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MG MGB Technical - What's the right temperature?

I am looking into buying a 1966 MGB GT, but I have a few questions first. The car seems to run a little hot to me. It runs at the far side of the quage. The person I would be buying it from told me that this is a normal thing, that these cars are a hot running car. Is this true? The second question is this: the car has a somewhat rough idle, and at 45mph in 4th gear there is a lurching sensation caused by the engine revs. It feels like I am pressing the accelerator and then letting of quickly. He says that this is normal too, that this is because "the car is telling you that it wants to go, to give it some gas" because these cars like to be driven faster. Is this true? He uses unleaded gasoline so I figure that the valve seats have been changed. (I've been told that needs to be done to this year of MGB). But I have not asked him about that yet. He has done a bit of engine work to it and when he bought it he was told that the engine had been rebuilt. Does anything that he has told me regarding this hold water? Any help would be greatly appreciated. Thanks Chris
Chris

Surging is NOT normal. These cars should drive very smoothly at any speed. If your car is telling you anything by surging, it's "fix me!"

A 1966 MGB GT should have a dual guage showing oil pressure and engine temperature. If it has the correct gauge you should be able to rear the exact temperature of the engine in degrees F. However, don't rely on an old gauge to be accurate! Assuming it is, my '65B typically runs best at around 190F.
Steve Simmons

What could be causing the surging? Is it something easily fixed? It does have the dual guage. When I was driving it did run at or just above 190F.
Chris

Likely a carb issue. Check the oil in the dashpots, fill to 1/4" from top. If that doesn't do it, pull them open and clean / inspect the jets. May as well renew the air filters while they're out as well.
Steve Simmons

I would be concerned about the rough idle, an MG with SUs will not idle as smooth as a modern car, but it shouldn't so rough it rattles your teeth. I would want to run a compression check before making a decision about a purchase unless the price of the car matches it's condition. If it runs at or around 190 degrees it isn't overheating. MG's up to around 75 didn't have hardened valve seats. The exhaust valve seats will eventually wear and the valve moves up in the head. They will run many miles before this happens. There is no way to tell if the seats have been changed without doing some disassembly. On the surging, if the carbs are in need of adjustment it may be minor but you need to be sure compression is good before dealing with the carbs. Bad compression = lots of work and expense to correct. Surging isn't normal, it indicates a problem. FWIW, Clifton
Clifton Gordon

Surging, combined with a rough idle, could be misfiring. Is the tach jumping about? If so it is an ignition LT problem, if not an HT or fuel problem. It should be running at about mid-way on the gauge. Mechanical gauges usually fail low, not high, implying that the temps probably *is* high. This can be caused by retarded or overadvanced ignition as well as many problems in the cooling system, or more serious engine problems. Having said that it *is* normal for them to read towards the high side of the gauge in high ambients and when under a heavy load like slogging up a steep hill in a low gear, and unless you are actually loosing coolant or steaming it isn't overheating.
Paul Hunt

Also...is it really overheating. Have garage aim an infrared temp gun at the place on the head where the temp sender is....passenger side, side of engine at front just below the thermostat housing...and see what real temp is. These temp guns are expensive for us hobbyists but most garages have one. Good insurance for a few bucks. The temp gauges can easily be off. Mine is off by 15-20 degrees.

Check that baby out carefully. This guy has his head in his nether regions if he is telling you the surge means it wants to go. Sounds like a bill of goods from someone who wants to sell something and doesn't know anything about the car.

JTB
John Bamford

I'd be very wary about buying this car. This guy is definitely hiding problems by filling your head with a bunch of BS about always running hot....normal surge...wants to be run hard...what else is wrong that you haven't found yet? or that he's glossed over. Find a knowledgeable person to inspect the car for you (local MG or British car club is a good source) and also suggest an approriate price. Most guys I know are very willing to check out a car and offer lots of unsolicited advice.
R. L Carleen

Mechanics are relatively cheap to repair on a B. The bodywork is not. If the body is in good shape I wouldn't be overly worried about the mechanics PROVIDED their condition is reflected in the price. Repairing the body can easily cost more than the car. A complete new engine can be as little as $1000 if you are willing to fit it yourself.

Iain
I D Cameron

This thread was discussed between 06/11/2004 and 09/11/2004

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