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MG MGA - Removing the Power Unit...

Yeah. The MGA Workshop Manual Section A.18. I am going to replace the power unit with an original MGA 1500 block that was rebuilt in October. This is a project I have been planning for many, many years to restore this car to as close to original as I can. The engine replacement is the penultimate project. The final project will be waxing it again!

I am confident I can do the work. But I need some guidance. My initial questions to help guide me on this...

So, why do I need to mark the propeller shaft if there is going to be a different motor? And where is the rear axle drive flange?

How important is marking the hand brake lever instruction? I am slightly bewildered by all the references to the hand brake system to remove the engine...but oh well.

What are all these nuts, bolts, and springs and the 'reinforcement bracket' inside the propeller shaft tunnel? I cannot locate them in any diagrams from Moss' catalog to reference their location.

Do I really need to remove the seats and floorboards??

As you can see...I am getting ready. But, as Richard Pryor once said, I'm not ready, ready.

Simi Valley, CA

Stephen Lofaro

Stephen, you do not need to mark the propshaft flanges at the joint. The only orientation issue with U-joints is that they both be installed correctly with respect to each other on the shaft, ie it is a prop shaft construction issue.
I don't believe you need to remove the shaft to remove the engine and gearbox together, or separately, so no need to touch the handbrake assy. or the tunnel braces.
The rear axle drive flange is at the differential.
Seats and floorboards can stay in place. You have to remove the transmission cover cap around the gearbox.
Make sure you can tilt your motor and gearbox on your lift.
Art Pearse

Hello Art,

I can remove the transmission and engine together. Do you recommend the Oberg tilt lift? I have a local friend that has one who would lend it to me and my next door neighbor has offered his engine hoist as well. So those issues seem resolved and in place for that moment in time.

I would be removing and replacing the transmission outside the car on the new motor?

I will plan on replacing the clutch at this time and check if I have a 10 spline or 23 spline. My friend who works on MG's locally has the clutch alignment tool.

As an aside, I removed the brackets for the pedals and master cylinder from the firewall shelf and cleaned them and primed them...they look great. Ready for paint when I finish the engine compartment. All good things and exciting when you love the old cars.

Thanks for sharing.

Simi Valley

Stephen Lofaro

Not only do you NOT need to remove seats, carpet, floor and tunnel, but you don't need to remove the gearbox either. I always pull the engine separately, whether the gearbox is coming out or not. And if you pull the engine by itself you don't need the tilt mechanism.

There are three different type propshafts. The 1500 has a one-piece propshaft with both U-joint cradles welded to the main tube, bolt flange at the rear and sliding spine coupling in front. That one cannot be installed wrong (but you could install the wrong propshaft, as there are two different splines an lengths).

The 1600 has a two piece propshaft with a sliding spline just aft of the front U-joint and bolt flanges on both ends. As long as you don't disassemble the propshaft it cannot be installed wrong. But if you disassemble the sliding spline joint you have to pay attention to putting it back together in the proper orientation with the U-joints parallel.

As long as you don't disassemble the tunnel you don't have to fiddle with the hand brake either. The tunnel reinforcement brackets look like this:
Barney Gaylord

I agree with Barney except that I do use a tilt to make getting the engine in and out easier.

You can speed up the process of getting things out quite a bit by removing the carbs as a complete assembly - use a 1/4 drive ratchet and socket to remove the four nuts holding the carb inlet manifold to the head and just prop it on top of the heater shelf with all the heat shield, spacers, cables and fuel pipes attached if long enough, otherwise just release the fuel pipe at the bulkhead. This saves all the fiddly stuff of cables and bolts, spacers, springs being dismantled and reassembled. To get the overflow pipes out you may have to remove the float bowl banjo bolts and manipulate them out individually, just put the banjo bolts back in place to hold the float covers and their gaskets in place and do the reverse when reinstalling the carbs. Depending on what you had as an engine before you may need to change the carb needles to suit your new motor and get the mixture correct.

When reinstalling an engine I use a 4 foot wrecking bar as a lever to push the engine back into the gearbox. Place the lower end of the bar into the chassis by the steering rack hole and apply leverage at the engine mount and it will slide back as soon as you have the input splines lined up. It doesn't take much pressure but saves a lot of wiggling to get things moving. You need to get the backplate parallel to the gearbox bell housing to make this easy, and this is where the tilter helps a lot.

Block or jack the gearbox from underneath so it rises up to the top of the tunnel too - this gives you clearance for the crank pulley over the steering rack without bending your timing markers on the chain cover. it also keeps the gearbox in a fixed position so you have one variable less working against you.

dominic clancy

I do not recommend the Oberg tilt lift. I used one once to remove an engine. It requires a half inch ratchet on the Oberg's drive mechanism. While using it, I left the ratchet in the drive mechanism. The engine suddenly shifted and jerked the tilt lift, tossing the half inch ratchet into my windshield. Cracked windshield. Of course, if you're not as dumb as me, you can get by with it. I much prefer the screw type tilt lift. Infinitely adjustable, less grunt required. And more forgiving to dumb asses.

JM Morris

I too have pulled the engine and trans seperate both in my A and when we had a B. I remember leaving the hand crank/front pulley nut and possibly the front pulley off too just for the extra clearance over the rack on the A
gary starr

I have always removed the engine and tranny as a unit. It's the method recommended in the shop manual. That said, I am curious to know how you avoid stressing the tranny input shaft and get the splines aligned when installing the motor? Do you somehow support the transmission to keep it level?
G T Foster


I support the gearbox on a trolley jack, and the engine is on the crane, so there is never any stress or excess weight on the input shaft. It is much faster and easier to remove the engine on its own than the two together, even though the book says to do them as a unit
dominic clancy

I followed the shop manual the first time I took it out too GT.I put the engine back in before the body went on. Seemed to me that once the car was painted it was just asking for trouble. So when engine problems resurfaced I took everything I could have off including the head before lifting out. Did the same on the install and used a floor jack under the trans
gary starr

I'm identical to Dominic. Also, despite what the manual says, I also don't remove the bonnet/hood.

Steve Gyles

I leave the bonnet in place too but remove the grille because the pivot of the crane buts against it otherwise
dominic clancy

At least for me, pulling just the engine is much less hassle and much quicker. I can pull the gearbox out later if needed quickly as well. Never needed a tilt and never had problems getting everything lined back up during installation. I can't say I had the same luck with my former MGB.
Tom Baker

This thread was discussed between 23/03/2013 and 26/03/2013

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