Sunday, February 15, 2015

Putting the Pistons In

<This post is part of the 'Winter Project 2014/15 - New Engine Rebuild' project>

In the last post, I managed to get the crank in without too much drama. Still high on the excitement of that achievement, I now need to move on to putting the pistons in. This should be a fairly straight forward job, however the only snag is that I don't have a piston ring compressor. As this is a fairly
critical tool for the job, I thought I would try to make one...
Testing on the test engine.
Usually the home made tool I create are relatively successful, but not this time. I made it out of an old oil tin and 2 jubilee clips, I could see no reason why it wouldn't work, but no matter how hard I tried I just couldn't push the piston out of the compressor into the cylinder. I tried varying the compression and it was either too tight or too loose. So I admitted failure and bought one as I didn't want to risk damaging the rings or the cylinder walls.

Proper Piston Ring Compressor

Oh well, you win some, you loose some, but as it only cost £12, it's not a huge loss. Now I have the proper tool, the work can commence. First task is to open the new big end bearings and press them into place on both the con rod and the caps and smear them with engine assembly lube.

Big end bearing

Next up was to cover the piston is engine assembly lube and clamp it in the ring compressor.

Plop it on and spread it round

Before it goes into the compressor though, I spaced all the ring caps equally around the piston.

Ready to insert.

After smearing plenty of lube on the cylinder walls, the piston was ready to insert. I placed a spare glove over the con rod so it didn't scratch the cylinder as it was inserted. I also set the crank position for this cylinder to BDC so the con rod didn't collide with the crank when it was inserted.

Protect the cylinder walls!!
It's also important to get the pistons in the right way round. If you get it wrong, the end cap will bang into the block when it is rotated, trust me, I have done it!

Ready to insert

On a number of videos on youtube and also in books, I have seem people tap the piston into the cylinder with the handle of a hammer. Although this seems to be an accepted method, I read an article that suggested it was a bad idea as it could damage either the rings or the top of the cylinder if the rings are proud of the piston.

To avoid this, I pushed on the cylinder with one hand while wiggling the compressor with the other and I have to say that all the pistons simply slid into the block without any problems using this method.

And it's in!!

Removing the rubber glove from the con rod, I pushed the piston down the cylinder and onto the crank where the end cap could be bolted in place finger tight for now. Repeating this process for the other three pistons, it was ready to be torqued up.

The Haynes manual has the torque setting for the bolts at 50 Nm or 37 lbf ft so I did them up in two stages, first at 20 lbf ft and then at 37 lbf ft.

Tipping the engine on its side, it was still possible to rotate the crank by hand although a little stiffer, there were no notches or sticking points, so that's another job ticked off the list...

Camshaft, coming up...

For updates, stick a 'Like' on Wayne's Mini Progress facebook page.

No comments:

Post a Comment