An M.G. Locost Build
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August 11, 2016
Back to Welding

Work has begun on restoring the old M.G. Locost back to its former glory, and possibly beyond. The car is parked for the duration in the favored position in the garage, where it's resting comfortably on jack stands. The cylinder head and oil pan have been removed, along with the pistons and bearings. Almost everything came apart much easier than we anticipated, and will possibly go back together just as easily, so long as we can find everything. We do need to buy a new radiator hose, although we don't need to go into any details about that.

  Future Locost hood, mint in package
click to enlarge

Removing parts from the car has provided enough clearance for us to bend our new aluminum hood to shape, which we'll do as soon as we cut it out of the big sheet of aluminum we ordered, which wasn't exactly what we ordered but more about that later. To meet our primary goal of fabricating a hood that won't fly off the car quite as frequently as the old one did, we ordered two new latches from McMaster-Carr, for the front of the hood. The old latches worked okay, except when they didn't, but they were small and cheap and apparently didn't lock all that securely.

Giant latches add more road-hugging weight  
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The new latches are spring loaded, with a positive catch instead of a simple over-center lock, which can wiggle loose as we've amply demonstrated. The new latches are possibly not as handsome as the old ones, but we'll get over it. We once helped remove the bonnet from a Caterham, and noticed the front latches on that car were similarly ungainly, and similarly unlikely to unlatch on their own. Obviously Caterham don't want bonnets flying off their customer cars, and have figured out a way to prevent it. Their latches were mostly hidden behind the wings, as ours will be.

When dismantling the engine we were excited to find the old pistons and rod bearings in really bad shape. The oil scraper rings had lost all of their tension, the gaps measuring barely the thickness of a fingernail, compared to the 5/16" gaps on the new rings. Similarly, the rod bearings were completely shot, all scratched up and measuring a full two thousandths thinner than the new ones. It's possible we left them in the engine too long, but fortunately the crankshaft journals are still okay, as best we can measure with our crude dial caliper.

  Rod bearing in last stage before total failure
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Our main reason for not doing a full rebuild on the engine was to avoid the need for any time-consuming and possibly needless machine work. This didn't turn out exactly as planned. The wrist pins in later M.G. engines are a press fit, and by 'press' we don't mean with your hand. Inserting press-fit wrist pins has been done before in a garage with simple hand tools, but not by us, and not without a certain percentage of broken pistons. So our rods and pistons are currently down at Novato Auto Machine, and will hopefully be ready by the end of the week.

Bent frame tubes gone  
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Meanwhile we have managed to repair the frame damage that we incurred when the car hit a concrete median strip up in Sacramento last June, and hopefully this will be the last time anyone around here mentions a concrete median strip. The repaired tubes have been sanded and primered, and a fresh coat of Rustoleum Hunter Green paint will have the damaged area looking good as new. As a bonus, during the repairs we found out that our welding skills haven't deteriorated nearly as badly as we thought they would.

  Sleeves added for extra strength and weight
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The first step in the repair was actually the most fun—cutting away the crushed tubes. Fitting new tubes was almost as fun, except for getting the lengths and angles right. We added 3" sleeves inside each joint, allowing us to weld the joints without risk of blowing holes in the tubes, but welding on the car was still difficult because a) we couldn't flip the frame around like we used to, and b) it was kind of dark in the favored position in the garage. But we did okay on the top and sides, and the bottoms are almost impossible to photograph anyway,

New tubes sleeved and ready for welding  
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Next up on the agenda is installing new pistons and bearings in the engine. Before we can do this we have to hone the cylinders so the new rings will have a chance to break in. We've never actually honed anything before, but there's always a first time and it doesn't look that hard. A search through the online honing community brings up the usual contradictory advice, everything from it's hardly even necessary, to don't do this at home or your engine will explode and you will die. We'll probably take a position on this somewhere in the middle.

Before the engine is back together we still have to bend up the new hood. We're not looking forward to it, due to a slight misstep on the part of our cut-rate metal supplier. We'd originally planned to make the new hood out of .040" aluminum, which would be lighter, more flexible, and easier to bend than our old .050 hood. But our metal supplier had a different idea and sent us another sheet of .050. Since we don't have the time to correct this, the new hood will be just as heavy as the old one, and the creased edges along the bottom will be just as badly formed.

  You can see all the way to the crankshaft
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But we're not going to worry about that now. However this turns out, we're encouraged by the progress so far. The frame is much stronger now, if a little heavier, and the engine has turned out to be not beyond repair. Our expectations are higher than ever, probably not a good thing but at least it keeps us motivated. We're more than curious what kind of performance we'll see with the new pistons, and how much oil the new engine uses, or how little. The new hood, even with its thick aluminum, should still look better than the old one, not a terribly high standard to meet.

You might think that all of this Locost work would remind us of our old build days, and if so you'd be partly correct. Welding is always fun, and now that everything is off the car we have a chance to clean all of the parts that were never easily accessible, which is basically every part forward of the engine. That said, there's still a major difference between this work and the work we did during the original build. Back then we thought building a Locost was about the most fun you could have with a car. Now that we've driven it, we know better.

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