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Discussion Starter #1
Okay, obviously I couldn't possibly provide enough info for the question as I'd like to because well, I don't know a darn thing about carbs, except that 4 is better than 2, 6 is great, and they all drink gas and have the potential to start fires...

I've got a 1975 SBC 350 with a 1985 4bbl Quadrajet -- all I had to use at the time.. whatever, it's got some nice plugs on it that never get used --

SOMETIMES it will open all 4 barrels and of course there's that distinctive tone when u can tell it's doing so... but that's more rarely than it is a "sometimes" thing...

Is there a way to keep the other 2 barrels open, or well... hell, I dunno..

What do you guys suggest?
(being cheap and not re-building or buying a new carb)

Thanks!
 

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Clean it?

Possibly the Aux air door is sticking or the engine isn't spooled up far enough. A good Q-jet won't let you feel it, or even see it. Most times you can hear though.
 

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Discussion Starter #3
Perhaps I'm expecting a little too much here...........

What I had originally posted says just what it says.... the other 2 aren't opening..

after some investigation..... (i.e. putting my eyebrows down to the carb)

I see the bottom doors of the carb ARE opening --- about... 1/2 inch......
(A carb I have laying around, which I wanted to use but cant due to it has a hot-air choke is from a 1962 Impala which the other two barrels open all the way, straight down. Q-Jet doesn't?.. If I pull the throttle all the way back - and yes, make sure the..... whatever the hell it is that opens the bottom "doors".... is all the way down, the other 2 will open 1/2"... but no more

Did I just get repetitive there? <grin>

However the top ehm... someone please, what do ya call the damn things that open and close to let air in?-- ::struggling for a word:: -- the top one doesn't open unless held open..... that I know is broken..... i'll just have to get something to hold it open...
 

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It's probably working correctly. You could loosen up the air valve setting but probably cause it to bog if you do. Make it way too loose and it will backfire and die when you mash the gas.
 

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butterflys

Doc here:pimp:

The word is Butterfly's ...which is what you should get in the pit of your stomach if they were opening...:D

The thing that most often locks up the secondaries on a Q~jet is the Choke lockout on the right side of the carb...Also depending on the model of the q~jet you may or may not have a Vacuum secondary unloader valve on the right rear of the carb.

Check the adjustment on both , the lockout is on the right about where the base plate is in between the linkages for primary and secondary...The unloader is a big vacuum modulator (if you have it, you cant miss it) on the right rear, going to the secondary linkage..

Also be sure your Automatic Choke is opening full on warm, That'll hose up the lockout too.

Doc :pimp:
 

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Discussion Starter #6
Thanks for the replies--


Doc I think I know what you're getting at, I might just post a picture of something to make sure I'm right about my assumptions and understandings..... but i'm pretty sure..


--

On a side note.....

Is there a way to.... rig up an old carb that uses hot-air for the choke to an engine? I've been told I need a line from the intake to the carb for it to work-- "Correctly"... how about MAKING it work incorrectly?
 

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You mentioned "some plugs" that weren't used. This isn't a computer carb is it?
 

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Discussion Starter #8
yeah it's got a bit of that bull**** on it..... it's not TOO computerized as it's an 85 and well.... it works on this engine how it did on the last one with all the crap plugged in... only diff is i had to run a hot wire to the distributor for the choke, that's about it. --- which by the way still takes about 3 minutes before the choke opens up completely-----

is there a better way to do this? other than going to the distributor? I don't really care, it's just that it must drink 2 gallons of gas warming up those 1st 3 minutes in the morning because the choke takes that long to open.
 

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Discussion Starter #10
Does anyone understand carb model #'s?

M4MC and M4ME

whats the difference? is there somewhere i can see these 2?

bending rods... sounds like fun! ;)
 

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HAC

Doc here:pimp:

Using a Hot air choke will take LONGER to open than using the electric.

The 3 minute open is not bad, norm is 1 to 3 minutes.

The only faster way is install a mechanical cable for the choke. But , you'll regret it the first time you forget to push it in after startup...the tank will empty mighty fast.

The 4EME and 4EMC are mechanical and computerized...but the numbers that really effect anything you are doing to the carb (like buying a rebuild kit..) are cast on the left side and will start off 1708-xxxx

If your using an 85 q~jet on that car, it probably has a roundish..sensor on the right front top with a 3 prong terminal on it, (fuel metering sensor) and a plunger type of sensor on the left side in front of the primary pump, (Throttle positioning sensor) with a pigtail coming off the sensor to a white plug. On a 75 vehicle, there should be no place to plug these in..It won't hurt anything, (except maybe mechanical bind on the TPS...)

The top rear butterfly opens on pure vacuum on WOT and also kicks in the high speed metering jets, If you can open it with your finger, it's probably OK.

Doc :pimp:
 

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Discussion Starter #12
carbureators are fun!

