OHV back to sidevalve

[Doc]

I have a 52 MM that has had a OHV engine put in it at some point. The original sidevalve engine and gearbox came with it and I would like to put it back in. No idea why it was swapped.
Does anyone know of any issues I should be aware of??

[geoberni]

It really depends what you want to do with the car, in terms of it's usage.

I'm sure some Sidevalve owners will give you their thoughts, I'm a SII guy myself, although my car had a transplant from it's 803 before I got him.

[oliver90owner]

No idea why it was swapped.

Could be good but might be whacked!

[philthehill]

I would advise that you strip the 918cc SV engine and examine the parts for wear and damage, then make a costing of what is required (machining and parts) before making any decision.
You may be very lucky in that the SV engine may only need a refresh but I would suggest that the SV engine was removed because it reached a point in its life were it needed a complete overhaul/re-bore/crank grind/etc and it was cheaper and easier to fit a later OHV engine.

[Chipper]

You could just try jury-rigging a setup to test the engine with it out of the car. You can strap them down to say, a pallet or similar frame, connect it up with basic battery supply to the ignition and a gravity-fed fuel tank, and have a go at starting it.

I did this with my Traveller's original 1098cc engine, to test it after sitting in the garage for years. I used an old rowing machine frame to hold it steady!

You may just get lucky, and find the engine is OK and someone just swapped it out to uprate it to new-fangled OHV technology at the time...

[myoldjalopy]

I am with Phil in suggesting that the old unit had 'gone round land' and that is why it was removed. Get it checked out before fitting.

[firedrake1942]

I think to put an OHV into a SV designed MM some alteration to the bulkhead will have been necessary. It may be that this is not too obvious if you put the SV back in, but the straight and curved bulkhead centres are very different.

[philthehill]

You may find that the normally handed engine mount towers have been swopped over to accommodate the OHV engine. Swopping will give a minimum of 3/4" inch additional forward placement of the engine. The gearbox mounts have enough slack to enable the gearbox to move forward.

[MM1949]

Of course the other consideration why it was swapped in the first place as there is a vast improvement in performance from an A series 948 onwards compared to a sidevalve.

So if you do swap back be prepared.

[oliver90owner]

Of course the other consideration why it was swapped in the first place as there is a vast improvement in performance from an A series 948 onwards compared to a sidevalve.

So if you do swap back be prepared.

We don’t actually know the present condition/performance of the OHV unit.

[Doc]

Thanks. Been to a meet today and taken a look at a MM still with the side valve in.
The bulk head is straight whereas mine is raised in the middle so I presume it has been altered at some point.
The first thing to do I know is to assess the engine (it turns by hand) but I am also thinking ahead.
Apparently the radiator is different. Not sure if the prop shaft would be? Exhaust connection?

[MM1949]

The prop shaft is different it is attached to the gearbox by 4 bolts as opposed to a spline, the gearbox mountings are different, the front pipe of the exhaust is different, the radiator is different, the clutch pedal operating mechanism is different, the engine towers are different

Depend on what gearbox you have now if it is a later A series box then you will need to change the gearbox cover as the sidevalve gear stick comes out closer to the parcel shelf.

[myoldjalopy]

The prop shaft is different it is attached to the gearbox by 4 bolts as opposed to a spline, the gearbox mountings are different, the front pipe of the exhaust is different, the radiator is different, the clutch pedal operating mechanism is different, the engine towers are different

Depend on what gearbox you have now if it is a later A series box then you will need to change the gearbox cover as the sidevalve gear stick comes out closer to the parcel shelf.

That's quite a lot of 'issues to be aware of'!