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Carburetor replacement ??? Suggestions
#753301 October 14th 2019 5:58 pm
Joined: Sep 2016
Posts: 90
J
journeyman
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I had this Rochester Quadrajet completely rebuilt last year. The Van is running terrible. At about 50 to 55 mph It bogs out and wont run. One mechanic that admittedly knows very little about Carbs suggested I get a replacement carb .
Ok but there's so dang many to choose from, Where do I begin.
Dodge
1988
B-350
360 motor
Rochester QuadraJet carb.

Re: Carburetor replacement ??? Suggestions
Jerry_XtraVanTastic #753302 October 14th 2019 6:04 pm
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Maniac
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I would start by getting a new mechanic. Getting your orginal carb professionally rebuilt by a reputable shop is your best bet. In fact, you can probably do it yourself. There are books and lots of videos and informational "how-to" posts on rebuilding the Quadrajet online. We are at the point where new mechanics aren't really trainedon how to repair and diagnose a carb, especially one as complicated as the Quadrajet. If you own a carbureted vehicle you pretty much have to know how to repair and maintain it yourself.

I would start by getting the factory service manual for your van and going through the carburetor fuel system troubleshooting section of the manual. 1988 was the last year the 360 was carbureted.


Windows- they're what make a van worth owning!
Re: Carburetor replacement ??? Suggestions
Jerry_XtraVanTastic #753303 October 14th 2019 6:15 pm
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old hand
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Have you eliminated all other things besides carb yet? New carbs are to the tune of $300. Id make sure all of your vacuum lines are properly connected and the timing is all working correctly. Id also get someone more familiar with carbs to give you a diagnosis. When did you start noticing the problems? Is it only that speed range? What does it do at start up and idle?

That being said, if you do swap it, the new Edelbrock AVS2 is a fantastic carburetor that we just put on a 350 sbc and its wonderful. The summit 600cfm carbs (made by holley) are really nice too. Im gonna swap one of those onto my 318 this winter. Both of these have annular fuel boosters which atomize the fuel considerably better than down leg fuel boosters which is more of a stream.


1987 B250 - Painkiller
Re: Carburetor replacement ??? Suggestions
Jerry_XtraVanTastic #753304 October 14th 2019 7:27 pm
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LOL Reed Ya Joe is a compressor repair man. I just asked him to ride along on a test run.
As for having it rebuilt , I did that last year one of the best rebuilders in the midwest. I could take it off and bring it to him I suppose , ask him to take a look at it.

yes I have the Manual you speak of for the van . It's like a greek novel , Might as well be written in Arabic. With pictures.
I have a knack for taking things apart.... they rarely ever work again an I usually bust something in the process.

The motor runs perfect A little hard starting but it's allways done that.
Once you've ran it It starts with the flick of the key.
If you only drove it in town you would never know it had a problem.
full throttle Bogs out around 45 to 50 every time.

Re: Carburetor replacement ??? Suggestions
Jerry_XtraVanTastic #753305 October 14th 2019 7:31 pm
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Forgot to say I recently dropped the fuel tank and repaired the sending unit. I wonder if I got some crap in the fuel filter.

Re: Carburetor replacement ??? Suggestions
Jerry_XtraVanTastic #753306 October 14th 2019 7:50 pm
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old hand
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It did that before the rebuild too? (bogging at speed)


1987 B250 - Painkiller
Re: Carburetor replacement ??? Suggestions
Jerry_XtraVanTastic #753307 October 14th 2019 10:17 pm
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Wel, I hate to say it, but if you can't comprehend the factory service manual then you really shouldn't try adjusting your carburetor. Your best bet is to take it back to the shop you had rebuild it and ask them to tune it for you. The quadrajets have some known quirks. Have the shop check the throttle shaft bushing wear. This can cause air leaks which lead to bogging and poor performance. The throttle shaft can be rebushed, but the carb has to be disassembled to do it.

It sounds like the carb starts to have problems once the secondaries start to open. This could be a misadjusted or ruptured diaphragm or gasket or a carb tuning problem. The quadrajet uses an air metering system on the huge secondaries that needs to be adjusted properly. The system is pretty good when it is working right, but if you don't know what you are doing it can be troublesome to set up.

However, I second what deathorvictory wrote. I would start by making sure all of your vacum hoses are still holding vacuum and routed correctly. Make sure the distributor vacuum advance pod (a) is hooked to the correct port on the carb and (b) still holds a vacuum.

Check this page out and maybe try contacting the company they reference. https://www.hemmings.com/blog/article/the-inner-workings-of-the-quadrajet/

Last edited by Reed; October 14th 2019 10:18 pm.

Windows- they're what make a van worth owning!
Re: Carburetor replacement ??? Suggestions
Jerry_XtraVanTastic #753308 October 15th 2019 7:29 am
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I don't have a list of all that the rebuilded did, It was a long list, but ya he (line bored) drilled the Throttle shaft and rebushed it.

He did tell me to check the vacuum with a gauge once I installed it. But he also said It would be very rare that it needed to be adjusted. I think he said 15 to 17 # .

Oh ya It ran good when I first put it on. Once in a while it would stumble on full Throttle take off . It did this before the rebuild.
Strange now that it's bogging out it doesn't stumble anymore.
But that's not what it's doing now.
It could be an air leak. I was thinking of taking it to a shop with a smoke machine an see what's what.
Thanks

Re: Carburetor replacement ??? Suggestions
Jerry_XtraVanTastic #753693 October 27th 2019 10:30 am
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Turns out Low vacuum was all that was wrong.
Adjusted Both Low end screws (which are NOT screws at all, had to buy a tool) brought vacuum up to around 20" . And it's back. Can't believe that's all that it was , But there it is.
I have a video of it running out on FB but it's to much to post it here.

The Carb rebuilder took about 15 seconds to tell me what was wrong.

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