OK, I may have found my pistons:
Volvo Manual lists piston heights from pin to crown (all are shaped
the same -- domed). If you look at far right hand column of Mahle
brand, in 1979 B27E changes to pistons that are almost 2 mm taller. Is
a bit confusing because 1979 B27F appears with same Mahle pistons that
were previously used in E series, but the manual does indeed show
1979-1980 B27E as 41.3mm vs 39.4mm.
That would account for higher compression.
Note that Demolin brand pistons used in F series before 1979 are
39.4mm -- same height as Mahle brand in concurrent E series.
Which begs the question: doesn't this mean E series before 1979 are
low compression?
Have never seen underside of my heads, so must accept Martin's
prediction they are concave ("open chamber").
Volvo literature definitely does not mention any differences in head
height or connecting rod length.
Only option is pistons...
Walt, grab hold of something -- I was wrong: pistons are NOT same size
between E & F series (after 1979).
Bill Robertson
#5939
>--- In DMCForum@xxxxxxxxxxxxxxx, Martin Gutkowski <webmaster@xxxx> wrote:
> Bill. HAVE YOU EVER SEEN THEM SIDE BY SIDE?
>
> I have.
>
> Consider the possibility that your book may be wrong.
>
> Martin
>
> content22207 wrote:
>
> >OK -- Volvo literature itself claims no difference between E and F
> >series pistons, crank, connecting rods, or head deck height. Where,
> >pray tell, does the extra compression come from? Every domestic
> >manufacturer did it with flat top combustion chambers (other methods
> >nothwithstanding)...
> >
> >Bill Robertson
> >#5939
> >
> >
> >
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