At idle I can feel a slight vacuum if I hold my hand over the rear carb. Pulled it apart and could see light around the butterflies. When I loosen the screws and reset them so no light comes through they are slightly stuck and after opening them I can see a little light when closed. It idles O.K. so is this something I need to worry about ? I installed a new shaft (operator error on the old one) but used the old butterflies, new butterflies? could I gently polish the barrel?
tripower rear carb vacuum leak
- Thread starter jeff hall
- Start date
Without looking back at any of your old posts, are the end carbs original three two carbs?
BB1960
Well Known Member
I'd assume you are running the thicker throttle blades (it not original 2gc non-tripower blades), if not, I'd start there. These can be lapped to the bore also, if you get some valve grinding paste, you can mount it in a vise and put a throttle return spring on the throttle shaft and snap it shut enough times to lap it all in correctly. I did this and afterwards it was water tight (ie I could pour water on top of the blades and it wouldn't run through).
But first steps first, if you aren't running the thicker blades you will struggle to fix the problem.
But first steps first, if you aren't running the thicker blades you will struggle to fix the problem.
BB1960
Well Known Member
I'm pretty sure the release you are talking about was to rectify issues from a warranty perspective, kind of like a band aid. I remember reading it somewhere when I was at the same point that jeff is at now.....
Read the note at the bottom of the page*.
http://www.348-409.com/forum/index.php?threads/tripower-carb-specs.21560/
This specifically applies to the quadrajet, but should be just as valid a fix on any carb. The liquid sealer, part no. 3938912, may be the same as used on the tripower carb plates.
http://www.google.com/url?sa=t&rct=...=wYcM6AS5Bd7cS-TkBr9rbg&bvm=bv.48705608,d.eWU
http://www.google.com/url?sa=t&rct=...=wYcM6AS5Bd7cS-TkBr9rbg&bvm=bv.48705608,d.eWU
Yup thick blades, the carbs are correct still have the tags on them. Got some lap compound coming in the morning, that looks the best method for me. Thanks again for the help. You all know the thrill when you finally fire it up for the first time and it sounds like it wants to eat you.
Jeff,
Can you explain the process you used to lap in the throttle blades?
Actually followed BB160's suggestion. Took the base off and clamped in a vise. Used water based lapping compound and a little paste brush I kept compound on the edge of the blades and the barrel. Used hand pressure and flipped the blades open and closed applying good pressure when closed. It took three sessions before I was happy but really went fast.
Thanks for outlining that process. I have the end carbs to do for my Buick and will give this a try.