Engine Drivetrain 1st Gen Cooper S GNAT - The Resurrection

News from the machine shop...

Runout in the bore is 3 thousandths. This means that my speculation of out of round cylinders is correct. Also shows us why the ring gaps keep trying to align themselves.

To fix this the cylinders will be bored true. I'll need a set of over-sized pistons. I've not given thought to the brand as of yet. That's something I'm going to need to look into and quick like too...

The crank has a some scoring on it, ya'll saw that one bearing that was about to go, it's not a surprise. It will be reground to remove the scoring. This will require a set of over-sized bearings. MINI does does make these so that is not a problem.

The head also has some issues. All the exhaust valves are leaking. These were all just replaced about 22K miles ago. I'm thinking the last machine shop did not get it right. Oh well, that's done and over. Recourse with them is just not worth the effort. Won't know if any of the valves need replacement till the head is torn down.

So how did this happen?

This engine has had two overheating events. The first was just after AMVIV in 2007 when climbing the hill outside of Vegas on my way to California. Being as it was about 15k miles after that event when the first fix was done to re-ring cyl 1 as the gaps had aligned on the rings I'm going with that was the event that put all this in motion. The bore was checked then but not to the level is was now. The engine was not pulled then. The measurement was all done in place. It's quite possible that it was just barely out of round at the time and not picked up.

The second overheat event was after I was already seeing misfire code on Cyl 2 already. It may have contributed some but I feel the initial damage was done quite some time ago.

And that folks is where we stand right now...

Stay tuned for more.

 

Update on pistons....

Have a set of RMW .20 over being sent for the rebuild. No compression changes from stock. Includes new rings and pins too.

Also with help from Jan instead of grinding the crank and going with MINI over-sized bearings I'll be getting a new OEM Reman Crank with Mahle Rod and OEM standard size main bearings.

 

Not stroked but bored.

Piston height and compression ratio stay the same. The bore is increaded 0.20. If my maths are correct the engine is growing from 1598cc to 1603.08 cc.

 

Ahh...new issues have cropped up. The head needs work. Looks like the last ones to play with this head did some stuff wrong.

Stay tuned for details and hopefully some pictures.

Now my own head is starting to hurt too...arrghh

 

Already is a Big Valve Head. Happens to be RMW's Jesus Head #2

I need to stress that this is not a problem with the product as it was delivered from Jan back in 2007 but is probably from an overheating incident along with poor quality work when the head was gone over in a previous rebuild.


In the last rebuild all of the exhaust valves and 2 intake valves were replaced. Something was not right with the intake valves supplied.

Take a look at the stem on the 2 intake valves on the left side of the image below.



Another small issue...heh... that was to be addressed in the last rebuild is shown below. Look in the spark plug hole. Yeah, that's not right.



The plan with the head going forward is:

1. Replace all intake valves.
2. Clean and re-blend all valve seats.
3. Repair cracks.
4. Replace all seals.
5. Clean everything and reassemble shimming to match the current OEM cam.

Why not put in a new hotter cam?

This rebuild is for reliability, not for all out HP/Torque.