Miglia Engine Build

16 05 2013

Sometimes I wish I could afford to pay someone else to do me a race engine but if I did it would be twice as long before we are out on track and it’s already looking like a 2 year build process… Besides, where is the fun in someone else doing it eh..?

I suppose I’m a bit old school when it comes to racing having been brought up holding the spanners for my dad whilst he fixed his race cars; picking up knowledge along the way. It’s an outdated idea now but everyone used to build their own cars after reading ‘Cars & Car Conversions’ magazine.  When I built my Mini7 back in 1997 it was mainly because of reading about Bill Sollis’ adventures in CCC. He made me and countless others believe that we could give it a shot, although it’s much harder than it looks! I think I’m part of  a dying breed tackling everything myself, but it’s the only way it is going to happen I suppose.

Anyway, after Andy Packer’s Autograss engine had left the workshop I set about building my Miglia engine.  All the rings, bearings, gaskets, oil pump etc were ready so the dry build commenced. It was a reasonably straightforward rebuild on the face of it. Firstly the block had to be made absolutely spotless. This process was helped no end by it having allen plug oilway caps which could be removed allowing me to access and see the oil galleries. I clean and airline these countless times when getting the block ready, it really does get a bit OCD. The cam bearings were in perfect nick so were reused, and the bore was spot on needing only a short blast on the glaze buster. A coat of ‘Thrasher black’ paint and some new core plugs and it was ready to go on the engine stand.

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As mentioned in an earlier post there are countless checks involved in an engine build.  The crank journal/bearing tolerance is a very important one often overlooked by some engine builders. A journal will have a top and bottom limit in order to work with a given bearing size. Sometimes if a crank grind hasn’t been done properly the size can be different on one side of a journal to the other, let alone what the others are like! All this was checked on my Selby EN40B steel crank beforehand. With copious amounts of oil the crank was lowered into the new bearings in the upside down block. Every step of the way I give the crank a little spin to see if anything goes tight, that way you only have to go back one step to find a problem. The thrust bearings and main bearing caps went in next, torqued up in stages (again checking for tightness)  and  then the endfloat was checked. I had to play around a bit with different thrusts to get the required tolerance so always an important check.

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Then it was time to check the ring gaps which more or less were very close needing the minimum of modification. This job can take a while sometimes but can be greatly reduced by buying quality rings and having a perfect bore…

Having then fitted the rings to the ‘Richard Longman’ forged Omega pistons (again plenty of oil) I carefully tapped them in to the bore using my ring compressor making sure the all important crank journals were protected from the con rods. Once they were all in I torqued the big ends up in stages, checking for tightness all the way. After spinning it over a few times and double checking everything I was happy to crack on with the timing gear.

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The SH Engineering timing belt kit is a work of art, and far better designed than anything previously available. As well as being beautifully made, it’s the only belt drive kit I’ve seen with a tensioner. Also it uses the oil seals used as standard on mini clutch and timing cover housings making it much easier to source spares than those huge ones used on other kits. On mine at least there are no dots drilled on the pulleys so you have to time it up the old fashioned way. After a few attempts I got it dead on the 100 degrees I was aiming for. Some like to set the cams slightly differently for low down or top end power but I thought I’d set it dead on 100 until I know how the engine behaves a bit better.

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Next stage is to put it on the gearbox and build up the flywheel assembly.

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