Piston manufacturers

[K1100]

I have been trying to find firm facts about the compression ratio of a set of pistons I have just bought for my A10. The dealer was slightly vague but "fairly sure they're 7.25:1".

I thought it would be an easy matter to track down GPM pistons on the internet and get the relevant information.  I had thought they were Italian but my searches have led to China and the Laizhou Xinrongxiang Casting Co., Ltd.
http://sdxinrongxiang.en.alibaba.com/product/445244593-212519179/auto_piston.html.

Does anyone know any different, or can anyone point me towards a way of finding  out precisely what I have got? the only marking inside the piston is 700H and on the crown 71 5 (which I think confirms it is +60).

[Brian]

Thats a 8.5-1 piston. It looks like a Gandini (GPM) but I'm not certain.

As a general rule,

Concave top is 6.5-1
Flat top with slight cut outs for the valves is 7.5-1.
Raised bevelled top with valve cut outs is 8.5-1

Obviously there are variations on this but as a "rule of thumb" that is how you identify them.

[kiwipom]

hi guys/Brian, do you know the comp ratio on these? i have no idea but came out of Hepolite boxes,cheers, Bob

[Brian]

Not certain as once you get above 8.5-1 it gets difficult, at a guess I would say around 9.5-1.

[K1100]

Brian .... thank you.

[chaterlea25]

Hi Kiwi,
I think not 9.5 :1 !!
The 8.3/ 5 have a raised portion all the way round and then flat on top it looks as your pistons are lower than this
with just a slightly raised dome,
I have a set of high comp pistons 9.5 or 10's these have a really high centre
I will add a photo later

HTH
John