ziegman Posted February 4, 2007 Report Share Posted February 4, 2007 Anyone have any suggestions. Just popped a piston skirt on a new shee I just bought used. Put in wiseco pro lites stock bore, hot rods 350 crank from Jeff. Went with noss head and 20cc domes. Compression test shows 125psi on stock head but 175psi on 20cc domes. Jeff and NOSS both think this is too high with 20cc domes. Waiting to hear from Jeff on Monday. Squish clearance is .052 and .053 elevation is 985ft. Test with brand new craftsman tester. Dont want to run race fuel. Did find tetraethyl lead to add to fuel to increace octane to 101 from 93. Any input is appreciated. Quote Link to comment Share on other sites More sharing options...
MotulMonsta Posted February 5, 2007 Report Share Posted February 5, 2007 Anyone have any suggestions. Just popped a piston skirt on a new shee I just bought used. Put in wiseco pro lites stock bore, hot rods 350 crank from Jeff. Went with noss head and 20cc domes. Compression test shows 125psi on stock head but 175psi on 20cc domes. Jeff and NOSS both think this is too high with 20cc domes. Waiting to hear from Jeff on Monday. Squish clearance is .052 and .053 elevation is 985ft. Test with brand new craftsman tester. Dont want to run race fuel. Did find tetraethyl lead to add to fuel to increace octane to 101 from 93. Any input is appreciated. That sounds pretty good to me. I usually shoot for about 165psi when I rebuild engines. I run on pump gas with no additives to increase octane. You don't have a stroker crank in there by accident do you? I mean 2mm stroker will fit in a stock case and you wouldn't even know it until you tried to run it. Then you'd blow it up when that piston slaps the head. I highly doubt the guy whom you bought the bike from shaved his cylinders down. So get another tester and compare results. Make shure you turn the engine over cold and by hand until the gauge no longer reads a pressure increase. Quote Link to comment Share on other sites More sharing options...
dlnoss Posted February 5, 2007 Report Share Posted February 5, 2007 Something just doesn't make sense. That's more squish clearance AND compression than it should be, which really doesn't make sense. I would have estimated .040" squish and about 160 - 165 psi. Did the domes have '20' engraved on them? Is there a compression tester you could borrow to double check with? Had the engine been run to burn off the assembly lube? Just some ideas... Quote Link to comment Share on other sites More sharing options...
Forcefed Posted February 5, 2007 Report Share Posted February 5, 2007 That sounds pretty good to me. I usually shoot for about 165psi when I rebuild engines. I run on pump gas with no additives to increase octane. You don't have a stroker crank in there by accident do you? I mean 2mm stroker will fit in a stock case and you wouldn't even know it until you tried to run it. Then you'd blow it up when that piston slaps the head. I highly doubt the guy whom you bought the bike from shaved his cylinders down. So get another tester and compare results. Make shure you turn the engine over cold and by hand until the gauge no longer reads a pressure increase. 2mm crank ? lol - who makes those ? Turn the engine over by hand ? ummm .... Quote Link to comment Share on other sites More sharing options...
Forcefed Posted February 5, 2007 Report Share Posted February 5, 2007 Something just doesn't make sense. That's more squish clearance AND compression than it should be, which really doesn't make sense. I would have estimated .040" squish and about 160 - 165 psi. Did the domes have '20' engraved on them? Is there a compression tester you could borrow to double check with? Had the engine been run to burn off the assembly lube? Just some ideas... Wonder what his piston -> deck height is ? Right on with the assy lube ... i`ve checked comp right after assembly, and one would be amazed at the comp gain by having a bunch of oil in there. Quote Link to comment Share on other sites More sharing options...
trex banshee Posted February 5, 2007 Report Share Posted February 5, 2007 2mm crank ? lol - who makes those ? Turn the engine over by hand ? ummm .... Same thing i was thinking, haha i would like to see this guy check his compression by hand! :yelrotflmao: Quote Link to comment Share on other sites More sharing options...
