Crankshaft journal diameters

RoverP6B · Post by **RoverP6B** » Tue Apr 08, 2008 10:15 am

There is a difference between the aforementioned diameters with respect to those specified for the Rover 3500 P6B from 1968 till 1976 and for the 3.5 litre engine as fitted into Land Rover Discovery and Defender models.
These latter specifications also apply to the 3.9 Litre and 4.2 litre engines as fitted into Land Rover Discovery and Range Rover Classic models.

P6B specifications
Main journal diameter.............. 2.2992" to 2.2997"
Minimum regrind diameter.........2.2592" to 2.2597"
Big-end journal diameter............2.0000" to 2.0005"
Minimum regrind diameter.........1.9600" to 1.9605"

Discovery/Defender specifications
Main journal diameter................2.290" to 2.300"
Minimum regrind diameter..........2.280" to 2.281"
Big-end journal diameter............1.990" to 2.000"
Minimum regrind diameter..........1.970" to 1.980"

Associated bearing clearances for the above are also more generous for the P6B when compared to the latter engines.

I would be interested to know where the specifications for the 3.5 litre fitted into the SD1 lies when compared to all of the above.

Ron.

ChrisJC · Post by **ChrisJC** » Tue Apr 08, 2008 11:55 am

Did the later engines specify 20W/50 oil?, or something thinner? ( I wonder if that's one reason for the differences)

Chris.

RoverP6B · Post by **RoverP6B** » Tue Apr 08, 2008 12:37 pm

Hello Chris,

As far as I can tell, changes in engine oil recommendations seems to be associated with the type of oil pump used, ie camshaft driven or crankshaft driven, the latter being much more efficient, and as such a thinner oil can be pumped with greater efficiency than is the case with the former oil pump design.

Penrite specify a number of engine oils for the Rover V8 in all its capacities. With the later engines, crankshaft bearing clearances for 3.5 through to 4.6 remain identical, as do the top end clearances, the only difference appears to be in the oil pump type used.

Any thoughts?

Ron.

badger · Post by **badger** » Tue Apr 08, 2008 4:14 pm

Ron, I have seen the figures you quote specified for varying engine model years, a lot of different manuals / books seem to quote different figures! I also have factory paperwork which shows a slightly tighter clearance on later (serpentine onwards) engines, so it seems to be a case of take what you will..... I sometimes wonder if things get altered slightly in conversion from metric to imperial and back again, depending on the number of decimal places taken!