Thread: head flow

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ok im used to turbocharged 4cylinder engines and looking at flow #s around 300cfm @ .400 lift for a ported head.

Ive always heard that SBC 350 heads flowed good but when I went to patriot performance and looked at their ported race head flow #s im seeing 230cfm and a maximum of like 290cfm at crazy high lift from what im used to. Whats up with this??? Is the cfm a measure of total head flow, or single valve flow? Why would a little head with tiny valves outflow a huge head with massive valves?

Originally Posted by ThirtyTwo

ok im used to turbocharged 4cylinder engines and looking at flow #s around 300cfm @ .400 lift for a ported head.

Ive always heard that SBC 350 heads flowed good but when I went to patriot performance and looked at their ported race head flow #s im seeing 230cfm and a maximum of like 290cfm at crazy high lift from what im used to. Whats up with this??? Is the cfm a measure of total head flow, or single valve flow? Why would a little head with tiny valves outflow a huge head with massive valves?

Each intake and exhaust port is flowed by it's self.
As far as the sbc head a std. 23 degree head if it is a good head will support over 700 hp natually aspirated.
What is it your trying to do?

the difference between your rice motors and an SBC is the number of valves.... multiple small valves are more efficient than single large valves... thats the one drawback of using old design engines is there are some newer designs that just cant be implemented.... i guess someone could make an aftermarket block to add valves to an aftermarket head... but you would have 32 pushrods and 32 lifters and 32 cam lobs.... thats a lot of somethin to go wrong....... its a lot easier to work these designs with an overhead cam... which i guess someone could make an setup to run an overhead cam on an older v8... such as the ford 427 cammer

They're available, Gurney-Weslake used to make and SOHC set for a Windsor....Just a bit on the spendy side though!!!!!

Takes one awfully wicked small block to need even 230 CFM, let alone more. Flow rates in the 180 to 200 CFM range are more then enough for anything but the most radical big cube, hi lift, roller cammed, 9,000 RPM monsters....

Another big difference is the straight shot of the intake runner to the valve on a 4 banger. Helps when it doesn't have to swirl around in some questionable plenum then wind it's way down an intake runner and eventually down into a valve....