MGB SU HIF4 Vents & voltage stabiliser

[ATE399J]

Next question.....

There are vents (from the float chambers?) on my 78 'BGT's SU HIF's. Currently they are left open, one has a pipe about 12-15" long attached and the other has been cut about 2" from the carb. Are these simply supposed to vent to atmosphere or should they be connected to something? I've looked in all sorts of places (Haynes, the workshop manual, etc.), but can find no reference to this.

Also, the voltage stabiliser (the feed to the instruments) seemed to be on the way out (not giving a stable output) so I have changed it. The new one is giving about 11.4 volts. Is that right? - I thought they were supposed to give 10v. If so then is the new unit a duff one? How good are modern replacement parts (I think I know the answer to that!).

Phil.

[na]

ATE399J said:

There are vents (from the float chambers?) on my 78 'BGT's SU HIF's. Currently they are left open, one has a pipe about 12-15" long attached and the other has been cut about 2" from the carb. Are these simply supposed to vent to atmosphere or should they be connected to something? I've looked in all sorts of places (Haynes, the workshop manual, etc.), but can find no reference to this.

no they are not supposed to vent to atmosphere as original, it's about engine breathing - try looking at a few John Twist videos (I can't look it up for you at the moment) or Paul's web site

ATE399J said:

Also, the voltage stabiliser (the feed to the instruments) seemed to be on the way out (not giving a stable output) so I have changed it. The new one is giving about 11.4 volts. Is that right? - I thought they were supposed to give 10v. If so then is the new unit a duff one? How good are modern replacement parts (I think I know the answer to that!).Phil.

again I think Paul's web site will give you an explantion, the original style VS switch on/off allowing a drop in voltage that averages out to 10v - check all connections and earths to it are clean, secure and protected - I'm guessing they should read arounds 12 volts when on

also IIRC the old style VS on that car has to be orintated correctly, i.e. facing the right way up, not sure why, again have a look at Paul's web site

you can get modern electronic replacements that seem more reliable than the old style VS

[SMGB]

ATE399J said:

Next question.....

There are vents (from the float chambers?) on my 78 'BGT's SU HIF's. Currently they are left open, one has a pipe about 12-15" long attached and the other has been cut about 2" from the carb. Are these simply supposed to vent to atmosphere or should they be connected to something? I've looked in all sorts of places (Haynes, the workshop manual, etc.), but can find no reference to this.

Also, the voltage stabiliser (the feed to the instruments) seemed to be on the way out (not giving a stable output) so I have changed it. The new one is giving about 11.4 volts. Is that right? - I thought they were supposed to give 10v. If so then is the new unit a duff one? How good are modern replacement parts (I think I know the answer to that!).


Phil.

The float chambers do need a vent to allow the fuel to enter and push the float up, otherwise there would be nowhere for the displaced air to go. They also work as fuel overflow dumps if the valve fails, all too common with modern petrol but cured by viton tipped needles. As the carbs are above the exhaust manifold on an A or B series engine the factory arranged them so the overflow dumped onto the road below the exhaust. A lot of USA MGBs expired this way when the leaky Solex (AFAICR) was fitted.
I have heard bad experinces with the solid state voltage stabilisers but probavly the usual far eastern rubbish.

[na]

sorry Phil I totally missed the '(from the float chambers?)' bit in my rush - I'm an idiot

[na]

as I put before just checking and perhaps cleaning up the existing voltage stabiliser and/or the connections and wires may get it working better

as for electronic voltage stabilisers -
I don't know if this one is still in business but it's the one I've had on my car for the last 5 years without problems - http://classicstabilizers.webs.com/

there's also this one on eBay - http://www.ebay.co.uk/itm/SOLID-STATE-VOLTAGE-STAB...

[ATE399J]

I now have a choice of either a twitching 9-and-a-bit volts or a stable 11.4. Think l'll send the new one back and try an electronic one.

So the concensus on the float chamber vents is to dump to atmosphere but away from the exhaust manifold?

Next stupid question will be along soon.......

[na]

ATE399J said:

I now have a choice of either a twitching 9-and-a-bit volts or a stable 11.4. Think l'll send the new one back and try an electronic one.

check your supply voltage before you do

ATE399J said:

So the concensus on the float chamber vents is to dump to atmosphere but away from the exhaust manifold?

some have a combination of rubber and solid pipes to direct the overflow, perhaps you could add a receptical to save the petrol and see how much is overflowing

ATE399J said:

Next stupid question will be along soon.......

no stupid questions, plenty of stupid answers

[ATE399J]

na said:

check your supply voltage before you do

It's the same supply in both cases so it MUST be more than the 10 volts the unit is supposed to supply to the instuments.

I must admit I quite enjoy driving the old girl. Not very fast but more entertaining than my Ka! For one thing I never know what's going to fall off / fail next! (Fan failed to cut in when stuck in traffic on the M20 this evening - a quick wiggle of the otter switch connection and off we went!).

[na]

I'm a bit lost as to what you mean so will quote from the eBay of one of those electronic -
'This is a solid-state voltage stabilizer for classic cars with 12v negative or positive earth. This is a direct replacement for the bimetal spring and contact breaker device that was fitted to classic cars originally.

The cars battery voltage is fed into a voltage stabilizer, which is normally 12v with engine off and about 14v when engine is running. The voltage stabilizer reduces this voltage to a steady 10v for the instrument gauges so they don’t fluctuate with the battery voltage.'

as for all electric connections and wires you need to check all are clean, secure and protected

for roadside cleaning, sometimes just disconnect and reconnecting a few times can clean up connections until you can do the job properly

testing the horns every few weeks can save embaressment at next MoT or worst or the road

if your BGT feels slow then it' not at its full potential yet then, they're not fast but they shouldn't feel slow, they usually feel faster than they are