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914World.com _ 914World Garage _ carbs sweating at gasket joint
Posted by: JFG Apr 24 2018, 01:03 PM
I was talking to someone at the weekend who advised it is likely to be the float height incorrect. Whilst i am in no under estimation of his knowledge i thought i would get some more input. No point opening them up twice.
Twin 40 weber idf. The motor ticks over very well when warmed up a bit and the short runs around the block (up to 2nd gear) runs nice. So no running issues so far.
The problem is at the gasket joibt in the carb itself, both of them sweat fuel from this point.
I've never had this before and my first thought was too much fuel pressure, i'm running a 3.5psi pump from cb performance but no regulator as yet.
I set the floats as per instructions i found so from here i'm not sure what to do.
These are my jet sizes etc
Chokes 28mm,
A.vents 4.5,
Mains 115,
Airs 200,
Em.tubes F11,
Idles 55,
Pumps 50,
N.valves 175.........
Posted by: nditiz1 Apr 24 2018, 01:09 PM
I was talking to someone at the weekend who advised it is likely to be the float height incorrect. Whilst i am in no under estimation of his knowledge i thought i would get some more input. No point opening them up twice.
Twin 40 weber idf. The motor ticks over very well when warmed up a bit and the short runs around the block (up to 2nd gear) runs nice. So no running issues so far.
The problem is at the gasket joibt in the carb itself, both of them sweat fuel from this point.
I've never had this before and my first thought was too much fuel pressure, i'm running a 3.5psi pump from cb performance but no regulator as yet.
I set the floats as per instructions i found so from here i'm not sure what to do.
These are my jet sizes etc
Chokes 28mm,
A.vents 4.5,
Mains 115,
Airs 200,
Em.tubes F11,
Idles 55,
Pumps 50,
N.valves 175.........
How old are the gaskets? Has the top of the carb loosened up? What is your current height for the float? I believe it is 10mm to top and dropped ~30mm
Posted by: JFG Apr 24 2018, 01:17 PM
The carbs are new spanish ones not flac cheap stuff.
The numbers you've quoted sound right from memory
Posted by: JFG Apr 24 2018, 01:25 PM
Posted by: Mark Henry Apr 24 2018, 01:38 PM
Has the top of the carb loosened up? What is your current height for the float?
loose top, float height (overflow), float valve leaking or too many shims under it, float valve leaking under shims, float full of fuel (hole, waterlogged), pump pressure too high. Also fuel enrichment valve stuck open.
The gasket at head and carb base is a vacuum point. fuel leaking down the carb is hard to see.
If it isn't leaking down the outside it could be leaking down the throats, if enough I guess it could fill it up to the point of leaking past a bad gasket.
Posted by: porschetub Apr 24 2018, 05:49 PM
Has the top of the carb loosened up? What is your current height for the float?
loose top, float height (overflow), float valve leaking or too many shims under it, float valve leaking under shims, float full of fuel (hole, waterlogged), pump pressure too high. Also fuel enrichment valve stuck open.
The gasket at head and carb base is a vacuum point. fuel leaking down the carb is hard to see.
If it isn't leaking down the outside it could be leaking down the throats, if enough I guess it could fill it up to the point of leaking past a bad gasket.
Looks like your jetting in pretty much right,as the carbs are new some answers don't apply however I would still check the float levels as mentioned.
I don't really trust makers pump output claims,do yourself a favour and fit a Holley LP regulator and quality fuel gauge,I tend to prefer 3.0psi as I have had spillover on Webers and Zeniths over 3 psi.
Pull the air cleaners and run it, if the throats are wet @ idle you have over pressure,good luck.
Posted by: MarkV Apr 24 2018, 08:24 PM
If the car runs right I wouldn't think the float lever was too high. Unless they are wet with raw fuel what you are seeing might be normal. My carbs get stains at the gasket seam because they are carbs and that is kind of just what they do.
Posted by: JFG Apr 28 2018, 08:55 AM
I had the car out and running today to check the suggestions above. The only thing i didn't have time to do was recheck the float height.
The throats didn't look wet when idling so i'm thinking pressure is not to great. Still going to fit a pressure reg next week as a precaution.
I tested the carbs with the synchrometer to and found that the barrel above number 4 would not adjust and would not idle above 3.5 whereas the other three are sitting at 4 happily.
What should the reading be for weber 40's on a 1.7? I'm thinking the drop on 4 is down to valve adjustment.
Posted by: rhodyguy Apr 28 2018, 02:57 PM
Air bypass screw on #3? There is no specific number on the synchro tool to be looking for. You want the readings to be equal.
Posted by: porschetub Apr 28 2018, 09:26 PM
Air bleeds need to be adjusted only a small amount ,if no response you have a valve clearance issue on that cyl or worse a leaking valve.
Do a full service on the ignition ,timing and valve clearance then start again if not done already 
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