Moparchat - Home of MOPAR enthusiasts worldwide!



Go Back   Moparchat - Home of MOPAR enthusiasts worldwide! > Technical Forums > Performance Talk

Click here to search for Mopar cars and parts for sale.


Reply
 
Thread Tools Display Modes
  #1  
Old 01-09-2007, 04:26 PM
71DemonZ's Avatar
71DemonZ 71DemonZ is offline
Inactive User
 
Join Date: Aug 2006
Location: racine/wisconsin
Age: 37
Posts: 27
Question I Got problem with the Carb Back Firing When Driving on my 273!!

OK,this is what i have a stock 273 with a 904 an a 8 1/4 with 3.21 posi, this is what i just did to it...swap the cam for a mopar performance with a duration of 260/268, Lift 430/450...and put a edelbrock performer with a Road Demon Jr. 525 cfm carb up top.....I left the stock ignition besides accel wires for now and timing is 10 degrees advanced....so it runs real smooth no problems at all but when i take it out for a drive ill give it gas an then it bogs down or back fires threw the carb....but when i give it more gas it stops doing it then it drives fine until iam below a certian rpm then it will do it again...i dont have a clue what it is, iam thinkn the demon carb or maybe i just need to upgrade to eletronic ignition??idk someone let me know.....

Today iam going to Change the plugs and see what that does.....
Reply With Quote
  #2  
Old 01-09-2007, 04:36 PM
perfmachst's Avatar
perfmachst perfmachst is offline
Inactive User
 
Join Date: Jun 2003
Location: yakima, wa.
Posts: 452
Default

hello, any time you put a bigger cam in a motor, the dist has to be recurved with a faster advance. then set timing at total at the rpm needed. what you have is lack of proper timing. just food for thought.
Reply With Quote
  #3  
Old 01-09-2007, 07:29 PM
Crank Crank is offline
Inactive User
 
Join Date: Aug 2001
Location: Mich
Age: 65
Posts: 438
Default

sounds like your secondaries are closing to far and need adjusting .
Reply With Quote
  #4  
Old 01-09-2007, 08:32 PM
jelsr jelsr is offline
Inactive User
 
Join Date: Dec 2001
Location: Dighton, Kansas
Age: 84
Posts: 1,253
Default

Spitting back thru the carb ususally indicates lean so make sure your accelerator pump is giving a good shot right from the gitgo. It won't pick up r's from low speed without it.
Reply With Quote
  #5  
Old 01-09-2007, 09:18 PM
Shaun Shaun is offline
Inactive User
 
Join Date: Dec 2005
Location: Grass Valley CA
Posts: 411
Default

Quote:
Originally Posted by perfmachst View Post
hello, any time you put a bigger cam in a motor, the dist has to be recurved with a faster advance. then set timing at total at the rpm needed. what you have is lack of proper timing. just food for thought.
I agree with this to a point. You must have your advance curve close(at best). Get your hands on an advance timing light(it will allow you to see where your at by the gun,instead of trying to see the marks on the dampner and you can turn the dial up and down-a big help) and set your total advance on the gun at 30*(to start). Rev it up to 2000 to 2300 and see if your light is at the TDC mark. This you may know,just trying to help.
Reply With Quote
  #6  
Old 01-13-2007, 02:11 AM
Tarrbabe Tarrbabe is offline
Inactive User
 
Join Date: Jan 2002
Location: Cumberland Plateau
Posts: 1,972
Exclamation Get a good timing light...........

Then find TDC and install timing tape. Make sure you have true top dead center and then run engine speed to 3000 rpm. Set timing at 35 - 36 degrees total and that sould solve the problem even with the stock ignition. Recurve the dist. should help even more.
Then............................. Have fun!
Reply With Quote
  #7  
Old 01-13-2007, 04:17 AM
charger_dan's Avatar
charger_dan charger_dan is offline
Inactive User
 
Join Date: Mar 2001
Location: Bend, Oregon
Age: 55
Posts: 448
Default

is the carb new?
i agree on checking the pump shot/arm adjustment.
Reply With Quote
  #8  
Old 01-13-2007, 02:55 PM
rarebird rarebird is offline
Inactive User
 
Join Date: Feb 2006
Location: LaGrange,Wi
Posts: 6
Default

I'm a super pro drag racer When you increase your lift you must set your timing back to compensate. with that lift about 31 to 34 degrees is suffient
Reply With Quote
  #9  
Old 01-15-2007, 04:04 AM
65TerrorCuda's Avatar
65TerrorCuda 65TerrorCuda is offline
Inactive User
 
Join Date: Mar 2003
Location: Albuquerque/New Mexico
Posts: 111
Default

I have a 273 that did the same thing. Pulled the heavier spring off the stock distributor, jetted a little richer, and properly adjusted the accelerator pump(Holley 390cfm). Now the car pulls through the lights much quicker.
BTW my axle ratio, cam specs, etc. are almost identical to yours.
Reply With Quote
  #10  
Old 01-15-2007, 11:36 AM
kamstra kamstra is offline
Inactive User
 
Join Date: Jun 2000
Location: ON, Canada
Posts: 293
Default

Quote:
Originally Posted by Tarrbabe View Post
Then find TDC and install timing tape. Make sure you have true top dead center and then run engine speed to 3000 rpm. Set timing at 35 - 36 degrees total and that sould solve the problem even with the stock ignition. Recurve the dist. should help even more.
Then............................. Have fun!

I agree with Shaun and Tarrbabe. It is likely ignition/timing related. Start by following the above advice!
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
slant 6 firing problem 6dart4 Slant Six Chat 7 09-17-2004 08:16 PM
Back firing?? charging in 74 Vintage MOPAR chat 4 10-10-2002 06:11 PM
Need help on back firing problem QUADDAK Performance Talk 6 07-28-2001 05:46 PM
Need help on back firing problem QUADDAK Performance Talk 2 07-27-2001 08:48 AM
NOW IT'S BACK FIRING THRU CARD moparsofcamelot Performance Talk 5 11-27-1999 09:09 PM




All times are GMT -4. The time now is 02:49 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
. . . . .