MYBAD79
Moderator
OK, some questions have been answered in two previous threads. I am hunting a carb and timing problem after I installed a new carb and a new intake.
My other two threads regarding this problem ended pretty much in a dead end - I installed smaller jets and swapped carbs, no success... yet....
Let's start about ten days ago: I removed my Edelbrock 1405 600cfm carb and my performer intake and installed a RPM air gap and a 1812 800cfm Edelbrock carburetor.
The engine was running fine before I removed these parts.... no timing issues either....:banghead::banghead:
Engine: 383ci, 9.8:1 CR, Comp 230-236 dur hydr roller cam, Edelbrock RPM heads with 64cc chamber and 170cc runners
I started the engine with the new intake and carb and before I even got to the timing it started misfiring. The fumes were horrible - found the jets are bigger that they're supposed to be.
Instead of waiting for smaller jets I re-installed the smaller 600cfm carb on the new intake (air gap). It ran fine in neutral but not under load....It misfired in 1st or 2nd gear, 2000-2500 rpm, I push the throttle and it stutters, bogs and misfires....
I pulled the plugs and they were black...
Yesterday:
Changed the spark plugs and installed the small jets from the 600cfm carb in the new 800cfm carb, installed 800cfm carb and with the new plugs it seemed to run great.... set the timing at 14 degrees (initial) and rev'd the engine a few times. Fumes were not as bad and it did not misfire in neutral. Set the timing to 12-14 degrees advanced. Noticed that it advanced to more than 36 degrees but it did not ping.... set timing to 12 degrees (end of timing tab) and thought it was all fixed....
Today:
Took it out on the road and again, it still misfires under load...
Checked the timing again: 14 initial. Vacuum advance seems to be too much, looks like it's pulling close to 40 degrees (estimating, no timing tape).... Now my question: a new intake does not change the vacuum ??? I mean, it's not pulling more vacuum (lower pressure) on the can.... ???.... The advance can is stock so it should pull 24 degrees, plus my 12 initial I should be at 36 total... I never had this issue with the old intake and I've tested the new carb with large jets, old carb with its jets, new carb with smaller jets.... only thing that remains is the intake...
My last "test" today was to simply disconnect the vacuum advance: I plugged the port on the carb and again, it runs fine in neutral but in gear it just bogs and misfires at 2000-2500rpm, afraid to force it higher than that....
I'll get the AR12 (1838) advance can and the MRG928G spring kit just to make sure the distributor is ok.... not too convinced it's the problem because it was running fine before I had the glorious idea to mess with it.... is it possible there's something wrong with the centrifugal weight (mech advanced) ???
$700 for a new intake and carb and the car doesn't run anymore... could have had that for less.....:banghead:
My other two threads regarding this problem ended pretty much in a dead end - I installed smaller jets and swapped carbs, no success... yet....
Let's start about ten days ago: I removed my Edelbrock 1405 600cfm carb and my performer intake and installed a RPM air gap and a 1812 800cfm Edelbrock carburetor.
The engine was running fine before I removed these parts.... no timing issues either....:banghead::banghead:
Engine: 383ci, 9.8:1 CR, Comp 230-236 dur hydr roller cam, Edelbrock RPM heads with 64cc chamber and 170cc runners
I started the engine with the new intake and carb and before I even got to the timing it started misfiring. The fumes were horrible - found the jets are bigger that they're supposed to be.
Instead of waiting for smaller jets I re-installed the smaller 600cfm carb on the new intake (air gap). It ran fine in neutral but not under load....It misfired in 1st or 2nd gear, 2000-2500 rpm, I push the throttle and it stutters, bogs and misfires....
I pulled the plugs and they were black...
Yesterday:
Changed the spark plugs and installed the small jets from the 600cfm carb in the new 800cfm carb, installed 800cfm carb and with the new plugs it seemed to run great.... set the timing at 14 degrees (initial) and rev'd the engine a few times. Fumes were not as bad and it did not misfire in neutral. Set the timing to 12-14 degrees advanced. Noticed that it advanced to more than 36 degrees but it did not ping.... set timing to 12 degrees (end of timing tab) and thought it was all fixed....
Today:
Took it out on the road and again, it still misfires under load...
Checked the timing again: 14 initial. Vacuum advance seems to be too much, looks like it's pulling close to 40 degrees (estimating, no timing tape).... Now my question: a new intake does not change the vacuum ??? I mean, it's not pulling more vacuum (lower pressure) on the can.... ???.... The advance can is stock so it should pull 24 degrees, plus my 12 initial I should be at 36 total... I never had this issue with the old intake and I've tested the new carb with large jets, old carb with its jets, new carb with smaller jets.... only thing that remains is the intake...
My last "test" today was to simply disconnect the vacuum advance: I plugged the port on the carb and again, it runs fine in neutral but in gear it just bogs and misfires at 2000-2500rpm, afraid to force it higher than that....
I'll get the AR12 (1838) advance can and the MRG928G spring kit just to make sure the distributor is ok.... not too convinced it's the problem because it was running fine before I had the glorious idea to mess with it.... is it possible there's something wrong with the centrifugal weight (mech advanced) ???
$700 for a new intake and carb and the car doesn't run anymore... could have had that for less.....
:banghead:
:surrender:
