Dadio

Ok, so it looks as though I will keep my existing 145,000 mile Discovery and
I am now turning into a bit more of a mechanic than expected. Needs
must....
1995 V8i 3.9
I have just replaced all the plugs and took the opportunity to compression
test each cylinder.
I did not do it quite according to the book but took one plug out at a time
(leaving the others in) and spun the engine for about 10 seconds with the
coil disconected and the accelerator depressed.
Results were reasonably consistent between 165 and 170 throughout.
Is this good, bad or average?
I am a bit confused by my Haynes manual as it suggests two different typical
compression results for the 3.9, one for the low compression version and one
for the high compression version.
How can I tell which engine I have (low comp or high comp).

Thank you

Les

Richard Brookman

so Dadio was, like...
> Ok, so it looks as though I will keep my existing 145,000 mile
> Discovery and I am now turning into a bit more of a mechanic than
> expected. Needs must....

Good to hear this. :-)

> 1995 V8i 3.9
> I have just replaced all the plugs and took the opportunity to
> compression test each cylinder.
> I did not do it quite according to the book but took one plug out at
> a time (leaving the others in) and spun the engine for about 10
> seconds with the coil disconected and the accelerator depressed.
> Results were reasonably consistent between 165 and 170 throughout.
> Is this good, bad or average?

Sounds pretty good to me. You really should have all the plugs out, but
your results look healthy. The most important thing is that they are
consistent - ideally within 10% of each other. Yours are well within this.
FWIW, mine were all around the 130-140 mark (3.5V8) and the engine still
goes well.

> I am a bit confused by my Haynes manual

You're not alone there!

> as it suggests two different
> typical compression results for the 3.9, one for the low compression
> version and one for the high compression version.
> How can I tell which engine I have (low comp or high comp).

I think it's cast on the top of the exhaust manifold. 9.3 (i.e. 9.3:1) is
high comp, not sure what low comp is, 8 point something. It's fairly
obvious when you see it.

HTH
--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)

Tony

There are two way's to tell the compression ratio: On the nearside of the
block there is a small flat with the ratio stamped on it or by the ignition
timing Low comp No CAT 2deg BTDC, High comp No CAT 4Deg BTDC, High comp
with Cat 6Deg BTDC.

As a matter of interest my 3.5 with a 9.35 comp has pressures of 165-170
across all cylinders.

--
Tony,
110 V8i CSW
S1 Discovery V8i