245 265 Race Heads

Conventional heads modified to produce up to 40 hp more at 4000 rpm and up to 60 lbs/ft more torque from 1000-3500 rpm

Negative Supercharging race heads are conventional cylinder heads that are modified with special porting, valve angles, high flow intake and low flow exhaust ports to control the Negative Supercharging process and enhance the supercharging effect. Cylinder heads from standard, race, cast-iron to aluminium may be used with Negative Pressure Supercharging. However, conventional race heads must have the exhaust modified to the Negative Supercharging specs.

NOTE
The Negative Supercharging specs improve the intake flow of standard 245 / 265 Hemi heads from 205 cfm to 240 cfm at .550" lift at 28" Hg. We found that the 245 Hemi head with standard 1.84" tulip-head intake valves and the 265 Hemi head with standard 1.96" tulip-head intake valves produce the same flow. We also found that without major porting both the 245 and 265 Hemi heads fitted with 1.96" flat-head intakes and the Negative Supercharging specs produce the same improvement in flow of 240 cfm at .550" lift. We use 1.96" flat-head intakes in the 245 and 265 Hemi heads because, 1) they flow 10-15 cfm more from .150 - .550" lift than 1.96" tulip-head intake valves and larger intake valves and 2) larger intake valves cause valve shrouding near the cylinder wall when the heads are bolted to the block which reduces air flow even more.

245 265 Negative Supercharging Race Head Specs

• 245 - 1.96" / 1.50" (intake / exhaust)
• 265 - 1.96" / 1.60" (intake / exhaust)
• Flat-head Intake Valves
• Tulip-head Exhaust Valves
• Open Chamber
• 8.5 - 9:1 Compression Ratio
• High Flow Intake Ports
• Low Flow Exhaust Ports
• Unshrouded Intake Valves
• Hardened Exhaust Seats
• Special 4 Angle Valve Job
• Special Pocket Porting
• HD Valve Springs (up to .550" lift)
• Valve Spring Retainers (chromemoly)
• Intake Valve Spring Umbrellas (stainless)
• Positive Valve Stem Seals (all rubber 2 ring type)
• Valve Stem Collets (hardened with reduced shoulders)
• K-Line Valve Guides
• Height of Valve Guides reduced to allow .550" lift
• Hi-Tensile Header Stud and Nut Set
• New Brass Frost Plugs
• Cleaned and Crack Tested