Banchetta Posted February 5, 2007 Report Share Posted February 5, 2007 Anyone have any suggestions. Just popped a piston skirt on a new shee I just bought used. Put in wiseco pro lites stock bore, hot rods 350 crank from Jeff. Went with noss head and 20cc domes. Compression test shows 125psi on stock head but 175psi on 20cc domes. Jeff and NOSS both think this is too high with 20cc domes. Waiting to hear from Jeff on Monday. Squish clearance is .052 and .053 elevation is 985ft. Test with brand new craftsman tester. Dont want to run race fuel. Did find tetraethyl lead to add to fuel to increace octane to 101 from 93. Any input is appreciated. First thing I'd do is get a second guage to verify those numbers. I would be scared to run 175psi w/ pumped gas. Most likely your compression will be even higher once you put about 4-8 hours on the machine. It usually goes up another 10-15psi on breakin. I agree w/ Dave, your squish is more than normal, but yet you have more compression. I'd call Jeff and have him send you some 22cc domes and go from there. I know Dave/dlnoss is very knowledgeable on this and helped me a great deal on my stroker. (thanks again dave :thumbsup: ) If anyone can help you it'll be him, but since you got the head off Jeff, I'd see if he'll hook you up and try some different domes. Quote Link to comment Share on other sites More sharing options...
ziegman Posted February 5, 2007 Author Report Share Posted February 5, 2007 (edited) Thanks for the replies. No I have not ran it. I am going to today ( with the stock head). It has new seal kit hot rods crank from Jeff and prolites as mentioned above. I know everything is tight. I will talk to Jeff today and also recheck after my ride today. i also have another tester, it is one of those auto store models that has the adapter that threads on the end. Those are junk because it adds a few ccs because the valve is not in the end of the adapter. Therefore it read about 110 on the stock head. This is why I bought the craftsman tester. The domes do have 20 engraved into the sides. Edited February 5, 2007 by ziegman Quote Link to comment Share on other sites More sharing options...
Banchetta Posted February 5, 2007 Report Share Posted February 5, 2007 110 is about right on a new set of pistons. Once you run a few tanks of gas and break it in, you'll be between 120-128 depending on elevation...let us know what you find. Quote Link to comment Share on other sites More sharing options...
ziegman Posted March 3, 2007 Author Report Share Posted March 3, 2007 110 is about right on a new set of pistons. Once you run a few tanks of gas and break it in, you'll be between 120-128 depending on elevation...let us know what you find. Found tetraethyl lead to add to fuel to raise to 100 octane. Ran for a few hours to burn of assembly lube. Now reads 168 psi. That a little better. Runs great, thanks for everyones help. Quote Link to comment Share on other sites More sharing options...
CadillacBanshee Posted March 3, 2007 Report Share Posted March 3, 2007 Sounds right to me. I have a bike with 189compression on 19cc domes. It did puzzle me for a while but the bike runs fine. Quote Link to comment Share on other sites More sharing options...
blowit Posted March 3, 2007 Report Share Posted March 3, 2007 Sounds right to me. I have a bike with 189compression on 19cc domes. It did puzzle me for a while but the bike runs fine. Your compression numbers are almost right on. Your elevation is lower than most so your number will come in a bit higher due to a denser air charge being delivered the the engine. 175 is right in the window for pump fuels in the banshee. Now, if you want things to get even better, remove the pistons and carefully shave 1mm on the exhaust port side to increase your exhaust port duration. This will increase port duration by 4 degrees and drop static compression by 10 psi. Your bike will run sweeter in the higher rpms and reduce the chance of detonation. In regards to the squish clearance, I am thinking we have a measuring problem. You need to make sure and measure the farthest part out right at the sleeve surface. As you move toward the center, that number will grow. You can also pop the head off and inspect for a zero deck condition that the banshee should have which means the piston edge comes up flush the the deck of the cylinder. You can then measure the gasket and squish depth in the head and calculate your squish in this manner. Quote Link to comment Share on other sites More sharing options...
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