850-R Piston Indentation Question!

[woody]

Hello all. I'm on the verge of replacing the Eng on my old girl (full thread to follow!).

A question if I may.

The original Pistons on the original Block have 2 small Valve-like indentations in each Piston on the Inlet side, are these part of the design?
The thing that got me thinking was, I recently acquired a set of 149mm 'H' beam rods and shortened Pistons and they do not have any indentations at all. Can anyone shed any light on this find?

Thanks in advance. Woody.

[Jamest5r]

Hi mate, wondered who bought those rods :)

No idea about the pistons sorry

[Jamest5r]

They do have a single letter stamped on the top to identify them though.

[p fandango]

didn't they change the rod length when with the introduction of ME7, so it can't be 850R pistons

[woody]

They do have a single letter stamped on the top to identify them though.

Hi James. Yeh it was me! Iirc the shortened Pistons have a 'D' stamped into the top surface with other letter/numbers too ( 'H' & 'G16')

James, did any of your pistons have those indentations?

I'm just wondering, were the tolerences on the Pre-ME7 Engine Inlet Valves and Pistons that tight that the indentations were vital? :confused:

[Jamest5r]

I just got new 0.4 oversize pistons from volvo and they came with D stamped on them the same as the standard ones that came out

[The Flying Moose]

Well im affraid it doesnt answer your question, but of the two engines I have removed the heads off both had two indentations on every cylinder.

In my opinion they look like they are supposed to be there as they are all equal but I couldnt be certain.

[Alan M]

Valve cutouts and interferance marks are two different things. Do you have a picture?

[woody]

Valve cutouts and interferance marks are two different things. Do you have a picture?

Hi Alan. I'll get a close-up photo tomorrow as I can't seem to find one now, bl**dy typical! :slap:

[The Flying Moose]

Here is a photo I took out of one of my lumps... do you mean marks like the ones you can see against this cylinder?

http://i1115.photobucket.com/albums/k549/EMLYNT5/P70701891600x1200.jpg

[woody]

Here is a photo I took out of one of my lumps... do you mean marks like the ones you can see against this cylinder?

http://i1115.photobucket.com/albums/k549/EMLYNT5/P70701891600x1200.jpg

Fantastic, yeh they're the fellas!

[Alan M]

Those are machined valve cutouts. If you have contact with a valve you will see marks just inward towards the centre of the piston close to the cutouts.

[woody]

Those are machined valve cutouts. If you have contact with a valve you will see marks just inward towards the centre of the piston close to the cutouts.

Cheers Alan.

Did these cutouts feature on Post 1996 Engines? and what was the difference to allow them to run without the cutouts Alan?

[nobananas]

Just to back up your answer, here's a piccy of my piston tops lol !

http://i106.photobucket.com/albums/m279/nobananas000/honedboreswithpistons.jpg

[Transient]

In a breif answer to the question about the cut outs featuring on pre 96 engines the answer is yes. The letters that are stamped in reffer to the batch manufacturer and also there are sometimes numbers, D is Mahle

[woody]

In a breif answer to the question about the cut outs featuring on pre 96 engines the answer is yes. The letters that are stamped in reffer to the batch manufacturer and also there are sometimes numbers, D is Mahle

Ahh, so that's that sorted, thanks very much. So, with Me7 Pistons mated to 149mm 'H' Beam Rods, inserted into a Pre-Me7 Block and be capped off with a Pre-Me7 Head? :rolling_e