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781 BBC flow numbers
Posted: Tue Nov 23, 2004 1:38 pm
by Walline
Can someone help me I am looking for stock, or mildley ported 781 BBC heads with stock valve size flow numbers. Any help would be great!! THANKS, CHRIS
Posted: Tue Nov 23, 2004 3:53 pm
by bill jones
-what is a 781? oval port or rectangular port? what era? what size valves?
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-Thinking it may be an oval port head from the 1960's and 70's:
-at 25" test pressure-
-at -----------------.100", .200", .300", .400", .500", .600"-
int-stock------------ 65----134----180---205---225----255
int-mild ported------65----134----192---230---250----264
exh stock------------54-----97-----120---149---169----186
exh mild ported-----62----109-----144---177---196----204
-This is with stock size valves, something like 2.060" and 1.72"
Posted: Tue Nov 23, 2004 4:22 pm
by Walline
Bill, thanks for the numbers. I was under the impression the 781 head was oval port only and 2.06 1.72. mid 70's. Again thanks for the numbers!
Posted: Tue Nov 23, 2004 6:51 pm
by bill jones
-I can't keep the numbers for all head castings in my head so I wasn't sure what 781's were, but it sounds like they are the normal oval port with the fairly large chambers of the 1970's.
Posted: Tue Nov 23, 2004 7:14 pm
by rfl28
hello chris....781's are oval port bbc oc w/ approximately a 265cc runner and came stock w/2.06 int and 1.72 exh as bill said, ....heads were cast in 1974 for 454's....fyi they respond well to 2.19 int and 1.800 exh and mild port...last set i had flowed 262 int and 197 exh stock,...i have seen chambers from 113cc to 118cc...work great on 470ci or less...hope this helps,....bob
Link to some flow numbers
Posted: Tue Nov 23, 2004 7:55 pm
by PFC1
Chris,
here is a link to some BBC flow numbers. Watch them though because...some of the exhaust are with flow tube on exhaust. They don't actually show the 781 but I think the 049 is pretty similar and the flow numbers are there for that one. But as it looks the guys have already responded to your question. It is still a good link!
http://www.chevyhiperformance.com/techa ... ndex8.html
Link to some flow numbers
Posted: Tue Nov 23, 2004 7:56 pm
by PFC1
Chris,
here is a link to some BBC flow numbers. Watch them though because...some of the exhaust are with flow tube on exhaust. They don't actually show the 781 but I think the 049 is pretty similar and the flow numbers are there for that one. But as it looks the guys have already responded to your question. It is still a good link!
http://www.chevyhiperformance.com/techa ... ndex8.html