1977 Cadillac carb
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 11 of 11
500, 472, 425, 368 Discussion, 1977 Cadillac carb in Cadillac Engine Technical Discussion; I have a 1977 Cadillac Sedan Deville, 425 v-8, TH400 tranny. My question is about the carb and adjusting it. ...
  1. #1
    77Cadillac is offline Cadillac Owners Member
    Automobile(s): 1977 Sedan Deville
    Join Date
    Aug 2014
    Posts
    4

    1977 Cadillac carb

    I have a 1977 Cadillac Sedan Deville, 425 v-8, TH400 tranny. My question is about the carb and adjusting it.
    We removed the carb after it started running rough and not wanting to idle. Turned out to be some varnish ect...
    screwing it up. Cleaned it out ect.... got a kit and installed and reassembled. Reinstalled on the car. After reinstalling
    the carb it starts up great, revs ect... Sits there and idles fine. To me it sounds like it is idling about right, don't have
    a tach to check it. So here is the problem......
    Whenever I place the transmission in reverse or forward the engine wants to stall, unless I hold the pedal down to make
    the engine run a bit faster. I believe the problem might be in a (vacuum brake??) deal on the driver's side of the carb. It has a slotted part fastened to the vacuum piece with a screw to allow it to be moved back and forth then tightened. I'm not sure I got this adjusted back to the same place as original. I have a Chilton that covers from 1967-84, but trying to discipher
    which direction go with which model carb is confusing.... I'm not use to all this extra stuff being on a carb, I typically a 1
    barrel carb from the 1950's guy.... LOL

    thanks John

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    deVille33 is offline Cadillac Owners Connoisseur
    Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
    Join Date
    Mar 2006
    Location
    Western Massachusetts
    Posts
    1,383

    Re: 1977 Cadillac carb

    You check the dashpots using a Mighty Vac. They have to hold vacuum for a specified amount of time. To adjust the carb properly, you will need a tach. I just answered a query like this one over on the other section.

  4. #3
    77Cadillac is offline Cadillac Owners Member
    Automobile(s): 1977 Sedan Deville
    Join Date
    Aug 2014
    Posts
    4

    Re: 1977 Cadillac carb

    Thanks deVille33...

    John

  5. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    74
    Posts
    44,600

    Re: 1977 Cadillac carb

    See if you can find the 8 X 12 paperback on Quadrajets by Doug Roe. eBay or maybe Google or Amazon. It covers all the QJs, right through the electric ones, including tuning and modification, jets and needles - the whole enchilada.

    https://www.google.com/search?q=roch...x-a&channel=sb

  6. #5
    77Cadillac is offline Cadillac Owners Member
    Automobile(s): 1977 Sedan Deville
    Join Date
    Aug 2014
    Posts
    4

    Re: 1977 Cadillac carb

    Thanks I'll check Amazon..... John

  7. #6
    the APEMAN is offline Cadillac Owners Fanatic
    Automobile(s): 1980 FBC
    Join Date
    Mar 2010
    Age
    52
    Posts
    169

    Re: 1977 Cadillac carb

    There is no such thing as a dashpot on a late 70's Cadillac. A dashpot is a device that makes throttle close to idle position gradually after letting foot completely off gas as used on stickshift cars.

    Sounds like the OP is referring to a primary choke pull off. The screw adjusts minimum choke opening position when car first starts and vacuum is produced. Maybe not. Hard to tell. Maybe he is talking about the electric choke thermostat. ???

    Things to look for with 472/500/425/368 bad ilde under load are:

    Vacuum leaks through bad lines, weak PCV valves, carbonated base gaskets, warped carbonater baseplates, worn out throttle shafts and leaky intake manifold gaskets.

    Sticking mechanical advance in distribitor causing over advanced ignition timing at idle. Also makes for brutal hot restarts.

    Carbon buildup on intake valve stems. Really causes heck on these engines more than other brands.

    All above assumes no vac line misrouting.

  8. #7
    77Cadillac is offline Cadillac Owners Member
    Automobile(s): 1977 Sedan Deville
    Join Date
    Aug 2014
    Posts
    4

    Re: 1977 Cadillac carb

    Doubt it has worn out throttle shafts with only 37,000 original miles on it. The electric choke is on the passenger's side of the carb if I remember right.....

    John

  9. #8
    deVille33 is offline Cadillac Owners Connoisseur
    Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
    Join Date
    Mar 2006
    Location
    Western Massachusetts
    Posts
    1,383

    Re: 1977 Cadillac carb

    [QUOTE=the APEMAN;13103322]There is no such thing as a dashpot on a late 70's Cadillac. A dashpot is a device that makes throttle close to idle position gradually after letting foot completely off gas as used on stickshift cars.

    Ok. APE, I used the wrong term here, vacuum brake it is. But they should hold vacuum for the determined amount of time to perform as they should. Basically telling him that the Q-Jet needs it's support units to operate properly.

  10. #9
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    74
    Posts
    44,600

    Re: 1977 Cadillac carb

    Many of those setups used either Vacuum Delay Valves (VDV) or Vacuum Check Valves (VCV) or a variant. The VDVs had internal bleeds for different "flow rates" to change pulloff timing for various levers and valves.

    The plastic valves are one-way - need to be inserted in the vacuum lines in the correct direction.

  11. #10
    deVille33 is offline Cadillac Owners Connoisseur
    Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
    Join Date
    Mar 2006
    Location
    Western Massachusetts
    Posts
    1,383

    Re: 1977 Cadillac carb

    The Vacuum check valves were used on the EGR system in these years to ensure against backfire through the EGR. The valve on the front controls the high idle cam release and is a Vacuum Delay Valve.

  12. #11
    the APEMAN is offline Cadillac Owners Fanatic
    Automobile(s): 1980 FBC
    Join Date
    Mar 2010
    Age
    52
    Posts
    169

    Re: 1977 Cadillac carb

    Primary choke pull-off and secondary choke pull-off.

    Primary usually used no bleed but many secondaries did.

    ----------

    Quote Originally Posted by 77Cadillac View Post
    Doubt it has worn out throttle shafts with only 37,000 original miles on it. The electric choke is on the passenger's side of the carb if I remember right.....

    John
    More complete and accurate original posts yield better responses.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting