This is my first post (i think) and I'm looking for some general good advice on what direction I should take...

Here is the background:
1972 Stingray, 350 CI, Manual, 56k miles, mostly origional

I have had idleing issues from the start of my ownership about 1.5 years ago. I also have a leak such that rainwater get's in the gas tank. Those combined makes it not start due to water in gas and when started it generally won't idle. Sometimes after it warms up it will idle, but not the other day when I tried.

I had a professional track down the water issue and replace all the fules system hoses. They also cleaned and adjusted the carb and it worked "okay" for a while. He mentioned some corrosion in the carb that would cause backfires and stuff but I could get away with it. They cleaned rust out of the carb from the water in the gas tank issue as well. From there, I got a new gas cap and that didn't solve the water in the tank issue. I got more water in the tank and I flushed it out myself.

Well, since then it's not idled properly and runs okay when I keep on the pedal. I've also got some questionable vaccum lines where some are just about toast. I think vaccum could be part of the issue as well but I don't know how to test this.

If I start it dead cold, it will idle pretty high, so I think the choke is working maybe, but if I even tap the throttle, then it just putters out. Also leaving it idle from a cold start it will eventually putter out without touching the throttle.

I'm pretty mechanical and have been into building 4x4's and building axles, suspension, cages, etc, but I'm not too familiar with carbs and vaccums. I'm looking for a starting point and a plan of action to evaluate this myself and go from there.

Thanks for your help in advance.

-Ryan


ps. Where is the best location to get online factory service manuals for a 72 vette? Alldatadiy only goes to 1985. I've found some places that sell CD roms or paper copies, but I want to make sure I'm getting a good quality one from a good vendor.

 

For the water in the gas tank when it rains check to see if the drain line hooked to the rubber boot by the gas cap is open. If the rubber boot fills up the water will get in the tank. If you stop the water then deal with other problems.

 

I got my books on Ebay

First off, fix the stuff you know is broke, order a new gas tank filler gasket, thats about the only place you can get water in the tank other than condensation.
Next, fix all the vacuume leaks, locate them with an unlit propane torch with the car idling, when you get on the leak, the idle will surge. Locate and replace the vacuume hoses that leak, check the vac canister for the headlights, verify the check valve and filter and the brake booster.
THEN move on to the carb, put on an external fuel filter, flush the tank and fuel lines. Once all is clean and you have the vac leaks fixed, dialing in the carb will be easy.

 

I've noticed that the drain line drains but only after the water level is up some. When I press down with my finger in front of the line then it drains dry. So in essence, it works but there is some water buildup before it drains. I don't think it's enough to get up around the cap, but I could be wrong.

 

Water in your carb bowls will give you those symptoms. Will not idle off choke or without positive throttle position. Under acceleration you have enough fuel to maintain combustion but as soon as you back off you are attempting to run on water!

I have had this problem and appears to be worst with Holley carbs due to bowl and fuel pickup position within the carb.

Agree with Sixfooter, last step should be to remove carb and fully drain moisture.

 

Will I need to drop the tank to get the new filler gasket on? Are you refering to the cup that catches water and drains out the tube or are you referring to a gasket that is between the flat tank surface and the filler neck?

Good idea on the propane. My issue is I can't keep it idling, so will this trick still work if I have a buddy keep it running at say 800 rpm via the throttle? Last night I could keep it running with the throttle at about 700 to 800 rpm but not any lower without puttering out.

The headlight motors and vac lines are all new when I bought it. I will check them again too. "verify the check valve and filter " Not sure what check valve and filer you are talking about. Please clarify. PCV valve? I put in a new one of those.

What sizes of vac lines does the corvette run? I seem to see more that one size. I can measure them up, but figured you al have the quick answer so I can pick them up on the way home. Advance Auto carries bulk vac hose I think. That will be sufficient right? Or should I order Corvette replacement hose from someone like Ecklers?