Thanks Doc, how about I just send this carb to u and u can fix it?

lol -- no, what I was looking at were rebuilt QJet's...... and of course the search for the carb is by the year make model engine......

so I threw in the whole 1975 Chevy G10 Van 350 4bbl info and it mentioned the 4EMC and of course when I looked up 1985 Chevy Monte Carlo with a 5.0L it showed me 4EME...

my worry there was only that the carb which is correct for a 1975 chevy g10 van might not have an electronic choke, as I remembered many vans that I've seen from that year had a manual choke.

Will the 4EMC have a electronic choke?

What happened was I bought that carb from that 62 impala 327 and i never looked into it deep enough and got stuck payin 50 bucks for a carb that needs hot air to open the choke...

but now, alas, I'm looking at buying a rebuilt Rochester... for one all that plastic on my carb looks ugly, number 2 it's a dirty carb anyway even though i clened it in gas a few times, and 3... i know a few things on it aren't working.. like the vacuum that opens the secondary butterfly? that's not doin too good, as it never pushes in or out by itself. and even when ya push it in it doesn't make any difference to the butterflies.... or out.. --- i went a lil dangerous the other day and held the throttle wide open for about 3 seconds.. didnt move.

and fourth and finally..... do you want to buy a carb for a 1962 327 with hot air choke??? hehehe
 

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Photo

Doc here:

Here is the photo I Mentioned in your PM. See if you can Identify what parts aren't working...or hanging up.

On the E Choke, where the 3 rivets go into the metal bowl, just get a #40 bit and drill them out, and remove the mount screws behind it, When you put it on the new carb, replace the rivets with appropriate Self taping screws...

Doc :pimp:
 

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Discussion Starter #14
I think it's gonna be the secondary pulloff valve... here's my own picture.

this is taken without the car running and I'm talkin about these 2 things here..

the item circled on the bottom im not sure what It does but.. if it's what I think it is, it appears as though there's a piece u can't see in the pic connected to the item in the bottom circle-- not connected to, but pushed against, which would move with vacuum to allow the seondaries to open? hell, don't let my assumptions confuse anyone, ui guys should know by the pic.

-Pete

thanks for takin all this time to deal with this matter.
 

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Discussion Starter #15 (Edited)
Another picture

Here is a picture of the carb I had laying around with the HAC

looking at this carb, im not sure where i would stick an electric choke on it....?

numbers are:

7042237
0312
 

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Discussion Starter #16 (Edited)
It also appears that this piece is bent and/or not working properly as it doesn't let me open the seondary butterflies on top without pushing it in.

After some research but im not sure
appears this damn thing comes from a 1972 Cadillac 472?

By the way, I had to laugh at this car.

http://www.dealsonwheels.com/search/detailbig.cfm/Autos__ID/77752
 

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linkages

Doc here:pimp:

The first picture covers your problem... The bottom circle is pri/sec linkages........if they are one top another , backwards they will lock the secondaries on WOT instead of opening them, Try it in both directions, only one will work.

On the second circle, the linkage appears to be straight and correct, If its sticking, check the Choke unloader (the place where the linkage goes on the front) for bind or adjustment.

Either one of these two if wrong will hang you up.

On the choke, I don't see mount holes for E Choke either. You may be stuck with hot air..

Doc :pimp:
 

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Discussion Starter #18
actually Doc, I just got a check in the mail today.. going to college is great, not only is the Fed. Gov't paying my tuition but the State of New York is giving me extra..

$1500 ..... maybe i'll get a rebuilt carb that belongs on a 75 chevy 350...

-- if I were to do so.... any suggestions?


I apologize if I'm indecisive like Kerry and all over the place here, but I like to look at the "whole" picture and gather my thoughts on how I want to proceed after doing so.

-Pete

THANKS!
 

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Not sure I understand your concern. A well tuned Quadrajet or any other vacuum secondary carb will open the secondaries only when engine demand requires the extra flow. I have a microswitch on the vacuum operating lever on my Holley 3-bbl on my 354 hemi that tells me when the secondaries crack open. 99.9999999% of the time around town it runs strictly as a 2-bbl. The secondaries only open when I punch the throttle at speed to pass. That's the beauty of the vac secondary 4-bbl and especially the spread-bore ones like the QJet. They run as economical small 2bbl carbs most of the time but have the secondaries in reserve to give you great top end performance too. Best of both worlds!
 

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Fragzem said:


the item circled on the bottom im not sure what It does but.. if it's what I think it is, it appears as though there's a piece u can't see in the pic connected to the item in the bottom circle-- not connected to, but pushed against, which would move with vacuum to allow the seondaries to open?
The thing we can't see serves to keep the secondaries from opening until the choke is completely open. Some people bend the pin in the secondary shaft out so it won't engage it, some people bend the thing so it won't engage the pin, & some people just wait for it to warm up. No, I am not that patient:D

If you're just revving the engine in neutral, it may be that the secondary air valve is just not being pulled open by the small amount of air flow necessary to rev the engine in neutral. My '72 Q-jet runs fine, but it's air valve only opens 1/4-1/2" before I have to let off the throttle to avoid over-revving the engine.
 
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