]

Just unpacked my new 21253 Hepolite pistons. There’s an arrow on the crown pointing to one side (parallel with the gudgeon pin). Am I right in assuming this points to the crank (fan) end of the engine?

by the way, I know two are fitted on way and two the other way.

[Cooperman]

Don't think it atually matters, but it's nice to get the lettering the same way round once the pistons are in the bores.

[SolarB]

Don't think it atually matters, but it's nice to get the lettering the same way round once the pistons are in the bores.

With some pistons the gudgeon pin is offset slightly to one side to reduce piston slap and if they have offset pins the piston crown is labeled with FRONT or has an arrow.
These have an arrow so I assume they are offset but I can't find a data sheet for them. I'm guessing the arrow points to the front or number one but I'd like confirmation.

[Pauly]

Most people (including me) have their 21253's with the lettering facing the front.

[Cooperman]

Don't think it atually matters, but it's nice to get the lettering the same way round once the pistons are in the bores.

With some pistons the gudgeon pin is offset slightly to one side to reduce piston slap and if they have offset pins the piston crown is labeled with FRONT or has an arrow.
These have an arrow so I assume they are offset but I can't find a data sheet for them. I'm guessing the arrow points to the front or number one but I'd like confirmation.

The 21253 is not an offset pin piston.

[SolarB]

The 21253 is not an offset pin piston.

Now that's interesting, any ideas why they have an arrow?

[Pauly]

21253's dont have front markings or arrows to say which way they go.

Edited by Pauly, 21 May 2010 - 07:28 PM.

[samsfern]

the only thing that would possibly matter is if they have offset dishes.

[SolarB]

Well, Minispares sold them as 21253s it they are labeled on the box as such.

 21253.JPG   118.36K   56 downloads

I can't actually measure any offset at home and have no idea of the difference I'm actually looking for, is it a few thou or tens of thou?
Will have a measure at work tomorow.

[GraemeC]

Arrow should point to the 'front' of the engine (ie the fan end).

[GreaseMonkey]

My 21253s are made by AE and look like this?



The lettering is at the front dizzy side on mine

[GreaseMonkey]

With yours the arrow should point to the fan end as Graeme said

[Sammy D]

One of my AE21253 pistons is 180 degrees out. Whoever put them on wasn't paying attention. No problem.

edit: mine didn't have markings or an arrow in the middle like the one above, only around the outer raised lip.

Mine;

http://img37.imagesh.../dsc04104a.jpg/


You can make out on the far left piston that the markings are the wrong way round;

http://img404.images.../dsc04124z.jpg/

Edited by Sammy D, 25 May 2010 - 09:35 AM.

[SolarB]

So, is 21253 a type rather than a manufacturers number? Or, do Nural manufacturer them under licence from AE? The lack of arrows on GreaseMonkey’s and Sammy D’s pistons doesn’t explain the arrows on mine.

Oh well, I’ll put them in with the arrows towards the fan.

[Cooperman]

I've never seen any arrows on a 21253 or even a 21251.
They are totally symetrical and it doesn't matter which way round they go, although convention is normally that the stamped lettering can be read from the front, i.e. dizzy side, of the block and that's how most engine builders assemble them. Sometimes a fitter makes an error and gets the rod offset the wrong way round, but it's better to live with this than to try to press the pin out and re-fit it, as that can easily damage a new piston.
The arrows are, probably, just to try to ensure that the builder keeps the job neat and professional looking - er, maybe.