Questions on broken piston

[montmil]

...I feel reassured that I can reuse the old piston...

Pretty sure you meant to say, "reuse the old cylinder". Correct? That broken skirt piston can be repurposed as a paperweight.

[Einar]

Yes thank you Monte, I have corrected my post to eliminate confusion.

Currently cleaned up the parts, removed the carbon debrie, and gave the cylinder the recommended bubblebath. I believe it has cleaned up quite nicely (close up picture attached #1)

Few question regarding the markings on the piston crown:
- 9,2 = ?? (picture attached #2). Is this compression rate?
- B = Weight category
- 81.97 = Size

I have found a piston + cylinder online with the following markings:
- 8,7
- B
- 81.97
Is that compatible?

Any input as always much appreciated.

[Einar]

To update the post:

The mystery 8,7 and 9,2 numbers are the compression ratios.

The R65 [1978 - 1985] = 9.2:1
Les R65 [1985 <] = 8.7:1

I will still try to fit the piston when I receive it, though I expect increased vibration and decreased performance.

[Tony Smith]

To update the post:

The mystery 8,7 and 9,2 numbers are the compression ratios.

The R65 [1978 - 1985] = 9.2:1
Les R65 [1985 <] = 8.7:1

I will still try to fit the piston when I receive it, though I expect increased vibration and decreased performance.

Please don't.....The results will not be good.

Some time ago I took a photo of a 1979 piston locked to a post 1981 piston by the simple expedient of placing the second piston up against the rings fitted to the first. This clearly shows that the difference in CR is entirely due to the difference in "height' of the piston above the top ring.

FWIIW i have 1979 pistons and iron bores fitted to my 1984 engine with what essentially amount to 1984 heads (big valves but 1979 squish band) - I could have done what you are proposing to do and i would not - and I am supposed to be a bit adventurous.

Please obtain a pair of pistons that match CR and use those, you will be glad that you did.

[Einar]

Hi Tony,

Thanks for the input. I will first and foremost check the height difference.
I prematurely bought the 8,7 piston to replace the broken one, but I will resist the urge to mount it then.

Essentially I need then either 2 x 9,2 CR or 2 x 8,7 CR, if I understand you correctly.

Thank you for your input. You probably saved my engine with this one!