Franc Buxton <fab@dcs.warwick.ac.uk> writes:
In general, what are the specification and feature differences
> between 3.9 s and 4.0 s? Are they the same bore and stroke dimensions?
> This is one little part of the Rover puzzle I would like to learn more
> about.
Hi all, I'm new to this list. I have a TR8 for which I'v just purchased a '98
Rover 4.0 short block (with cross bolted mains)to replace my 3.5. I'm now
pondering what to do about heads, etc. My question is this... Besides the
deletion of the lower row of holes for the head bolts, what are the differences
between the 4.0 and 4.6 heads and the earlier (SD1 type) heads. Is the
combustion chamber size the same? How about the flow characteristics and valve
sizes? Do the 4.0 and 4.6 engines use the same heads? If the newer heads are
a significant improvement I want to try to track down a pair. If not, I'll
just use the heads from my 3.5. Any information would be greatly appreciated.
Thanks,
Fred Smith
Orinda, CA
> T I A.
>
> Regards,
>
> Dave Kernberger
>
I have just checked with some local Rover contacts of mine, and
for general information, the difference between 3.9 and 4.0 engines is
this:
The 'interim' engine is a 3.9 - actually 3947cc, with some of the
improvements applied to the 4.6, namely the same 'crossbolter' block, but
without the crossbolt holes being drilled. It may or may not have main
bearing caps suitable for crossbolting, some of the earlier ones had old
pattern caps which did not sit flush with the sides of the housings, so
nowhere to drill the holes. (I know that bit from experience!) The main
journals are of the smaller size, despite the common block with the 4.6.
The 'interim' front cover has the new-design concentric oil pump on the
crank nose, but has a distributor hole. A worthwhile modification to any
Rover V8, if you ask me! (see website). This engine came equipped with
Lucas type 14CUX 'hotwire' fuel injection.
The '4 litre' engine is the fully-evolved version, distributorless
and with the large-journal crank. Capacity is the same at 3947cc, as are
bore (94mm) and stroke (71mm). This one uses the Lucas 'GEMS' engine
management system.
Hope this helps/informs!
Regards,
Franc.
(Have I ever contributed here before, or just lurked? If the latter,
Hi, guys, interesting reading - keep 'em coming!) F.
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