First real drive! Not tragic but not good. I think I need carb advice.

Ricko1966 said:

We need a pic with the air cleaner off. Need to see where the stray hose connects to the carbureator. In your second Pic that is the can for the vacuum advance,connect it to manifold vacuum. You still need to check accelerator pump shot. Put a piece of hose on the vacuum advance and suck on it does the diaphragm move you can feel the Plunger on the back with your finger. Does it hold vacuum or do you have to keep drawing on it?

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OK - I finally took off the air cleaner housing - which was way easier than I was expecting.

With it off I did find an idle hose that I think came off that diaphragm so I put that back on. It didn't seem to change anything. I fiddled with the moving parts a little to see if they're moving cleanly - they are. One little adjuster I don't think I was supposed to mess with as it didn't pop back into place. Any idea what this is?

Here's the pics from right after I removed the cover (before connecting the vacuum line)

And also - this was that mystery hose - it was coming off of the air cleaner housing connected to something called AC. Thoughts?

See photo

Also get number off the side of the Quadrajet. For example my ‘75 Quadrajet is 7045583 YZ.

One strong recommendation is to immediately convert it to HEI ignition. It is very reliable, and does not require periodic adjustment like you will need with your points ignition.

Lots of large cap HEI distributors available from aftermarket, or you could even get one from pick and pull. Check the reviews carefully if you buy aftermarket, since some may have very unreliable internal parts. Not need to buy anything special, you just need OEM equivalent for 75+ trucks.

Need more pics, with air cleaner off....then people will be able to help

well I also took this one but there wasn't anything interesting on this side.

RaisedK5 said:

See photo

Click to expand...

So that one you marked in blue must be that second line coming from the air-cleaner.

Just keeping this effort alive. Despite a 4 day weekend - I only had about 3 hours to finally work on the truck.

I started checking compression and replacing plugs in cylinders 1-4 but ran out of light. The headers that are on there completely cover cylinder 6, 7 & 8. I think I can reach 7 & 8 from underneath.

Compression so far seems fine I think. On the gauge it's reading 135, 137.5, 135 & 135 (so far). The plugs all look the same...DARK brown ceramic and dry but the threads were pretty oily. They were screwed in tight so that seemed weird.

With just the 4 plugs changed it didn't change anything in the behavior (I know that doesn't mean anything). I tried running it without the air cleaner just to see if it was maybe running rich but it seemed to run the same (starts like a champ but slowly dies after about 6 seconds of idling unless I really rev it).

One question I had was this - I didn't see anything here to connect to the air cleaner.


Here's a pic from the side


Is this 7047687 the model?

Doing a little research on this model number I found...that's either not the model number or this carb didn't come on this truck, or I found bad intel.

This code would mean it was made in 1977 (truck is 1974) and this is a Varijet for a manual transmission.

Before messing with the carb, make sure the dwell, ignition timing, and the rest of the ignition is in good working order. You will never get the carb right if the ignition is less than perfect.

If the carb does need work, be smart and keep the Q-Jet. Get with Cliff Ruggles at Cliffs Q-Jets, he will spec an overhaul kit that includes good quality parts, and the stuff to calibrate it for whatever changes have been made to the engine. Make sure you have the carb number, it’s on the drivers side rear of the carb.

You won’t match the performance economy, or drivability of a properly built and tuned Q-Jet with a Holley or edelbrock.

Chris64 said:

Doing a little research on this model number I found...that's either not the model number or this carb didn't come on this truck, or I found bad intel.

This code would mean it was made in 1977 (truck is 1974) and this is a Varijet for a manual transmission.

Click to expand...

1000% likely. You’re not certain it’s original I presume. Not the issue, fundamentally. Doesn’t mean the carb ain’t pooched though.

The tube coming out the side is a vacuum port that goes to the air cleaner thermo switch that controls the heat stove valve.

Chris64 said:

Doing a little research on this model number I found...that's either not the model number or this carb didn't come on this truck, or I found bad intel.

This code would mean it was made in 1977 (truck is 1974) and this is a Varijet for a manual transmission.

Click to expand...

What you are looking for should be on the drivers side of the carb, towards the rear:

Cliff’s site here

A Varajet is a progressive type 2 barrel carb used on 4 bangers.

You have a non mod quad, so it’s 1975 and earlier design.

Look at the picture of my ‘75 Quadrajet and you can see the number (7045583) on the throttle linkage side. In the other picture you can see 3 ports on the front.
- small fitting on the right goes to the vacuum advance
- slightly larger port with a raised ridge is for the vapor canister (I apparently have California emissions)
- just under the block with the word Filter on it you can see the 3/8” port for the PCV
- There are also 2 more small vacuum ports on the front near the choke side. One is capped and one goes to the choke pull-off.

So if I have a non-mod quad - is that a bad thing?

OK - while looking around for black Friday deals I found an auto part store near me that is going out of business (all sales final) but they had really good prices on a bunch of new stuff. I ended up getting an Edelbrock AVS2 650, air cleaner, mounting plate, fuel filter and all the hardware for a little over $400. Even if the stock carb is better, mine, in it's current state, doesn't appear to be better. This will give me something to use and compare while I figure out what to do with the non-mod-quad. I may put this on and it does the exact same thing in which case I have a nice spare.

This is leap frogging my current diagnosis. This weekend I planned to finish up the compression and timing and tweak on my steering a little.

I am also on the lookout for an HEI to replace the points distributor. Any recommendations?