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MG MGB Technical - Doubts on milage

I have an engine from a 68GT that I was promised had only done 27000 miles before being laid up for 20 years and knowing the history of the vehicle it looked genuine. I intended to swap it over for the one in my 71 roadster that was getting a bit tired and rattly.
I have stripped the replacement engine down and found one of the cam followers broken in half and after removing the cylinder head, the pistons are all stamped plus 30.
I would think it unlikely but would an engine have come out of the factory with +30 pistons fitted,or this engine has had a major rebuild in its short mileage life.
Trevor Harvey

It certainly would not be +30 thou rebore straight from the factory. Could it be a Gold Seal reconditioned engine? What is the engine number? You say a cam follower is broken in half. Do you mean one of the components that sits on top of the camshaft into which the push rod sits? These are accessible by removing the side plates on the engine. How the devil do you break one of those?
Mike Howlett

Gold Seal engines have a different prefix - 48G then a three digit number, as well as being painted gold (originally).
P Hunt

Mike, I doubted that it would have come from the factory with an over-bored engine but I have been assured that the car had only done the mileage quoted.
I think gold seal engines were always finished in a gold colour, this is in an original maroon colour.
The broken cam follower that sits on top of the camshaft is of the slotted type and when it was removed was in two pieces, broken across the slots and it looks as if it has been like it for some time.
I thought I had been very lucky, picking up an engine that had done so little mileage but it now looks very suspect.
Trev
Trevor Harvey

Trev. How did the previous owner document that the engine/vehicle had only done 27,000 miles? I inspected an early MGB for a fellow in California. It, too, was presented as an original, low mileage vehicle. The state of the engine, engine compartment, and rocker panels told a story of much higher mileage than the owner claimed. When I asked if the owner had repair receipts and a maintenance history on the car, he stated he did not. When I asked how he determined that the vehicle had only 37K miles on it, he looked at me like I was an idiot and pointed to the odometer which showed that figure on it.

Thus, it would be of interest to know how the previous owner documented his claim that the vehicle was low mileage, that the engine was low mileage, and that the engine was original to the car.

Les
Les Bengtson

Les, The previous owner bought the car new from a local dealer, it still had the dealers sticker on it.
It was laid up in 1990 to have some corrosion problems sorted. They never got done. So the car was left out to rot. A friend and I took the car apart for the spares. He wanted the axle and some other parts and I wanted the engine. We were assured that the mileage was genuine and looking at the bits we took off it looked to be true as very little wear was evident but I now find that the engine is the exception. I can only guess that there must have been a problem in its early life that needed a re bore.
There is no paperwork so I cannot check if this is original engine.
Trevor Harvey

It is possible that the engine suffered some sort of failure in its early life, + 30 suggests that bore grooving had taken place as a normal first overbore due to wear would be + 20.

Goldseals are never oversize - part of the process included sleeving back to standard bore, any goldseal with non standard pistons has been subsequently rebored.

Does the engine have an engine number?
Chris at Octarine Services

Trevor,

Given the circumstances under which you got the engine, it is what it is. It would be interesting to know the real history, but the bottom line is that you have to fix it if you intend to use it. For that, the history is irrelevant.

Charley
C R Huff

I have found a number stamped on the block alongside of the water pump that I think must be the engine number it is 12085 I cannot check this against the vehicle details as all the documentation was lost whilst it was laid up. It had no registration plates on when it was dismantled and only parts were kept that would be useful for spares. I am beginning to think that this had an engine swap at some time as I think as well as a re bore, the crank has been reground. I removed a big end and main bearing cap. Amongst other numbers were 010 U/S on both shells. Am I correct in thinking these are 10 thou under size?
Thanks all for your thoughts. Trev
Trevor Harvey

Trev,

I would agree that the crank has been turned.

Charley
C R Huff

Yes, 10 thou undersize. The engine number should be on an alloy plate riveted on a ledge just over the oil filter housing.

