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Old 01-27-07, 06:36PM   #1
hoosier daddy
Join Date: Jan 2007
Location: new carlisle,indiana
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Default Carb cfm rating for '73 400 wk code

Hello, I have a 1973 wk code 400 that I believe came out of a GP. I will be installing this in a 79 firebird. Problem is I do not have the original carb and does anyone know the cfm's for the original? I read that the wk code was installed w/manual trans and a 4 bbl. Any help would be greatly appreciated!!
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Old 01-30-07, 03:44PM   #2
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Probably 780. Depending on what's been done to it, cam, heads, headwork, ect, a 750 should work fine.
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Old 02-01-07, 01:50AM   #3
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Join Date: Mar 2005
Location: Middletown Ohio
Posts: 958

I am not sure what was original but depending on use...and the amount of mods....If its for the street and middle of the road wild to stock I would use a 650 double pumper....If its mostly dragrace and pretty wild yet still close to 400ci I say a 750-850 double pumper.

Butler Performance was pretty adament in telling me my 850 was too big for my 425/450 horse 406ci motor...They told me on the street a 650 would be perfect. They said for the 505 I was looking at that the 850DP HP style I have would be great....I hate vacumn secondary carbs. I will always use a mech. secondary forever more. My personal pref. But with any cam at all a vac. carb doesn't work well.
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Old 04-21-15, 04:18AM   #4
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Location: Niles MI. 49120
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A 750 Q-jet was the original size & that is the size you can use depending on your mods. When you know what your going to build then you can figure out the carb size.
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Old 11-01-16, 02:08AM   #5
Join Date: Apr 2015
Location: Niles MI. 49120
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Heres a little bit of info on the Q-jets. All Q-jets were either 750 or 800 cfm. No matter which car it came on it is one of those 2 sizes. Then after 1975 all Q-jets are 800 cfm. The Q-jet is a great carb & if you use them you'll find that if there put together correctly they will work for almost any engine you have. The 800 cfm came on mostly large cube engines before the 75 models & are hard to find . But again all the Q-jets after 75 are the 800 cfm carbs & will preform very good. These carbs are considered an as needed cfm carb so they will adjust for your engines need when it's needed. Also if the engine did come out of a G/P it would not have been a stick car as there were no 73 G/P's built with a stick in 73. It would have to have been in an A-body car to be able to be a stick car as there were no big cars with a stick also.
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