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MG MGA - Gasoline odor

Hello,

I have recently had my 1960 MGA engine completely rebuilt (1600) by a local and very reputable outfit specialized in British autos. Since the rebuild, I have put no more than 100 miles on the car, and somehow think I am in for a nasty surprise.

I have used (burnt) approx. 1/2 pint of oil since rebuild, which I expected would be normal during the break-in period. However, I am detecting a slight gasoline odor in the oil. Oil does not appear to be thin or diluted, though not sure what grade was put in.

Although still under warranty, my ambition is to avoid putting mu car back in the garage and miss out on another 2-3 weeks of driving. Does anyone have a clue what may be causing this odor?

Thanks,

Johné
John Donovan

I think you should spend some time driving the car, each time for an hour or so (more is better) to heat it up enough to boil out the gas in the oil. As you get the engine broken in, you'll have a better idea of your situation. You may have a float or needle valve sticking open sometimes. But if it runs fine, I'd just drive it. You can always change the oil if the gas smell worries you. These cars smell like old cars, the float bowls vent to the outside, they leak fluids that get on the tailpipe and smell, they get musty inside after a rain, it's all part of the experience. Experts recommend not letting the cars idle with the choke out for too long, as the rich mixture is washing down the cylinder walls. This could be where the slight gas smell is coming from in your oil.

You may feel better asking your mechanic to check things out, and he'd probably like to see how his engine rebuild is doing. But from your post, I wouldn't think anything is out of line.
Tom

Hi John. A couple of things come to mind. Excessive use of the choke would cause raw gasoline to run into the intake manifold, and then into the cylinders. It would then leak past the piston rings and get into the motor oil. Much the same thing would happen if the carburettors were set too rich. Check your exhaust pipe. Run a finger inside the end of the muffler. If your finger comes out black, with fluffy soot, then your carbs are likely set way too rich. You should then have the carbs re adjusted, that is leaned out, by raising the jets on both carburettors. As for break in oil, you want non synthetic oil, and very inexpensive 20 W 50 wt oil. You want "cheap" oil because it doesnt have lots of anti wear additives! You want the engine to "wear in", and anti wear additives inhibit the process, as would synthetic oil! You also want to keep the engine well under redline, and you want to vary the engine speed constantly. It is beneficial to accelerate, and then back off the gas. This sucks oil up into the cylinders, and helps lubricate them, and carry away metal particles that are wearing off from the piston rings, as they "bed in" As the engine gradually breaks in, you can use progressively higher revs, and for longer periods. After 500 miles or so, change the oil, and refill with more cheap oil. Run the engine for another 500 miles, after which your engine "should" be completely broken in. Once the engine is fully run in, I would recommend switching over to a high quality synthetic oil, grade 20 W 50. Hope this helps! GLenn PS, I would also recommmend that synthetic motor oil be used in the transmission. 10 W 30 is fine.
Glenn

Glenn,
Do you have any synchronization problems using synthetic motor oil in your gearbox? I had always read that synthetic motor oil was too slick for the syncros to work properly. I run Redline MT90 in my gearbox, and it is synthetic, but it is designed for manual gearboxes, and has friction modifiers to allow the synchros to work properly.

Jeff
Jeff Schultz

Tom and Glenn,

Thanks for your input. Will follow advice and hope for the best. Loking forward to putting my first 500 on her!!!

Cheers,

John.
John Donovan

Hi Jeff. I find no difference in synchro function when using synthetic oil as opposed to regular oil. However, on disassembly, the tranny running synthetic oil had significantly less wear on the layshaft, even though it had been run many more miles than the gearbox that was filled with regular 30 wt oil. cheers! GLenn
Glenn

This thread was discussed on 16/08/2005

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