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Old 12-05-2013, 10:02 AM
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Carbureting a 4.3 Chevy V6 questions

I've got a 1994 Chevy 4.3 V6 that I'm converting to a carburetor. I'm using a 1985/6 truck manifold designed for a 750 quadrajet and using an EFI distributor with both advances. I have a 4bbl Carter carb off of a good running 1959 Chevy 348. I'll need vacuum ports for the distributor, power brakes, a 2004R transmission, and pcv. However, I only have a large port at the base of the carb and 1 port on the intake manifold. How do I adapt the setup for the vacuum ports I need? Is there carb adapters that do this? Also I'll need a braket for the trans TV cable. I've included pics of the setup hoping some one can ID the carb size and year. On the Carter carb back is WCFB, on the top plate is 6-1396, and on the bowl is O-1241. Thanks for any help with this.
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Old 12-05-2013, 10:27 AM
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Maybe you could tell us more about the engine beyond the intake,carb,dizzy.
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Old 12-05-2013, 10:43 AM
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The engine is from a 1994 Chevy Blazer. I removed all the computer wiring, intake, distributor, power steering and alternator mounts, and converted the oil filter from remote. The trans is a 1984 2004R overdrive. Its all mounted in a 1950 Jeepster with a Fatmans front suspension and 1994 2WD Blazer rear.
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Old 12-05-2013, 03:16 PM
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Why not use a quadrajet that has all the ports including the tranny hook up. You won't need an adaptor then to put that carb on the intake.
If you need more vac sources find a vacuum tree to replace the one you have(has a yellow cap on it).
Look on Ford motors for vac trees.
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Old 12-05-2013, 10:50 PM
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750 is too big
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Old 12-06-2013, 03:03 AM
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I do know the 1985 Astro's cam with a 4.3 and Q-Jet.This is all set with electric choke and TV cable bracket for a 700R4.Certainly no where near the size of a 750.I would think Edelbrock still offers a carb correctly sized for the 4.3.Stock SCR 4.3 with a stock cam/heads I am thinking those carbs are in the vein of 500 to 550 max.
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Old 12-06-2013, 07:59 AM
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I'd bet you that carb on the Astro is a normal 750. It's all controlled by the secondary air valve. You only get as much air flow as your motor needs.
Or he could look for a dual jet that would bolt on to that intake.
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Old 12-06-2013, 11:15 AM
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Well I know about those 4 barrel Astro's because I owned one.I really don't think those where that big.
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Old 12-06-2013, 12:17 PM
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I was gonna say that there were 4 bbl 4.3's. I did a 4.3 to 350 swap in a mid 80's Chev truck and it had a stock 4bbl carb and intake on a 4.3. I dont know if the engine was OEM for the truck though.

peace
Hog
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Old 12-06-2013, 12:25 PM
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I am unaware of a Quadrajet that is smaller than 750. Unless I am misinformed, they only came in 750 and 800 cfm sizes. The photos clearly show a Quadrajet intake manifold, so mounting a square bore carb on it will require an adapter to accept the WCFB (Will Carter Four Barrel) or (White Cast Four Barrel) or (Wrought Cast Four Barrel), depending on who you believe. I had one of these little carbs on a 259 Studebaker motor that I used to drag race in G/Stock and seem to remember that the flow was ~400 cfm, although I have heard estimates from 375 to 500.

Although I dislike adapters, I would use one in this instance to eliminate the cost of a different carb and use the little square bore carb, something like this.....
http://www.summitracing.com/parts/edl-2696/overview/
Edelbrock.com - Installation Items - Adapters & Spacers

Here is just one example of a vacuum tree that you can find by the dozens in boneyards, on Ford motors particularly, as RWENUTS stated earlier....
1985 86 87 88 Ford Ranger Truck Aerostar Intake Manifold Vacuum Outlet Tree | eBay
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Old 12-06-2013, 12:39 PM
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There is always the holley (quad replacement ) PN 80555C, it is 650 CFM with vac secondaries, electric choke..if he is looking for new..
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Old 12-06-2013, 09:28 PM
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I appreciate all the responses. I was originally going with a new Edelbrock 500 cfm and use an adapter. And then along came this Carter carb option, so I thought I might save some $. Either way I'll need an adapter, TV bracket, and deal with the vacuum setup and linkage. I could try and find an original quadrajet and rebuild it, which might give me better mpg, but I'm not sure I want to deal with that or not. I would like some opinions on which would be the best, easiest, and most reliable installation. thanks for all your help, Tom.
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Old 12-06-2013, 10:19 PM
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Quote:
Originally Posted by T Evans View Post
I appreciate all the responses. I was originally going with a new Edelbrock 500 cfm and use an adapter. And then along came this Carter carb option, so I thought I might save some $. Either way I'll need an adapter, TV bracket, and deal with the vacuum setup and linkage. I could try and find an original quadrajet and rebuild it, which might give me better mpg, but I'm not sure I want to deal with that or not. I would like some opinions on which would be the best, easiest, and most reliable installation. thanks for all your help, Tom.
Tom, I'd rather run through 400 yards of broken glass than rebuild a Q-Jet. Although I consider them to be the world's finest 4-bbl, I have little patience with small parts any more. I understand that the Q-Jet guru, Mr. Cliff Ruggles, has a backlog of 6 months to rebuild your Q-Jet.

What am I saying? Buy the adapter.
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Old 12-07-2013, 01:19 PM
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Quote:
Originally Posted by 1Gary View Post
I do know the 1985 Astro's cam with a 4.3 and Q-Jet.This is all set with electric choke and TV cable bracket for a 700R4.Certainly no where near the size of a 750.I would think Edelbrock still offers a carb correctly sized for the 4.3.Stock SCR 4.3 with a stock cam/heads I am thinking those carbs are in the vein of 500 to 550 max.
((I do know the 1985 Astro's cam with a 4.3 and Q-Jet.))Yep, and that Q-jet was a 750, or 800. That is the only 2 sizes they come in...
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Old 12-08-2013, 06:24 AM
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With a 4.3 your somewhat limited in carb selection. The spread bore holley would work, but would require a 2 inch spacer, plus the adapter plate, to get it high enough to clear the distributor. On the 4 barrel 4.3's there is very little room between the carb and distributor. Your easiest carb choices are a Quadrajet, which will run great on it, or a Edelbrock or carter afb carb with adapter plate or a Street Demon which comes with a thin plate adapter. You can also use the carb you have with a adapter plate, however I do not like adapter plates, as they can not only disrupt flow and cause vacuum issues which lead to driveability problems.
I have a 4.3 in my 1992 Chevy truck that's overhauled. I installed a larger Isky roller cam, Vortec heads off a 1998 4.3
A marine Vortec intake with Quadrajet pattern that I have a Street Demon carb sitting on top of with it's simple thin plate type adapter that works well.
For spark I have the 1985 4.3 HEI with mechanical and vacuum advance. I removed the factory 3 wire module and adapted a 2 wire Pertronix flame thrower module. The engine has alot of other performance items on it.
It's got a 5 speed behind it and at wide open throttle it pulls hard, but due to the open plane intake it's got, it don't have alot down low where I like it so I'm the process of building a plenum divider for it. It also likes gas, it seems to get worse mileage than a small block would. So after some thought I think before long I'm going to push the 4.3 on a friend of mine who wants one to do a turbo project with and I'm gonna build a 327 small block I've been meaning to build for years now as I have several parts to it.
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