finman Posted March 28, 2006 Report Posted March 28, 2006 Does anyone know what formula to use to figure the total engine CC's after mods. I have a +4 crank, pistons are 6.550, also a port job if it matters. Pro Design Cool head with 18 domes. Running 110 octane, 380 mains. Also just wondering for people running same set up what ratio of syn 2 stroke oil you are mixing. Thanks, Finman Quote
Wallrat Posted March 28, 2006 Report Posted March 28, 2006 (edited) Well stock the bore and stroke is 64x54 to give 347cc's. So you'd be 70.55x58 or 409.1cc's. Stock heads are 22cc so I dunno if that factors in. Edited March 28, 2006 by Wallrat Quote
odaen Posted March 28, 2006 Report Posted March 28, 2006 cc's = (bore/2)^2 * pi *stroke * #cyliinders /1000 Quote
finman Posted March 28, 2006 Author Report Posted March 28, 2006 Well stock the bore and stroke is 64x54 to give 347cc's. So you'd be 70.55x58 or 409.1cc's. Stock heads are 22cc so I dunno if that factors in. 493665[/snapback] I thought it was around 400CC's. Right now I am running 32:1 amsoil. Would I be safe in going to 40:1? Finman Quote
Wallrat Posted March 28, 2006 Report Posted March 28, 2006 Sure as long as you jet accordingly. Quote
lowriderb Posted March 28, 2006 Report Posted March 28, 2006 http://www.web-cars.com/math/displacement.html click on metric and 2 cylinders. put in the stroke and bore to find out cc's... like was said stock stroke is 54mm's so a 4mm crank will make it 58mm's stock bore is 64mm's as well.. it looks like your cc's is 390.868cc's with a 65.50 bore.. Quote
bkabina Posted March 28, 2006 Report Posted March 28, 2006 391cc 40:1 is just fine Stroke and bore are the only things that will change your displacement. Quote
Wallrat Posted March 28, 2006 Report Posted March 28, 2006 (edited) Ah my bad...when he said 6.550 I was thinking he went big bore. That decimal point just cost you 19cc's! Edited March 28, 2006 by Wallrat Quote
finman Posted March 28, 2006 Author Report Posted March 28, 2006 Sure as long as you jet accordingly. 493676[/snapback] Wallrat, When going from 32:1 to 40:1 what effect would that have on jetting. Would that lean it out a little? Running a 380 main jet right now and it is a little on the rich side. Also I have an adjustable timing plate but set at 0. Would I be safe advancing it at all when also changing to 40:1 ratio or would that be way to lean. Thanks, Finman Quote
sheefreak Posted March 28, 2006 Report Posted March 28, 2006 It would actually richen it. Think of your jetting in terms of air to fuel, not fuel to oil. If you take away oil and have same size jet, more gas can get through jet. It might not even make a big enough difference to rejet just going from 32 to 40:1. Quote
finman Posted March 28, 2006 Author Report Posted March 28, 2006 It would actually richen it. Think of your jetting in terms of air to fuel, not fuel to oil. If you take away oil and have same size jet, more gas can get through jet. It might not even make a big enough difference to rejet just going from 32 to 40:1. 493747[/snapback] Ok, so I might need to drop to a 370 if it runs a little fat. Got it. Thanks, Finman Quote
finman Posted March 28, 2006 Author Report Posted March 28, 2006 It would actually richen it. Think of your jetting in terms of air to fuel, not fuel to oil. If you take away oil and have same size jet, more gas can get through jet. It might not even make a big enough difference to rejet just going from 32 to 40:1. 493747[/snapback] Sheefreak, what effect would it do if I adjusted to +4 timing? Would it lean it out a little? Would that kind of cancell out switching to 40:1? Thanks, Finman Quote
Chemical Castration Posted March 28, 2006 Report Posted March 28, 2006 http://www.bansheehq.com/forums/index.php?...topic=58546&hl= Quote
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