7040205 carb
Thread Starter
Melting Slicks
Joined: Mar 2010
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From: Randolph nj
7040205 carb
I recently bought a 7040205 Rochester carb for my 70 454 390 the carb was originally on a chevelle or camaro I think it seams to be missing the rear vacuum plug or nipple that would be for the power brakes now my question is did the carb just have a plug or was their a nipple that was just blocked off. maybe someone has a picture of the back of the carb that I could look at . I looked at the AIM and it does not show the carb too well thanks in advance
Drifting
Joined: Mar 2011
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I can only tell you that my '74 has a 1/4" pipe tap in the center rear of the throttle plate that was used for the power brake booster. If you didn't order the power brakes, the factory installed a hex head plug there.
Maybe you can get vacuum for the PB from the manifold tap in front of the distributor instead. Or try to tap the throttle plate yourself......
Maybe you can get vacuum for the PB from the manifold tap in front of the distributor instead. Or try to tap the throttle plate yourself......
Last edited by gcusmano74; Dec 14, 2011 at 09:05 AM.
Race Director
Joined: May 2006
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Isnt this the part that screws into the back of the baseplate?
http://willcoxcorvette.com/product_i...oducts_id=6544
http://willcoxcorvette.com/product_i...oducts_id=6544
Race Director
Joined: May 2006
Posts: 18,503
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I think I mislead you, The pipe pictured in the link above screws onto a fitting like shown in the link below. The baseplate of the carburetor would have a plug. There are different types of fittings based on the number of ports required. Strange that you cannt find it in AIM, did you try looking in the brake booster area?
http://www.ecklerscorvette.com/intak...ng-2-port.html
http://www.ecklerscorvette.com/intak...ng-2-port.html
Last edited by MelWff; Dec 14, 2011 at 12:53 PM.
Melting Slicks
Joined: Mar 2008
Posts: 2,023
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From: Austin Tx
Here are some pictures that might help you out.
Here's a picture of a carb with a non-power brake plug in it.
Here is a picture of my original carb, on my car (72 SB) with power brakes. You can see the pipe does not screw directly into the carb base plate, it screws into a fitting, that screws into the base plate.
Here is a picture of a spare base plate, and power brake pipe that I have. You can see that they look like they will screw together, but there is actually a fitting that goes between them.
Here's a picture of a carb with a non-power brake plug in it.
Here is a picture of my original carb, on my car (72 SB) with power brakes. You can see the pipe does not screw directly into the carb base plate, it screws into a fitting, that screws into the base plate.
Here is a picture of a spare base plate, and power brake pipe that I have. You can see that they look like they will screw together, but there is actually a fitting that goes between them.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
I believe that Chevy always used the fitting on the rear of the carb base plate for power brake vacuum supply. I don't think I've ever seen a Chevy with P/Bs fed from the intake manifold.
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Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
Here are some pictures that might help you out.
Here's a picture of a carb with a non-power brake plug in it.
Here is a picture of my original carb, on my car (72 SB) with power brakes. You can see the pipe does not screw directly into the carb base plate, it screws into a fitting, that screws into the base plate.
Here is a picture of a spare base plate, and power brake pipe that I have. You can see that they look like they will screw together, but there is actually a fitting that goes between them.
Here's a picture of a carb with a non-power brake plug in it.
Here is a picture of my original carb, on my car (72 SB) with power brakes. You can see the pipe does not screw directly into the carb base plate, it screws into a fitting, that screws into the base plate.
Here is a picture of a spare base plate, and power brake pipe that I have. You can see that they look like they will screw together, but there is actually a fitting that goes between them.
Melting Slicks
Joined: Aug 2008
Posts: 2,200
Likes: 3
From: Lehigh county Pennsylvania
Safety Car
Joined: Sep 2007
Posts: 4,430
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From: Indy Indiana
there are alot of experts out there that will tell you what number carb had what jets and rods and what carbs had specific vacumm hose connections.. but the truth is, the carb will built out of a pile of parts to a certain spec.. who knows what base and vacumm tube was used...
Thread Starter
Melting Slicks
Joined: Mar 2010
Posts: 2,259
Likes: 373
From: Randolph nj
I know for fact that that my car came with power brakes and it getting its supply of vacuum from the manifold but is that right ,, it looks original even though I am running a edelbrock carb now
Melting Slicks
Joined: Aug 2008
Posts: 2,200
Likes: 3
From: Lehigh county Pennsylvania
Except the PCV hose was connected to it. The vacuum source and power brakes were connected to a single intake manifold fitting.
Melting Slicks
Joined: Apr 2007
Posts: 3,189
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From: Tolland CT
You may want to check with your AIM if you have one.
I've seen both configurations, manifold connection or carb.
Here's a pipe for the manifold connection...
You'll need a special fitting for the manifold...
http://www.parts123.com/parts123/yb....Z5Z5Z50000050G
This one for connection to the carb...
http://www.parts123.com/parts123/yb....Z5Z5Z50000050G
I currently use the later, connected to the carb. I'm not sure whether it's the correct configuration. I may check my AIM later...
If you look up the LS5 option in the AIM it may tell you. If not, try J50, look closely to see if there are any notes about the LS5 application.
I've seen both configurations, manifold connection or carb.
Here's a pipe for the manifold connection...
You'll need a special fitting for the manifold...
http://www.parts123.com/parts123/yb....Z5Z5Z50000050G
This one for connection to the carb...
http://www.parts123.com/parts123/yb....Z5Z5Z50000050G
I currently use the later, connected to the carb. I'm not sure whether it's the correct configuration. I may check my AIM later...
If you look up the LS5 option in the AIM it may tell you. If not, try J50, look closely to see if there are any notes about the LS5 application.
Melting Slicks
Joined: Apr 2007
Posts: 3,189
Likes: 111
From: Tolland CT
Looked up application in AIM
According to the AIM for 1970, the LT1, LS5, and LS7 used part #3981090 for the power brake vacuum tube. This tube connects to the manifold, not the carburetor base. Most vendors carry this tube and the manifold fitting required.
The part number for the manifold fitting was 3973474 (standard trans) or 3986116 (auto transmission).
All others used part #3973470, connected to the carburetor base.
The last revision on my copy of the J50 option was dated 1-23-70. It's possible this may have changed for later builds in that year.
The part number for the manifold fitting was 3973474 (standard trans) or 3986116 (auto transmission).
All others used part #3973470, connected to the carburetor base.
The last revision on my copy of the J50 option was dated 1-23-70. It's possible this may have changed for later builds in that year.
Last edited by BBCorv70; Dec 18, 2011 at 11:59 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Well, it appears that the Holley equipped engines did NOT use a fitting on the carb base. Interesting....
But, the Q-Jet carb mentioned above (7040205) IS correct for the '70 Corvette with the LS5 engine. So, it would use the fitting at the rear of the carb base for power brake vacuum source.
But, the Q-Jet carb mentioned above (7040205) IS correct for the '70 Corvette with the LS5 engine. So, it would use the fitting at the rear of the carb base for power brake vacuum source.
Last edited by 7T1vette; Dec 17, 2011 at 11:55 PM.
Drifting
Joined: Sep 1999
Posts: 1,970
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No vacuum fitting on the 70 Q-jet base plate for PB. Funny how much miss info you can get.
Tapped off the intake. Check Dr. Rebuild for a drawing of the fittings for different applications. http://www.docrebuild.com/dr-r-web/CARB-GSKT.pdf There's alot of them.
My 70 L-46....
Tapped off the intake. Check Dr. Rebuild for a drawing of the fittings for different applications. http://www.docrebuild.com/dr-r-web/CARB-GSKT.pdf There's alot of them.
My 70 L-46....