First off, what is a good operating temperature for my 340 67' Lark'? Second, my car runs fine then dies, runs fine then dies when it idles down at the lights, runs fine then dies when put in gear. The carb sat for two years, and I tore it open to clean it. What is the correct way to tune in a carb? I have no idea. It seems to like the choke closed in the morning but when it gets hot and comes to a stop it wants or does die. But starts right up and runs fine when I adjust the choke to a leaner setting with the choke a bit open. And how do you know where to adjust the front screws to? It is a square bore Edelbrock. Any help will suffice if I don't have to push my car off the road daily. Thanks.
Get a vacuum gauge, connect to manifold vacuum. At hot idle, adjust two screws in front to achieve HIGHEST vacuum. As you adjust the two mixture screws, if the idle gets too high, turn the idle speed down as needed. Keep adjusting for best vacuum at idle. Go back and forth to each screw. Once you've achieve highest idle, turn each screw in (lean) about 1/4 turn. You want to drop the idle vacuum about 1/4 inch with each screw, 1/2 inch total. Leaning the mixture slightly will make a HUGE difference in the smog emitted by the car. Note: This is best done at hot idle, IN "Drive". If you choose to do it in gear, BLOCK THE WHEELS AND APPLY THE PARK BRAKE. Any chance there's a defective or missing idle daspot or solenoid on the carb? Do you have a switch pitch torque converter that isn't going to high stall at idle? You'll need to find specs and procedure for adjusting the choke pulloff, too. Comes with a rebuild kit, or is listed in the service manual for your car.
This is very important for this carburetor it seems...you need to have the right gasket for the baseplate of the carburetor--to the manifold. Get a plain Mr. Gasket four hole gasket...your problem sounds like a vacuum leak and Edelbrocks are different enough from Carters that you need that gasket...I had a similar problem and this solved it. I believe it's number 4510 or something like that but I could be wrong...it's an easy to find gasket at a decent parts store...
Thanks for the help. I will definitely buy a replacement gasket because mine is warped and deteriorated. As far as the switch pitch torque converter, yes I have one, how do I tell if it's going into high stall at idle? Does the vacuum advance on the transmission have anything to do with my problem? Just wondering because I have two holes on the back of my intake manifold and I don't know which one it is supposed to go to. There is a smaller one on the left,if your facing the front of the engine, and a larger one just right of that one. If so, should I plug the one not used so that I am not having a vacuum leak?
The vacuum can on the transmission is a modulator, not a vacuum advance. The modulator controls shift firmness and timing according to engine load. Nope, not a source of the problem unless the thing is defective. You'll know it's defective if there's trans fluid in the vacuum tubing. Are you telling us that you have one or two open vacuum ports on the back of the manifold? PLUG THEM. Key on, engine off. Pull the throttle linkage open, and listen close. You should hear the solenoid in the transmission "click" to shift the converter from high-to-low (or low-to-high, I can't remember) stall. You could also run the engine without the wires connected to the switch (secure and tape them so the hot wire doesn't ground and pop the fuse.) I forget which way the converter goes without power to the solenoid, but you'll either have poor acceleration or poor top speed. Connecting the wires should make a MAJOR improvement in either acceleration or top speed.
Yes, modulator,sorry. No, there is no fluid in the tubing when I disconnect it from the intake manifold. Yes, there are two vacuum holes in the rear of the intake. I assume the transmission vacuum line connects to one of them right? Because when I disconnect the line from the intake and shift the gears they shift HARD, and they shift smoother with the line connected. I replaced the gasket on the carb, adjusted the idle, set the screws with a vacuum gauge, installed a fuel pressure regulator inthe fuel line so I could control the pressure(set it to manufacturers specs), cleaned the fuel filter, adjusted the dwell correctly, amongst other things. The problem seems to still exist.Drove it around for thirty to forty minutes or so while braking hard and sitting at stop signs for extended periods of time.It died twice. Once just sitting there, and once when I punched the gas from a stand still. It also surges when accelerating and flooring it almost kills it. Doesn't die when the vacuum line from the tranny is disconnected from the intake though but shifts way hard. That's why I think maybe it is tranny related. Please, help with any info. I could use it.
1. the modulator seems to work and does not leak fluid-so-save your money there. It's fine. 2. I'm still not clear: Do you have OPEN vacuum ports that are sucking air? 3. If you changed the dwell, you changed the timing. Get a timing light and re-adjust the timing to spec. Assure that both the centrifugal and vacuum advance work properly. 4. Is the torque converter going to high stall at idle? 5. Good compression (and leakdown, if you can find a leakdown tester) on all cylinders? 6. If all the above are good, I'm thinking time for a carb overhaul. Why install a fuel pressure regulator? Are you using an electric fuel pump?
1. Yes, the modulator seems to be fine after all. 2.Yes, I have two vacuum ports on the rear of the intake that are sucking air. I have my vacuum line for the tranny hooked up to the larger one right now, don't know that it's correct but looks like the only obvious place for it to go. 3.Can I set my timing without a timing light. The specs say 21/2 before TDC for my car. I was taught a trick by someone to set the crank mark at where you want it at as far as degrees. The pull the plug out of number one and hold it close to the block while rotating the distr. clockwise and when it sparks you know that no. 1 is firing at that degree, then tighten down the dist. and re-install the plug. Sound the same to you like a good way of telling timing? 4.Yes, my high stall is working on the tranny. I checked like you said and I hear it clicking. 5.Yes, I think I need a carb overhaul because I have cleaned it time and time again but I still am not getting any fuel out of the left bank(1,3,5,7) fuel spray nozzle when the car is running, only the right. Is this normal? The accelerator pump is connected to that fuel bowl ont he left so I wonder if that's causing the problem?But my car surges going down the road badly like it's running out of gas, maybe thinking that was the problem and it is just staying running off of the right cylinders firing? 6.I bought a fuel regulator in case I needed to adjust down the pressure but it isn't installed at this moment. 7. Any more ideas for me?Thanks, you've been real helpful.:TU:
You can set timing without a timing light. Years ago, we used to joke about a (insert prefered minority group here) timing light: close your eyes, stick your finger in the #1 plug wire boot, and have someone start the engine. Every time you get shocked, open your eyes. Set the timing by looking at the timing marks when your eyes blink open. Your method will work, but I'm NOT fond of it. And rotating the distributor clockwise only works if the rotor normally spins counter-clockwise. You need to spin the distributor the opposite direction from the way the rotor turns. If you have any interest in working on your own vehicles, BUY A LIGHT. PLUG THE AIR LEAKS!!!!!!!!!!!!! If the carb won't supply fuel, you'll spend the rest of your life adjusting the timing and it won't help. Fix the carb! By the way, if you look at the manifold, the left side of the carb supplies two cylinders on the left, and two on the right. Same with the right side of the carb. It'll supply the two center cylinders on one side, and the two end cylinders on the other.
Thanks for all the help. I ordered a carb rebuild kit yesterday, hopefully I can get it working correctly. And your right as well on the light(funny story by the way), I will pick one up just because it's more accurate and also I will need it as long as I have my Lark, which I hope is a long long time. Thanks.:beer
Maybe someday you'll get posted to GFAFB. We'll make that thing run! (No, I'm not AF, just live near there)
