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Old 01-15-2011, 10:17 PM   #1
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carburetor choice?

I know there are some people here that know something about carburetors. Last summer I was having some problems with my 1984 Holiday Rambler Chevy 454 backfiring through the carb. It finally stopped running about a mile from the Chevy Truck Service center I was heading for to have it tuned up.
I had to have it towed into the dealership. While it was there piling up an ungodly bill, the mechanics suggested I replace the Quadrajet carb. They tried a Quadrajet from a local parts store but it didn't have an electric choke or proper vacuum ports, so they sent it back and installed an Edelbrock 1406. The Edelbrock 1406 is a 600cfm and runs quite well until you go up a hill or grade. It just doesn't have much power to keep the speed up. My question is, would an Edelbrock 1411 with a 750cfm work better and will it fit in place of the 1406. Or would it be better to have the old Quadrajet rebuilt and reinstalled. My knowledge of carbs is that I know where they sit on the motor and I know basically how they work. Beyond that, I'm pretty ignorant.
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Old 01-15-2011, 11:35 PM   #2
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The 1411 is recommended for the 454 and Ford 460..and is set up for a ~ 2% leaner mixture than the 1407, saving some fuel. I would think the 1406 is a little too small, especially considering its set up 'out of the box' more for car applications, not truck.

You could try and retune the 1406 for a richer mixture to work better under load, but then your running on the rich side most of the time and still tending to starve the motor of air under heavy load.
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Old 01-16-2011, 12:29 AM   #3
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Quote:
Originally Posted by QuietWater
I know there are some people here that know something about carburetors. Last summer I was having some problems with my 1984 Holiday Rambler Chevy 454 backfiring through the carb. It finally stopped running about a mile from the Chevy Truck Service center I was heading for to have it tuned up.
I had to have it towed into the dealership. While it was there piling up an ungodly bill, the mechanics suggested I replace the Quadrajet carb. They tried a Quadrajet from a local parts store but it didn't have an electric choke or proper vacuum ports, so they sent it back and installed an Edelbrock 1406. The Edelbrock 1406 is a 600cfm and runs quite well until you go up a hill or grade. It just doesn't have much power to keep the speed up. My question is, would an Edelbrock 1411 with a 750cfm work better and will it fit in place of the 1406. Or would it be better to have the old Quadrajet rebuilt and reinstalled. My knowledge of carbs is that I know where they sit on the motor and I know basically how they work. Beyond that, I'm pretty ignorant.
Have the rochester rebuilt and check your fuel presure under. A load, also check your distributor advance , mechanical and vacuum. You cant beat that rochester for reliabilty.
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Old 01-16-2011, 12:39 AM   #4
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If you find that its too far gone to rebuild... : edelbrock 750 carb.
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Old 01-16-2011, 08:36 AM   #5
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Use this for carb calculations:

CIDxRPM/3456xVE=Size(CFM)

454x4000/3456x.80=Size(CFM)

1816000/2767=656 CFM (cubic feet per minute)

Key:
CID - Cubic inch displacement
RPM - top RPM you will be operating at (if higher RPM, it will make that 656 CFM requirement bigger)
3456 - constant
VE - Volumetric efficiency (.80 is for a good running stock or nearly so engine)

The Edelbrock 1406 is way too small for that 454 'hard working' engine.

There is another problem as well - the intake manifold that originally had a Quadra-jet on it is, even with an adapter, not suited for an Edelbrock. The front venturis on the Q-jet are very small for economy while the rears are very large for your power band

Summit Racing have many Q-jets listed: Search Results for Quadrajet - SummitRacing.com

Rock Auto Parts, depending on the model have many as well: RockAuto Parts Catalog

Don't think I'm not a "lover" of Edelbrock carbs as I use them exclusively on my street rods, it's just that there are other ways that work better for a particular combination, and on a GMC/Chevy 454 - there is a better way.

Dave W
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Old 01-16-2011, 08:44 AM   #6
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The QuadraJet works fine, it is just hard to work on and it takes a GOOD mechanic to rebuild one provided it is not worn out. I can work on the Quad, but I hate to do it...it is a big pain.

Ken
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Old 01-16-2011, 08:44 AM   #7
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I like that Rock Auto site. Found my carb.( if I ever need one, I have a spare)
RockAuto Parts Catalog
J
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Old 01-16-2011, 11:03 AM   #8
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Since your old carb is jetted for the rig I would make no change except having it rebuilt by a professional shop....

