car and intake questions

by Bret Mullikin Sun May 11, 2014 8:35 am

I finally had some time to replace the intake manifold and carb on the 74 Chevelle. I went from a single plane and Holley to a stock dual plane and quadrajet. The number of inlets on both have increased and there are some size differences between the inlets. I embarrassingly confess that I'm not sure what hoses and sensors go where, or even what they all are. I can't even use the right terms to find a diagram online. Can anyone help with explaining which hoses and sensors go where?

Thanks,

Bret

by 77mali Sun May 11, 2014 9:10 am

Post some pics. That might help us help you. What year is the Carb (ID #'s?)

Usually Q-jets will have Vac Lines that connect to:

1. Brake Booster (large line in rear on most models)
2. PCV Valve on Valve Cover
3. EVAP Canister (smaller line in front)
4. Vac Advance on the Distributor (smaller line in front)
5. Air Cleaner Housing (if using stock) could have 1 Lg & 1 small going to the filter assembly & air intake duct.

IIRC- there are only 3 sizes of hose used, 3/8", 5/16" & 1/8". You may not need to use all the vacuum inlets on the carb depending on how your car is set up. Autozone has plugs for them in kits for short money. As far as sensors- the only thing I can think of is the special connector for a electric choke.

by Bret Mullikin Sun May 11, 2014 9:32 am

Thank You. I will post pics someday, I promise. I have a few specific questions. Please don't laugh. I'm not sure what the big threaded port in the back center of the qjet is. I have a sensor with a long spring wrapped wire that threaded into the front driver side of the Weiand intake. I think it may be the water temperature sensor. There is no port up there on the GM intake. What is it, can it go in a different location on the GM intake, and how do I replace it because the brass threaded adapters are frozen together and will not be salvaged? Does the hose from the brake booster go down just in front of the distributor?

by 77mali Sun May 11, 2014 9:44 am

There is a metal line that threads into the back of the carb (9/16" nut) which the rubber brake booster line will connect to. usually there is a bracket that will house the lines for the gas pedal and/or trans line that is mounted on the rear of the intake manifold (same side as your spring connectors for the carb) that the booster will "pass through" on it's way from the carb.

You can connect that sensor (assuming it is for water temp) into the side of whichever cylinder head is easier for you to connect it to. Usually drivers side works out good- there is a threaded plug on the side of the head which you can remove & insert it into (above the spark plugs usually).

by 77mali Sun May 11, 2014 9:49 am

When you remove that plug- coolant will leak out- be read to go or there will be a pretty big mess you'll have to clean up- LOL

by Bret Mullikin Sun May 11, 2014 10:08 am

OK. I threaded the brake booster nipple and attached the line to the manifold through a vertical port between the carb and the distributor - must be the wrong one. That sensor was in the old intake, not the cylinder head. I really thought it would be a straight forward swap, but I found a way to mess it up.

by 77mali Sun May 11, 2014 11:58 am

Happens to us all- have you read MY thread? LOL

We learn from our mistakes Very Happy

by ant7377 Sun May 11, 2014 12:13 pm

SOunds like you got the booster hooked up correctly. You want vacuum there all the time (manifold vacuum) .

by 77mali Sun May 11, 2014 6:39 pm

*sorry those drain plugs are located on the block, on the heads as I wrote earlier. (brain spasm) See pic below.
car and intake questions P1040510

by Dinomyte Sun May 11, 2014 9:11 pm

Give me ten minutes I'll go snap some pics. I did the same thing years ago when I went from the 2 barrel Rochester that was stock on the 305 to a 4 barrel, and had about the same issues. There are specific locations for each vacuum hose. Sorry I can't find the diagram I have / had with all that stuff. . .

by Dinomyte Sun May 11, 2014 10:21 pm

Here you go. . .

When you're done it should look like this.
car and intake questions Dsc02211

The braided line in my hand is the vacuum to the distributor advance, (red tape on the end) in at the front, below the fuel line (the hard steel one)

car and intake questions Dsc02212

Next the the PCV line, from valve cover to the front of carb, (the one I'm pointing at)

car and intake questions Dsc02213

Now the big yellow cap dead centre on the front of the carb is for the carbon canister (I don't know how that cap got there)
The white one on the left of that is for the air cleaner (if you've got a stock one on)
The white one on the right of that is for the EGR (if used - can also be swapped with the distributor vacume advance)

car and intake questions Dsc02214

The brake booster vacuume is in the back you can just see the nut on the end of the hard line in this pic, and the throttle bracket you'll need. There's a better pic of the bracket later.

car and intake questions Dsc02215

There is also a second bracket for the transmission kickdown, that I can't get a good picture of. You can see the brake booster hard line goes through it, and the blue end of the trans kickdown cable in it here.

car and intake questions Dsc02216

If you're hard pressed to find right bracket for the kick down, you can take the bracket from a 2 bbl and bastardise it. BUT you can't use it for everything as the cable aren't the right length.

car and intake questions Dsc02218

The right carb throttle cable bracket looks like this.

car and intake questions Dsc02219

lastly if you're stuck for caps, just take a piece of hose and screw a bolt in the end and use it like you see in the first few pics. I didn't get to putting the caps I bought the day after the carb went on till now . . .

Good luck

by dynchel Mon May 12, 2014 7:39 am

That one nicely detailed engine dinomyte Thumbs up

by Dinomyte Tue May 13, 2014 8:09 am

Thanks Dynchel. It was a lot of work. I just hope the pics and pointing help Bret.

by Bret Mullikin Thu May 15, 2014 5:17 pm

Dinomyte,
These are fantastic! Thanks everyone for the help. I didn't think I would need it for this - next time I won't.

Thanks again.

by Dinomyte Fri May 16, 2014 8:41 am

Bret - it was my pleasure. It was a good excuse to get out in the garage.

enjoy,
Dino

by Hawk03 Fri May 16, 2014 8:50 am

Thanks Dyno, the pics will come in hand for me as well. I was having a hard time figuring out the vacuum lines on my new intake and carb.

by Bret Mullikin Sun May 18, 2014 11:46 am

Guys,
I have another question. My throttle cable has a ball stud connection but the qjet has a post with a Jesus clip connection. What is the best way to make it work? The post is riveted/permanently on the carb; I'd like to refrain from grinding it off.

thanks,

Bret

by Dinomyte Sun May 18, 2014 12:57 pm

Replacing the throttle cable with the right one, I don't know that anyone has any other solutions like adapters. I had the issue that my cable was too short when I replace the 2bbl with a 4bbl on my old motor and I ended up at the junk yard . . . after many hours of searching for another solution online.

by Bret Mullikin Wed May 28, 2014 9:55 am

Has anyone found the right new cable? I searched everywhere with no luck. I bought one from NAPA for a 75, but it is too long and the firewall plug is too big. I filed the plug down and attached it, but it has a very long loop because of its length. Any brands and part numbers?

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