I took off my carb and cleaned it while I was replacing a head gasket. When I put the carb back on the car started okay, but now will only run when the choke is closed. Once the car warms up and the choke opens, it's like it gets no gas. I pumped the throttle to see if i could get it to fire that way, but no luck. When it does run, it idles really fast and won't slow down. All I did while the carb was off, was to use Gumout to clean what I could, and a toothbrush to clean the throttle plates. I had the carb upside down while spraying cleaner through all of the little passages, could this have done something to it?
It is likely that one of two things happened; either the gaskets are not sealing, causing a leak, ofr the lines are incorrectly reinstalled, possibly causing the EGR to stay open. Spraying around sealing surfaces with carb cleaner may show the leak. Disconnecting the hose to the EGR line will close the valve, unless it is stuck, which light tapping will address. Let us know...
Once that happenned to me and it was a piece of gasket stuck in the primary venturi of the carb. Otherwise, you have a major vacuum leak. Did you connect your pcv valve properly? :bglasses:
No, I don't even know where the PCV valve connects. o No: It wasn't connected when I got the car and I don't use the ram air system, I just have a generic air cleaner. I think it's an air leak, as I sprayed carb cleaner around the carb base plate last night and it seemed to settle down a bit. If it's an air leak, will that make it idle high? Can a leak make the motor sound and feel as if it's misfiring?
When you put the carb back on you did use a new gasket didn't you? After years of use the old gasket will not reseal. The PVC valve plugs into the engine behind the carb into the valley cover and is the big hose connected to the carb base or into the manifold. Rich
There's your problem.......you need to connect it before going any further. Basically, a pcv valve is a calibrated vacuum leak, and it's absence will upset your idle mixture. The benefit of having it to suck out crankcase gasses outweighs the benefits of not using one at all, even if you compensate for it's absence. (IMHO) :bglasses:
Where would it connect to, since I'm not using the original air cleaner setup? The PCV Valve is in the manifold, I just don't have a hose going to it.
The nipple that goes to the pcv valve is a big one (about 1/2" dia.) and should be on the base of your carb, most likely on the front side but I have seen them on the back side too. Can you post a picture of your carb?
Here's the only one that I have at work. I have some more that I just took, but they are on my camera at home.
I saw one larger vacuum port on the base plate on the rear of the carb, but it is hooked to the round vacuum canister on the firewall. Is that where it should go? It's got a different type of vaccum hose on it, it's a harder, plastic tube, that doensn't bend at all, but it isn't big enough to go over the PCV valve. Initially, I was thinking that we were talking about the EGR Valve, that goes from the valve cover, to the air cleaner, through the little foam insert. I'm on the right page now.
That big fat hose on the bottom right next to your fuel inlet is your PCV hose. If it's plugged, unplug it (or just replace it) and connect it to your PCV valve. I don't know how your motor is set up, I'm a little less familiar with 455's, but be sure that your breather cap is open so there is a way for fresh air to enter your crankcase. Sometimes when custom valve covers are installed engine breathing is overlooked.......don't use a solid cap unless you are running a stock system with the rubber hose that connects to your air cleaner. :bglasses:
The rear nipple is a vacuum source. The foam thingy on your air cleaner is the breather I was talking about. You have a closed pcv system, and it uses a plain (non vented) valve cover cap.:bglasses:
Joe, After I sent the last reply, I found another picture of the carb on the memory key that I use at work. I had forgotten that I loaded some pictures from home on there last week. I found a picture that showed the carb from the side, before I took it off. It clearly shows the big hose, going form under where the transmission spark gadget is connected to the front of the carb on the passengers side. It shows it going right around to carb to the PCV valve. ou: There is a lot of stuff connected to one area on that side and I never noticed it before. My fianc didn't understand why I take so many pictures of the car while I'm working on it. I had to replace the rear brake shoes and took picture so I'd see how all of the springs were, before I messed with them, and now I take pictures of everything before I start. p
BTW, an EGR valve was used starting in '73, and it is almost always mounted on the intake manifold on the driver's side. :bglasses:
