Rochester 2gc - Chevy 400

M Brand 505B · 02-11-2017, 09:21 PM

Anyone have a 1970-75 Chevrolet parts book that confirms which part numbers were on the Chevy 400 2gc? Trying to confirm which CFM carbs were available. On the blue print specs it only shows a 1.25 carb which I believe is the 381 cfm.

Thanks,

Greg Reimer 7376 · 02-11-2017, 09:45 PM

Look out for an OEM carb, then measure the ventures. Some of these are the 1.375" venturi, and the alternate carbs shown on the blueprint specs on your Tech Bulletin specify the smaller venturi,even though the car originally came with the larger one. Some replacement parts differed from the OEM.

MAURICE BLENDHEIM · 02-11-2017, 11:54 PM

Michael… 1970: 7040117, 7040118, 7040119, 7040120. 1971: 7041118, 7041137. 1972: 7042118, 7042838. 1973: 7043118, 7043119. 1974: 7044118. 1975: (4 barrel only). 1.25=381cfm, 1.312=423cfm, 1.375=435cfm. The are all referred to as "Large Base" starting in 1970. I hope this helps…Maurice.

NORMAN BARNARD · 02-12-2017, 12:33 AM

Maurice, what is the test pressure being used to arrive at those flow numbers?

FED 387 · 02-12-2017, 01:48 AM

3.0-fed387

V M Kauffman · 02-12-2017, 11:33 AM

Quote:

Originally Posted by NORMAN BARNARD

Maurice, what is the test pressure being used to arrive at those flow numbers?

4 bbl 3.0
2bbl. 1.5
1 bbl. 1.0
All are SAE Specs

Run to Rund · 02-12-2017, 11:38 AM

Under vacuum, 3" was used for 2 bbl since originally at WOT that was about the vacuum achieved; 1.5" was used for 4 bbl carbs. The conversion factor is discussed in Doug Roe's book, and for example the 1-3/16" venturi carbs would give 247 cfm on the 4 barrel scale, 1-5/16 about 299, and the 1.25" iirc around 280.

M Brand 505B · 02-13-2017, 05:40 PM

Thanks for the help so far. The particular carb number that is listed for the 74' 400 is 7044118. If anyone has this carb laying around can you please measure the venturi size for me?

Dave Noll · 02-18-2017, 10:35 AM

This might be of interest .......

http://www.ebay.com/itm/GM-Chevy-Che...NX~WfV&vxp=mtr

02-11-2017, 09:21 PM	#1
M Brand 505B Member Join Date: Jul 2007 Location: Georgia Posts: 154 Likes: 2 Liked 30 Times in 9 Posts	Rochester 2gc - Chevy 400 Anyone have a 1970-75 Chevrolet parts book that confirms which part numbers were on the Chevy 400 2gc? Trying to confirm which CFM carbs were available. On the blue print specs it only shows a 1.25 carb which I believe is the 381 cfm. Thanks, __________________ Michael Brand II 505B - F/SA

02-11-2017, 09:45 PM	#2
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,111 Likes: 164 Liked 649 Times in 208 Posts	Re: Rochester 2gc - Chevy 400 Look out for an OEM carb, then measure the ventures. Some of these are the 1.375" venturi, and the alternate carbs shown on the blueprint specs on your Tech Bulletin specify the smaller venturi,even though the car originally came with the larger one. Some replacement parts differed from the OEM.

02-11-2017, 11:54 PM	#3
MAURICE BLENDHEIM Senior Member Join Date: Jun 2011 Location: Langley (no igloos), British Columbia, Canada Posts: 551 Likes: 269 Liked 228 Times in 78 Posts	Re: Rochester 2gc - Chevy 400 Michael… 1970: 7040117, 7040118, 7040119, 7040120. 1971: 7041118, 7041137. 1972: 7042118, 7042838. 1973: 7043118, 7043119. 1974: 7044118. 1975: (4 barrel only). 1.25=381cfm, 1.312=423cfm, 1.375=435cfm. The are all referred to as "Large Base" starting in 1970. I hope this helps…Maurice. Last edited by MAURICE BLENDHEIM; 02-12-2017 at 12:12 AM.

02-12-2017, 12:33 AM	#4
NORMAN BARNARD Member Join Date: Mar 2006 Location: EL PASO, TEXAS Posts: 156 Likes: 0 Liked 2 Times in 2 Posts	Re: Rochester 2gc - Chevy 400 Maurice, what is the test pressure being used to arrive at those flow numbers?

02-12-2017, 01:48 AM	#5
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,349 Likes: 327 Liked 280 Times in 150 Posts	Re: Rochester 2gc - Chevy 400 3.0-fed387

02-12-2017, 11:38 AM	#7
Run to Rund Senior Member Join Date: Sep 2007 Posts: 574 Likes: 6 Liked 44 Times in 22 Posts	Re: Rochester 2gc - Chevy 400 Under vacuum, 3" was used for 2 bbl since originally at WOT that was about the vacuum achieved; 1.5" was used for 4 bbl carbs. The conversion factor is discussed in Doug Roe's book, and for example the 1-3/16" venturi carbs would give 247 cfm on the 4 barrel scale, 1-5/16 about 299, and the 1.25" iirc around 280.

02-13-2017, 05:40 PM	#8
M Brand 505B Member Join Date: Jul 2007 Location: Georgia Posts: 154 Likes: 2 Liked 30 Times in 9 Posts	Re: Rochester 2gc - Chevy 400 Thanks for the help so far. The particular carb number that is listed for the 74' 400 is 7044118. If anyone has this carb laying around can you please measure the venturi size for me? __________________ Michael Brand II 505B - F/SA Last edited by M Brand 505B; 02-13-2017 at 07:01 PM. Reason: Typo

02-18-2017, 10:35 AM	#9
Dave Noll Senior Member Join Date: Nov 2007 Location: Div. 6, Eastern, WA Posts: 694 Likes: 2,257 Liked 219 Times in 105 Posts	Re: Rochester 2gc - Chevy 400 This might be of interest ....... http://www.ebay.com/itm/GM-Chevy-Che...NX~WfV&vxp=mtr __________________ Dave Noll, E/FS ,L/SA 6526