right, just some more on what I've worked out and found out -
I've been looking at my collection of XU10 engine parts, namely a gti6 bottom end complete, as well as the top end inc 10 bent valves (hence avatar) a set of 2.0 Mi16 pistons and rods, and some Newmans cams.
Some quick measurements with a dial gauge showed that there is next to bugger all room in the standard J4RS piston for any worthwhile camshaft upgrades, but I remembered that I had a set of Mi16 rods and pistons about and that they have a deeper cutout and a flat topped piston.
This combination with the gti6 head gave something roughly like 4.9mm valve clearance unsure.gif plenty for some half decent cams, and what is a slightly higher than standard compression ratio if I'm not mistaken :wacko
now I can't seem to fathom what I've missed going through my workings out and what data I can find on both engines.
40cc head combustion chamber,
10.4-1 compression ratio
1.20 mm gasket.
37.2cc head chamber volume.
10.8-1 compression ratio.
1.20 mm gasket.
I've worked out that the RFY piston + rod with a RFS head would give somewhere in the region of 10.9-1 compression unskimmed, and low 11's -1 skimmed to 36cc from 37.2cc.
I do realise that they dont come flush to deck like the gti6 piston, but are flat topped, but I have heard that this allows the use of an 88mm crank to push the capacity up to 2044cc, that'll still have a fair amount of space @ TDC for some nice cams over the RFS piston.
going off the basic data above I worked out the RFS dish to be 6.64cc, and the RFY to be 5.99cc (not dished but has cutouts and sits below deck)
I found some information just now in a topic on here;
Block height = 234.8mm (At least we found it to be that when measuring)
Rodlength Xu10J4 = 152mm
Piston Compression height = 39,1mm
Half the stroke 86/2 = 43mm
234.8 - 152 - 39.1 - 43 = 0,7mm
Which means that in a standard XU10J4 the pistons sit 0.7 down the bore.
Adding the extra 1mm with the 88mm crank will make them sit 0.3mm over the deck..
So, if I use 88mm crank for a 2044cc build with no other changes, I'll have circa 42.5cc combustion chamber volume for a 13.0-1 compression ratio
To be confirmed, but there would be something like 3.9mm total valve clearance, less 1.5mm safe running clearance you could maybe run 2.4mm Lift @ TDC pretty safely.
need a part number? get on here - http://public.servicebox.peugeot.com
Bring on the Trumpets.