Throw that thing in your toolbox (never throw anything away) and run a hose directly from the small nipple on the left front (driver side of car) of your carb to your distributor advance........you'll be surprised how much better she'll run after that. :bglasses: (I couldn't tell but it looks like it already may be done)
Well, things are really weird now. I took the carb off last night and spread black, hi temp sealant on the gasket and put the carb back on, and it seems to be working fine. There is no hissing sound around the base. The motor still idles down and quits when it gets warm, but I turned up the idle adjustment screw and it stays running. I'm wondering if I didn't bend the little arm on the carb or knock the screw out of adjustment while I had it off. On my other thread, I was having and issue with oil not coming out of the pushrod and thinking that I had a bad lifter. Well, for some reason, it has started working. Oil is squirting out of the rocker arm hole just like the rest of them. The only thing that is still a problem is that the car is misfiring. I tried to read the sticker on the fan shroud about adjusting the carb mixture, but can't make out the steps. I'm going to replace the sparkplugs tonight, who knows, I might have cracked one while removing the head or one might just be bad. I don't know if the mixture if off or not, but it's hard to stay in the garage long enough to work on the car, as the exhaust is really hard to deal with. It's very acrid smelling, like a kerosene heater when you get a bad batch of kerosene. It makes my eyes burn and makes it hard to breathe. Can someone post up the procedures for setting the mixture screws?
Setting idle mixtures are simple, but, in order to get right, it takes a little time. The easiest method is to set the idle speed to about 700 rpm. Then adjust each idle speed screw for either maximum rpm or minimum HC's if using an exhaust gas analyzer. On some of the emissions carbs, it will be encessary to aloow the leaner idle mixture that does not involve the highest idle, since the delivered fuel is limited by carb internals. Adjust both screws, using the same method. If the idle speed exceeds 850, readjust the speed, to assure that you are on the idle ports, not the off-idle slots. Before attempting to adjust the mixture, be sure the timing is set, the ignition is operating correctly, and that the choke is completely off. Good luck, and advise of results.
Scott, you must fix that misfire before you attempt to adjust your carb mixture screws. It could be a bad dist. cap and rotor, wires, or even a carbon track on your coil. Have you checked the compression? Might as well if your going to replace the plugs anyway........just don't mix up the firing order (have you checked that?) Also, if you have compressed air, try removing the mixture screws and shoot some air in the holes, that will blow out any crap that may be in there. Then back the screws out about 1-1/2 turns each as a initial adjustment. I'm wondering if your firing order isn't just screwed up.......check it. :bglasses:
Well ya know, it was all of the above. p I went home last night and changed the plugs with some Champion RV12YC (I think), the plug wires, and the distributor cap and rotor. I had changed the cap once before, but got interrupted and when I went back outside to finish, I picked up the old cap and put it on, but mistake. ou: I picked up the "other" cap last night and noticed how clean it was, and knew what I had done. I ran better, but was still missing, like a puff, puff, puff, but not horrible. I just happened to be looking at the plug wires and the firing order, and decided to check them once again. As it turns out, the #2 and #4 were reversed. I just about fell over when I saw that!! I readjusted the idle back down to 600 RPM at idle with the vacuum advance plugged, and took her out for a trip around the block (once I connected the vacuum lines up). She ran good, once I was above 15 or 20 MPH, but sorta bogs down below that. I got back home and could hear a noticeable vacuum leak from what sounds like the rear of the intake manifold area. It was too hot to run my had down the back of the intake, so I parked it for the night and will start it tonight and see if I can find that leak. I'm almost betting that it is where the end of the rubber gasket runs up the head, I bet I didn't get enough black sealant in that area and that's where it's leaking, or I might have moved the rubber seal when I put the intake back on. If that's all it is, I'll be a happy camper.
Glad to hear you are making progress............did you use the correct carb gasket? You should never use sealer on that gasket. I would make absolutely certain everything else is air tight before removing the intake again.........it is unlikely that just the lack of sealer would make a leak that noticeable.........perhaps something got pinched in the gasket? Your "boggy" feeling at low speeds is probably due to a vacuum leak somewhere. You can also try eliminating the vacuum hoses one at a time by pinching them with the engine running.........look carefully for cracked hoses and replace those that are. :bglasses:
