Slant cylinder head vs. strait cylinder head

noco said:
Ok I found my answer timing needs to be retarded after 7000rpm due to faster burn caused by turbulence. In general it is lower than a 4stroke due to heat on the piston face. Well ethanol should help reduce that heat. Now ethanol engines you want you highest pressure at 10degrees Atdc instead of 15 to 20 degrees. Hmm... Maybe I'll try keeping the stock timing and figuring the timing issue out after...if your saying that retarding the timing at high rpm helped maybe the stock timing might just be right...

Happy riding...
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If you read everything at the link in my post it explains pretty well, basically the timing being too far advanced keeps the rpms down, and the stock ignition they claim is for a four stroke and is totally wrong for these engines. This may be true since I saw a definite gain with the Jag ignition. Also the Jag is fun for me since it has more tuning to play with. (Lots of experience in racing karts, midgets, drag racing and street rods along with 30+ years of mechanical, and fabrication experience so trying to get speed out of one of these has been fun).
 
I saw that link bill...it actually sounds like a good product...the rpm is held down by the combustion speed causing the max pressure to occure at too vertical of a crank angle...after you left me that link I kept researching the topic abit...I wish I saved some of the links...now the more vertical crank angle might be good for me playing with ethanol due to its slower and cooler burn...now I need to find a machine shop since the one I had been using just pissed me off after they checked a head for me said it was fine then I rebuilt a jeep 4.0l with a cracked head...it took every bit of self control not to throw that head through their window....I've saw earlier that someone here had planed .25 to.30 off the head...does anyone know what psi compression that would make???since ethanol is 104 to 105 octane depending on additives for cold start you can increase the compression quite abit...you kinda need to if you want to get the mileage and power back from when you switched from gas...and my other question is can the cheepo bottom ends handle the added compression...well anyways that sounds like a different thread...well I guess I may be the first to try this stuff...ugh...it's always best to have someone else go first...after learning on that car I'm just not afraid of it any more and it's kinda fun...

Ride fast...take chances!!!
 
I was measuring my clearance to the spark plug today and its huge...I think I can almost take 1/4 off!!!lol...I don't know what ratio that could be...does anyone know about what compression ratio(psi) comes with planing???how much is how much to 1 maybe
 
Here is a simple method for a 66cc motor... thread a plug into the head and make sure it is level. Say you want a compression ratio of 10:1, take 6.6 cc of water, and put it into the combustion chamber. Mark the level at the edge. This will be slightly low to surface tension resulting in a higher cr, though likely less than .1. Note this does not take into account the volume of the head gasket, which can be found by (17.35xgasket height in cm). If you subtract this volume from the 6.6cc, you can use the resulting volume as the volume of water to use in the combustion chamber. Also be aware that the cr is not static, but dynamic in a two stroke due to the open ports and effects of an expansion chamber. There is also a factor of stretch due to the elasticity of the rod and pins.
 
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