I have a 454 that is pretty much stock except for a performer intake and headers. I am running a Quadrajet carb. Sometimes when I stab the throttle I get a backfire or blowback through the carb. I am running 8 BTDC. My question is should I retard the timing a couple of degrees to fix this problem? This was suggested to me by an acquaintance.  

The addition of the intake, and the headers in particular, are allowing the motor to pull more air in-out. When headers are installed, there is almost always a need for more fuel, to even out the improved air flow. Usually when there is popping out of the carb. it is a lean fuel condition. Did you look at the color of the plugs? There is also the possibility of more vaccum in the intake tract. This could prematurely pull the secondary air valve open, when the engine is not ready for it.This will cause a brief lean condition. On the drivers side, top,back of the carb, where the secondary air valve shaft resides, there is a spring adjustment to control secondary opening rate. You will have to loosen the lock bolt from the bottom side before you can turn the adjustment. Carefuly note the position of the adj. screw, prior to new adj. Tighten the screw clockwise, 1/8 turn, and see if your problem goes away. Adjust as nessesary, 1/8 turn at a time. Never exceed one full turn from zero spring load, as this will damage the spring.8-10 deg. BTDC should work fine for your engine. Make shure you have vaccum disconnected and plugged when setting initial timing. Hope this helps. JW.  

there is one more tip for Quadrajet owners... most of the mid to late 70s versions have a   hidden adjustment inside...  it is the item marked in the rebuild instructions.. DO NOT ADJUST..   it is the adjustable stop for the primary metering rod hanger.. there is a plug in the top of the carb that can be removed only with the lid removed.. center front under / just in front of the air filter mounting gasket...  it takes a double D tool to adjust it through the top of the carb... one can make them with a proper selection of small tubing and a hammer to make it a double D shape without smashing it flat... sometimes you can just cut a slot across the tube and that will turn it..

be careful the threads are really fine pitch.. and will cross thread easy... way too easy..

this sets the lean mixture for the primarys... .

it will affect how much fuel economy you can get... and  how much primary power you can have...  it also affects the emissions... so it almost needs to be adjusted on a smog machine in manual mode on a dyno...    but with some care and not going overboard... it can be done with some part throttle driving..

most times... if you can lock the throttle linkage at about 2500 rpms you can adjust this for the best engine speed with the linkage locked..


these are on the non electrical versions of the quadrajets...  teh first versions of quadrajets had them also... but they were in the base plate... and not very accessable...   for those who have had a early q jet apart... they are the little metal tab  that hits the bottom of the primary plunger..  yep... it goes through the float bowl... but you can only see it when the piston is pushed down in its bore....


i don't know if this adjustment is covered in the Q jet books..  hopefully...  this was a factory adjustment.. so no specs were ever printed on heights to set it to...