Author Topic: 1979 Trans Am 403 Desmogging Procedure  (Read 4129 times)

david bolender

  • Active Forum Member
  • *
  • Posts: 30
1979 Trans Am 403 Desmogging Procedure
« on: December 30, 2011, 04:15:17 PM »
Hello everyone, and Happy New Year!

Can someone give me detailed, explicit instructions on how to "desmog" a 403 1979 Trans Am? I already have a 50lb piece removed from the exhaust system, if you know what I mean... what else is there to do? Thanks,

David
VR
MAJ David Bolender
25th ID Deputy Public Affairs Officer
Schofield Barracks, Hawaii

Jeff Rager

  • Oracle Forum Member
  • *
  • Posts: 1438
  • Chattanooga, Tn, 2000 WS6 Formula
Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #1 on: December 30, 2011, 04:37:16 PM »
remove the charcoal canister, re-route vacuum hoses, remove the smog pump if it still has one on it.

Grand73Am

  • Oracle Forum Member
  • *
  • Posts: 7804
Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #2 on: December 30, 2011, 04:57:00 PM »
Here are a few pics I had from my 79 403. The top one shows that I removed the EGR valve and made a blockoff plate from some steel plate(ignore the yellow arrow..that was for something else). Use an EGR gasket under the plate. Plug the pipe on the carb labeled "egr".
The 2nd pic shows the vacuum hose routing illustration for a 79 403. You don't have to connect that SVB-TVS thing. Instead, connect the rear vac break hose to the manifold vacuum pipe that's on the back bottom of the carb.
And the 3rd and 4th pics show where the vac hoses go on the carb and charcoal canister. The numbers on the canister relate to the numbered ports on the carb. This works fine if the charcoal canister is in good working order. My canister apparently has a bad check valve which made my engine run rich. So, I disconnected the canister hoses at #2 and #3 from the number #2 and #3 vac sources on the carb and intake and plugged those ports. Those vac source were sucking in too much gas fumes into the carb and intake causing a too rich condition. The #2 and #3 canister ports can stay open or run hoses from them to under the car for venting. I kept the hoses for the vent line from the gas tank and the fuel bowl vent(#1) connected to the canister. Works very well that way.




« Last Edit: December 30, 2011, 05:04:08 PM by Grand73Am »
Steve F.

Ben

  • Oracle Forum Member
  • *
  • Posts: 2227
Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #3 on: December 30, 2011, 07:19:24 PM »
Freer flowing exhaust, remove EGR, and adjust the distributor advance to match and you should be done (obviously for more performance rear gear swaps, compression and cam changes are going to be in the mix).  I leave the charcoal canister on all of my cars as all it does is keep tank fumes from spreading, which goes a long way towards keeping people from complaining about your car stinking and does not harm performance in any way.
Trans Am-less at the moment...

Home of the Mess

david bolender

  • Active Forum Member
  • *
  • Posts: 30
Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #4 on: January 25, 2012, 06:48:05 PM »
Thank you everybody!!!
VR
MAJ David Bolender
25th ID Deputy Public Affairs Officer
Schofield Barracks, Hawaii

BBATCAR

  • Active Forum Member
  • *
  • Posts: 286
  • I'd rather be cruisin'
      • http://s250.photobucket.com/albums/gg268/BBATCAR/
Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #5 on: January 27, 2012, 09:43:04 PM »
Freer flowing exhaust, remove EGR, and adjust the distributor advance to match and you should be done (obviously for more performance rear gear swaps, compression and cam changes are going to be in the mix).  I leave the charcoal canister on all of my cars as all it does is keep tank fumes from spreading, which goes a long way towards keeping people from complaining about your car stinking and does not harm performance in any way.
X2 mine was already de-smogged, but I'm putting the Charcoal Canister back in for sure.
1978 Trans Am WS6, true Blk/Blk/T-Top
Olds 403 bored .030 => 409
CompCam 1.6 Rocker/Pushrod Kit
Heads Machined and Larger 2" & 1.625" Valves
Custom Cam 488/496 216/226 113*
Thornton Reproduction Larger Manifolds & Magnaflows
Built Up 350TH Trans, 1600 stall, 3:23 rear ratio
Jet Black w/ SE decals

ig109

  • Active Forum Member
  • *
  • Posts: 223
Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #6 on: March 11, 2015, 12:29:26 PM »
Is there any harm in removing the charcoal can.. plugging the bowl vent with a cup plug.. and running a vented gas cap?

Other than the fuel smell (which is part of the old car experience)

firebirdparts

  • Jedi Council
  • Oracle Forum Member
  • *
  • Posts: 15314
Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #7 on: March 11, 2015, 12:36:21 PM »
You can never plug the bowl vent on a carburetor.  having the fuel bowl at the same pressure as the air above the air horn is essential.
I want to be like Paul Kenny when I grow up
Joe Bays

ILLTA77

  • Oracle Forum Member
  • *
  • Posts: 3283
Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #8 on: March 11, 2015, 01:57:25 PM »
No need to remove the EGR Valve, Just cap off the vacume source, the other vacume hoses can stay on, they have no effect on performance. 

Re: 1979 Trans Am 403 Desmogging Procedure
« Reply #8 on: March 11, 2015, 01:57:25 PM »
You can help support TAC!