Lost phone with disassembly pics, don't remember piston order
 

Hey guys,

My phone was stolen during my recent trip to Europe and unfortunately, it had all my engine disassembly pics. Now I'm worried about the piston order. Does the original order really matter if I replace all the journal bearings and piston rings?

Thanks!

Pix not on cloud or dropbox or somewhere?

Martsink;

Since you are replacing the parts that would matter in piston order, no problems. UNLESS, the factory balanced the engine, which is unlikely. To be sure, weigh each piston and rod. As long as their weights don't differ by more than a few percent, order won't matter. If you find bigger differences, balance them out yourself. I'll bet there are YouTube how-to videos for that.

Cheers,

Dave

Unfortunately not. It was my work phone, so cloud storage is prohibited.

Hello martsink,

if you don't know the original positions you definitely have to use new piston rings. The other problem is the rods and the rod bearings. These wear differently. So every rod bearing has to be replaced.

If you have to interchange the pistons you should clean the pistons and heads as good as you can, because the deposits on top of the pistons and in the heads fit together.

Also it is not uncommon that cylinders are not 100% round in diameter over the whole length of the cylinder. Depends on wear. If that is the case it is not a good idea to use a piston in a cylinder that didn't belong there. But in that case it is always better to overbore the cylinders and use new pistons.

If the engine previously was fine balanced than an interchange of pistons can cause problems. There are several methods for fine balancing. The most common is to balance the crankshaft and then to bring the wight of the piston and rods to equal. The other is to do that and after that fine balance the crankshaft with installed rods and pistons, which gives an excellent result but means from that on nothing is interchangeable.

Hope that helps.

Regards, Markus

Thanks for the input. I've already done most of the above. Boring out these blocks is not an option, the only thing you can do is resleeve, and that's definitely not in my budget. I guess that next question is, are M96 engines balanced?

Hi martsink,

well, the common way if you must overbore the cylinders is to use steel sleeves. There are a very few engine builders over here in Germany that offer overbores in combination with a new Nikasil or nickel / ceramic coating. It's not a very common solution, but it's possible and it is much more expensive than steel sleeves. That is why most people prefer the steel sleeves. Problem with the steel sleeves seems to be that they loose the hone pattern over time. Also if you use steel sleeves you also should use forged pistons, because of the thermal expansion. So there are pros and cons.

Regards, Markus

Martsink,
Have you been following Ahsai's thread on rebuilding Cringely's engine? There is 13+pages of info there.
blown engine - Rennlist Discussion Forums.
The bore/taper issue is serious.And the equipment and techniques to measure it accurately are beyond what most engine builders would use. Rebuilding an M96 to Miata or Jaguar standards may produce a working engine but won't be optimal. I found it to be quite a 'learning experience'!
Your final problem will be how to reconnect all the vacuum lines ! Yes there are diagrams but it ain't quite that simple. And that just about summarizes everything to do with the M96. It requires much higher standard of skill, tool, equipment and knowledge than I expected.

Thanks! I've read through several builds, but never came across this one...
I'm trying to take my time with this engine and buy the necessary tools if I have to. I'm also fortunate enough to be able to borrow some precision instruments from work.

http://986forum.com/forums/attachmen...1&d=1465279490

http://986forum.com/forums/uploads02...1465279284.gif

http://986forum.com/forums/uploads02...1465279297.gif

The numbers are not idea, but that what I have to work with. I plan to replace the valve guides, but I probably won't do anything about the cylinders.