Hey all, I've been experiencing a couple different issues with my 69 skylark after the engine gets up to temp. It's a completely stock 350 2bbl engine, and it runs great most of the time, but it acts up in a couple of situations. If I'm sitting at a long red light with the engine at operating temp, the engine will start to miss after a while, and then have a sluggish throttle response when I finally get to go again, but this clears right up after it gets going. The water temp hasn't gotten over 205-ish, and it took a REALLY long light to get there. Usually doesn't go much over 195 in normal city driving, and stays a bit under 190 on the move. Also, if I park the car warm and leave it for 20 minutes or so, it'll have to crank extra before it fires, and then for the first few minutes of driving a left turn will make it sputter and/or die. After a minute or two, that also goes away. Once or twice I had it try to die on a very sharp left u-turn after a long red light, but not enough times to call it a pattern. I've been assuming the fuel is evaporating/boiling, and took a few steps to alleviate that, but either I haven't done enough or that isn't the problem. I insulated the fuel hard line and moved it away from the block some, and put a small phenolic insulator under the carb, but it was only a 1/4" thick one. What steps should I take from here? Thicker carb insulator with a heat shield? Raise float level to try and keep more gas in the bowl? Could my (stock, mechanical) fuel pump be going bad?
Sounds like you're on the right path there with the boiling fuel/vapor lock. Water temp. doesn't seem bad to me. I'd keep trying to isolate the carb more from manifold heat. Also some very sharp minds will chime in shortly!
I would confirm the choke is pulling off completely and check for timing chain worn badly. It is 40 plus years old. Had a recent one for timing chain. Guy kept replacing points and plugs. But plugs where fouling due to low timing
X2 , its flooding due to today's fuel and how easy it vapor locks! You very likely have room to install a 1/2" phenolic heat spacer under the Carb which with some longer bolts should clear up the issue. Don't wait too long to do this because your loading up the motor oil with fuel and you know where that can lead! You might at the same time drop down to a 185 thermostat if you have a 195 in there now.
it can't vapor lock and flood at the same time. that's not possible. your carb needs rebuilt. it is leaking gas out of the fuel bowl and flooding. the most likely reason is the float is not as buoyant as it once was and allowing a higher fuel level in the bowl. these are the classic symptoms. order a kit, it's very easy to do.
Yes. It’s not vapor lock . It’s too cold out to vapor lock. You are looking at the wrong parts. Pull spark plugs after running, check if wet or sootie. Then check timing. By hand rotate engine forward then backward to see if timing chain has lot of play by how much the distributer rotor moves or doesn’t move. When changing directions
I can't remember which car that was experienceing similar symptoms. What I did remember was the fuel line that runs from the tank to the frame had rubbed itself against the frame right where the axle. Kick up was. This was visible from outside the frame not from underneath. The line had rubbed itself so thin and finally dislodged itself. When I was able to splice the line the piece itself was Inside the line. After I cut it I saw it.
I rebuilt the carb last winter because it was sticking and pouring gas everywhere. These other problems are not new, and rebuilding the carb didn't affect them. It only happens when the engine is at operating temp and left to sit. It doesn't happen on cold starts, and it doesn't happen on short drives where the engine doesn't heat up all the way. On a cold start it fires on the first or second crank every time, runs smooth, and has no problems making turns. I also changed the spark plugs a month or two ago and they looked fine. They didn't actually need changed, but I had a set so I stuck them in. as for the weather, it only got cold in the last 2 or 3 days here. I haven't driven it for the last couple days, either.
did you replace the float with the rebuild? it may still be set too high or the plugs on the bottom of the carb are leaking. does it stink like fuel under the hood? any staining on the carb body?
I don't remember if the kit I got had a float with it or not. I want to say yes. No gas smell under the hood, no staining on the carb.
Stumbles. Sometimes it'll catch back up and not die at all. if I straighten up before it dies it'll catch back up all the time. When it does die, it always starts right back up. Then after a minute or two as the water temp comes back down after being parked, it clears up and drives fine again.
that's classic flooding out.. i would run it for a while with the breather off. turn it off and immediately lock the throttle blades wide open and look down the carb throat with a flashlight and see if it is wet and dripping. it's very possible the carb is still leaking but going direct into the intake.
that symptom leads me to believe you didn't replace the float. when it is cold the float is bone dry. it takes some time for it to get saturated with fuel and lose it's buoyancy. that's pure speculation.
E10 gasoline probably evaporates/boils somewhat faster than gasoline without ethanol. You may be a bit low on the float level, and the added heat/evaporation, lowers it further causing the symptoms. I always though low float level causes stalling or sag on turns. I would try a higher float level.
I'm still confused. if it's happening because the float is losing buoyancy, then wouldn't it also happen during normal driving, rather than just for the first couple minutes after a warm start? wouldn't an empty float bowl also cause a delay on a cold start since there's no gas to run in it? Neither of those things happen. but there IS a delay before it fires on a warm start. it has to crank extra before it fires, and I was assuming that was refilling the bowl that had evaporated all the gas out. Larry's thought makes more sense to me.
i think we all agree its a carb problem. rather than stab in the dark pull the carb and measure the float height. if the float is that low the car would fall on its face under heavy acceleration and highway speeds. i would say it starts hard when warm because it's flooded from the leaking fuel. I'm interested in the solution for sure.
I'm still not convinced it's leaking fuel. It was rebuilt not even a year ago, and when I had it off the car since then to put the spacer under it, it definitely had gas in the bowl, after having sat for at least a day. I know cause I spilled it. as for heavy acceleration, I don't really ever put my foot down in it so I dunno. It seemed to do ok on the highway though.
