Hey everyone, newbee here.

I've been a fiat owner for three years now, and have done lots of top end work, but recently removed the engine from the car to investigate some smoke that was blowing out the rocker cover cap. After the removal of the pistons, the problem was easy to find; two of the rings had seized. Pretty small problem really. EXCEPT when I was taking off the rings, the small section of metal that keep the upper two rings separate snapped off . This happened to two pistons!

So I need new pistons. Any ideas of which ones are superior? the pistons that I was running were 65.97 with a small raised section. Should I run flat top pistons, or go for a higher compression piston? I can't seem to find my original ones anywhere. The engine is the standard 903cc, with a DIC30 and nothing except the original parts. Any advice will be much appreciated!

I did try and post pictures, but apparently you need more posts before they are allowed. Perhaps you could access them from my gallery? I'm not sure.

Thanks for looking!

Hi,
The issue which you have described is not unusual. If the head has been milled a few times, flat top pistons are probably close to 9.5 to 1 compression. You'll need to shop around to find the correct step top pistons.

Cheers.

When I had a Fiat 850 Coupe I used pistons made by Borgo (Italian, I think) and also Mahle (German). Maybe something might turn up on a websearch of these names? The early Fiat 127 was also 903c.c. but I think was a lower compression ratio and the crank turned clockwise instead of anti-clockwise as on the 903 Coupe engine so the piston pin offset might not be correct for use in the Coupe engine, hope this helps.

Al.

F123C said:

When I had a Fiat 850 Coupe I used pistons made by Borgo (Italian, I think) and also Mahle (German). Maybe something might turn up on a websearch of these names? The early Fiat 127 was also 903c.c. but I think was a lower compression ratio and the crank turned clockwise instead of anti-clockwise as on the 903 Coupe engine so the piston pin offset might not be correct for use in the Coupe engine, hope this helps.

Al.

Click to expand...

From memory the piston offset is no different on the 127 version of the motor, so flat top pistons are interchangeable. Should be easy to check.

Thanks guys, I ended up finding some at my local supplier here in Adelaide. Brand is "kolbenschmidt," they are 66m, 9.3:1 compression. But now as it turns out, the cylinders have to get sleeved, so off to the machine shop for the block. its only costing $400 for full boring, sleeving and honing which I was pretty impressed about!

I have TONS of 1972 Fiat 850 Spider parts if you need anything!