sary can Posted June 20, 2014 Share Posted June 20, 2014 Hi all, I am getting ready to rebuild My Saracen's engine (Rolls Royce B80), and had the following idea. Please anybody with any facts or just opinions, chime in! I tend to believe in keepinng things orginal, but what if Someone were to use a modern piston in a rebuild, modern alloy could mean perhaps a slightly closer fit to the liner wall, a slight increase in compression could be included, say 7 or 7.25:1 instead of the 6 and a half, the piston might be more resilient, tougher, less subject to expansion/contraction. Maybe a very slight increase in reliablity and fuel economy could be realized, with out changing the the engines operation otherwise. I see from My workshop manual that the early mk B81 engines had the higher compression and used the same carb and a fairly similar camshaft as the B80s. Bad idea to try to improve a good thing? Has it already been tried? Quote Link to comment Share on other sites More sharing options...
Starfire Posted June 23, 2014 Share Posted June 23, 2014 Compression ratio is defined more by the shape of the combustion chamber and the piston's profile/pin height than its diameter and ring fitment. The main reason that the B series has such a low compression ratio is to allow for the use of very poor quality fuel before pinging was an issue. If you stick to modern fuels, you could up the ratio a bit without any problems, the easiest way of doing this would be to shave the block a little, or use a thinner head gasket. Because of the side exhaust valves, you won't be able to take it too far though. Of course, if you're not too interested in authenticity, the B80 is a big, strong, slow revving engine with a low compression ratio - which makes it perfect for forced induction. A medium sized turbo (in the GT-30 to GT-35 range), running around 10 PSI of boost would be awesome on one. Fuel injection would make it really come alive. Cheers, Terry Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted June 23, 2014 Share Posted June 23, 2014 Shave the block? Skim the head is the obvious choice, working out exhaust valve to head clearance. For more power, fit a B81, more cubes! Quote Link to comment Share on other sites More sharing options...
Starfire Posted June 23, 2014 Share Posted June 23, 2014 Richard is right, skimming the head would be easier, or you could build up the combustion chambers with welding, if you have an iron head (alloy can be done too, but is harder). I still want to turbo or supercharge one Cheers, Terry Quote Link to comment Share on other sites More sharing options...
attleej Posted June 26, 2014 Share Posted June 26, 2014 If you were not worried about external originality you could do electronic fuel injection with a "megasquirt". It would give you excellent starting, probably more power and efficiency and you would not need to mess around with the guts of the engine. All you would have to do mechanically is to fabricate an inlet manifold. AND the manifold would not have to be jacketed or anything. Also if you wanted to revert to a carb that would be quick and easy. John Quote Link to comment Share on other sites More sharing options...
sary can Posted July 6, 2014 Author Share Posted July 6, 2014 Thanks everyone, Yeah, I'd thought about TBI, maybe electronic ignition. Turbo? Supercharger? That would be the most awesome sound!! But, I better go historical on this one. Maybe someone has a project head/block/crank they would part with, then let the games begin! Cheers, Edmund Quote Link to comment Share on other sites More sharing options...
Starfire Posted September 2, 2014 Share Posted September 2, 2014 The B80 is pretty powerful anyway and has lots of torque. The Saracen can get up and move with a little persuasion. I would suggest a pretty standard rebuild and then fit a jolley electronic ignition kit and maybe fiddle up the rev limiter. Also, you might want to consider just buying an NOS engine, Tim Vibert at Empire Trading has them and it'll probably work out cheaper than having yours rebuilt. Cheers, Terry Quote Link to comment Share on other sites More sharing options...
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