flat top pistons
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flat top pistons
Does anyone know if i could get some flat top pistons to fit my std 1098 bores.Im hoping that some other model motor may use something that may fit?
Not easily - it's not an engine that was modified much because of the long stroke. However - 998 Mini pistons are +65 thou diameter - but longer from pin to crown so would stick out top of block - you could machine the extra off and end up flat-top! Better still - use a 948 crank in that 1098 block - bored +65 thou, and there are special 998 Mini pistons available in forged/flat-top style - but not cheap!The 948 crank is same stroke as Mini 998 engine - so you will have a 998 Minor engine which will rev nicely! But be sure to use a crankshaft damper - whatever you do.
Im looking to maximize the squish,those dished pistons just go against the grain for getting good combustion.I really just want to build and optimised engine,,not out right performance.Thanks for the info' it looks like im on a sticky wicket here though'please correct me if im wrong but this 998 route will be revvy where im more interested in tourque which is i guess where the long crank throw wins?ive got to admit i really dont know much about cars as this is my first after a lifetime of bikes.Thanks for the input 
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linearaudio
[quote="bmcecosse"] However - 998 Mini pistons are +65 thou diameter - quote]
Sorry if I'm being thick- aren't 998 blocks same bore as 1098? From my edition of the Bible the 948 bores are -65 thou to both 998 & 1098. Would you have enough meat left if you machined .150" from 998 piston tops? If so it would give a useful compression hike, and the later 998 pistons are probably a bit tougher than the originals, but of course you should really be trying to sell him on the 940 head ( and the ....... brakes, obviously!)
Sorry if I'm being thick- aren't 998 blocks same bore as 1098? From my edition of the Bible the 948 bores are -65 thou to both 998 & 1098. Would you have enough meat left if you machined .150" from 998 piston tops? If so it would give a useful compression hike, and the later 998 pistons are probably a bit tougher than the originals, but of course you should really be trying to sell him on the 940 head ( and the ....... brakes, obviously!)
Yes - 998 and 1098 blocks are same bore - and they are both +65 thou on a 948 block (which is same bore as an 848 block ). So - to make a 998 Minor engine - use 998 pistons and overbore the 948 block by +65 thou - OR use a 1098 block at standard bore, and use the 948 crank in either block. The pistons won't need any machining - but 998 or 1098 rods will be necessary. The 1098 block is better because it has cam bearings on all 3 journals - the 948 only has a proper bearing on the front journal.
And - on the A series engines, dished pistons are considered to give the best power - NOT flat tops, although I imagine the difference will be tiny.
And - on the A series engines, dished pistons are considered to give the best power - NOT flat tops, although I imagine the difference will be tiny.