Hello, I have a '71 Mav with a 200 engine, auto transmission, no a/c. Twice now, at about five miles into my journey--which is the longest I've driven it recently, the car idles roughly and stalls. The engine seems to run fine--as fine as it can with a points ignition--prior to stalling. The first time it happened (with the engine cold), as I was removing the one-barrel Carter YF, I discovered that the right nut from the intake stud was a bit loose, so I tightened it, started and covered the carb with my hand, and it died almost instantly. But I didn't drive it five miles (or had it running for that amount of time) since I didn't think there was any problem after this fix. The second time this happened, I pulled over, took off the filter assembly, turned the car on and covered the carb with my hand--it didn't stop the engine. With a screwdriver and wrench, I carefully tightened what little I could and then did the carb-stop test. It did stop the engine, but took considerably longer to do so. I've seen videos and have been told how to use carb cleaner to check for air leaks, and I may also take the carb to a carb shop and have them test it, but I've also been told that the manifold may have developed a crack. But my last tightening of the screws (without hopefully over-torquing), proved to me that something isn't right with the carb or the mating surface, in spite of having gaskets. I did replace the gaskets when I rebuilt the carb almost a year ago, could those gaskets be bad? Thanks for your help, Mav and Comet kin!
Take a look at the PCV valve and hose coming from the adaptor plate at the base of the carb. Look at the vacuum lines to the distributor and where they attach to the carb and manifold. Look at the vacuum connection to the transmission. Re-examine your gasket, PCV adaptor and the base of your carb. You might have a crack or bad gasket. It should not be loosening once you mount it. Did you use the special nuts for mounting the carb? I believe there should be a lock washer under the nuts. If you car did not do this before you rebuilt the carb, then your problem is associated to what you did. If you sidetrack yourself by changing things that don't appear to be the problem, solving it will be more difficult. I doubt you cracked the manifold when you tightened down the carb. You would have broken the ears off the carb or adaptor or stripped the nut before breaking the cast iron manifold. Take your time. Examine everything. Make sure you have all the right gaskets and everything is assembled correctly. Check for vacuum leaks. I bet it is something simple. As a side note, did you possibly mess with the plug wires? Double check if you did. Report back. Micah
Hello Comet Fever, 71gold, and 71Mavrk! Thank you for your responses! Is there a specific torque for the stud nuts? Will a hardware store lock washer be sufficient or will I need to get an "automotive grade" washer, if there is such a thing? Could the gasket that comes with the rebuild kit be too thin, like the included junk batteries that come with a tv remote? The PCV valve fits loosely. Would that bringing in more air than needed? I ought to replace the grommet, but I think I'd have to pull off the cover, then get a gasket and sealer, right? Does anyone make a riser tube for it, or do I have to use the all-purpose aluminum tube with the heat resistant material sleeve? Bye, Renton5
The carb does not need an excessive amount of torque to hold it down. A good hand tightening is sufficient. A general lock washer should be fine. The gaskets in the carb kit are not always the best. I would look for a Felpro replacement. There should be two gaskets. One for carb to PCV adaptor and one for adaptor to manifold. Better gaskets often have a plastic ring around the stud hole to keep them from being over compressed. You might have to order them but they are not expensive. Look at Rock Auto. You should replace the PCV valve and grommet. It can be done without removing the cover. Not expensive parts. Examine the PCV hose. They are often cracked at the adaptor. To me, it seems like you have an excessive vaccum leak. I would make sure you have them all sealed up. I suggest taking a good look at the rebuild you did on the carb while you have it off. Years ago, I rebuilt mine and used Teflon tape on the fuel filter threads (I was 15). It got into the carb and it ran like crap. The hear riser tubes are available. Getdiskbrakes.com has them. (download the catalog or call. Their website sucks.) Micah
Does anyone make a riser tube for it, or do I have to use the all-purpose aluminum tube with the heat resistant material sleeve? Bye, Renton5[/QUOTE] You can order a heat riser kit from Summit if you want.
Check the fit of the Carb Gasket on the Intake Manifold surface . Then check the same Gasket on the Carb base surface. Check for a bowed Carb base surface-as this could case an air leak. Block of,or pinch shut all vacume lines ,including PCVand Brake Booster to see if idling improves. Check for loose body screws in the bottom of the Carb where the Carb and base adapter come together.
Thank you 71Mavrk, Comet Fever, Maverick Dude, and Eastern Raider! At the local parts store, I got a Dorman valve cover grommet, I figure that'll work. I'll get a Felpro valve cover gasket, because I know I'll have to pull it off to get to the old grommet out as the rubber is rock hard now. The pcv is very loose fitting in it. I'll look into replacing the carb-to-spacer gasket and check the spacer-to-manifold gasket--and of course the various hoses.
Hello Everyone! I've looked at the carb, hoses, and gaskets the best I could and didn't find anything wrong, so it's at a Mustang shop for a closer inspection. The mechanic told me that on these straight sixes, the intake/head do tend to crack at the carb mount. If the block isn't warped, I was thinking of getting a replacement head with valves. Any thoughts on a good source for that. I'm just preparing for a "worst case scenario". Thanks!
not implying that I have the same experience with that little motor in the quantities you may have.. but I do know for a fact that if that area were subjected to extreme enough temps to actually cause cracking?.. the carbs base plate would look like a bowl and crack long before the cast iron would give way. Luckily the fuel flow cools the area during run time. Now after shutdown and substantial heat soak periods?.. well, that's another story altogether. Is this engine, specifically the carb itself, getting hot enough to cause vapor lock?
Hello groberts101! On both days, the outside temperature was warm, not hot, so I doubt that vapor lock is involved. The car was running well...I believe until recently. After getting the trans rebuilt in the early spring and replacing the radiator soon thereafter--coincidence, not connected-- I'm not sure if I drove the car much beyond five miles, which is when the two stallings occurred. The first time, when in the morning with the engine cold, I found one nut on the mounting stud was a bit loose, I tightened it and it seemed to fix it--having placed my hand over the carb with the engine running, it immediately stalled, as it's supposed to. The second time, after having driven close to five miles, it stalled, I tightened whatever I could just a fraction more--without snapping anything--then did the carb test and it took longer to die, but I was able to drive home without incident. Each time, the problem got worse as I continued to drive, I guess as it reached it's operating temperature. Maybe things just need to be tightened more, but I'm afraid of breaking a screw or bolt.
pull the carb off and check the baseplates flatness with a straightedge. while you have it off.. go through it once again and make sure it's clean.
does it stall at 5 mile intervals all the time? if so, loosen the gas cap and see if it runs longer. fuel system may be creating a vacuum... I had this happen on two different cars...vent line collasped.
excellent advice. sometimes the little things disguise themselves as bigger things. another easy check for fuel supply issues would be to manually confirm that there's sufficient fuel bowl volume to still deliver a good pump shot from the accelerator pump after the engine stalls out.