MGA Forum

Just began engine rebuild (by qualified rebuilder). When ordering parts I discovered that the valve diameters are less than MGA specs. Investigating the engine block number (15A-N-H 166937), I found that the engine is a Nash-Metropolitan product that apparently was used in some MGAs and others. Are there who have made this same discovery and what modifications were required, what changes did you make. Chris.

Hello Chris, welcome to the forum.

To be precise, the Nash Metropolitan engine is a BMC product. Although externally the same, as you have discovered there are some internal differences. The MGA engine was built for a little more power, had provisions for a cable driven tachometer, etc.

see: http://mgaguru.com/mgtech/variants/vt103m.htm (as a matter of fact, I suggest all MGA owners bookmark the MGA Guru's Tech pages - http://www.mgaguru.com/mgtech/ Anything knowable about the MGA can be found there.

I assume the Metropolitan version of the engine can be modified to MGA specs (different camshaft, bigger valves, dual carbs, etc) but It might be easier to source either an MGA engine or early MGB engine. The 3-main bearing MGB 1800 engine can be a bolt-in transplant giving a bit more HP yet looking exactly the same as an MGA engine. Later MGB engines can also be fit but require a few more modifications/combinations of parts. All is well explained here: http://www.mgaguru.com/mgtech/power/pp201.htm

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Eric Russell ~ Mebane, NC
1961 MGA #61, 1̶9̶8̶1̶ ̶A̶l̶f̶a̶ ̶R̶o̶m̶e̶o̶ ̶G̶T̶V̶6̶, 1984 Alfa Romeo Spider, 1991 Honda ST1100

The only issue I see with rebuilding the engine is if the block does not have a provision for an oil filter. Some BMC applications of the 1500 engine had no oil filter. If that is an issue then look for another engine. If the block does have an oil filter then just rebuild the engine with the components you like. As far as the head goes, the machine shop can install bigger valves or just get a better head.

I like the idea of getting a 3 main 1800 MGB engine.

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CAUTION!!
Life's uncertain, eat dessert first
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Thanks, everyone, for your responses. Here is the situation, currently, as I see it. In fact, it looks as though the block is in the true fashion of an MG block. It does have an oil filter, it does have a tachometer drive right where it should be, and most importantly it is set up for and has two SU carbs. I don't think I would have bought the car if the motor did not look like the MG of my youth, externally. The difference is in the head. When measuring the valve diameters for re-ordering they were too small as compared to those offered by the parts house. Investigation led to the conclusion that it is a Nash-Metropolitan motor based on the engine number and includes the fact that it was painted green under all the grease and grime as reported by the machine shop. (This is characteristic of Metropolitan motors of the time.) But, the only difference seems to be in the head. That I've decided to have modified in the following way: The machine shop will open up valve seats to accommodate the standard MG valve and harden the metal. I am going to have put in the standard MG Cam. (The Metro cam and small valves yielded low power). Of course, new guides, springs, tappets and push rods. I think my only remaining concern might be the length of the valve stems.

Anything else that i should worry about? Thanks, Chris.

I would suspect low compression pistons, less cam, and a head that would have to be replaced rather than being modified.

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (375 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

Chris,
This is curious. I had a Metropolitan a great many years ago. All be it a beater of a car, heavily rusted and this was a throw away car to me at the time. This was a dismal performer, under powered with a 1200cc engine.

In any event what I find curious is the mechanical tachometer drive on the engine block. I am quite sure the Metropolitan never had a tachometer fitted , and also I thought only MGA & Riley (15G &15R) engines came fitted with this mechanical tachometer drive.

Not sure if this is pertinent, but I will ask, is the engine you have fitted with a timing chain tensioner?

B

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Life's most persistent and urgent question is, "What are you doing for others?"



Edited 1 time(s). Last edit at 2020-11-08 11:52 AM by riley1489.

Good thought, Bruce - maybe he has the Riley engine with 68 bhp, in which case I'd just leave it alone. Same spec as the earliest MGAs

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (375 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

Interesting, I had 2 1500 Magnette engines in my shop and both had the tach drive. The 3rd engine, from a Magnette, I had was a 1600 and obviously an MGA engine. It also had the tach drive. All had an oil filter. Of course no body knew the history of those engines.. Any one of those could easily be installed in a Metro or have been from an MGA.

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CAUTION!!
Life's uncertain, eat dessert first
Know the rules well so you can break them effectively. Dalai Lama

Journal index
https://www.mgexp.com/journal/Charles-Durning.2966/toc

I guess they were throwing things together from parts that were at hand. We'd like to think that they would have taken more care with consistency when assembling our precious little British motor cars. But economies of scale are always foremost. Thanks for the feedback. Chris

3 Bearing MGBs also had the tach drive.

Herb

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Yes of course, but the OP has a 1500, (1489) engine and only 2 applications of this ubiquitous engine had the mechanical tachometer drive.

B

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Life's most persistent and urgent question is, "What are you doing for others?"

I'm going to add a 'maybe' here. The early Mk 1 TVR Grantura came with several engines including a 1500 MGA which I believe had the tach drive. we are only talking about a handful. My Mk 3 Grantura had a 1622 with a serial number different from all of the other 1622s as well. I can't really tell much from the only pics I could find - can you? And there is bo saying that the engines shown are even the original engines, but pics of the early cars are hard to come by.

They also sold some 1588 cc MGA engines to TVR.

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (375 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

My '56 MGA 1500 came to me (in 2014) with a Nash Metro engine substituted for the original engine. Since it was running OK with no over-heating and no ominous noises, I just left it in there and enjoyed the car for the first few years, while I sorted brakes, suspension and electrical systems. Someone had installed twin SUs, so that helped, I guess. But, even with the stump-puller rear end that was in there (nom it wasn't the stock 4.3 dif.....it was MUCH lower than that!), performance was only pretty mild.

So, after finding and purchasing three 18G engine cores, I rebuilt one and installed it in the MGA. Not quite a straight bolt-in operation, but pretty close to one. With a strong (but stock) 18G installed it just ripped through the gears. I mean, it got through third and fourth just as quickly as it did second. But, I wanted to do some long distance touring with it, so I switched to a 3.9. Not as quick off the line, of course, but great for touring.

I retired the H4s in favor of a pair of HS4s from my parts stash and a buddy of mine rebuilt a 25D distributor for me. So, the engine runs real sweetly and pulls like a train. So, I'm quite pleased with it.

You could also use an emblem from an Austin 1800 from the 60s.

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (375 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

Hi Got this from somewhere But cant remember where.Have been told it is a nash Metropolatin Has the casting for a tachdrive but covered over with blanking plate.Also thinkit has a fuel pump casting too also covered over.Terry