Pistons identification

CD's with documentationElectronic distributor
Aris64
Posts: 10
Joined: 05 Sep 2021, 19:38

Pistons identification

Unread post by Aris64 »

Today I opened my 818.303 engine for check and overhauling (if necessary). Head and block appeared in excellent condition but apparently the engine has been repaired in some extent. Head bolts 1 & 2 were in irrelevant positions, cylinder walls have been honed, no "teeth" on pistons's edge trail, almost zero carbon deposit on pistons ' top , gasket in good condition ... BUT pistons marked 6/10 on their top. As far as I could measure cylinders are just 77.0 mm. I will go deeper of course to check crank shaft and bearings but what 6/10 means? Also head gasket measured 1.15 mm, so what could be the initial thikness 1.20 mm or 1.40mm? Finaly TDC is slightly offset, 8 is not aligned with 1/4 but with the bullet mark measured with dial gauge. Photos attacked.
Attachments
20210911_194314_resized.jpg
20210911_194500_resized_1.jpg
20210911_191650_resized.jpg
20210911_191630_resized_1.jpg
Huib
Site Admin
Posts: 1778
Joined: 17 Dec 2008, 10:12

Re: Pistons identification

Unread post by Huib »

My guess is that the 6/10 means the piston is for a cylinder of 77.6

If the engine has been overhauled once, it is hardly possible that it still has the standard size of 77.0
You should in any case measure the pistons and cylinders further down. Remember to measure ovality too. You will probably have to go to 77.8 but more likely 78.0. Talk to the machine shop what is necessary to get zero ovality as well as a perfect honing pattern.
Aris64
Posts: 10
Joined: 05 Sep 2021, 19:38

Re: Pistons identification

Unread post by Aris64 »

Huib wrote: 12 Sep 2021, 23:12 My guess is that the 6/10 means the piston is for a cylinder of 77.6

If the engine has been overhauled once, it is hardly possible that it still has the standard size of 77.0
You should in any case measure the pistons and cylinders further down. Remember to measure ovality too. You will probably have to go to 77.8 but more likely 78.0. Talk to the machine shop what is necessary to get zero ovality as well as a perfect honing pattern.
It seems you are right, going further it is most probably a 77.6 mm cylinder accommodating oversized pistons by 0.6 mm. I will check with my workshop for sure. I did an other post for main and conrods bearings. It seems that they are oversized also by 0.1 mm. I posted photos with their ID codes. If you could take a look I would be grateful. Thank you indeed!
Post Reply

Return to “65 Fulvia”