shawn941 Posted June 2, 2010 Report Share Posted June 2, 2010 How much did you shave? Elevation? feet,0.30 it bumped it 35 psi Quote Link to comment Share on other sites More sharing options...
shawn941 Posted June 2, 2010 Report Share Posted June 2, 2010 feet,0.30 it bumped it 35 psi 4-600 feet,,,sorry Quote Link to comment Share on other sites More sharing options...
dajogejr Posted June 2, 2010 Report Share Posted June 2, 2010 Guys... Compression ratio, not cranking compression dictate the need for race fuel or higher octane fuels.... And I've cc'd stock heads anywhere from 22 to 24ccs...no BS. Quote Link to comment Share on other sites More sharing options...
shawn941 Posted June 2, 2010 Report Share Posted June 2, 2010 Guys... Compression ratio, not cranking compression dictate the need for race fuel or higher octane fuels.... And I've cc'd stock heads anywhere from 22 to 24ccs...no BS. so what your saying by just using a good compression tester and kicking her til shee stops will not give me a reading on whether or not to run race gas? Quote Link to comment Share on other sites More sharing options...
m4f1050 Posted June 2, 2010 Report Share Posted June 2, 2010 Just FYI I'm reading this thread, going to do a rebuild soon and would like to know my "head" options The use of O-rings sure sounds good, since you can take off, inspect, put back together with same O-ring (keep in mind you haven't burned the O-ring by overheating) Kinda off topic: I use ADA racing on my Kawi 150's (jetskis) and I love them! Quote Link to comment Share on other sites More sharing options...
shawn941 Posted June 2, 2010 Report Share Posted June 2, 2010 Just FYI I'm reading this thread, going to do a rebuild soon and would like to know my "head" options The use of O-rings sure sounds good, since you can take off, inspect, put back together with same O-ring (keep in mind you haven't burned the O-ring by overheating) Kinda off topic: I use ADA racing on my Kawi 150's (jetskis) and I love them! well the only real advantage to a coolhead is the interchangability of the domes,,,if you will be wanting to raise and lower your compression,,,your lookin at $300,,,,,shave your stock head and im borderline race gas at 160 psi for like $40,,depends on what your gonna do with it,,,oh ya,,,coolhead also gives the bling look,,,but stock shaved is the sleeper look,,,,lol Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted June 2, 2010 Report Share Posted June 2, 2010 (edited) Uhm, I'm not sure Let's see Stock squish is around .068" using stock gaskets, .080" with a moose head gasket. You shave off .025" to safely run premium, typically, which puts your squish at around .043" Another .010" would put yout squish at around .033", which is about the limit. You could probably get abay with 50/50 race gas/ premium unleaded at this stage. If you plan on running race gas or alky, you should get the head re-chambered. Mull engineering does it for a good price. Pump gas or 50/50, a stock shaved head should work.It is always recommended to check your squish first and your compression after. .025" is definately be safe for pump gas though, unless you run no head gasket. I just wanted to add to this that if your engine is ported, than you can shave a little more off the head to get the same compression as stock, to what extent is determined by the level of porting that is done. For instance a drag ported cylinder with the head cut .035" which is pretty much the max will likely be ok to run with pump gas, due to the fact that when the exhaust port is raised the piston does not begin compressing the mixture until later in the stroke; it decreases the amount of trapped volume. Even with a dune ported cylinder, you could probably shave .035" off and get away with pump gas, if the squish clearance will allow. Again always measure squish before cutting and compression after. Edited June 2, 2010 by SLORYDER Quote Link to comment Share on other sites More sharing options...
