Kelvin,
My compliments. Well written response to the excellent questions posed.
Bill, Kelvin has given you the straight stuff. John Twist's technical
manual can give you much insight into these and other matters that the
workshop manual tends to gloss over, or not mention at all. If you
don't have John's address, please advise and I'll supply.
Bill
Dodd, Kelvin wrote:
>
> Bill:
>
> Here is a try.
>
> >What is a Gulp Valve and what does it do?
>
> Used from 70ish onwards. When the carb. butterflies close there
> is a moment when there is raw fuel still spewing into the intake
> manifold. With closed butterflies the manifold vaccuum goes high
> opening the gulp valve. Air from the air pump then enters the intake,
> mixes with the raw fuel and a nice combustable mixture goes into the
> engine. No more cloud of hydrocarbons upon backing off the throttle.
> An operating gulp valve will not affect engine performance.
> Problems. Drivability, back off throttle, engine tends to
> continue to run. Less engine braking. If the gulp valve fails open
> (unusual) or leaks the mixture will be diluted. Tuning becomes a major
> problem. Requires operating air pump to be effective.
>
> >What is an E.G.R. valve and what does it do?
>
> Similar to the Gulp valve, the EGR valve opens on deceleration
> and dilutes the fuel rich intake tract with exhaust gas. Added benefit
> is that the exhaust gas at this time is fuel rich too, so some of the
> hydrocarbon rich exhaust is recirculated. The exhaust gas also heats
> the intake charge which is of benefit under some conditions. An
> operating EGR valve will not cause any real reduction in performance.
> Problems. Again if the valve fails open or leaks the mixture
> will be diluted. Requires the silly log type manifold to operate.
>
> >Same for Anti-run-on valve?
>
> A very useful device which is activated when the ignition is
> switched off. The circuit runs through an oil pressure switch which is
> normally open. Oil pressure keeps the switch closed until the pressure
> drops following engine shutdown. The valve allows intake vacuum to
> reach the carb. float bowl cavity. With the float bowl under vaccuum no
> fuel gets sucked into the engine. No fuel, no run on, The engine shuts
> down nicely without trying to claw it's way out of the engine
> compartment.
> No problems. I have seen this device used to cure run-on caused
> by high compression pistons and incorrect idle advance on race cars.
>
> >How important is the Fuel cut-off valve and what does it do?
>
> The silver cut off valve was located behind the brake/clutch
> assembly. It was a mechanical flow valve that would shut fuel flow off
> if the car went upside down. The valves tended to leak and most have
> been removed. The late cars also had an electrical shut off switch
> under the dash that shuts power off to the pump. The electrical switch
> is nice insurance. MGBs' though do not tend to burn on impact.
>
> > someone local suggested that I remove all
> the "emissions crap". What are the mechanical consequences (let alone
> legal) of doing that?
>
> Kept in good tune, a 62-67 MGB will perform well and pollute
> less than a poorly maintained later car with defective controls. It is
> important to understand completely what each part in the system does
> before removing it. The engine systems were designed to work together.
> The most important thing is to make sure that the engine crank case
> breathing is not plugged. This is a common error leading to excessive
> oil burning and leakage. Check the legality before doing any
> modifications. Check here if you have any doubts of how a system works.
>
> Hope this helps.
>
> Kelvin.
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