carb questions
June 29th, 2012, 04:18 AM
#1
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carb questions
Sorry for all the newbie questions been out of it for awhile.
Can anybody tell me the difference between a 7040251 carb and a 7040257? i need a 70 and a 72 carb for both my cars one has a chevy carb on it the other has a buick!!!
Thanks
Can anybody tell me the difference between a 7040251 carb and a 7040257? i need a 70 and a 72 carb for both my cars one has a chevy carb on it the other has a buick!!!
Thanks
June 29th, 2012, 04:23 AM
#2
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2) subtle changes in exact jet sizes, power piston spring selection, etc.
June 29th, 2012, 04:39 AM
#3
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Drop Q-Jet guru Lars Grimsrud a line v8fastcars@msn.com, and he'll send you his service papers no problem. Most Q-jets are quite similar, but the metering rods, orifaces, and power piston springs can vary a pretty good amount. May seem like little things, but can make a huge difference, when properly set up for your particular engines application.
June 29th, 2012, 08:21 AM
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Last edited by 69'442; June 29th, 2012 at 10:17 AM.
June 29th, 2012, 09:26 AM
#6
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As mentioned, get hold of Lars's papers, as lists all this information, including the metering rod and jet orifaces used in them. The #251 carb is from a 70' Olds basic 455, with the #257 being from a 70' Olds W33 455, auto tranny.
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