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Posted by: SuperSquid Jun 29 2020, 06:54 PM

I installed my new AA piston in my type 2 bus engine yesterday and was wondering if it matters how the pistons are oriented in the cylinders? I guess I have a 50/50 shot of getting it right! Any thoughts? Thanks

Posted by: 914e Jun 29 2020, 07:17 PM

Since the pistons are clearanced for the valves, if you have it upside down the valves will hit the pistons. It has been over 30 years since I built an engine, but I'm pretty sure the valves are at the top of the head.
I will let others confirm.

Posted by: roblav1 Jun 29 2020, 08:00 PM

Since the intake valves are bigger and have more lift and duration, I'll swag and say they're correctly oriented. But someone with more expertise than I would know.

Posted by: Montreal914 Jun 29 2020, 09:25 PM

Sorry to break the news but your pistons are upside down

Posted by: davep Jun 30 2020, 06:55 AM

I don't quite understand. I have 3 different types of 2.0 pistons. The deep dish bus, the shallow dish North American, and the no dish European piston. None have valve clearance reliefs. My pistons also have arrows that point to the flywheel.
If my flat top pistons do not require valve pockets, then that would suggest those pistons do not have valve pockets either, just a relief to lower compression. This does not mean that you do not have them upside down.

Posted by: barefoot Jun 30 2020, 07:58 AM

Yes, the valves angle upwards, so you're upside down. These are aftermarket pistons intended for cams with more than stock lift. Both intake & exhaust are side by side, not hemi like as in Porsche 6 cylinder heads

Posted by: SuperSquid Jun 30 2020, 08:51 AM

Thank you everyone for the great advice. The top of the pistons is flat with a concaved grove so I do not think the valves can hit anything. I think I am going to flip them just to be safe.

Posted by: SirAndy Jun 30 2020, 10:18 AM

Hold the head right next to it and look at the angle of the valves in the head and which way they will move when mounted.

You'll know exactly where the relieve needs to go ...

Posted by: Carbon-14 Jul 1 2020, 12:28 AM

Better be sure the rings are gapped to the correct dimension, yes, you did have them upside down. Check the cold clearances of the piston to cylinder wall, to make sure it won't seize when running. Measure piston's height to cylinder head clearance, important to avoid big bangs for bucks. Buy new rod bolts and torque to spec, you did measure clearance's of new bearings. Everthing is spotless clean, right ?
Easy to do things wrong, without instruction or experience.
All the info is right here.
https://sites.google.com/site/stpsgarage/TechnicalArticles/preparingpistonsandcylindersforinstall
https://jalopnik.com/heres-what-happened-inside-my-badly-overheating-volkswa-1819961495

Posted by: Mark Henry Jul 1 2020, 07:33 AM

Upside down

So is my pic

Posted by: 914e Jul 1 2020, 07:42 AM

I'm guessing valve clearance is still checked with modeling clay. Generally when pistons are relieved for valve clearance there is a higher chance of contact do to higher compression and/ or higher cam lift. I would assemble it and check the clearances.

Posted by: Mark Henry Jul 1 2020, 08:00 AM

It's for a low CR bus with camper special heads, as long as you're not running a wild cam you only have to worry about the deck height and the CR calculation.