Under Construction

September 29th, 2008

Please pardon our dust while we improve the website over the next few days.  If you need anything please feel free to call 616-301-2888 or email Mike.  Thank you!

Q & A: Problems with Running Gear on MGB 1973

Thursday March 27th, 2003
Q & A, MGA, MGB, MGC, MG T-Type, Midget
John,

First, let me apologize up front for bothering you - I am at a loss as
to where else to turn at present.

I have recently purchased a 1973 MGB in excellent physical condition
however I have several problems with the running gear.

As near as I can tell, the person who was doing the restoration replaced
the SU carbs with carbs from an earlier model - it has twin HS-4 carbs
not the expected HIF-4 carbs.

The fuel pump never stops - I thought that it was supposed to stop when
pressure built up. My mechanic seems to think that they never stop
pumping.

The emissions gear has been all removed prior to my getting the car.

I have 3 main problems with the car:

1. The car has a tendency to fall on its face at around 3000 rpm (this
is when under load - with no load it seems to run fine).
This actually varies depending on the gear - 1st will rev to about 3700
- 4000 with no problem then it breaks down. 2nd gets to about 3300, 3rd
and 4th to about 3000. Backing down on the throttle eliminates the miss
but power is gone.

2. The car runs hot (depending on the ambient tempreture) above about 80
degrees it gets to just below the "H" on the gauge. An infrared
thermometer shows about 185 degrees at the thermostat.

3. The overdrive works some times - usually when the car is cool - I
drive 40 miles each way to work daily and after about 30 miles, the
overdrive will not engage if I have to stop in traffic. Sometime it acts
like it is trying to engage - throttle on is direct drive, backing off
the throttle drops rpm's to where they should be if the overdrive is
engaged. I don't think it is a clutch problem as it is solid when
working. The 3-4 switch does not work ad I have a hunch the vacuum swith
is not working as well.

We replaced the distributor with one from my parts car - a 1979 MGB. It
is the electronic with the separate amplifier(?). there was no
difference in the rpm problem.

Main question - could the rpm problem be related to the fuel pump? I am
getting to the point of considering a Weber downdraft carb kit to try to
get this resolved.

Glenn Vaughn


Glenn!

I apologise or taking so long to reach you and help you with your MGB problems.

The car should run just fine with those HS carburetters, as long as the timing is correct AND the needles ar... read more