P3 Engine Replacement

[Pendle]

The engine is seized on my newly acquired P3 75. I am trying to free the engine, but at the same time will begin investigating potential for replacement. I have the opportunity locally to buy a P4 90 engine with transmission and overdrive. Would this fit a P3? What are the issues and considerations?

Thank you

Chris Young

[Bernie Hurren]

Quite a few P3s in Australia are fitted with P4 engines. I have a 90 engine that I will be fitting to mine someday.

[roverreiver]

After 6 months of trying to free my p3 75 pistons back in 1987 I was advised to fill the bores with vinegar. Next morning they gave in to a large aluminium drift and a club hammer. The crankshaft was removed much earlier.
John Kirkland

[roverreiver]

Last year I replaced my P3 75 engine with a P4 90. Big job but the best thing I ever did. Now have greatly increased torque, fewer gear changes and smoother progress. My work limited to P4 engine, clutch, and 1950 Land Rover clutch release sleeve to enable use of existing good P3 gearbox and drive train. You could do same. Using full P4 drive train would mean reworking the gear change mechanism and possibly a different length prop shaft. Overdrive would be a significant benefit which I do not have. Happy to share my experience if it helps.
John Kirkland

[Pendle]

Thank you for the responses. I have been contemplating a scope similar to that described by John - leave the P3 transmission and drivetrain. Am I correct in assuming that the main considerations in replacing the clutch are the condition of the original and the (un)availability of spares for the original?

Thank you

[roverreiver]

Correct, even in the 1980s Rover clutches for the P3 were long obsolete and we were dependent on reconditioned items. Mine was rebuilt by the late and much lamented Richard Stenning, an engineer for whom I had great respect and who wrote substantial chunks of the P3 Manual published by the RSR. After 25 years this clutch was inclined to judder badly at critical moments when full power was required so the attraction of the Borg and Beck clutch available for P4s and Land Rovers was one factor in deciding to try the P4 90 engine. The
other was that the rebuild of my original engine (which had never been re-bored) was not entirely successful although entrusted to an acclaimed company. It always got me home but it was never a happy engine and after more than 20 years of coping with its foibles I finally lost patience with it. I bought the 90 engine blind on ebay withe idea of comparing the reconditioning costs of the two. In the event the 90 turned out to be an exceptionally good buy requiring little more than the freeing of some sticking valves and a decoke to get back on the road quickly. Fingers crossed. Richard Stenning put a 90 engine in his P3 75 and wrote up the process in Freewheel -copies available from the RSR librarian. His description of the work he did to modify the clutch release mechanism left me cold and I can only assume he did it that way because he could not get a 1950 Land Rover clutch release sleeve at the time. Mine came from Craddocks, Land Rover parts suppliers in the West Midlands.

[Pendle]

I am proceeding (slowly) toward the engine change out - putting a P4 90 engine in my P3 75. I would like to find out what others have done with the engine auxiliaries when they exchanged engines. I am planning to put in a P4 SU carb, but would like to know whether it is possible to use P3 75 distributor, starter, and dynamo. Thank you

[djm16]

I am sorry you are swapping out the original motor for a P4 90 motor. The originals must be getting pretty rare indeed, although they are quite rebuildable as many spares are common to the Series 1 Land Rover engine.

Yes, my P4 90 is much smoother and more powerful than my P3 75, so when I want to go fast I take the 90, when I want "ultra-cool" with a sunroof, I take the P3.

Still, each to their own, just don't scrap the original motor.

[DavidRuddy]

I have a ROVER 90 cyl head
which I would be happy to part with.I fitted 2.6 7 bearing crank engine ex 6 cyl landrover I retained original engine which I intend rebuilding one day in distant future

[Pendle]

David,

Thank you for the offer, but I believe that the head on my recently acquired P4 engine is good (I was told that it had been recently overhauled). I have just finished installing the engine - I succeeded in getting everything to fit, with a few adjustments required. I'm waiting for some ignition parts to arrive so I can test it. Then about another year to complete the cosmetic restoration.

Chris