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Old 02-10-2013, 10:12 AM
ssmonty ssmonty is offline
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I know some will say I'm being irresponsible by suggesting something I haven't actually run, but I thought I'd suggest a couple of options you may not have considered, or at least something to think about.
Building a stroker myself, I ran into a problem with what I thought may be too much compression.
I tried to flycut the pistons I had, so that they resembled more of a trough type valve relief to gain some more volume. I checked to see that there was enough material under the location I intended to mill, and it was strictly just my opinion that there was. I first had them flycut straight accross from the back of the exhaust valve relief, but didn't get the volume I thought I wanted, so I had them cut even with the back of the intake valve relief by a different shop(much smoother). Went from 5cc initially to 7cc.
I later realized that I was removing material that would reduce the amount of the squish effect from the close proxcimity between piston and headsurface. Also the pistons had a little too much bore clearance for the 0.030" bores, so I bought some new ones for a .040" overbore.
The new pistons didn't have the same extra material between the 2 valve reliefs on the underside of the piston head that the previous pistons had, so I decided not to flycut them, and to try something else.
I had read about modifing the heads with grooves to suppress detonation. I don't know if they work, but some say they can make a difference between an engine that will run on pump gas, and one that won't. Honestly think that the grooves will fill with carbon to a certain extent, but that the velocity of the squish will keep them from clogging completely, but thats JMHO. They are supposed to creat a jet of mixture that promotes turbulence, thus quicker burn . I think that they also make for a path of flame to get to the far side of the chamber quicker than normal before the far side can detonate from exposure to the heat/pressure of normal combustion.
Like I said, I can't say from experience that they will help in any way whatsoever, but the logic behind them, and testamony of those that have tried them gives me enough courage to give it a shot. Mind you I didn't do it for any increase in power, but just to help the engine live on what I think is too much compression on todays fuel.
By the way I only gained around one cc polishing my chambers.
Also I've heard of more detonation problems by using a thicker gasket to lower CR than a thinner one originally used, but I haven't tried personally.
Like I said, just some things to think about FWIW.
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