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.

02-11-2017, 09:21 PM	#1
M Brand 505B Member Join Date: Jul 2007 Location: Georgia Posts: 158 Likes: 2 Liked 31 Times in 10 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: 1,139 Likes: 172 Liked 727 Times in 221 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: 570 Likes: 311 Liked 286 Times in 88 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: 3,429 Likes: 564 Liked 336 Times in 183 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 Location: Henderson, NV Posts: 586 Likes: 9 Liked 56 Times in 29 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.