Sunday, January 10, 2016

Crankshaft Install - MkII

Well it's been almost a whole year since I installed this crankshaft into this engine block. Little did I know at the time that soon after, it would be coming right back out again as it wasn't at all well balanced with the flywheel, giving me a rather horrible driving experience.

Although it was a bitter disappointment at the time, I did learn a very valuable lesson when it comes to engine building; "Never assume it will be okay - If in doubt, check it out!!" So with my own advice ringing in my ears, I did just that in the previous post. After I picked up the newly balanced crank from the machine shop, there were doubts, so back it went to have them checked out!!

Arriving at the machine shop, I could see the crank had been test fitted in the block and that it rotated freely by hand, if felt very smooth in fact. I have to admit it was a massive relief to finally have some good news at long last. Also having professional advice that everything was okay was very reassuring.

Lugging the engine to the boot of my car, I couldn't wait to get it home and get started, but alas this was my lunch hour and that fun had to wait until after I had finished work. Once home though, it was lifted out of the car and plonked down on some cardboard and a bin bag where I could examine it properly.

I decided to remove the crank from the block again as I wanted to make sure that it was as clean as I could possibly get it. I also wanted to re-examine the main bearings as I knew one of them was a little more scratched than I was happy with. Once the crank was out, I gave it a thorough clean with some carb cleaner and made sure all the journals were spotless.

While doing that, I noticed the crank journal that was previously damaged, was now looking all shiny and perfect again. This seemed a bit strange, as the machine shop made no mentioned that they had re-polished it, so it's either somehow fixed itself or they fixed it and didn't tell me. Either way, I'm not particularly fussed, I'm just glad it's been done.

Ready to roll!

So with the crank sorted, my attention turned to the scratched bearing that I caused a few posts ago when I first tried to test fit the crank. While I could probably get away with using it, I didn't want to assume it would be okay as I had my doubts, and we all know the rule about doubts (See above!!). I didn't really want to pay for a full set of new bearing though, just to replace one of them.

Luckily for me, I very rarely throw anything away so of course I'd kept hold of all the main bearings from the previous attempt at this engine. If you remember, these bearings were nearly new, as the completed engine drove less that 5 miles before it was stripped apart again. While some of them had the odd scratch here and there, there was one that was near perfect and was an ideal substitute. Phew, problem solved and not a penny spent.

Before I refitted the bearings into the block, I made sure that both were clean and free from oil and debris. Once all the bearings were pressed in to place, they were coated in a layer of engine assembly lube.

Clean Block
Lubed Bearing

Now the crank was carefully lowered into place and once I was happy with the way it felt the copper thrust bearings were slid down into their gaps either side of the centre journal.

Copper thrust bearings
in place
Sitting pretty!

Onto the caps now, which also received the same cleaning and lubing process as the block, the first thing worth mentioning here is that I always find it easier to 'glue' the thrust bearings in place on the centre cap with lube, before it is put in place. The other thing is that the centre cap is the only one you could potentially put on the wrong way, so if there is any doubt, remember that it's always 'tab to tab'. So as long as the little locating tabs on the bearings are together, you're sorted.

Once the caps were tapped into place, the bolts were torqued down to 63 lbf ft (85 Nm) as prescribed in the Haynes manual. It's always a good practice to go in stages, so I started at 20 lbf ft checked everything felt okay. Then moved up to 40 lbf ft and checked again. Then finally up to the maximum 63 lbf ft with one final check.

The result: Well I have to say, it feels pretty darn good! So much so that it's even better than before I started and as results go, that's a good one! The first good one in a while in fact to it is more welcome that most other good results.

Before I can go ahead and start patting myself on the back though (if that were even possible!), I do need to check the crank end float. The last time I assembled this crank in this block with these thrust bearings it was within tolerance, so I'm pretty confident that will still be the case now.

To be sure though, it's always best to check, so out came my good old set of feeler gauges and after a few tests the end float was confirmed to still the same as last time at just over 0.05mm. This is just within the required limits given in the Haynes manual which are between 0.051mm to 0.076mm. As a bonus though, it's at the lower end of the limits, so in theory at least, it gives a good 0.02mm of potential wear before the upper limit is breached.

So now that the crank is finally installed and checked and looking good, I can at last give myself that well deserved pat on the back (I've tried and it is possible).

Next on the 'to do' list is to get the pistons installed...

**UPDATE****(10th Jan 2016)*************
Since publishing, a few fellow Miniacs (thanks guys, you know who you are) have pointed out two things:

1 - It's best to measure the crankshaft end float with a Dial Test Indicator rather than a feeler gauge. This I have done and 'low and behold' found it to be 0.02mm below the lower limit!!! Don't use those pesky feeler gauges for this guys!! - (Now Sorted Here)

2 - Use Plastigauge to measure the crank journal to bearing clearance, best to be sure rather than guess.- So I've ordered some plastiguage and started to remove the crank again so everything can be cleaned in readiness to start again and this time take the necessary measurements. (Now Sorted Here)

I really don't want to be stripping and rebuilding this engine a third time so it's better to be safe than sorry and catch things at this stage.

Maybe the pistons will have to wait!

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