Oil consumption

[Geoff Dowdle]

Peterg ,
you keep talking about distortion of the block .
I have been working on Bristol 6 cylinder engines for over 40 years and have never heard or experienced distortion in the block as you described .
My guess is that the liners are badly worn which would probably cause your excessive oil consumption.
Have you measured the pistons and compared it to the diameter of the bores as I suggested earlier.

JP pistons are cast copies of the original 8.5 compression forged Bristol pistons with three wide compression rings and segmental oil rings.
In my opinion the cast split skirt piston you have are a far better designed and made piston than the JP . Why does your engine man think that your pistons are not suitable for modern petrol ?? It sounds very strange .
Post a few photos of your current pistons .

But on the other hand I have fitted the JP pistons to a number of engines and they run quite well for road use. They are quite a bit heavier than the original forged pistons .
Why do you want 9.5 pistons ? Your block and head have probably been machined a number of times over the years and the 9.5 pistons could give you 10.5 to 1 compression . Unless you are racing it is not ideal for normal road use . What octane fuel is commonly available in UK .
I use 98 or 95 octane unleaded (with no Ethanol ) in my Bristols in Australia,
you would need that at anything above 8.5

There are probably a number a different good quality pistons available in UK far better than the JP pistons .

Ross Pistons in USA make a 8.5 piston for 2 litre Bristol , they are forged , two thin compression ring , flatter crown than high domed original 8.5 .
Overall better design and quality

Geoff