Greetings!

Spring is here and I'm anxious at getting my car out of storage but
concerned about it's performance and lingering gas fumes. My good friend
loaned me a carburetor from his collection to get my car running until a
suitable replacement could be found. When I bought the car 4 years ago,
it came with a Holley which, was not correct. The loaner, a Rochester
Quadrajet - 7040507.

I have a few questions to ask.
What is the difference between this carburetor (7040507) and
the 7040207 or any other 70-72 4-speed Quadrajet? Is it restricted?
Are there different components in it? Could it prevent the 4 barrels from
opening up completely?

Next, I smelled gas lingering in the garage after I shut the car off.
I wondered if the rubber lines that come off the front of the carburetor
would have anything to do with this.

On the 70' 7040507, there are two nipples, one large and one small.
The larger hose goes directly into the left valve cover. I can't remember
if it goes into a PCV valve or not.

The other, smaller nipple at the front of the carburetor;
I can't remember if it's capped off or routed somewhere to the
right rear of the motor. The car is in storage, away from my home,
so I can't run out and look at it.

Way back when on my 72', 350/200hp 4-speed, I faintly remember
the (2) rubber lines at the front of the Carter carburetor, were routed
differently than the 70' Rochester.

On the 72' Carter, the larger of the two hoses went to a Tee in the
left valve cover, connecting to a PCV valve? The hose on the other side
of the Tee and the other smaller hose from the front of the carburetor were
routed down, somewhere into the left front fender. But to what?

Is my 70' supposed to be routed the same way?
Could this account for the lingering gas fumes?

I don't have any photos to show this,
but I hope my description can help you answer my questions.

Any info would be appreciated.

 

Greetings to you;

I have 2 '70 L46 350/350 cars like yours. The 7040507 carb you have on your car is the California emissions version, option code NA9. The other number, 7040207, is for the other 49 states. Unknown which carb your car takes without some investigation, but chances are its a federal (207) car. You might look for a ECS canister mounted on the drivers side inner fender. That would be for the NA9. I can't tell you what it looks like, I've never seen one.

Regarding smelling gas, some is normal at shutoff I believe, but you shouldn't smell any after that. You say "rubber lines", do you mean from the carb to fuel pump? If so, change that out immediately. Also, check the "S" hoses from the fuel lines to the fuel pump for cracks and condition. You don't want gas leaking here.

You should have 2 nipples in front, the larger one is connected to the PCV valve. The smaller one would be for the vacuum advance, routed either to the distributor, or the TCS switch.

If you would want some pics, I could post some, or I'm sure someone could chime in.

BTW; if you are looking for a real nice 7040207 carb, there is one on that auction site now, expiring in 1 day. Not mine, I have no connection, but know the owner. It's a good one, and very hard to find.

Good Luck!

 

Here's 2 pics.... the first is I believe a 7040507, due to that capped off tube by the vac break diaphram . I want to say that tube connect to a vacuum hose used on the smog system that wasn't on the 207 version. I've yet to have someone confirm this, but that's my take on it.

The second is off my L-46 and is a correct 7040207. You'll notice no tube there at all.

 

Hello and thank you for your responses.

The next time I go to the barn, hopefully tomorrow,
I will look for the ECS canister you mentioned.

The "rubber lines" I mentioned are not from the carb to fuel pump.
The carb to fuel pump lines are all new as well as the fuel pump and
there is no leak, but thanks for asking just the same.

As we have discussed this, my memory does recall I think,
having the 2 nipples in front, the larger one is connected to the
PCV valve and the smaller one is going to the vacuum advance at
the distributor.

Rudy

 

Dennis,

I see in the first photo, the vacuum line at both the
front and rear of carburetor connect to the spark control solenoid.

What is the primary function of the spark control solenoid?
Do I really need it? I noticed your not using yours. Since I do not
have one currently, I assume in the second photo (your setup)
the smaller rubber line in front going to the metal tube which,
bypasses the spark control solenoid goes to the vacuum advance on
the distributor?

Where then is the rubber hose that comes off the back of the
carburetor going to? Also, do you have a rubber cap on the other
small nipple on the far right front side of your carburetor?

Thanks again.

Joe



[/QUOTE]

 

Dave,

I found out the black canister in my drivers side inner fender is to retain
the vacuum for my wiper door and headlights. Is this the same as an
ECS canister?

Also, the 7040507 carburetor has (3) nipples in front,
(2) smaller, (1) on each side and the larger one which goes to
my left valve cover.

Your carburetor, I assume is 7040207 only has (2) nipples -
(1) small and (1) large? If so, then there's a difference right there
between the 7040207 and the 7040507.

Thanks.

Joe

 

Joe, the ECS canister is for emission controls (hello, California!). I think it gets expanded to all models after 1970 as my 72 has a charcoal filled emission control canister to absorb fuel vapors. The canister also has a hose going to the carburetor that runs side by side with the PCV hose.

cc

 

Joe.. The tube at the rear air the carb is a vent. In theory, the hose connected to it and the solenoid, provides a vent for the distributor to release vacuum. Sort of a vacuum break.

I have mine disconnected but all there. Runs much better dialed in at 12* BTDC

Also the 207 doesn't have the small a small tube on the driver front. Wonder if that's a 507 thing. Geez can't get a clear answer on this. Any idea's what connects to that other front tube??

 

The third one goes to the charcoal canister.

See CCrane72 post below.

 

Only there is no charcoal canister on a 70'.
It's a vacuum tank which stores vacuum to operate
headlamps and wiper doors after engine shutdown.
1972 or possibly 71' I believe was the first year of the charcoal canister.

 

7040507 is a California carb. California cars had the canister in '70.

This is what the canister looks like:
http://www.ecklers.com/product.asp?p...2&dept_id=1247

Don't confuse it with your vacuum reserve canister.

 

Joe, earlier you asked what the purpose of the Transmission Controlled Spark solenoid was. It eliminates vacuum advance except in certain circumstances.

First, if the engine temperature is below 82 degrees or above 232 degrees it will allow vacuum advance through then it will cut it off until you shift into 4th gear.

It is very disconcerting at first to be in fourth gear and slowing down because the idle remains somewhat high, around 1500 rpm, and as soon as you shift out of fourth it drops to normal idle speed.

cc

 

It allows vacuum in 3rd gear as well.

 

All Corvettes have a vacuum reserve tank, at least until they stopped using vacuum headlights. Then I couldn't tell you if they had them or not.

cc

 

Must have been a change in 72 then. My shop manual says fourth only.

cc

 

Smokin BBC,
My Bad! I owe you an apology.
There are charcoal canister's on a 70' from California.

I meant to say my "Michigan Car" has a 7040507 California
emissions carburetor (Incorrect) with a vacuum tank, not the
charcoal or fuel vapor canister.

I just wanted the 7040507 to work properly and efficently on my car,
trying to use as close to correct carburetor (7040207) which, I can't afford.
The original carburetor either was trashed and or apparently went by the wayside
when the original block blew up in 1974 and was replaced.

So with a cap on that nipple, will the carburetor still work without causing poor performance?

Thank you.

Rudy

 

The 507 and 207 share the same rods and jets. Cap it off and and give it a go.

 

I must apologize, I've been to a bock beer fest today, just got home. The beer was VERY good! Your buddy's 507 carb should run fine with this set-up. FYI, I ran a '69 (7029207) 350/350 carb on one of my cars for a while, and it did fine. Much more common, and easier to find.

 

3rd and 4th on a manual. High gear on an auto.

 

Gotta love a beerfest!