Author Topic: Rebuild: Pistons (Read 3040 times)

badboypolar · « **on:** March 01, 2007, 09:01:33 PM »

I installed my crank and pistons today.
The crank turned fine with no binding,
but when i installed the pistons, they introduced tightness at 90 and 270 degrees.
Its not stuck, just really tight. A lot tighter than I'm used to.

Is this normal? Or do I need to re-torque them?

2002maniac · « **Reply #1 on:** March 01, 2007, 10:11:19 PM »

check the gap on the rings. This can happen if they are too tight.

check the wrist pins and small end bushes too.

badboypolar · « **Reply #2 on:** March 01, 2007, 11:50:35 PM »

The wrist pin was .005" oversized and the bushings had to be micro-honed to fit the new pistons. While out of the engine they felt great. I have to think it is the wrist pin or bushings.

The ring gap looked good when fully compressed so I don't think it is the rings.

nickmpower · « **Reply #3 on:** March 02, 2007, 12:31:45 AM »

my engine is like this too. though its not that much harder to turn. I think it just because of the angles of the con rods and the fact that the pisting are moving a greater distance then at tdc or bdc

nickmpower · « **Reply #4 on:** March 17, 2007, 07:47:56 PM »

any thing happen with this

1991318is · « **Reply #5 on:** March 18, 2007, 11:20:09 PM »

granted my experience is w/ v8's. I would say you should atleast dig into this a bit, cuz I've never heard of that, and I know it's not supposed to bind w/ those motors, and their a lot bigger than these, so I figure you would notice it more if they did w/ more mass rotating.

nickmpower · « **Reply #6 on:** March 18, 2007, 11:47:49 PM »

its not binding, its just harder to turn then when at tdc. My engine is in the car already

badboypolar · « **Reply #7 on:** March 19, 2007, 09:22:35 AM »

I asked a BMW mechanic and he said it is normal that is gets more difficult because it is where the rod starts to change direction. As long as it isn't to difficult to turn and it doesn't bind then it is okay.