 

Will the water eventally get pushed through after running it a while or should I just pop off the carb and flush it out? I'm no carb specialist, so any information, links or advice on that would be great. I am mechanically inclined so it's only a matter of time and reading before I will be able to handle it myself.

Thanks!

 

I had to remove carb and physically empty bowls.

There was no way the fuel would push out the water due to the design of the carb. The bowls on the Holley held the water just like a water trap.

I did attempt to use methyl hydrate and a water dispersal product but that leads to a silt byproduct left deposited in the carb(another problem). So yes, the best way to remove water in my opinion is carb removal.

 

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I had water in my tank a few years ago. Replacing the filler adapter gasket fixed that problem.

 

Not sure what that means? Lurk is the name of the icon? I assume it's intented to give me grief or laugh at a dumb question.


Anyways, I ordered a whole kit to replace vac lines and heater hose from Ecklers and hope that should provide me with all that I need to take the variable out of the equation.

 

That's good to hear. I've already ordered the replacements on friday from Ecklers and they should be here soon. Do I need to drop the tank to replace that?

 

Hey Chuck, was this what you replaced?
http://www.ecklers.com/product.asp?p...2&dept_id=1498

 

dannyman,

I'm new to carbs but mechanically inclined. Is it simply to remove the carb and turn upside down and blast with cleaner and such or to I need to remove items to get the bowls empty.

I've got a Q-jet book on the way so I will also be reading that to figure it out as well.

 

Hey VT
Sorry I wasn't paying attention to this thread
You do not need to drop the tank to get that gasket changed, it is a flat round gasket with bolt holes that goes between the filler neck and the tank
If you have not fixed the idling issues yet, try this:
Disconnect all the vac lines for all the accesories and cap the vac ports, then do the propahe test. That will eliminate all the hose related leaks and let you deal with just the motor and carb until you have that part right, then reconnect the acessory hoses and test one at a time.

Here is the check valve I was talking about. It goes on the accesory line after the carb and before anything else
http://www.ecklers.com/product.asp?p...7&dept_id=1326

The PCV valve should be connected to the lower front vac port on the carb, it gets full vacuume, make sure there is not a T left open somewhere

 

The gas tank filler neck seal wil come off and go on thru the gass fill door. There is no need to drop tank.

What do you expect the car to idle at? You indicated that you had a buddy push in the throttle unit it reached 700-800 RPM. What engine and transmission do you have? The owners manual for my 70 indicates idle speeds of from 700 to 1000 for manual trans cars. Your idle should not be set below 700

 

Ryan, I removed and disassembled my Holley to remove the water and fully clean the carb. You did not previously indicate whether or not you have a Holley carb.

Says here that you ordered a Q-jet book. You will have to look at the bowl configuration that your carb uses. My previous statement was intended to bring to light that some carb bowls, due to their design, actually act as a water trap because of the position of the jets in relation to the bottom of the fuel bowl.

Depending on your carb you may have a sight gauge (screw access) on the side of your fuel bowl that you could remove to empty the bowl without a complete carb tear-down, however the carb would still have to be removed from the intake manifold.

 

I didn't see this flat round gasket with the bolt holes that you mentioned for the filler neck on Ecklers. I will look more and check other sites to find it, but if you know who carries it or if you have a link then that would be awesome.

Good info on the vac items. I will follow that procedure and see what I can find out. Thanks!

 

You can rebuild your q jet after you get your book.

In the interim, syphon as much gas out of the tank as possible, put in a water removal product and some fresh gas. It will cure it for now.

As suggested earlier, plug all the vacuum ports on carb and manifold except for pcv system and test and adjust the carb for idle. Then reconnect one by one and look for rough idle. After all is reconnected/rplaced then readjust your carb.

If you are idling at 700 or 800 now, the carb isn't that bad, but a self rebuild is cheap and worth it.

If you have ordered a new tank boot, just remove the old one for now to prevent any new water entering the tank.