dajogejr Posted June 2, 2010 Report Share Posted June 2, 2010 That's an on the border call. A few things I see wrong with that. You could have a bike with 160 PSI because of a high exhaust port but the UCCR could be 14 or 15:1 depending on the cut of the head. Pump gas won't last long in that motor... Regardless of the cranking compression...which as you said will vary based on port timing, fuel is rated for compression ratio. And...not to mention, if I had a drag port cylinder the last thing I'd do is run pump gas... Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted June 2, 2010 Report Share Posted June 2, 2010 (edited) I just wanted to add to this that if your engine is ported, than you can shave a little more off the head to get the same compression as stock, to what extent is determined by the level of porting that is done. For instance a drag ported cylinder with the head cut .035" which is pretty much the max will likely be ok to run with pump gas, due to the fact that when the exhaust port is raised the piston does not begin compressing the mixture until later in the stroke; it decreases the amount of trapped volume. Even with a dune ported cylinder, you could probably shave .035" off and get away with pump gas, if the squish clearance will allow. Again always measure squish before cutting and compression after. That's an on the border call. A few things I see wrong with that. You could have a bike with 160 PSI because of a high exhaust port but the UCCR could be 14 or 15:1 depending on the cut of the head. Pump gas won't last long in that motor... Regardless of the cranking compression...which as you said will vary based on port timing, fuel is rated for compression ratio. And...not to mention, if I had a drag port cylinder the last thing I'd do is run pump gas... On a stock head? I put it the way I did just to get the point across that there are more factors involded with this than compression vs. cut If you are sticking with a stock head and are running a drag port, the best bet will be to get it machined by someone like Blowit (mull engineering)if you are after every last hp. And I'm sure that 98.634% of the people looking to mill their stock head will not be building an all out drag engine, so it is pretty much irrelevent anyways. Exactly what factors influence UCCR? Do you have a formula to determine it? Edited June 2, 2010 by SLORYDER Quote Link to comment Share on other sites More sharing options...
dajogejr Posted June 3, 2010 Report Share Posted June 3, 2010 Several factors influence UCCR...most people don't take the time to measure things up. Just the first calculator I found. http://www.csgnetwork.com/compcalc.html I've seen plenty of people run stock heads on all out drag cub motors and stock cylinder. Before there were cool heads and aftermarket heads available, you had someone cut, rechamber and Oring a stocker...it's all you had. I had a cut stocker on my 10 mil, I like the chariot better. I've seen some of Mull's work and Brandon and I pass ideas back and forth from time to time...I'm certain he does fine work. Quote Link to comment Share on other sites More sharing options...
m4f1050 Posted June 3, 2010 Report Share Posted June 3, 2010 So what's the verdict on the cool heads, which is best and which is worse? Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted June 3, 2010 Report Share Posted June 3, 2010 (edited) Several factors influence UCCR...most people don't take the time to measure things up. Just the first calculator I found. http://www.csgnetwork.com/compcalc.html I've seen plenty of people run stock heads on all out drag cub motors and stock cylinder. Before there were cool heads and aftermarket heads available, you had someone cut, rechamber and Oring a stocker...it's all you had. I had a cut stocker on my 10 mil, I like the chariot better. I've seen some of Mull's work and Brandon and I pass ideas back and forth from time to time...I'm certain he does fine work. So is the trapped volume a factor or the entire volume above BDC? Also at higher rpms when the pipe is returning the pressure wave its amplitude will affect the final compression inside the combustion chamber, correct? Edited June 3, 2010 by SLORYDER Quote Link to comment Share on other sites More sharing options...
Chariot Performance Posted June 3, 2010 Report Share Posted June 3, 2010 I guess the better way to word the exhaust port cooling effect on horsepower is that it can restore robbed horsepower not add it. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted June 3, 2010 Report Share Posted June 3, 2010 So is the trapped volume a factor or the entire volume above BDC? Also at higher rpms when the pipe is returning the pressure wave its amplitude will affect the final compression inside the combustion chamber, correct? This is a great conversation right here....going way beyond "head" talk. I gotta get on the road in a little bit for work, but I'll try to clarify some of this later today if someone doesn't beat me to it first....although I understand it's workings in my head and in practice, I want to be careful how I word it so it's accurate yet understandable... From the outside looking in, it might look like sloryder and I are bantering a bit. Quite the contrary....putting this stuff in the open and discussing it is the best way to learn and think.... Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted June 3, 2010 Report Share Posted June 3, 2010 (edited) This is a great conversation right here....going way beyond "head" talk. I gotta get on the road in a little bit for work, but I'll try to clarify some of this later today if someone doesn't beat me to it first....although I understand it's workings in my head and in practice, I want to be careful how I word it so it's accurate yet understandable... From the outside looking in, it might look like sloryder and I are bantering a bit. Quite the contrary....putting this stuff in the open and discussing it is the best way to learn and think.... Upon further thought, what Daj is saying makes sense. Although you lift the E port 2mm say, its relation to the entire trapped volume is likely small in relation to the .010" you take off the head and its associated reduction of the compressed volume at TDC. So, to be safe .025"=Pump gas .030"=50/50 race fuel, pump gas .035"(squish allowing) race fuel Methanol=Re-chambering This should be a safe medium timing and other things considered. Edited June 3, 2010 by SLORYDER Quote Link to comment Share on other sites More sharing options...
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