nigels_world Posted January 13, 2009 Report Posted January 13, 2009 My Banshee is showing 110-112 psi which sounds low but I am at 4700 feet and I still have the stock head. It runs really good and has lots of power. I am thinking about getting a head for it but need some advice on what size chamber for my elevation. Most every thing I have read about has dealt with much lower elevation than mine. I want to stay on 91 octane and currently run Yamalube R2 at 32:1. Timing is currently stock and will never go more than +4. Quote
RIPPEN Posted January 13, 2009 Report Posted January 13, 2009 http://www.nossmachine.com/banshee_heads.htm Thats a link to NOSS's site where he has a table that gives you a rough idea on what kinda domes your gonna be after for desired PSI.. Recently the whole compression topic had been thrown around lately so I may get blasted here or proved wrong but on 91 cranking comp I personly wouldn't go much over 155 psi or so.. There are tons of factors that go into actual compression over cranking compression so it gets tough but like I said, my rule of thumb is anything over 150-155 I start to mix and everything over 175-180 psi I start to go to full race fuel.. I have cut 18cc domes(4mill) and I have 170 psi cranking compression.. Previous build was a stock stroke with 17ccs right around the same PSI both with aggresive dune ports and +4 timing.. Both setup I ran on the safe side with 50/50 mix fuel.. Iam thinking you would be after 18's and still ok with pump fuel.. As far as your current comp I think its fine considering the altitude. Most the stock bikes I have seen tested around here were not much higher than that.. Maybe 120's on the fresher bikes with a milled head if I remember correctly... RIPPEN Quote
nigels_world Posted January 13, 2009 Author Report Posted January 13, 2009 Iam thinking you would be after 18's and still ok with pump fuel.. Thanks a bunch for that link. I am thinking 19s... 18s scare me. Any one else at my elevation? Quote
bansheeseat$$ Posted January 13, 2009 Report Posted January 13, 2009 your compression #'s sound right for your elevation.stock shees at 4500 have between 115 and 120.20cc domes should put you at around 130ish.You can run 91 octane with that all the time with +4 timing. Quote
nigels_world Posted January 13, 2009 Author Report Posted January 13, 2009 your compression #'s sound right for your elevation.stock shees at 4500 have between 115 and 120.20cc domes should put you at around 130ish.You can run 91 octane with that all the time with +4 timing. You think 19s would be too much? Quote
Wildcardracing Posted January 13, 2009 Report Posted January 13, 2009 You'll be just fine with the 19's, I've seen people get away with 18's at out elevation...but it's pushing it a bit. Quote
nigels_world Posted January 14, 2009 Author Report Posted January 14, 2009 You'll be just fine with the 19's, I've seen people get away with 18's at out elevation...but it's pushing it a bit. So if I go with the 19s and decide to venture out to Glamis it would just require burning race fuel for the weekend (and obvious rejet) correct? Quote
Handyman Posted January 14, 2009 Report Posted January 14, 2009 So if I go with the 19s and decide to venture out to Glamis it would just require burning race fuel for the weekend (and obvious rejet) correct? if i remember corectly...there will be about a 20-30 psi increase from 4500ft elev. to glamis...you will notice a hell of a difference in power...a lot more of it... Quote
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