[ROVERNET - UK] Re: Rover P5 compression ratio and fuel
jhdolan at sover.net
Fri Aug 10 01:02:39 BST 2007
> Message: 4
> Date: Wed, 8 Aug 2007 17:16:40 -0700 (PDT)
> From: Eric Russell <p6rovers at yahoo.com>
> Subject: [ROVERNET - UK] Rover P5 compression ratio and fuel
> To: Rovernet at lyris.ccdata.com
> Message-ID: <569449.57850.qm at web34308.mail.mud.yahoo.com>
> Content-Type: text/plain; charset=3Diso-8859-1
> 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=92s P5 could be a 7.5:1 or and 8.5:1
> compression ratio car and I don=92t 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?
> According to the P5 MkI through III parts book, these are the possibili=
> MkI and Ia: 7.5 (engine # prefix 631 or 731) or 8.75:1 (prefix 630 or 7=
> 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=20
> 8.75 pistons probably require 89 or 93 octane depending on where the=20
> spark is set.
Hi Eric and Steve-
I have a chart of P5 models which includes compression ratios here:
The info there and Steve's provision of engine prefix numbers might=20
help. If you'd like any numbers looked up for a P5, just let me know.
Been well here in Vermont, and hope this finds all the same. Time=20
flies- just the other day I was remembering when Rovernet had 6 members-=20
how it has grown! I still follow it, but, as you can tell, mostly just=20
lurk. That is an outdated page, photo-wise, and the vehicle is no longer=20
jim in VT
'61 LR SWB
'60 P5 MkI LHD 4 spd w/OD
and a few other P5's
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