CarburetorsCarb discussion and questions. Upgrading a Third Gen carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
Welcome to ThirdGen.org!
Welcome to ThirdGen.org.
You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!
My car doesnt seem to run so strong after 30mph and I assumed that thats because its a 305 but It just seems... bad after 30 / 40 mph. After messing with the air / fuel ratio and making it even for all four mixture screws with this Demon, the sluggish higher mph's seems worst! So I'm looking at the vacuum secondaries and noticed that they dont move at all. I'm in the garage revving the **** out of the engine but I see nothnig. I even held the rpms up high for as long as it was conformtable but saw no motion.
Ok troubleshooting time... I was able to manually move the secondaries from it's linkage with the primaries. Lol wow... the engine rocks the car and sounds awesome as you hear it suck down the gas from the carb. I'm starting to think that this is my missing power on the road. So I proceed to take the vacuum pod off to see if there was anything obviously wrong. There is a small vacuum port with an o ring on it going to the vpod, looks good, diaphragm in the vpod looks good... I tested it with a hose and sucked a light bit of air from it, it moves just fine and seems to pull strong with a light bit of vacuum... I then hooked my vacuum guage up to the port on the carb and gave it a few revs and saw NO Vacuum at all! Ok yea.. that pretty much explains why this thing never moves... So one last test before I gave up for the night. I tried to blow air into the vpod's vac port and it went through just fine as I can hear the air hissing somewhere in the carb. Oh btw I'm not sure how accurate this gauge is cause the needle is stuck at 5 instead of zero... but the numbers seem to read 15lbs of vac.
More info for something simple!... After researching and troubleshooting I'm finding that vacuum decreases when you floor it. If thats the case... how does the carb ever creat vacuum to pull the secondaries open? I guess I dont understand how this vacuum pod is supposed to work but I wish I had a mechanical secondary.... Any tips pointers or suggestions would be appreciated. I'll post any info for the record here that I find.
I'm getting mixed statements about if you see them or not while reving in a garage... I just might put a web cam on it, hit record and go for a test drive lol
__________________ 9 years.. same bird.. in love with every second
vacuum hold the secondaries shut. when you go to wot, that vacuum is cut off allowing them to open
you could drive it without the hood and air cleaner on it for a short distance and see if they are opening. make sure all the linkage and everything moves freely when its turned off. also, I'm not an expert but making all the air/fuel ratio screws even probably isnt going to help. it needs more fuel at higher rpms and less at idle. so each one needs to be adjusted correctly, not just all of them made even and assumed it should run right.
__________________ 1984 z28 5.0 L69 H.O. T5 tranny with 3.73 gears and posi trac.
Ha... it was the tv cable that became a bit loose. Time to upgrade the hardware, this one looks a bit worn and could continue to become loose. Holly makes a good one that holds the throttle, Tv and cruise control for only 30 bucks. Man this auto trans is going to be the death of me. Cant wait to safe up for the swap kit. You don't even want to hear the story about the trans lines and dip stick.... lol
Thanks for the replies. I see now that the engine has to be under a load and if I want it to open up sooner then I'll install some lighter springs in my vacuum pod. Orileys actually had a pack of these!
__________________ 9 years.. same bird.. in love with every second
