I have noticed since the engine went in well over a year ago that the top gasket on the carb. was always wet and could smell gas at the air cleaner intake. The gas mileage hasn't been stellar either, took it on a two hundred and fifty mile round trip and only got 16-16.5 mpg imperial measure (13.5 US). I had to turn the idle mixture screws out a fair ways, about 3.5 turns. We have to take a quick five hundred mile round trip and are going in the Electra, so today I thought that I would try and fix the wet gasket issue. The float level was fine, but I know that the tops can warp if tighted too much and I suspected that was the problem with mine. I used a straight edge to check and it did look a little warped so I tried the trick that has been suggested here before and took two gaskets, coated one side of each with a heavier weight oil then installed together. When I started the engine it wasn't running very smooth, even with the choke on. I turned the mixture screws out another 1 1/2 turns and is idling much smoother now, though the idle increased and I can't adjust the base idle screw down anymore (couldn't before I did this either). So what happened, did I plug a fuel leak up top by double gasketing that was causing a slight rich condition or is something else going on? I know that I have the mixture screws out a long way and I will be doing the idle circut mod in the near future to fix that. I was also thinking on adjusting the screw that controls the power piston travel depth to see if I can richen the mixture a little and turn the screws back in. Also, I am at 19" of vacuum and have never had it that high before. Tomorrow I am going to retard the initial timing a couple of degrees as I think it is a little too far advanced. The carb. is from a '77 Buick 350 and I am using manifold vacuum and no egr. The distributor has been recurved and the engine is stock. Thanks, Greg
Maybe you know this but adjusting the idle screws only effects your carb when you're idling. They really have nothing to do with your mpg while driving unless you are sitting and idling a lot in traffic. And maybe not even so much then... What is your initial and total timing? It sounds like you have more of a timing issue. MARK
You'd be surprised how fast you can go before activating the main metering system. On many stock-geared cars, the idle circuit is still active at 40 mph. Probably more than that with modern overdrive transmissions. 'Course, you richen the APT and then lean the idle mix--if the overall amount of fuel delivered is the same, mileage won't change.
I drove the car to work today and it started great! I didn't have to feather the gas at all to keep it running right after starting and it didn't threaten to stall once, same story coming home. Before, when starting the engine warm or hot we would often have to give it a small shot of gas to get it to start, it now starts without need to touch the gas pedal. I'm thinking that it was running a little rich before and now it is running leaner since I did the above mod, the exhaust doesn't sink as much either. I started checking the timing tonight, the initial looks like it is advanced a little too much and while I was revving the engine to check the total I noticed that the water pump gasket was leaking . When will it ever end :ball: . Greg
To properly set the idle mix screws: 1.disconnect and plug the vacuum line to the vac advance canister 2. block all 4 wheels 3. connect vacuum gauge 4. start car and put it in gear 5. adjust idle mixture screws to achieve max vacuum and smoothest idle (make sure they are equal turns out and start at 2 full turns out) 6. re set idle speed (it should rise with the right idle mixture setting) 7. go back and check initial timing 8. As an extra step I then go back and fine tune the idle mix screws again but this time just adjusting a 1/8 of a turn to get it perfect This works well for me, but what do I know....
Whn you double gasketed the top you helped seal some passages between the top and main body . With those passages leaking you were nt getting the right signal to other parts of the carb and fuel flow . The Vacuum for the metering rods can be lost from a warped top , also the fuel shot fron the accelerator pump will be lost or rather can be . Just a little added info .
Thanks to all that replied. I backed off the timing two degrees and it idled a little better. The mechanical advance plate needs to be lubed as it doesn't always return completely to the "no advance" position. Does anyone know if I can lube it as installed or do I have to take the distributor apart to do so? The trip went well, got a best of 18.5mpg imperial and the car went up the moutains no problem. It took the hills better than the '81 Malibu 305 wagon that we used on the last trip we took some years back. Due in part I am sure to the torque of the Buick 350 and the diff ratio. Greg
Glad to hear its running better. You can lube the mech advance with graphite lube just remove the cap and rotor and lube it that way. Are you using the crane vac advance canister and light springs from the kit? If not use that (ask for a chevy 350 application) it works fine on the buick just mounts backwards. Limit the canister to 10 degrees of advance using a small nut and bolt then adjust the rate of vac advance using the provided allen key. I picked up a solid mpg with this mod alone. By the way I run 34 total yiming plus the 10 deg on vac advance on my late model motors, even the stock ones.
Dont put any kind of graphite under the distributer cap for any reason. the stuff will lead the spark to ground. the factory says to lube the advance mechanism with a very light film of grease. just enough to keep it from rusting. no more. graphite is a very good conductor. dont use it inside the dist. to set the idle; First, first, first, warm the car up for at least 20 min at idle. shut the engine off. leave the vac advance connected up. remove the air cleaner to get at the idle mixture screws Remove the idle mx screws and check them to see if the points on them are ringed or distorted in any way. If they are forget it , you will never get the idle mx. right. replace them. If they are good put them back in all the way to the bottom[gently] and back out to 1 1/2 turns. that is the basic setting. start the engine. s-l-o-w-l-y and gently turn the i/m screws in untill the engine begins to run rough, then back them out untill it runs smooth. stop. do this for each screw. If you like you can hook up a vac gage and adjust for the highest manifold vac. A lot of guys do this if they have a hot cam with a lot of lope.
I agree on the graphite , can cause many problems , I use a lite touch of white lithium grease . On my timing I run a total of 32 degrees with NO vacuum advance , all initial and mechaical . Any more or less timing and mine becomes a slug . But that is just the way my motor wants it , each motor wants something different depending on the combo , just have to let the engine tell you exactly what it wants ,
Yup, I used the Crane advance kit. I limited the vac advance to 11 degrees. I am going to get another distributor or I will pull mine apart as what looks like what needs to be lubed can't be accessed unit the shaft is out of the housing. I did lube the weights with lithium grease as it is the lightest grease I had and GM isn't specific as to what grease to use, at least in the '75 shop manual I have. I am using an external coil, but I thought about replacing the 32 year old module and pick-up coil. I have read before that the modules can lose some of their "strength" with they get old and power and mileage can suffer. Anyone else heard of this? Thanks, Greg