Look around for "Cliff Ruggles" website and simply call him, The person here on the "Left coast" used by me is "SMI" carb shop in Hunting beach http://www.smicarburetor.com/
Depending on the condition of your carb the throttle shafts probably need to be rebushed and a very good cleaning out of the idle circuit.

Sean Murphy DID bump my main jets up by 1 (73 to 74) but did add the "APT" access to tweak it a dab.....Have a slight off idle stumble which can be dialed out by the "APT" but I'm toooo lazy to dig into it.

Roughly 1 week is the turn around time with Sean and don't know about Cliff's turn around time, You might think about sending in a spark plug along with the carb so the techs can read it and adjust the jets accordingly......

Also the power spring which allows the "ROD'S" to dump fuel when your engine vacuum drops below 11 inches could and should be cut down to 6 inches or so your NOT dumping fuel into the engine on slight hill climbs when the vacuum starts to drop...

http://www.cliffshighperformance.com/

Jim
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Old 01-16-2011, 11:36 AM   #9
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Thanks, guys! I really appreciate the replies. It sounds like I need to have the old Quadrajet remanufactured and reinstalled. I like that idea. I was under a time limit when I took my MH to the Service Center and I'm sure they put the best carb they could get quickly on the MH. It got me where I needed to be but it wasn't ideal for the engine. Why don't these carburetor sites list motorhomes on their selections? It only gives P30 stepvan. That's not necessarily the right choice. Thanks again for all the help!
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Old 01-16-2011, 11:54 AM   #10
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Quote:
Originally Posted by QuietWater View Post
Thanks, guys! I really appreciate the replies. It sounds like I need to have the old Quadrajet remanufactured and reinstalled. I like that idea. I was under a time limit when I took my MH to the Service Center and I'm sure they put the best carb they could get quickly on the MH. It got me where I needed to be but it wasn't ideal for the engine. Why don't these carburetor sites list motorhomes on their selections? It only gives P30 stepvan. That's not necessarily the right choice. Thanks again for all the help!
That's what we have, modified step van frames. (gassers from the old days)
J
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Old 01-16-2011, 01:38 PM   #11
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Thanks, guys! I really appreciate the replies. It sounds like I need to have the old Quadrajet remanufactured and reinstalled. I like that idea. I was under a time limit when I took my MH to the Service Center and I'm sure they put the best carb they could get quickly on the MH. It got me where I needed to be but it wasn't ideal for the engine. Why don't these carburetor sites list motorhomes on their selections? It only gives P30 stepvan. That's not necessarily the right choice. Thanks again for all the help!
Motor homes are such a "Low priority" with any parts I can understand why no parts shops carry specific parts of any kind...

My first RV was a winny 22 (454) and ws jetted way to rich (76) and handed out 5 MPG, Heck it only weighed 10,250 pounds and with proper jetting and ignition settings it handed out over 9 MPG...

That is the one reason I ask you to send in a spark plug so the carb guru can look and see how rich/lean conditions the carb is handing out...

Jim
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Old 01-16-2011, 02:03 PM   #12
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Motor homes are such a "Low priority" with any parts I can understand why no parts shops carry specific parts of any kind...

My first RV was a winny 22 (454) and ws jetted way to rich (76) and handed out 5 MPG, Heck it only weighed 10,250 pounds and with proper jetting and ignition settings it handed out over 9 MPG...

That is the one reason I ask you to send in a spark plug so the carb guru can look and see how rich/lean conditions the carb is handing out...

Jim
Jim, do you have smog checks in your part of CA?
J
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Old 01-16-2011, 02:16 PM   #13
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Jim, do you have smog checks in your part of CA?
J
Yes to those ornery smog checks.....

Every year they continue to tighten up the test parameters and now with the fuel tank pressure test your system best be good..

Jim
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Old 01-16-2011, 06:19 PM   #14
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I went and pulled out my old Quadrajet and looked it over. All this time I thought I had an electric choke. That's what the mechanics told me and just what I had heard from other people. After looking at it I see that I have an air heated choke. That makes a lot of those websites make more sense since they didn't show an electric choke Quadrajet for 1983-84 P30. However, now that I have a wire already there from the Edelbrock, converting over to an electric shouldn't be too hard. I got a recommendation for Guaranteed Carburetors in Largo, Florida to either purchase a reman or have them rebuild mine. Their prices are very reasonable, much less than others I've looked at. Has anyone had any dealings with them?
Here's their website: CHEVY & GMC TRUCK and MOTORHOME (8Cylinder) 4 Barrel Carburetor - all - Guaranteed Carburetors
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