cl350rr said:
what should the uncompressed ring gap be on a 1" bore cast iron sleve IC engine with 2 cast iron .050 width rings?
thanks
R
G'day R, the uncompressed gap isnt too critical, the compressed gap is. The tension is required to give a machanical seal under cranking conditions, once the engine fires its the combustion pressures which press the ring onto the bore. Id go just a smallish gap as too much tension will increase the friction drag, small engine produce small power, drag is your enemy.... 8)
Using full sized engine theory, its 4 thou gap per inch of bore size.. thats 'UP TO' ... so a 1" bore could have a 4 thou end gap and be expected to work, a little less would be better with very thin rings.
Dont forget that the problem is that the ring will expand as it heats and the gap will close as it does.... so a 'correct' minimum gap will stop seizures and too much gap will not allow start because of low compression...... Ive had a Triumph seize up on me due to insufficient ring gap, not fun....
To check end gap in bore, place the ring in the bore and use the piston to square it up, then feeler gauges are used, as has been stated.
Be aware that the 4 thou quoted IS full sized engine stuff with thick rings and therefore more expansion when hot... might be worth turing up a test cyclinder the same size as the bore and putting a ring into it and heat to operating temp to see how close it gets.... maybe not....
Good luck
Rob