Pistons identification
Pistons identification
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.
Re: Pistons identification
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.
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.
Re: Pistons identification
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!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.