question on domes

[drbanshee]

I have a 4mil banshee with 64mm bore, port and polished, sheaerer drag pipes, 19cc domes, pro design coolhead, v3 reeds, 35mm mikuni carbs, +4 timing. I'm looking for more performance. Any of you guys know what size of domes I could go with 17 or 16cc. And what kind of octane would be best to use to get a little more power? My elevation is 5700ft. I'm running 91 octane right now. Thanks for any information guys.

[rascal]

use 110 octane race gas.. anything over 140psi is to dangerous for pump gas.

[firebanshee]

Sea Level 1000' 2000' 3000' 4000' 5000'

18cc 197 178 171 170 165 145

19cc 183 167 160 158 152 137

20cc 169 156 149 146 140 129

21cc 156 145 138 134 128 121

[firebanshee]

Sea Level 1000' 2000' 3000' 4000' 5000'

18cc 197 178 171 170 165 145

19cc 183 167 160 158 152 137

20cc 169 156 149 146 140 129

21cc 156 145 138 134 128 121

so 18cc at 5000ft would be 145.

[camatv]

depends on the porting the higher the exhaust the lower the comp..

[jbooker82]

I don't think the charts are verry accurate for 4mill. I have a fast dune port with 19cc domes at 2,200 ft elevation. My banshee kicks around 185-190 psi.

 

19cc domes on a stock stroke will have less compression than on a 4mill.

 

I would talk to who ported your cylinders. See what he recomends for domes to run straight race fuel. On race fuel you want to shoot for 185-190 psi of compression.