Cracked Intake Manifold?

Discussion in 'General Maverick/Comet' started by Renton5, Oct 17, 2015.

  1. Renton5

    Renton5 Member

    Joined:
    Aug 31, 2011
    Messages:
    122
    Likes Received:
    4
    Trophy Points:
    46
    Location:
    Van Nuys, CA
    Vehicle:
    1971 Maverick, 200 engine, 2dr
    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!
     
  2. 71gold

    71gold Frank Cooper Supporting Member

    Joined:
    Apr 9, 2002
    Messages:
    26,456
    Likes Received:
    2,835
    Trophy Points:
    978
    Garage:
    1
    Location:
    MACON,GA.
    Vehicle:
    '73 Grabber
    if you haven't driven it much you may need to go back through the carb.
     
  3. 71Mavrk

    71Mavrk Member

    Joined:
    Jul 27, 2011
    Messages:
    1,206
    Likes Received:
    423
    Trophy Points:
    238
    Garage:
    1
    Location:
    Nevada
    Vehicle:
    1971 Maverick Grabber Clone, 1971 Maverick project
    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
     
  4. Renton5

    Renton5 Member

    Joined:
    Aug 31, 2011
    Messages:
    122
    Likes Received:
    4
    Trophy Points:
    46
    Location:
    Van Nuys, CA
    Vehicle:
    1971 Maverick, 200 engine, 2dr
    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
     
  5. 71Mavrk

    71Mavrk Member

    Joined:
    Jul 27, 2011
    Messages:
    1,206
    Likes Received:
    423
    Trophy Points:
    238
    Garage:
    1
    Location:
    Nevada
    Vehicle:
    1971 Maverick Grabber Clone, 1971 Maverick project
    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
     
    Last edited: Oct 19, 2015
  6. Maverick Dude

    Maverick Dude Member

    Joined:
    May 23, 2015
    Messages:
    991
    Likes Received:
    269
    Trophy Points:
    197
    Garage:
    1
    Location:
    Cranbrook, BC Canada
    Vehicle:
    1973 Maverick Two Door 302 C4 LDO
    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.
     
  7. Eastern Raider

    Eastern Raider Member

    Joined:
    May 23, 2011
    Messages:
    727
    Likes Received:
    24
    Trophy Points:
    93
    Location:
    middle Ga. warner robins
    Vehicle:
    1970 maverick ford mustangs 1993 f150
    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.
     
  8. Renton5

    Renton5 Member

    Joined:
    Aug 31, 2011
    Messages:
    122
    Likes Received:
    4
    Trophy Points:
    46
    Location:
    Van Nuys, CA
    Vehicle:
    1971 Maverick, 200 engine, 2dr
    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.
     
  9. Renton5

    Renton5 Member

    Joined:
    Aug 31, 2011
    Messages:
    122
    Likes Received:
    4
    Trophy Points:
    46
    Location:
    Van Nuys, CA
    Vehicle:
    1971 Maverick, 200 engine, 2dr
    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!
     
  10. Craig Selvey

    Craig Selvey Indiana State Rep - MCCI

    Joined:
    Mar 9, 2002
    Messages:
    18,218
    Likes Received:
    1,308
    Trophy Points:
    878
    Location:
    Albany, Indiana
    Vehicle:
    1972 Maverick Grabber - Color: Orange Also, 1976 Ford Maverick 4-door, 1977 Mercury Comet 2-door.
    I have never, in all my years, seen a crack in this area.
     
    Ronald Hopkins likes this.
  11. groberts101

    groberts101 Member

    Joined:
    Apr 22, 2007
    Messages:
    4,166
    Likes Received:
    535
    Trophy Points:
    297
    Garage:
    1
    Location:
    Minneapolis, MN
    Vehicle:
    1971 Comet GT
    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?
     
  12. Renton5

    Renton5 Member

    Joined:
    Aug 31, 2011
    Messages:
    122
    Likes Received:
    4
    Trophy Points:
    46
    Location:
    Van Nuys, CA
    Vehicle:
    1971 Maverick, 200 engine, 2dr
    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.
     
  13. groberts101

    groberts101 Member

    Joined:
    Apr 22, 2007
    Messages:
    4,166
    Likes Received:
    535
    Trophy Points:
    297
    Garage:
    1
    Location:
    Minneapolis, MN
    Vehicle:
    1971 Comet GT
    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.
     
  14. 71gold

    71gold Frank Cooper Supporting Member

    Joined:
    Apr 9, 2002
    Messages:
    26,456
    Likes Received:
    2,835
    Trophy Points:
    978
    Garage:
    1
    Location:
    MACON,GA.
    Vehicle:
    '73 Grabber
    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...:huh:
    I had this happen on two different cars...vent line collasped.
     
  15. groberts101

    groberts101 Member

    Joined:
    Apr 22, 2007
    Messages:
    4,166
    Likes Received:
    535
    Trophy Points:
    297
    Garage:
    1
    Location:
    Minneapolis, MN
    Vehicle:
    1971 Comet GT
    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.
     

Share This Page