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MG MGA - Flywheel for 1800 conversion

I am mating a 18V engine to a 1500 transmission. In doing so I need a new flywheel. I understand the flywheel I need is off of the 18GB engine. How do I identify which is the correct flywheel? What is the diameter and how many teeth on the ring gear. Does anyone have a correct flywheel for this application and want to part with it?

V. H. Brown

It's the same diameter as your 1500 flywheel but lighter and was used with the non-synchro transmission with the MGA type "crash" starter.
D Sjostrom

OK, let me state my question a little more clearly. I know that the flywheel and ring gear need to match the transmission in the car.

I have not dissasembled the car as there isn't room to store it in the shop with the engine out while the new 1800 engine is being built. The new engine can not be built without a flywheel: it needs to be balanced with the other reciprocating parts.

A potential flywheel vendor wants to know the diameter of the flywheel and how many teeth are on the ring gear so that we can be sure it is the correct one.

So my question is how does one identify the correct flywheel without removing the one in the car?
V. H. Brown

VH,
I have my 1500 out of the car. On my conversion I used a 1500 low starter backing plate machined to take the 18GB rear main seal. This is how I know that the 18GB flywheel is the same diameter and number of gear teeth are the same. If they weren't, the starter wouldn't mesh up.

So...The correct ring gear has 120 teeth and measures 12 inches across the major diameter of the gear itself.
BOl,
Doug
D Sjostrom

The required flywheel is indeed from the 1800-GB engine, model years 1965-1967. Easy to tell on the engine, amall diameter flywheel, and no mechanical tach drive on the 5-main bearing block.

Off the engine, the small flywheel has 120 teeth on the ring gear. The 5-main flywheel has smaller center bore to fit the 5-main crankshaft, and two dowel pin holes in addition to six bolt holes.
Barney Gaylord

Thanks very much; the hunt begins.
V. H. Brown

You will also need to find afront gearbox cover & clutch fork for the 1500 MGA box if you are using the diaphragm clutch as the spring type clutch is different height. You can also use a Morris Marina 1800 clutch flywheel - this is only 3/16 thinner than the MGB 18GB flywheel & will work ok.
Garth.
Garth Bagnall

Thanks for your help. Just by chance, I found, at the machine shop doing the rebuild, a flywheel that fits the 18V crank and is smaller in diameter and thicker than the 18V flywheel (there is no ring gear to count the teeth). The machinist didn’t know anything about the flywheel other than it was for an MGB. We are guessing that the flywheel is off an 18GB. Now I see why, if the clutch pressure plate for the 1800 is thicker than the MGA, that there could be a clearance problem inside the bell housing.

I have an MGB 3 syncro gearbox as a spare. At the very least I can use the clutch fork. I am not sure I understand the term “front gearbox cover”. Do you mean the part of the gearbox forward of the joint with the aft part of the gearbox. I assume that this will bolt up to my MGA 1500 gearbox. Is this all correct?

I can’t bolt the whole MGB 3 syncro gearbox into the car as I don’t want to modify the rear transmission mount. The car is an Elva Courier not an MGA and modifying the frame would be a huge job as it is bonded to the body.

Thanks again for your help.
V. H. Brown

The MGB pressure plate is thinner than the MGA part, but may be slightly wider at the shoulders where it could just touch the bellhousing of the 1600 gearbox.

The early B flywheels G, GA, or GB, have the same dimensions as A flywheel, except for the pilot diammater and bolt pattern for the GB. The MGA MK-II and early MGB flywheels are 8 pounds lighter than the MGA 500/1600 flywheel.

Gearbox front cover is the plate in front that caries the front seal and the clutch release arm pivot bolt. The B part puts the pivot point farther forward to match the thinner B prewssure plate.

You can install the MGA 1600 gearbox rear housing on the early B gearbox to have the A type rear mount. This does not work with the 1500 type rear housing.
Barney Gaylord

VH,
I have the bolt-on MGB clutch fork transmission front cover you need. I was going to use my 1500 tranny with the five main 1800 exactly as you're doing until I decided to go with a Sierra five speed conversion. Let me know if you're interested.
BOl,
Doug
D Sjostrom

Doug,
I am definitely interested. Please e-mail me.

Regards,
Sandy Brown
V. H. Brown

This thread was discussed between 15/06/2006 and 16/06/2006

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