Buick Q Jet Carbs, 750 and 800 CFM Questions

chris ok · 02-05-2013, 09:37 AM

I've read q jet carbs up to 1970 were all 750 cfm. Including 455 engines. Starting in 71 they were all 800cfm. Is this true?
I have 2 carbs a 1970 factory replacement for a GS350 7042944 KH 0032 and a 1973 7043240 LA 0253 oem from an electra.
Looking to use the better model of the 2 on a 455. Not stock eliminator, street resto of moms old Buick.
Thanks, Chris.

tj310 · 02-06-2013, 08:37 AM

If the Electra was a 455 it probably has the higher cfm carb . The difference is on the primary side diameter around the venturi. Look into the throats of both carbs there is a noticeable bump in the casting adjacent to the idle speed screw.---Trevor

chris ok · 02-06-2013, 07:53 PM

I did last night at my engine builders shop. Then went home to confirm my eyes findings on NHRA Blueprint guide. Definitely a difference in size, and booster styles. 73 it is, w new bushings and float. Thank you for confirming my findings.
Chris O'Keefe.

02-05-2013, 09:37 AM	#1
chris ok Senior Member Join Date: Jul 2002 Location: Long Island, New york Posts: 592 Likes: 131 Liked 46 Times in 29 Posts	Buick Q Jet Carbs, 750 and 800 CFM Questions I've read q jet carbs up to 1970 were all 750 cfm. Including 455 engines. Starting in 71 they were all 800cfm. Is this true? I have 2 carbs a 1970 factory replacement for a GS350 7042944 KH 0032 and a 1973 7043240 LA 0253 oem from an electra. Looking to use the better model of the 2 on a 455. Not stock eliminator, street resto of moms old Buick. Thanks, Chris.

02-06-2013, 08:37 AM	#2
tj310 Member Join Date: Sep 2009 Location: Dresden On. Canada Posts: 460 Likes: 0 Liked 0 Times in 0 Posts	Re: Buick Q Jet Carbs, 750 and 800 CFM Questions If the Electra was a 455 it probably has the higher cfm carb . The difference is on the primary side diameter around the venturi. Look into the throats of both carbs there is a noticeable bump in the casting adjacent to the idle speed screw.---Trevor

02-06-2013, 07:53 PM	#3
chris ok Senior Member Join Date: Jul 2002 Location: Long Island, New york Posts: 592 Likes: 131 Liked 46 Times in 29 Posts	Re: Buick Q Jet Carbs, 750 and 800 CFM Questions I did last night at my engine builders shop. Then went home to confirm my eyes findings on NHRA Blueprint guide. Definitely a difference in size, and booster styles. 73 it is, w new bushings and float. Thank you for confirming my findings. Chris O'Keefe.