Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Mentioned: 1 Post(s)
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"If I feed it slowly, it's better...but still bogs around 3500 rpm"
If your secondary flap opening "pops" open too quickly, it will gulp air before creating the needed airflow to draw in the gas. There is a small spring on the side of the carb that is held in place by a small allen screw on the underside of the spring. You will also see a very small screw on the side which is turned to make this adjustment. You insert a screw driver into the screw slot, then loosen the allen screw just enough so you can turn the adjusting screw. Turn the screw, I believe clockwise, to tighten up on the spring, but only go about 1/4 turn from your starting point. Then snug down the allen screw (DON'T OVERTIGHTEN or it could strip out, its small) to lock it back into place.
What this does is tighten the rate of opening on the secondary air flap. This will slow down down the opening of the secondary flap because the flap will encounter more resistance and should in turn allow the air going into the secondaries to develop more velocity and pull the gas from the secondary wells to get the gas flowing BEFORE the secondary air flap pops wide open - you won't be sucking in a big gulp of air without the gas and then waiting for the velocity to catch up and get the gas flow going through the secondaries.
IF this shows and improvement in any way, then you know where your bog is coming from. If not, then you have eliminated one possible cause that I have experienced on a number of occasions in years past. The early Q-jets have a cut-out/square notch in the secondary flap while the later (beginning in the early 1970's) did not and are solid. Pontiac found that the flaps with the notches allow too much air through before the gas flow began - bog.
Could also be the secondary metering rods/hanger are not the correct ones and you need to "fatten" up the secondary flow of gas - your engine needs more gas when you go wide open throttle.
So check all the obvious first as suggested previously because it could be a fuel delivery problem or an electrical issue.