I recently took off a holley 830 DP and put on a 800cfm Q-jet. Went from 9 mpg to 12 in the city, haven't check the freeway miles. My problem is when it sets for any longer than 12 hours, the fuel is gone out of the carb. Is there some kind of drain back problem I am having? Does this ring any bells? I can't figure it out. ou: Thanks
Since the fuel inlet is rather high in the fuel bowl I wouldn't think its draining out the inlet. Did you epoxy the wells on the underside of the main body right under the jets? Sometimes they leak fuel into the intake manifold. If its a slow leak you may not notice any flooding problems from it.
They have epoxy on them, but maybe they didn't do a good job. The truck sure loves the Q-jet! I will take it off and check. Thanks
fuel drain back What fuel filter are you using? If you're using a late Quad with the long fuel filter inlet, use the stock filter....it has a one-way valve in it that will help this problem. As far as the fuel wells, regular epoxy won't last there. It must be fuel-resistant.
Thanks, I am going to take it apart and re-epoxy it with some of that special epoxy. It probably has just a quad filter. I probably should pick up a new one anyway. I wonder who has the best? Rick
Before assuming that you have a problem, you might look for related posts on this site. Poor fuel can cause the problem you are having. If you are losing the entire float bowl's contents in less than 12 hours, the source should be notable, especially with the air cleaner off. Look for vapor, or dripping. Let me know... Ray
Yes I remember seeing vapor. Let me guess, its the fuel dripping on the hot intake manifold? I have ran 4 tanks of 76 and two tanks of Shell, so I know the fuel is fine.
Ray's not talking about "bad" gas, just the fact that modern gas formulations evaporate much faster than 60s gas did
One other thing I have noticed with the more "modern" formulations is that when they evaporate, they leave deposits that sometimes make the float stick in the closed position, preventing the bowl from refilling. I have found my share of fuels requiring carb disassembly to fix the problem. Shop carefully, or drive it at least three times a week. I was also successful at spraying carb cleaner at the needle and seat, and the built up fuel pressure forced the needle off the seat. Just a word of caution. Ray
