I am running triple Rochestors 2g's with all the right setup with blank idle screw plates on front and rear carbs and progressive linkage all from HotRodCarbs.com. I am sure all the carburettors need a rebuild and last time I did that was at least 5 years ago. This problem may have been present earlier but I wasn't taking the air cleaners off to look at this. The problem is that if I start the car normally and run using just the center carb as main fuel source on idle then when I shut off fuel leaks into the the front and rear carbs and pools on top of the throttle plates and gradually leaks down into the manifold. Of course when I try to start again there is a lot of fuel already there and it is difficult to start on first go. I have just taken the front carb top off and reset float level and drop to specs provided and it appears that the needle is dropping as it should. Haven't done the rear yet but will probably buy 3 new reco sets to do all the carbs with new gaskets,floats and needles and reset float and drop. The fuel is leaking into the throats but not sure where from? Just drip drip drip after shutdown and then stops. It is strange that this problem seems to have started just recently after I did a couple of things that may just be a coincidence . Had the plugs cleaned at local old school mechanics shop who has the old fashioned sand cleaner. After refitting plugs we did a timing test and he said it was about 12+ degrees advanced and we took that back to 8 degrees. Car ran fine and started OK for a couple of days and then the flooding started. I am running a mechanical pump with a holley pressure pump adjustment set at 2.5lbs which hasn't been changed forever. I think the full rebuild will be necessary anyway after all this time but just truoble shooting first.
I have read that a return line will decrease the residual pressure that is present when you shut down (I think it of it like breaking a syphon but I am unsure if that is completely correct). I know this is true of Strombergs so I thought I would toss that out there. Is the issue with your avatar? I could be completely a sea here; but first response to a problem should be worth a beer at least.
I think replacing the needle and seat assemblies is a good idea. I would also put a gauge on the system and see what your fuel pressure really is. Might do that before replacing the carb parts.
No anytime now. Just start and run for a few minutes and then shitdown and it starts leaking fuel into the carb.
Almost has to be the float, needle and seat OR, and I had this happen on my brothers boat Rochester, the metal gasket under the seat isn’t sealing. Make sure you put the correct gasket under the new seat.
I chased the same problem on a Pontiac, to solve it I installed a cheap-o fuel regulator from Mr Gasket, one of the round dial types. Set it to 2.5 and the problem went away and the car ran much better. From what I read, the 2G floats can not take much pressure.
Ditto for me! I've been using the small round dial type regulator for over 40 years on my 3x2's and have it dialed in at 2.5 lbs and it has worked flawlessly. Only other thought is to make sure your floats are not full of fuel. A pinhole in a float will drive you nuts too!
I had pretty much the same problem with my Pontiac tri power years ago. My brass fuel filters were slowly disintegrating, causing my needles to get jammed up in the seats. Little bits of brass would be in the float bowls every time, but switching to paper filters cured the issue, on mine.
I've been through most, if not all, of the flooding probs. with the rochesters. -the round Mr. Gasket type regulator is wrong. I used a test gage (accuracy 1/10%) on mine, it was way off-like 4.25 at 3, over 3 at 2.5, etc. Each one is different, recommended set is 3 psi. per Mike's carb works (excellent souce of info and parts). -float is always suspect, even a new one (which are chinese i think). Check it in hot water. -the Daytona float valve is killer, no pin/needle type. Research it. -the hardest one for me--the float "bar" that holds the float to the base would work out of one hole after a few pops, or just sitting for a long time before starting. Float now crooked, free flow. A dab of JB weld fixed that. --------and i found that alcohol played a gigantic part of my problems, enough of it made everything go away.
I always set the 2 outer carbs float levels lower than recommenced. When driving with 3-2’s and not using the outers much or not at all the vibration of the engine would allow fuel to flow in. With a lower float setting the extra fuel would hold the needle and seat tighter. Used stock fuel pumps and never had a problem with 4 psi from one.
I agree the Mr Gasket regulator is not accurate, but it doesn't matter, I set it till the flooding stopped and the engine still ran good. I don't care what the actual pressure is as long as it works.
I probably should stay out of this thread, since the carbs are no longer Rochester because of the imitation bases. What else has been changed? In a different lifetime, I had a factory tripower on a 1964 GTO. Ran SIX AND ONE/HALF pounds fuel pressure with ZERO ISSUES; BUT I used the factory orifice fuel valves (0.086) not the generic valves which come in the FLAPS kits. Amazing how much those factory engineers really knew about fuel systems. But today, the Reid Vapor Pressure of modern fuel (it ain't gasoline no more!) is probably causing the issue. A return line from the fuel inlet on each carb which goes back to and dumps in the top of the fuel tank should solve the problem. As to the inline dial-type regulators, they are just about as reliable as a career politician! Jon.
I followed up on where I bought my rebuild kits last time,Quadrajet.com and it appears that it no longer operates and Greg Gessler who I guess was the owner died back in July 2022 and only 61 years old.
MEOW I don't understand what you mean "no longer Rochester" just because I used a professional carburetor service(Larry at HotRodCarbs.com) who specialises in Rochester carbs,rebuilds and specialised parts and linkages. I purchased the special bases without idle screws as is required for a proper tri-carb setup. Also the progressive linkage that Larry provides is absolutely the best. Not a setup that looks like it was made from coat hangers. Just look at his website to see the quality of the product and 40 years experience. http://hotrodcarbs.com I did see a mention that after 40 years he is selling. However it is difficult to order online from him and not even sure he ships to Australia anymore. Just found his email address in my system that I hope still works and sent him some questions. His rebuild kit has just the parts you need to rebuild my carbs(serial numbers 7040110 and 7040112) and not like the other kits that have so much extra in them that you don't use.
I'm going to throw out a little something here. Holley's were real bad about dripping after shutoff if the needle and seats were not Viton's. I don't think it's so much of a too much fuel pressure issue as it is leaking needle and seats. When it's running it's fine , when you shut it off the remaining fuel pressure leaks through the needle and seats and drips in the throat of the carbs. It stops after it bleeds off the remaining pressure, Then has to crank awhile to get out of the flooded cylinders condition. JMO, unless you have some really high fuel pressure. Lippy
I do think it is leaking needles and seats. I fixed this issue once before and that was when I had too high fuel pressure. Fixed that and took it down to 2.5psi but I think now after 5+ years since I rebuilt the carbs it is just a simple rebuild,new gaskets,needles and seats and even new floats to fully ensure that everything is cleaned up. The unleaded fuel we use doesn't help with longevity of gaskets and seals. waiting to hear back from Larry Fulton re ordering kits.
Note to OP: Apologies, I was not trying to ruffle your feathers, only suggesting an avenue (the return lines) that virtually always works for your issue. As to fuel pressure, did you read where I mentioned that 6 1/2 psi works great on GENUINE Rochester tripower carburetors? Note to self: in future avoid the desire to help in Frankencarb threads. Jon
Jon, do the return lines helping have something to do with the fuel we have now? Just wondering. Sometimes I forget about the shitty stuff we have. Lippy
Yes, the return lines allow the pressure being built in the lines after shutdown to bleed back to the tank. Note the comment in my first post about Reid Vapor Pressure. EDIT: This link explains the issue in detail: https://www.thecarburetorshop.com/Troubleshooting.htm#Fuelleak Jon
Jon , you know I read your first post again and the only thing I can think of saying to you is I must have been in Old Fart mode when I read it the first time.
If there is no return line, I run one. I use 1/4" steel. I mount a Tee in the supply side of the fuel pump or even better, get a fuel filter with the return port. I quit filling my vehicles up, I stop for $25 to $35 in fuel every other day.
The Jalopy Journal
