mofoka Posted October 3, 2008 Author Report Posted October 3, 2008 Those aftermarket heads should be sounding pretty good right about now maybe??? No sh!t... I'm still wanting to run pump premium on this. I'm at 4500 where I'm riding so I'm just looking to boost the compression to 150-155. From what I've seen my best guess to bring it up to that is should only be a .030 - .035 shave and with that little coming off the head there wouldn't need to be any welding or squish concerns. Someone smack me for being naive if that's not the case. Then I'll need to start looking at coolheads too Quote
Wildcardracing Posted October 4, 2008 Report Posted October 4, 2008 You're not going to get that much compression without going through what deckhieght described, but you can get away with .030". That's the most I'd reccomend, because your squish gets pretty tight beyond that. That should put you right in the 135 range and you'll be OK on pump premium. Quote
deckheight Posted October 4, 2008 Report Posted October 4, 2008 I have only done a couple 100 octane Banshee heads where (for whatever reason) the individual just had to have the OEM casting. So based on that limited experience, I wouldn't feel comfortable taking much more than .060" without the welding. Even then there is only going to be about 1/16" of material left, pretty thin IMO! If things are done correctly, an OEM casting cut for 92 octane fuel should be a noticable improvement on the old "Butt-O-Meter"... Not sure why your "meter" didn't register??? I am assuming when you mention "re chambered" you are referring to cutting the squish band? Assuming this, it is MHO again that removing more than .020" requires cutting the squish to keep all the numbers where they should be. And, since they are not a machined area from the factory, OEM casting squish areas should probably be cleaned up as part of the machining process anyway... They are kind of a mess! i knew there was more to this than just shaving a head.the heads i have had shaved in the past made little to no difference.the last one i had done i had it re chambered and there was a slight seat of the pants difference.deckheight how much can be taken off a stock head after rechambering it,not to be to thin to weld the aluminum plugs into it.and what would be the cc results. Quote
deckheight Posted October 4, 2008 Report Posted October 4, 2008 I wouldn't call it "naive". It kind of caught me by surprise the first one I did and I have done a lot of heads for a lot of different applications over the years... Banshee heads look just like all the rest and have plenty of material, except in those two areas??? Take a look at my other post in this thread about cutting the squish band. Once the head is indicated on the fixture it is not much more time to just go ahead and make the squish cut. Interesting avatar BTW. Kind of mesmerizing... Someone smack me for being naive if that's not the case. Then I'll need to start looking at coolheads too Quote
mofoka Posted October 6, 2008 Author Report Posted October 6, 2008 I wouldn't call it "naive". It kind of caught me by surprise the first one I did and I have done a lot of heads for a lot of different applications over the years... Banshee heads look just like all the rest and have plenty of material, except in those two areas???Take a look at my other post in this thread about cutting the squish band. Once the head is indicated on the fixture it is not much more time to just go ahead and make the squish cut. Interesting avatar BTW. Kind of mesmerizing... is this what you are referring to cutting the squish band? How would you do that? Quote
deckheight Posted October 6, 2008 Report Posted October 6, 2008 Yeah that should do it. Slight overkill IMO with all the swirling pattern cut into it but that is pretty much it. The swirling pattern in the squish band area seems to become fairly popular every few years and is supposed to increase turbulance and atomization as well as direct the fuel charge toward the center of the combustion chamber for a more efficient burn. It is arguable wether or not the swirling does anything at all however... Besides the same thing is accomplished with an appropriate MSV for the application. Regardless, assuming all the numbers add up that head in the pic a very, very nice peice and whoever cut it does excellent work IMHO. Quote
mofoka Posted October 6, 2008 Author Report Posted October 6, 2008 Besides the same thing is accomplished with an appropriate MSV for the application. Regardless, assuming all the numbers add up that head in the pic a very, very nice peice and whoever cut it does excellent work IMHO. What is a MSV? How would I make those cuts? That picture is courtesy of Trinity Racing. But for 140 bucks I'd be on my way to get a coolhead. Quote
deckheight Posted October 7, 2008 Report Posted October 7, 2008 (edited) MSV = Maximum Squish Velocity. It is an indicator of combustion chamber turbulance, usually measured in meters per second. Or how fast end gases in the combustion chamber are traveling toward the center. In general, too much turbulance tends to promote a faster flame front in the combustion chamber. Thus, maximum chamber pressures would tend to occur too early, promoting detonation. Not enough turbulance would do the opposite and part of the unburned fresh fuel charge would leave through the exhaust port with the rest of the exhaust gases. You would have to purchase tens of thousands of dollars worth of computer assisted machining equipement and tooling to cut a head like that. Or you could do it the old fashioned way on manaul equipement, but it would take forever and cost a lot more than $140! Did you happen to notice the O-ring grooves... At any rate, my point was that the "swirly thingys" are probably not doing much, if anything, other than looking shiney. On the other hand that particular head is only about $15 - $25 more than a comparable non "swirly thingy" head... Edited October 7, 2008 by deckheight Quote
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