need C3 advice on judging

**Barry K.** · February 14, 2006, 10:33 AM

Re: need C3 advice on judging

Mark
if I'm not mistaken I believe that if the carb is the correct make and model as the stock unit and the only thing incorrect is the dating than your loss in judging is only about 8 points.

**Mike M.** · February 14, 2006, 11:47 AM

Re: need C3 advice on judging

Mark,
I believe the float in your carburetor is bad. This is the most common problem that I have seen in Q-Jets. The second is bad choke pull off diaphrams. Replace the float, install the needle valve "hook" correctly on the float, reset the float level and I bet your problem goes away.
Mike

**Mark #44888** · February 14, 2006, 12:28 PM

Re: need C3 advice on judging

Mike - I replaced the float recently with a GM-correct float. No change. I will send you a pic tomorrow of how I have the needle valve positioned (gotta go to work now).

As far as the choke pull-off, is there a test I can do to see if that's the cause (or do you just replace it) ?

I might just ship this carb off to someone who's an expert.

Mark

**Steve Wallach** · February 14, 2006, 01:07 PM

Re: need C3 advice on judging

I have had good service from Chicago Corvette, I bought a set of correct dated
Tri Carbs for my 68 from them, they took care of getting them "show" rebuilt and I then sent in my 67 carb to have it rebuilt. I would highly recomend this
service!

Good luck,

Steve

**don 42616** · February 14, 2006, 06:10 PM

Re: need C3 advice on judging

Mark, The fact that it started leaking "all of a sudden" means that the float is sticking. Try tapping the Carb. body (carefully) where the float is & you may get lucky. Don

**Charles P.** · February 14, 2006, 07:56 PM

Re: need C3 advice on judging

To test the choke pull off, remove the hose, press in on the spring diaphragm. Place your finger over the air inlet. The pull off should "hold" or stay depressed until you remove your finger. If it does not, and you have done this correctly, you will need to replace it.

**Mike M.** · February 15, 2006, 06:56 AM

Re: need C3 advice on judging

Mark,
The "Needle Valve Pull Clip" is installed so the clip is positioned around the front (the edge that faces the plastic float) of the part of the float arm that contacts the needle valve. The front of the float arm has a half round shape where it contacts the needle and the clip hangs from the half round area. Most rebuild kits do not give instructions on the installation of the clip and many put it through one of the holes in the float arm near where the needle valve contacts the arm. This is incorrect and will tilt the needle, therefore not allowing it to properly seat.
Just this week I repaired a Q-Jet on an '80 L-82 with the same problems you are seeing by properly installing the pull clip. This may not be your problem, but thought that I would mention it as I see more improperly installed pull clips than correctly installed.
Mike

**Mark #44888** · February 15, 2006, 02:14 PM

Re: need C3 advice on judging

Mike -

I re-measured the float again, and it "appeared" to be slightly off. It's supposed to be 3/16" for my engine and it was a little less than that. I will wait and see if that does the trick - it usually takes a day or two before this leaking appears. I checked the choke pull-off diaphram. I removed the hose, pushed it in all the way and then put my finger over it. It backed out about 1/8" but stayed there; it didn't travel any further. When it's running cold, it stays in all the way. Here'a a pic of the needle clip position. I think I have it right. Mark

Attached Files

IMG_0258.jpg (21.1 KB, 6 views)

**Mike M.** · February 16, 2006, 12:32 PM

Re: need C3 advice on judging

Mark,
Yes, your needle pull clip is correctly installed. And one more question, when measuring the float level you are measuring it 3/16" back from the nose of the float. This is properly shown in most rebuild kits. A lot of the early replacement floats had a raised line cast on the float to denote where to measure float depth, but I haven't seen this in awhile.
Mike

**Mark #44888** · February 16, 2006, 04:04 PM

float level adjustment

Mike

I am measuring it from across the float at the far end of it, opposite the needle. Is that the correct place? It's still weeping gas out of the gasket

I have another question/comment. I noticed yesterday, while the garage door was open, the sun was shining on the back of the car...When I removed the fuel line from the carb, it continued to dribble gas out of the fuel line for several minutes. I loosened the gas cap; it had built up a little pressure. Shortly afterwards, the fuel stopped flowing out of the line.

Is that normal, or should it be vented? I thought maybe that might be causing gas to enter the carb at a high enough pressure constantly, that maybe that would cause the seeping I'm getting. Long shot, but who knows? I don't!

Mark

**Harold# 43147** · February 18, 2006, 12:49 AM

Re: need C3 advice on judging

Mark I have a 7040507 I just restored I was going to put on Ebay next week. Your problem is One of 4 things 1 Float level is to high should 1/4" from body to toe of float 2 spongy float 3 Bad needle and seat 4 to much fuel pressure 6-7 PSI Max.I have a 7040207 I just took in today I think it is a March date will have to look. This Carb is rare and exspensive.When I restore this one it will go for about $900.00-$1100.00.I have a 7029207 Listed on Ebay (4614034015) same jetting as 7040207.The 7040507 has restricted idle air fuel mixture ant no hot idle bowl vent on front.I also have a 7029204 listed (4614429346)if you want to see Pics.

need C3 advice on judging

need C3 advice on judging

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