[ROVERNET - UK] Rover P5 compression ratio and fuel

[S Manwell]

Eric,

According to the P5 MkI through III parts book, these are the possibilities:

MkI and Ia: 7.5 (engine # prefix 631 or 731) or 8.75:1 (prefix 630 or 730)
MkII Auto: 8.0:1
MkII 4spd/OD: 8.0 (prefix 771) or 8.75 (770)
MkIII 4sp: 8.0 or 8.75 (796 or 795)
MkIII auto: 8.0 or 8.75 (801 or 800)

I believe the 8.75 ratio is more common on the LHD export MkII 4spd and 
MkIII's, but I'm not sure of that.

If the pistons have been replaced, then the compression ratio may have 
changed...

8.75 pistons probably require 89 or 93 octane depending on where the 
spark is set.

--Steve


Eric Russell wrote:
> One of club members in eastern Washington state has
> acquired a new (for him) 3 Litre Rover.  He has a
> question about engine compression and fuel needs.  Can
> you give him some idea?  I'll pass the answer along.
>
>  Geoff Murgatroyd’s P5 could be a 7.5:1 or and 8.5:1
> compression ratio car and I don’t know how to make the
> determination.  Since this affects the type of
> gasoline to use in the engine, it is something that I
> need to know.
>
> Question:  How does a person determine if a 3 Litre
> engine has a 7.5:1 ratio or a 8.5:1 ratio?
>
> Eric
>
>
> Webmaster of The Rover Car Club of Canada
> Website:  http://www.roverclub.ca/
> Webmaster of a variety of sites from:
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