CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
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Hey guys, I have a 305 LG4 with a CC Qjet on it.
I have two issues with it atm.
1st: When it's cold (the motor), fire her up, tap the gas to the floor real quick to take her off of fast idle. Driving along and i get into it. It bogs horribly for a few seconds, my AFR gauge dips way down in lean (actually dissapears). After a few seconds the motor lights up and is strong. Now this issue goes away if i keep her pinned down for 5 seconds ish and let her pull up to 5k. Once i do that 2-3 times, runs nice and strong until i park it and the motor cools again (normally 24 hrs)
2nd: When cruising along and at 1/2 throttle everything is fine, AFR shows ideal/tad rich. Second i get the secondarys barly open, AFR dips lean motor seems to run okish, dosnt pull real hard until a few seconds of having my foot down, then she shoots up to ideal/rich and pulls hard.
Last time i checked dwell, it was good. (month ago)
The mixture of the secondaries is not controlled by the dwell. You may need to swap in larger rods and a better hanger and/or adjust AV tension. Have you perused:
The off-idle stumble could be a bad booster providing no, or a weak, booster shot. You should see what the dwell is doing when this happens.
__________________ "A man who voluntarily drives a car like that and still manages to maintain such impervious confidence that it will faithfully start the next time he turns that key is an encouragement for us all to take greater risks in life."
ok, i did some reading, my motor atm has headers, full 3inch cat, no emissions (no cat, or smog). I read a G hanger and DR rods would be good, correct?
I will test the dwell this afternoon. What am i looking for to indicate a bad booster (accelerator pump?)?
With the engine off, pull the throttle back and you should see a healthy shot of fuel dump into the primary throats from the booster shot. While you're there check your choke pulloff. With the vacuum line disconnected you should be able to push it in, hold your finger over the nipple and it shouldn't come back out until you release your finger.
__________________ "A man who voluntarily drives a car like that and still manages to maintain such impervious confidence that it will faithfully start the next time he turns that key is an encouragement for us all to take greater risks in life."
If it only bogs when you dig into the secondaries, the problem is almost certainly with the secondaries. Too fast an opening on the secondary air valves (not enough spring tension, vacuum cansiter releasing too quickly), secondarry fuel enrichment tubes fallen out of the underside of the airhorn casting (gotta take the top off the carb to veryfiy this) and bent/broken secondary parts like the secondary hanger, secondary air valve cam and such wuld be where I start.
DR secondary rods and a G hanger are good parts for tuning a little more power into it, but even with the stock tune it shouldn't act that way. Something's not right with the basic functioning of the secondary side of that carb.
