Putting a three litre in a 90.

#1
Howdy and greetings from New Zealand. I have a 90 that I bought with a very good 3 liter engine that I want to put in it. The 3 liter was attached to an auto but I want to use the manual box from the 90. The boss, or what ever it is, on the end of the crank has a larger diameter by about quarter of an inch than the locating ring on the 90 flywheel but otherwise the bolt patterns seem identical. Has anyone ever done such an install and if so could you tell me how you went about it.
 

ghce

Well-Known Member
#2
Hi and welcome to the forum, I am sure someone will know of a conversion, got any photos of the car?

Cheers Graeme in NZ
 
#3
Tim

I'm pretty sure the P5 crankshaft was different for manual 3 litres than auto 3 litres throughout the production run until the P5 Mk III came along when (I think) they managed to introduce commonality. Is it a DG autobox? If so it is from a Mk II or earlier P5. You will need a manual crank for sure but even then I cannot be 100% certain it will fit a 90 box but I am fairly sure it will though you may need the P5 bell housing. I'm afraid you've choosen a tough way to go about the mod, fit the auto box (if it will fit) or change the crank, so no easy route to a solution. You may get further posts on here or try the P5 club forum but I think you're setting yourself up for quite a bit of work. TBH I am punching slightly above my weight with this info so don't take anything as gospel but I'm fairly confident the straightforward (is any swop ever straightforward?) route is to retain the 3 litre + original box set up. 95/100/110 engines have greater commonality with a 3 litre as well so you're losing out on two counts by mating it to 90 running gear!
 
#4
Thanks Alan. Looking at the 90 manual flywheel it looks as if it would bolt to the end of the crank on the 3 liter except that the locating ring on the engine side of the flywheel is of a slightly smaller diameter. I am wondering if anyone has ever turned down the end of the crank to make it fit.
 
#6
The following is from another forum and might give some more background info.

:Late P4 110 3 litre and P5 3 litres | Rover P5 Club Forum

A 95 engine is virtually the same as that in a 110 (P4, not Landie :) ) except that the 110 has a Weskake head). The 6-cyl engines in the 95,100 and 110 are short-stroke versions of the 7-bearing engine introduced for the 3-litre; they're different to the earlier 6-cylinders in the 90, 75s and the 105.

The manual gearbox in the MK11 3-litres onwards has different ratios to the earlier 3-litre. If you know your engine number we can probably work out which model it was in originally. The comment above about crankshafts is correct in that Mk1 and MK11 auto cranks were different to the manual ones but MK111 were the same.


I've no idea how easy/difficult it is to do what you're considering (I've just re-read your original thread and realised that the 95 reference is a red herring but I've left my comments as originally typed!)

What age is the 90? Those up to1956 had free wheel, 56 onwards had overdrive as an option.
 
#7
One last thing. (I think) The 3 liter is the model with the Westlake head.
The following is from another forum and might give some more background info.

:Late P4 110 3 litre and P5 3 litres | Rover P5 Club Forum

A 95 engine is virtually the same as that in a 110 (P4, not Landie :) ) except that the 110 has a Weskake head). The 6-cyl engines in the 95,100 and 110 are short-stroke versions of the 7-bearing engine introduced for the 3-litre; they're different to the earlier 6-cylinders in the 90, 75s and the 105.

The manual gearbox in the MK11 3-litres onwards has different ratios to the earlier 3-litre. If you know your engine number we can probably work out which model it was in originally. The comment above about crankshafts is correct in that Mk1 and MK11 auto cranks were different to the manual ones but MK111 were the same.


I've no idea how easy/difficult it is to do what you're considering (I've just re-read your original thread and realised that the 95 reference is a red herring but I've left my comments as originally typed!)

What age is the 90? Those up to1956 had free wheel, 56 onwards had overdrive as an option.
 
#8
My first post has clouded the waters as I mistakenly said the car was a 90. It is a 95. The 95 is a late model as it has steel doors, boot and bonnet. I pick the car up in a few days and will post the ID of the vehical then. Thank you for taking the time to consider my challenge!
 
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