I have a 472 cad in my Mercury and it runs awsome but it floods on start up after I run it a minut it runs great. i did have to put a electric fuel pump on it and it runs a quadrajet carb. Do you guys think I need to run a fuel pressure regulator on it or do I need to check the needle and seat and the float. I think the problem is too much fuel pressure but the pump is rated to only 4.5 psi which I think is fine for a quadrajet.
Check needle and seat, also the those floats will sometimes saturate, check it in a separate can of gas and make sure it floats for a while. I think the stock pump puts out around 5 so that should not be a problem, but i would check it a holley red street pump was shipped to me one time with the Blue spring , and it made my 750 dbl pumper look like a fountain. LMD
i will have to pull it off and check it out. i might see about puttin on a guage and see what it is pump at. I have played with carbs a little but I am not an expert so I wanted to get advise before I do it.
If it does it when it's hot, you can blame it on modern gasoline, which boils easily. If it does it when the engine is cold, maybe you need to adjust the choke.
The boiling is a good though. The quadrajets have problems with the plugs leaking in the bottom of the float bowl.
I think later this week I will pull it off and rebuild it. I have rebuilt my bike carbs for years and never a problem. I watched a youtube video and it doesn't look too hard of a job to overhaul a quadrajet and I think it is time to learn. I think I will epoxy the plugs at the bottom to make sure it does not leak from them too. Thanks for the advise.
If it doesnt have and isolator/insulator between the carb and manifold, that can lead to the gas boiling-I always install them now due to todays fuel.
Saltflats has a good point. Chevrolet Q-jet carbs had solid plugs in the metering rod wells but Buick, Cadillac, & Olds carbs had aluminum plugs that likely had little o-rings. If you put them in the Methylene Chloride dip pail suring a rebuild, the well plugs would leak like a sieve. The kits did not come with o-rings for them. A person would have to pull them out and find a way to seal them. I replaced a Q-jet on an old 68 Wildcat I had with a spread bore Holley just to eliminate this problem back in the day.
weigh your float. should be 7grams = 1/4 oz. http://quadrajetparts.com/rochester...-4mv-m4m-nitrophyl-carburetor-float-p-28.html
If you have a Q-Jet apart, always go with a new float, don't mess around with floating one in gasoline, or weighing it. A lot of them get heavy over the yrs., on one that old I always just sat it on a smooth surface, if it was heavy it would stay there, if it was alright it would tip over on the bail end, if I could not get a new one, I would use one like that.
I think if the float was a problem it would flood all the time. You can use epoxy on the plugs to seal them up after you clean the carb.
I have been adjusting the air mixture screws and I readjusted the timing a little and it did help but if you leave the motor for very long it still floods but it is better. I think I will epoxy the plugs but don't want to put too much into it because I plan to to put a eldebrock intake on the motor along with a new carb in the spring. thanks for the advise
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