ToomeySheeLE Posted July 13, 2009 Report Share Posted July 13, 2009 I have a set of both 19cc and 20cc noss domes, I am kicking over 145psi in each cylinder with both sets. I took my head off and am getting some new o-rings as the ones the fit along the domes are questionable.. When looking at the domes its obvious to tell they are cut different.. Is this they way 19's should look in comparison with 20's? I'm running them in a 4mm with spacer plate. Bought the one set from a member, i forget who.. and I'm basically just wondering if they look cut for a different application, the 19's have the smaller combustion hole, but its deeper. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted July 13, 2009 Report Share Posted July 13, 2009 Measure the cc of both. The problem is...it will not be accurate. Because they are recessed/cut for a 2mm stroker, you can't account for that with normal measuring. To measure cc's, get a piece of plexiglass larger than the dome. Use some grease and seal the dome to the plexiglass, drill a hole in the middle of the plexiglass, to add fluid. Put a spark plug in, use a graduated syringe, and fill the domes. One should be 1 cc more/less than the other. Again, the cc number will be off because they're cut for the 4 mil crank, but one should be larger than the other. My guess is, if you're doing the compression test properly and with a known, working gauge, they're the same cc, just different chamber design giving you the impression one is larger than the other. Quote Link to comment Share on other sites More sharing options...
stokes77 Posted July 13, 2009 Report Share Posted July 13, 2009 Dosn't it say the dome size on the side of them? Quote Link to comment Share on other sites More sharing options...
okbeast Posted July 13, 2009 Report Share Posted July 13, 2009 Dosn't it say the dome size on the side of them? Yes some do, but when they're cut for the 4mm crank it all changes. Quote Link to comment Share on other sites More sharing options...
ToomeySheeLE Posted July 13, 2009 Author Report Share Posted July 13, 2009 (edited) yes.. one set has "19" scratched into the sides, and the other has 20 scratched in.. neither set is suppose to be cut for the crank, I am running a spacer plate.. I am more or less asking if that is the way 1cc difference usually looks.. I was expecting them to be cut the same in the center and one just not as deep... Considering both sets have me kicking 145psi, my thought (until i'm able to cc them) is that they are both 20cc - one set is mislabeled and they are cut for "different" applications.. but that is jumping to conclusions. Edited July 13, 2009 by ToomeySheeLE Quote Link to comment Share on other sites More sharing options...
AWR Posted July 13, 2009 Report Share Posted July 13, 2009 he never said they were cut for a four mill.....you should see about a 7-10 lb increase from 20-19cc dome-normally Quote Link to comment Share on other sites More sharing options...
dajogejr Posted July 14, 2009 Report Share Posted July 14, 2009 What do they squish out at? Quote Link to comment Share on other sites More sharing options...
ToomeySheeLE Posted July 14, 2009 Author Report Share Posted July 14, 2009 Both sets squish around .045 Quote Link to comment Share on other sites More sharing options...
dlnoss Posted July 14, 2009 Report Share Posted July 14, 2009 The one on the left looks like it may have been intended for alcohol with the wide area. That wouldn't change the compression. If you are running gas, I'd probably use the one on the right, I know that's not what you are asking. -David Quote Link to comment Share on other sites More sharing options...
Streettrends Posted July 14, 2009 Report Share Posted July 14, 2009 (edited) My advice to all would be check your compression and domes before you crank it and ride. I had my engine built and it seized with 2-3 hrs on it. Everything was looking good. Rebuilt the top end and out of curiosity I did a compression check, it kicked over at 168 cold. I'm supposed to have 21cc NOSS domes (that's how they were ordered, sold, and marked). With the compression it's closer to 19cc domes. Stock carbs 25 pilots 320 mains 32:1 GN2 400ft elevation upper 80's Very light port work 50 over NOSS head Fatty's and Power Core 2 ETA: My buddy used the same gauge and checked his new motor with a few hours and it kicked 135 cold with 21cc domes. Edited July 14, 2009 by Streettrends Quote Link to comment Share on other sites More sharing options...
ToomeySheeLE Posted July 14, 2009 Author Report Share Posted July 14, 2009 The one on the left looks like it may have been intended for alcohol with the wide area. That wouldn't change the compression. If you are running gas, I'd probably use the one on the right, I know that's not what you are asking. -David It seemed to run good off both sets, although I'll take that advice if they are perhaps better for gas. Thanks Quote Link to comment Share on other sites More sharing options...
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