Carb Ideas

[JayGT6]

Right then, I've got a set of late Strombergs on my GT6 which are leaking fuel and I suspect overfueling. So here's the question do I
A Get the Strombergs looked at and serviced
B Get a set of early Strombergs (I've been told they are better as they don't have a bimetallic strip fitted??)
C Get a set of SU's compete with linkages and manifold?

I'm tempted to go for C but which SU's do I need as some won't clear a GT6 bonnet?

[rotoflex]

From where are they leaking fuel?

It may be just a bit of trash stuck in the needle valves that needs cleaning out - could happen to su's or strombergs.

Also, have you replaced the fuel pump recently?  It may be putting out too much pressure.

[JayGT6]

Looks to be leaking from the float chamber. The fuel pump is brand new, fitted a year ago, used properly for the first time yesterday, so could be the pressure. What can I do to reduce fuel line pressure?

[Pete Lewis]

most needle valve leaks are du to small peices of rubber hose cut off when you refit hoses to bundy tubing, ,
have a good flush and look right behind the valve,
beware there are a number of float  chamber gaskets as the years  evolved that all look similar but will leave some areas or the chamber periphery unsealed in a corner .

the bimetal temperature adjusters are part of an emission control  idea to allow air to bypass the throttle plates and increase idle speed and lean the mixture when very  hot.
ther are two small flat o ring seals to stop air ingress around the casting , take out two screws and look at their condition.


the main problems with these is if open when should be closed or both are set widley different you cannnot adjust the main mixture and idle  as there is a constant air bleed thro these little devils.  
so without any complicated test gear adjust the nut inside the small casing to make sure they are SHUT ,  the bimetal opens a small plastic plunger
you can turn the small nut to get both set with the same plunger tension, ... or....block the holes to render the idea inoperative. or block the hole linking the gasket faces of carb/manifold .

what you dont want is bypass in operation when setting the initial adjustment ,,  both must be in a known  closed state  

its  very common to find the plunger has no tension and is open all the time on olde units


hope thats a clue

Pete

[rotoflex]

8328 wrote:

Looks to be leaking from the float chamber. The fuel pump is brand new, fitted a year ago, used properly for the first time yesterday, so could be the pressure. What can I do to reduce fuel line pressure?

You can add a fuel pressure regulator, or get a replacement pump.

You need to get a fuel pressure gauge - I'm afraid it's essential that we have access to one now when replacing a fuel pump.  Fuel pressure should be about 1.5 psi to 2.5 psi

If the fuel pressure is OK, then you need to take off the float bowls from the bottoms (noting the different length screws) & see if the needle valves can be fussed into correct operation.  It's best to have a spare float bowl gaskets on hand, as Pete Lewis says.  Old gaskets sometimes come apart when taking the bowl off.

Pete, thanks so much for the info on which way to adjust the bimetallic strip once it's decided they're out of original operating parameters.  With the information that the throttle bypass valve can be just blocked off (usually by a piece of soda can cut to the outline of its gasket), that pretty much locks up how to deal with CDSE's once the emissions ancillaries are outside of operational parameters.  I tried to adjust the themostatic valve via the hot water & thermometer technique on a set of carbs, & the result was unsatisfactory.  Just leaving the valve closed is straightforward & reliable.

[JayGT6]

Thanks for the advice guys. Once the weather brightens up I'll have a tinker. In the mean time I'll order a service kit and see how we go. I can't seem to find a fuel pressure regulator looking on Rimmers. Anyone got one fitted and can recommend a good one? Thanks again

[Pete Lewis]

the std needle set up should contain a std mechanical pump pressure , its only a spring making the load on the diaphragm .

always worth a look for nice photo's on how to is the Buckeye site ,  never mind its TR the  basics are usable

http://www.buckeyetriumphs.org/technical/technical.htm


if the carbs are the later then there a possibility the float is fitted upside down they have two needle arms and can be clipped in both ways up.

the correct is to have the flat side of float up and the contoured side down ( floating)  set the float to the 18mm from the face


the problems with gasket sets is if you get  a universal  they have up to 5 generations of float gasket, they all look ...thats it , but  hey ho

some sneaky little design change means a corner is left open to leak ...   a CD gasket wont suit a CDS  or CDSE   guess there's some tee shirts for that one .

if you dont have the adjusting tool you can use a long allen key but  MUST  hold the air piston from rotating or you can tear the diaphragm

tip if you remove the top cover and the diaphragm is swelled by oil contamination , makes itoversize and  hopeless to refit   give it a soak/wash in petrol and it will return to size.    

Pete

[rotoflex]

8328 wrote:

Thanks for the advice guys. Once the weather brightens up I'll have a tinker. In the mean time I'll order a service kit and see how we go. I can't seem to find a fuel pressure regulator looking on Rimmers. Anyone got one fitted and can recommend a good one? Thanks again

A fuel pressure regulator is really more of a hot rod shop item.  The best thing really is to get a pump that puts out the correct pressure.  Check the fuel pressure you have, first, then see whether it's even something you'll have to worry about.

[cook1e]

Malpassi Filter King is the most popular brand of adjustable fuel pressure Regulator and has a built in fuel filter. Some of the more expensive versions have a fuel pressure guage.

See link below to the demon tweeks website. Lots available cheaper on ebay...

http://www.demon-tweeks.co.uk/performance/fuel-filters/malpassi-filter-king-fuel-pressure-regulator-and-filter