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62STUDEGT
07-19-2012, 07:08 AM
I finally got some time to look at my 62 GT and see if I can find why it's running rich and getting terrible fuel economy.

It didnt take long to find that the vacuum hose was disconnected from the vacuum advance so I installed a new hose and hopefully that will improve things.

I wanted to check and adjust the mixture screws on the carb and was following instructions using a vacuum gauge but I couldnt find a port to connect it to. I disconnected the hose going to the advance but I understand that is ported vacuum and not the place to connect the gauge. Thats the only vacuum line I see- is there a nipple or port on the carb itself to connect the gauge to? I believe it is a WCFB carb.

bezhawk
07-19-2012, 07:31 AM
A good rule of thumb is to screw in the adjusting screws all the way, and then back them out 1 & 1/2 turns. then start the car. Screw each (one at as time) in till it runs rough or stumbles at idle, and back out till it smooths out, and add 1/4 turn.

Bud
07-19-2012, 07:36 AM
There is a pipe plug on the intake manifold behind the carburetor on the left side of the manifold. You can install a hose barb fitting in the port to install a vacuum gauge. If I remember correctly without going out to the garage, the fitting should have an 1/8th pipe thread. Bud

BobPalma
07-19-2012, 07:44 AM
What Brad said in Post #2, Mark.

'Really no need to fool around with a vacuum gauge unless you are trying to impress your wife/GF as to being High Tech, in which case Bud's advice in #3 is also correct. :rolleyes: BP

Mike Van Veghten
07-19-2012, 08:24 AM
You all forgot one thing...

Don't bother adjusting much till the engine is up to it's running temperature (180ish).

I'd leave out the last 1/4 turn also. That's just adding extra fuel. If you want, like I do, gust open the screw the width of the blade slot extra. Most dont need a ton extra, unless there's a vacuum leak somewhere.

Just turn in the screw till the engine stumbles a little, then slowly back it out till the engine smooths out. Then go to the second adjusting screw.
After you do this one time, do it a "second" time. Why...because most probably the second screws original setting was letting the system run a little rich. Now...with the screws adjusted a "little" better...make things better yet, by doing it a second time. It depends on may things as to how much the second adjustment helps. Not worth the extra 2 minutes to not give it a second round of adjustments.

Mike

62STUDEGT
07-19-2012, 09:07 AM
I did do the mixture screws the "rule of thumb way" and it runs very nice- I'm just concerned about running it too lean and causing damage. If it is too lean what would be a sign- hesitation or stumble?

62STUDEGT
07-19-2012, 09:11 AM
What Brad said in Post #2, Mark.

'Really no need to fool around with a vacuum gauge unless you are trying to impress your wife/GF as to being High Tech, in which case Bud's advice in #3 is also correct. :rolleyes: BP


Thats a good one but I've been married too long to impress my wife with my mechanical skills. My projects usually end up involving bandaids or burn cream. When I mention working on the Stude she just rolls her eyes and mumbles something about 911.

BobPalma
07-19-2012, 09:24 AM
I did do the mixture screws the "rule of thumb way" and it runs very nice- I'm just concerned about running it too lean and causing damage. If it is too lean what would be a sign- hesitation or stumble?

Mark, that circuit being adjusted is only the idle circuit. Obviously, the engine doesn't spend much of its total running time on the idle circuit.

If the idle circuit is too lean, it might contribute to a little stumble as it transfers to the main system when accelerating, but such a condition is more normally caused by a bad accelerator pump.

Realistically, if it idles smooth but is a little lean, it would take decades of daily operation to do any damage. So if it idles smooth and runs well, listen for detonation at road speed and address that due to other circumstances if it is present. But it won't be from a lean idle circuit.

Bottom line: If you've adjusted it as we discussed here and it runs well, you're done. BP

Bud
07-19-2012, 05:36 PM
My vacuum gauge is one of the tools that I use often along with a compression tester, tach-dwell meter and timing light. If you understand what it is telling you, an accurate diagnoses can be made to most gas powered engines. I can tune the idle jets on a carburetor by ear, but most people don't know what to listen for. A vacuum gauge along with a tachometer is great for adjusting the idle mixture by people that don't do it very often. Bud

62STUDEGT
07-20-2012, 03:21 PM
Well I adjusted both mixture screws - 1 1/2 out and back in until stumble and back out again until smooth but it is still running very rich with black stuff coming out the exhaust and splattering on the cement. It runs great but something is not right.

So now what- carb rebuild?

41 Frank
07-20-2012, 03:28 PM
The black stuff splattering out could be normal exhaust condensation mixed with whatever has built up inside the exhaust system. Take it for a drive up to highway speed until warmed up and then check it again upon returning home. Most older vehicles will spew out water particles until fully warmed up.

Well I adjusted both mixture screws - 1 1/2 out and back in until stumble and back out again until smooth but it is still running very rich with black stuff coming out the exhaust and splattering on the cement. It runs great but something is not right.

So now what- carb rebuild?

JoeHall
07-20-2012, 06:17 PM
If it is a WCFB, the vac advance line should be connected to manifold vacuum at the carb. I do not believe the WCFB had a ported vac connector anywhere. In other words, you could not connect to ported vac on a WCFB if you wanted to.