An M.G. Locost Build
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May 4, 2013
Tuning

When we first started the engine in the Locost, it didn't run all that well. It coughed, sputtered, misfired, surged at idle, and threatened to quit if you revved it up. We adjusted the carbs as best we could and at least got it running on all 4 cylinders, but we ended up with the mixture almost full rich. The car started every time, and ran reasonably well when it was cold, but it would start to balk as soon as it warmed up. You could tell it wasn't happy. Which was kind of a mystery because it ran fine in the donor, and we didn't change a thing.

Except for the one thing we changed. When we first got the donor running, we didn't know what all the hoses connected to the engine were for, so we just blocked them off or removed them altogether. The engine ran fine, so obviously the hoses were unnecessary, probably just some kind of attempt to keep unburnt hydrocarbons out of the upper atmosphere. Later on we learned that at least one of the hoses was supposed to connect the crankcase to the intake manifold, thereby creating a slight vacuum in the crankcase, which would draw oil mist through the engine.

  Giant vacuum hose
click to enlarge

That sounded like something we wanted, so when we installed the engine in the Locost we ran a giant hose from the giant tube leading off the intake manifold to the giant tube on the side of the crankcase. This should've created a giant vacuum inside the crankcase. What it actually created was a giant vacuum leak. We don't know how or why of course, because vacuums are like electricity. You can't see them, so it's hard to understand how they work and what they do.

But we do know that a vacuum leak will cause an engine to idle badly, so we took the hose off, plugged it with a giant bolt, and the car immediately settled into a smooth idle. It sounded great when you revved it up, too, much more refined, even quieter. Unfortunately the tube that leads out of the crankcase now vents to the open air, where it's free to wreak all sorts of havoc, not only to the environment but without that oil mist, who knows how many bad things could happen to our engine. So maybe we still need the connection, but with some kind of restrictor. We'll play around with that and see what works.

Throttle cable should be good for several years  
click to enlarge

We got our new throttle cable installed. It really is a nice design, and it should last a lot longer than the stock MGB cable, which only made it 40 years. And actually still worked when we removed it from the donor, but of course the sheathing was worn, and bent slightly near the pedal, so I'm sure it was about to go. I doubt it would've made it another ten years. Also, our new cable is adjustable, and we got to adjust it. The throttle now starts to open as soon as you hit the gas pedal, and opens all the way when the pedal goes to the floor.

Of course the pedal doesn't go to the floor, because first of all it isn't headed that way, it's headed toward the firewall, and second of all the cable reaches its limit long before the pedal even gets close to the firewall. So that means we're probably going to need some kind of pedal stop so we don't stretch the life out of our new throttle cable. The MGB had a pedal stop, but it was only about an inch tall and we're about 3" from the firewall, so we can't use it. We think we should be able to make something similar, but you never know. We'll have to see.

  Glove box now part of the dashboard
click to enlarge

We finally have a handle on our glove box. Our German glove box latch arrived the other day and it works just like we wanted. And better than we hoped. Twist the knob and it pops open, push the door and it clicks closed. We also got the glove box mounted to the dash, and it's a nice fit all around but two things: 1) The glove box flange and/or scuttle hoop need to be modified, since they both want to occupy the same space in the upper right corner of the dash, and 2) If the glove box ends up being much deeper than the flange, and it almost has to, it's going to interfere with the offside defroster vent.

So we're looking at materials for making the box portion of the glove box, something nice and light, and although plastic or cardboard are often used, we wouldn't be opposed to something a little more flexible, like for instance leather. We could extend the base of flange so the glove box floor was rigid, and we could still stuff all we want in there so long as it fits around the contours of the defroster vent, and any other tubes, pipes, or wiring harness trunk lines that happen to be passing through the area.

We could also make the glove box out of fiberglass. That way we could mold in all the contours we need. But of course something like that would take forever, and we've already spent way too much time on this thing, so probably not. Right now we're happy that the glove box door opens and closes. If we can actually stuff things inside and not have them fall out the back, bonus. This isn't exactly a required component, you know. In case we didn't mention it before, very few Locosts have glove boxes.

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Comments:  
posted May 5, 2013 at 06:02:55  
Hi Nick,
regarding PCV and crank case oil mist, I do recall that my dad's old car (based off of 1960's Hillman Hunter) had the pipe connected to the intake filter housing, which is/was before the Carb, and therefore no risk of creating a vacuum leak. You can probably pass it through a catch can as well.

Masoud