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float bowl overflow

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dbnoaol Avatar
dbnoaol doug bowers
milford, OH, USA   USA
this is a continuation of previous discussion on my fuel leak.
front carb HS2

everything fine at idle..
at driving rpms the float bowl pours fuel thru the overflow port.

so the answer is float height adjustment and valve...
float is new, and new grose valve installed....doesnt fix my issue.
adjustment measurements I read about are all over the place from 1/8" to 11/16".....so i ignore that and just keep trying to tinker with it until it works...

but here is what i'm not understanding...

if the float and valve shut off the fuel and dont overflow at idle when fuel demand is lower...why then does it overflow at higher rpm when fuel demand is greater and being sucked out of the bowl faster???
it would seem logical that, higher rpm =more fuel consumption ...therefore the bowl should never have a chance to overflow....!!!

what am i missing in the theory of operation or the mechanical physics here?

if the float was not rising to contact the valve and shutting off fuel at idle, it too would overflow at idle since the fuel pump would just keep pumping in fuel- yes?
but that doesnt happen- so this tells me by logic that the float and valve are functioning.
so whats different at higher rpm?

by the way, the rear carb float bowl leaks very very little thru the overflow pin hole- just vapor really..hardly noticeable...and it has the original 50 year old float and arm with a new viton type valve...
front carb had a new viton, dumped it for the "improved" grose valve while chasing this problem...now i read reviews saying the grose valves are trouble...either way, the problem remain with either valve.
grose or viton = coke or pepsi..is there really a difference?



Edited 1 time(s). Last edit at 2018-06-07 02:17 PM by dbnoaol.

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refisk Rick Fisk
Frankenmuth, MI, USA   USA
Grose jets usually cause a lot more problems than they fix. What fuel pump are you running?

ice Avatar
ice Gold Member Larry Ice
Lawrenceville, GA, USA   USA
What kind of fuel pump are you using? 2-4psi is all our road cars need. Too much pressure = overflow. Yes, I agree with Rick on the Grose seals aren't always better.



Iceman

Atlanta GA

60 AH MK1
62 AH MKII
67 Midget
71 Midget

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dbnoaol Avatar
dbnoaol doug bowers
milford, OH, USA   USA
Its an SU pump..already been over that with a couple of the guys..they said the pump was fine.
I'll see if i can find the model # again.

I switched the jet back to the Viton and original float and tried to really shut the fuel flow off...it seemed to work somewhat...couldnt duplicate the leak running the engine at about 4k rpm...thought I had it solved..
took it for a spin...noticably sounded different...putt putt note from the exhaust, lack of power...it seemeed i proved to myself the fuel COULD be cut off...

so i gave it the usual drill- doing left hand dounuts in a parking lot...it took a lot more laps but the fuel leak began again...front carb, overflow port...ugh.

heres another bit...
the float bowl, should it be rigid to the body of the carb or have a little play in it as though it could swivel left and right about an 1"-1 1/2" ???
front bowl swivels a good deal...rear bowl only half as much.

dbnoaol Avatar
dbnoaol doug bowers
milford, OH, USA   USA
heres the fuel pump


Attachments:
SU fuel pump.jpg    29.9 KB
SU fuel pump.jpg

Kerr Avatar
Kerr Platinum Member Norm Kerr
Ann Arbor, MI, USA   USA
it would be better to add to your existing thread, so all of your information would be included, rather than starting a new one and going over all the same old questions again

zabond Russell Meehan
Neerim East, victoria, Australia   AUS
1966 MG Midget "Bridget"
my understanding is the bowls should only swivel a small amount, if your front bowl can swivel that much it could be shaking that much that the fuel is spilling out the overflow, on mine the bowls only move about 1/2" and feel as if their rubber mounted

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ice Avatar
ice Gold Member Larry Ice
Lawrenceville, GA, USA   USA
The floats are mounted in rubber but don't think there is supposed to be a 1/2" movement in them. If you have that much movement the carbs are not assembled correctly.



Iceman

Atlanta GA

60 AH MK1
62 AH MKII
67 Midget
71 Midget

Poundingsand Avatar
Poundingsand Silver Member Peer Ebbighausen
Los Angeles, CA, USA   USA
Doug, can you post a few pics of your carbs so we can see what you have going on?

Also, next time it overflows feel the float bowl. Is it hot? The problem may not be overflowing but fuel boiling, which can be caused by a lean running condition (I just experienced this.) It wouldn't necessarily show itself when the car is not under load.

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littlecars Avatar
littlecars David Bassett
Nashville, TN, USA   USA
1965 Chevrolet Corvair "Ski Team Transport SOLD!"
1965 MG Midget MkII "Buffoon"
1966 MG Midget MkII "Swiss Cheese...SCRAPPED"
1970 Triumph Spitfire MkIII "Tamara's Turd... SOLD!!!"    & more
I don't believe the float bowls were ever designed to "swivel" but a little compensating for wear. If I am reading your measurements correctly, it sounds like they would be constantly swinging against the side of your heat shield and could actually cause overflow and a fire! Mine have moved maybe 1/8" but you are saying they practically spin on the manifold in an arching fashion?

dbnoaol Avatar
dbnoaol doug bowers
milford, OH, USA   USA
heres pictures of the bowl movement- its a 1/4" as best I can measure...my previous claim was apparently mis-estimated..so I put a ruler to it.
front bowl moves a bit easier than rear bowl...
all rubber washers and mounting parts are there- the mounting bolt that passes thru the bottom of the carb is as tight as it will go.

so I'm assuming this is normal- they are not supposed to be rigid.

first pic is bowl rocked all the way right ( looking from front of car) 1/2" to face of carb
2nd pic rocked left toward engine 3/4" to face of carb.
3rd pic float tops orientation
4th pic the leak- comes from the overflow port- notice the gas puddle on the screw of the heatsheild


Attachments:
float 1.jpg    40.6 KB
float 1.jpg

float 2.jpg    43.7 KB
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float bowl angle.jpg    46.7 KB
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carb leak 2.jpg    36.8 KB
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ice Avatar
ice Gold Member Larry Ice
Lawrenceville, GA, USA   USA
Doug, 1/4 " seems ok to me. However, next time you have the carbs off look to see if the rubber vibration isolators are in good shape on the inside of the carbs. Sometimes they look ok from the outside but can be mush on the inside.



Iceman

Atlanta GA

60 AH MK1
62 AH MKII
67 Midget
71 Midget

1974MGMidget Avatar
1974MGMidget Silver Member Jack Orkin
Grayson, GA, USA   USA
Those carbs don't look like mine - where is the overflow port you mention? Mine has an overflow nipple sticking out of the top where the inlet/outlet hoses are attached. Is there a small hole there that I can't see that's the overflow? Also, my float bowls are tight - they don't wiggle, but, as mentioned, my carbs may be a little different.

Kerr Avatar
Kerr Platinum Member Norm Kerr
Ann Arbor, MI, USA   USA
"Is there a small hole there that I can't see that's the overflow? "

Hi Jack,
yes, there was a photo and a description in his previous thread, but instead of adding to it he started this new one, creating this disconnect/confusion

1974MGMidget Avatar
1974MGMidget Silver Member Jack Orkin
Grayson, GA, USA   USA
Well, I'm easily confused!

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