Sunday, May 10, 2015

Setting The Idler End Float

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

It seems like the engine build has been dragging on for ages with little progress recently as I've spent ages rebuilding the gearbox, but before I can race ahead and attach the gearbox to the engine, I need to make sure the end float on the idler gear is correct. I'm aiming for between 3-4 thou. The problem is though when I checked it, it was so tight it was locking the idler gear in place. Hmmmm, what to do...

What to do indeed... in this post I could document the catalogue of disasters and unnecessary work I had to endure as a result of being impatient and lacking in knowledge...  so I will!

When I bought the engine, it came with a selection of gaskets, one of which was for the clutch transfer housing. Little did I know though that the thickness, compressibility and general all round quality of this gasket is fairly critical when it comes to setting the idler end float. If I have known this at the time, I would have chucked the gasket in the bin and bought a decent quality one and avoided the following fiasco...

Using the gasket I had at my disposal, I mounted it on the transfer housing and bolted it to the gearbox with the idler gear in place, as you should in order to check the idler end float. Once the bolts in the housing were torqued up, the idler gear was nipped so tight it wouldn't even move, let alone have any clearance! Now even I know that's not good!

Rather than suspect that the gasket was the issue, I looked to solving the problem by altering the shims. I had a few shims from other gearboxes and tried the smallest set I had, unfortunately it was still too tight though. As I didn't want to stump up the expense of a new set of thinner shims, I set about adapting the ones I had. I mean, they are £20, each!! I'm not paying that!

I had the idea that maybe I could shave off a few thou if I rubbed the surface of the shim on some 'wet and dry' emery paper on a flat surface and hopefully take them down to the size I need.

Starting with the smallest shims I had, which were 132 thou, I set to work with some 800 grit and slowly and patiently worked the shim on the paper. Through a process of rubbing and measuring and rubbing and measuring and... you get the picture, I did managed to get them to the size I needed. So chuffed was I at my achievement, I even made a video...

All was going well, I felt I'd beaten the system by adapting the shims I had, rather than buying new ones and I have to say that I was starting to feel a little smug about things. At this point, everything could have been bolted up and it probably would have been fine, however one last test fit later and I managed to somehow tear the gasket!! Although this was annoying at the time, it was probably for the best.

How could this be for the best? Well it forced me to go out to Mini Spares and get a 'proper' (for want of a better word) gasket. Compared to the old gasket, the new one just seemed superior in every way, it felt sturdier, the holes lined up and it wasn't prone to tearing.

New gasket.
When I test fitted the new gasket though I found to my horror, the idler end float was now a mile out! How could this be? I measured the thickness of the gaskets and visually checked the them side by side and though they were a little different, it couldn't account for the large change on the end float! It had gone from a very respectable 3 thou to about 12 thou!

Gaskets were both about 30 thou.

The only thing it could be was the fact that the gray gasket must be getting crushed down more as the housing is being torqued. It did seem to be a softer material, so I guess it was possible. What to do now though. I had gone through all that of effort making two of the shims smaller and now they were useless!! There's a few hours I won't get back! Thankfully, I still had to shims left that hadn't been too messed about with and by pure luck, when I tested them with the new gasket, these shims gave me the 3 to 4 thou clearance I needed. Phew, we were golden once more!

Back to the magic 3-4 thou.

This was a strange exercise for me really with both highs and lows, I felt pretty chuffed with myself for re-sizing the shims, but it was all for nothing when I tore the gasket and was forced to but a new one. Thankfully though the replacement was a much better quality item and for the sake of the few pounds it cost me, I'm glad I have the peace of mind that it's up to the job.

The biggest thing I'll take from this whole experience though is that I spent a long time solving a problem that didn't need solving as it was of my own making. Next time, and there will be a next time as I have got the 'engine building' bug now, I'll know just how critical having the proper gasket can be.

Thanks to recent shenanigans, it's something I'll never forget!

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