There should also be date "clocks" on the block under the oil filter and under the rocker shaft assy on the top of the head.
Chris at Octarine Services

Trev. Thank you for the information on how the mileage was obtained.

"The previous owner bought the car new from a local dealer, it still had the dealers sticker on it."

I do not know what it was like, back in the UK in 1968, but do know what it was like here in the US. MG was still making cars and BMC had just been taken over by BL. There was an active dealer in Orlando, where I was living at the time, and several independent mechanic's shops which catered to the sports car trade. The cars were something special back then, but only because we few appreciated the joys of driving a fine British sports car, not because they were not making them anymore and they were collector's items. Thus, we drove them--a lot. Somewhere between 10K and 20K miles each year. Our sports cars were our regular means of transportation as most of us could not afford to own one as a pleasure car and have another car to use as our daily drivers. I never met, during the period that MGs were in production, anyone who owned an MGB as a "week end driving" car, especially GTs. We drove them and drove them a lot. They were replaceable, if necessary.

So, the concept of a 1968 MGBGT, put away in 1990 (twenty two years old and at a rate of about 1K miles for each of those years) is interesting. And, the fact that this very low mileage car had to be put into storage because of corrosion damage is even more interesting. The mileage would indicate a garaged vehicle, owned by someone of means, used as a rarely driven show car. But, such a rarely driven show car would not be expected to suffer corrosion damage during its pampered life. (How do I know it was a rarely driven show car? By the fact that it still had the "dealer's decal" on the window. I got rid of the dealer's decal before I drove my new 79B off the dealer's showcase floor--you could not see out the window well with it in place.)

Might I suggest, sir, that, especially with the lack of supporting paperwork available to you, that the situation is not as it might have been represented to you? That the car might well have 127,000, or more, miles on it which would explain an engine rebuild.

You have, it would seem from this and your other thread, what may be a relatively low time rebuilt engine. But, the only way to actually determine that is to do a complete tear down inspection of the engine and measure the diameters of the main and rod journals of the crankshaft and the diameter of each cylinder bore. If everything is within tolerances, and all of the parts seem to be good (except the broken tappet/cam follower), I would hone the bores and install the pistons with new rings. I would replace the broken tappet and install new rod and main bearings along with a new set of thrust washers. Replace the timing chain if it seems loose (should be a fairly tight fit when trying to get the sprockets on the crankshaft and camshaft) and the timing chain tensioner if it shows significant marking from the chain. Use the Payen cylinder head gasket.

At that point, you will know what you have--a good, reliable engine for your car.

Les
Les Bengtson

MGB odometers (at least of that vintage) are well known for failure and unreliable for proof of mileage. I bought a 70 MGB with 12K on it when it was a year old and the odometer quit at 44K. The speedo still worked perfectly and was still in the car when I sold it in 1988. Replacement cast was out of sight. My MGB dealer back then estimated that half of the odometers in MGBs failed due to the plasic gears driving the odometer. I doubt the person selling the engine knows this about MGBs. Leaded gasoline engines of that vintage averaged a valve job about 40 to 45K, and an engine rebuild at about 75K intervals. At the first 75K, you could get by with knurling the pistons and not boring. Also, the crank usually made it with polishing until the second overhaul interval at about 150K. That information is based on reasonable maintenance and street use. It sounds like this engine is way over 27K, but if the work was done probably with little or no compromise to the internal engine balancing, it still should be a good engine.
Rick Penland

Chris, The number on the ali. plate is 18GG RWE H 5449 The date clock ( did not realise that is what it is) looks like 28 3 69 So it looks like a replacement engine as I believe it was a 68 vehicle.
Les, thanks for your input, what you say makes sense.
The local dealers sticker was a small chrome plate attached to the sill. The previous owner was wealthy enough to have two other vehicles at the same time as the MG and when stripping the car, the parts were in very good order, showing little sign of wear, so I was hopeful that the engine would be the same. Making me think that it might be a genuine low mileage car. Live and learn as they say. Trev
Trevor Harvey

This thread was discussed between 05/12/2009 and 07/12/2009

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