rec.motorcycles.harley
General
Philosophical
Synthetic
Oil
Technical
Wrenching
Dyna Frame
Bad Vibes
Rake and Trail
TC88
Cam Specs
Carburetors
Extracting Broken Screws
Fuel Injection Intro
Heads -- Evo BT
Heads -- Shovel
Hop-up Suggestions -- BT
Hop-up Suggestions -- 883
Ignition
Lighting Mods
Neat Stuff
Oil Cooler Fans
Packin' (tools)
Painting & Finish Maintenance
Pipes
Replacement Seats
Roadside Electrical Troubleshooting
Shocks
Tire Specifics
Tranny Lube
Riding
Buying
Selling
History
Harley
.net Resources
Et
cetera
Design and content © 2004
Mild Bill (Asshole #27)
StephG (Asshole#108)
r.m.h VB&G logo design © Jim Combs
Evo Heads
Mfgr. Flow Ratings
All numbers below were pulled from the various manufacturer's specifications and are therefore NOT directly comparable, because of the variations in testing methods. All were normalized to 10 inches of water by Jon via his fancy engine simulation software. The Fast Company numbers were provided by Bob Schleiger, who notes "These numbers are at 10 inches and were done with my S&S intake attached to the intake port."
-
H-D stock intake: 94 cfm @ .500" exhaust: 99 cfm Branch intake: 128 cfm @ .500" exhaust: 110 cfm B. C. Gerolamy intake: 139 cfm @ .500" exhaust: 120 cfm Edelbrock intake: 147 cfm @ .600" exhaust: 120 cfm Fast Company intake: 148.5 cfm @ .500" exhaust: 99.4 cfm intake: 152.5 cfm @ .600" exhaust: 107.6 cfm RevTech intake: 145 cfm @ .550" exhaust: 107 cfm S&S 158 cfm @ .600" S.T.D. 145 cfm @ .600"
"Remember, this still is not apples to apples. To quote D. William Denish, "Valve size, valve lift and anything attached to the port during the test, such as an intake manifold, carburetor or radius entry flange, will affect results." -- Jon Boulle
" S&S uses 2" intakes and oversize exhaust valves in their heads, unlike all the others. That, IMO is an advantage that is integral to their design, as is their piston shape." -- Christopher deHahn
Optimal Flow Rates
"I was going through my HeadQuarters catalog and found this chart for flow rates that are the optimal rates for different engines at different rpms. HQ says that the too much flow is as bad as too little and suggests that you stick pretty close to these numbers."---------------------------------------- ENGINE SIZE (cubic inches) 82 89 97 106 ------------------------------ RPM FLOW (cubic feet per minute) ---------------------------------------- 5700 121 131 144 157 5800 123 134 146 160 5900 126 137 149 162 6000 128 139 151 165 6100 130 141 154 168 6200 132 143 156 171 6300 134 146 159 174 6400 136 148 161 176 6500 138 150 164 179 ------------------------------------------ Jon Boulle