MGB Answer to a question creates more new questions....

I solved the mystery of the odd metal piece that fell out of my bell housing last week. After putting the engine on a stand and dropping the pan (mainly just to inspect, no actual suspicion of problems but while its on the stand is a good time to check), the remnants of a rubber plug fell out of the rear engine plate. There was enough of it left to match up the impressions on the inside with the mystery metal piece and they were a perfect match, so it appears the metal disc was some sort of stiffener for this plug, and not a foreign object that got introduced. The next question is of course, why is there an extra 2 inch or so hole in the engine back plate? Nothing could be attached there because the oil pan is less than an inch forward of it, its useless for inspecting anything since the only thing exposed is the front side of the flywheel which has nothing on it (and with the oil pan in place it is effectively hidden). No engine backplate drawings in the exploded diagrams of the manual or catalogs show this rather large hole, although both Moss and Victoria British sell the plug for the hole they don't show. What is it for? The oil that came out of the engine before removing the pan was pretty clean (it had been run very little since the last change a decade or so earlier), but there was a lot of sludge buildup in the bottom of the pan. After removing the pan I flipped the engine over to get a good look at the overall inside condition. There was some very light surface corrosion on surfaces that did not have any close fitting adjacent parts, but what I could see of the cylinder walls looked very clean and shiny, as did the visible portions of the camshaft. Oil pump appears to be aluminum and very clean, strainer was perfectly clean and shiny as were all the bearing caps. I cleaned all the gunk off the bottom of the pan (nothing metallic just thick black goo) but need to clean up the mating surfaces so the new gasket will seal properly. What is the best way to get the old (apparently glued on with some sort of sealant) gasket residue off the bottom of the block - preferably without getting residue inside the engine. I have the engine on a stand with a full 360 degree rotating mount so I can position it at any angle to work on.

I found an answer!!

I stumbled across a site that had all the various engine back plates photographed, and they showed my plate with the extra mystery hole. And explained that it was normally closed with a metal backed rubber plug. Its purpose was to allow access to the torque converter bolts on cars with the automatic transmission. The explains both of the things which formerly made no sense to me...

(and on a disrelated note, thanks to our fantastic host here who showed me where to change editor settings, I have paragraph breaks now)

Engine (or at least the back plate) must be out of a Marina. I know of no production MGB automatics.

DrEntropy said:

Engine (or at least the back plate) must be out of a Marina. I know of no production MGB automatics.

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According to Wikipedia:

"In late 1967, sufficient changes were introduced for the factory to define a Mark II model for the 1968 model year.[SUP][14][/SUP] Changes included synchromesh on all four gears with revised ratios, an optional Borg-Warner automatic gearbox (except in the US), a new rear axle, and an alternator in place of the dynamo with a change to a negative earth system. To accommodate the new gearboxes there were significant changes to the sheet metal in the floorpan, and a new flat-topped transmission tunnel."

"except in the USA"

I sit corrected. :wink:

DrEntropy said:

"except in the USA"

I sit corrected. :wink:

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:thumbsup:

DrEntropy said:

"except in the USA"

I sit corrected. :wink:

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If Doc didn't know of their existence, they gotta be rarer than the Loch Ness Monster, Sasquatch and the residents of Area 51 combined!

My W.A.G. with this is: The engine in the '73 had at some point been replaced. Someone found a Marina unit which had an automagic gearbox, tossed that and bolted up the four cog standard one and all MGB ancillaries to stuff it into the B body.

Does that unit still have the serial number tag? That would go a long way to putting some answers on the table.

There was someone a while back who had leg problems and shifting was becoming a big problem, was looking for one of those slush boxes, I can't remember what site it was on. Good for a handicapped person, at least he could still enjoy his MGB. Never heard if he ever got one. PJ

I just heard on one being imported to my area...it is a GT. He is very proud of it and had it restored in the U.K.
Will see it next show here.

DrEntropy said:

My W.A.G. with this is: The engine in the '73 had at some point been replaced. Someone found a Marina unit which had an automagic gearbox, tossed that and bolted up the four cog standard one and all MGB ancillaries to stuff it into the B body.

Does that unit still have the serial number tag? That would go a long way to putting some answers on the table.

Click to expand...

My W.A.G. is that it is the original engine/drive train - There weren't enough Marina's and there were enough B's that if a swap were necessary it seems more reasonable that they would swap a B engine. Therefore my theory is that is was (most likely) owned by a serviceman who took delivery in Europe and had it shipped - or if not a serviceman that the car was not sold new in the USA.

I have NO IDEA of the history concerning the original engine/transmission combination. I am sure it is not the original drive train for the 1973 because I bought the 1973 as an empty shell (basically a body and wheels) to become a surrogate body for my rusted and not properly repaired 1970 B. I have reason to believe the drive train (or at least the engine) is NOT original to the 1970 because it is likely an 18V block (the plate riveted to the engine block is long gone but there is an 18V stamped directly into the casting on the flat spot where the plate should be) which is not correct for the 1970 it came out of. However it does also take the earlier style cork strips that go between the sump and end bearing caps (which I know because I bought both types and the later ones were much too large). If I remember it had the double valve springs so it may be an earlier head on an 18V block, and I suspect it has the single timing chain based on the thickness of the timing chain cover. The engine itself may be a collection of various years for all I know.

I expect having an engine back plate with that extra access hole is not entirely uncommon, based on the fact that both Moss and Victoria sell the replacement rubber plug for the hole in their MGB parts lineup (they just call it "gearbox mounting plate cover" with no clues as to why that hole is there to be covered in the 1st place).

Unfortunately this car is going to end up being a bit of a Frankenstein B at the finish because even though its a 1973 body, everything I have to go into it or on it (seats/dashboard/instruments/bumpers/grille/etc) are off the 1970 car and the engine is a bit of an unknown (the transmission may be the original 1970, I have no way to determine that). I have no actual 1973 parts other than the body and suspension itself, but since my intent is to have a car for driving more so than one for show, not having everything be year-correct is not a priority - it just all has to fit together, work properly and pass safety inspection. The 1970 and 1973 are pretty close copies of each other pretty much everywhere except the interior, although the 1970 has the split rear bumper and a slightly different front grille but they seem to be able to mount to the 1973 body reasonably well once I add 2 small holes in the 1973 for the rear bumper bracket bolts. I will have to figure out something to do about closing off the ports behind the dashboard in the 1973 body for the face level vents which do not exist on the 1970 dashboard.