New camo developed for hiding in a bowl of tomato soup

Originally posted by Gunner
Hi Richard:

Hi,

The fuel leak caused by the original torn diaphram actually led to a brief but exciting engine fire!

More excitement that is generally desirable.

Any advice you can throw at a couple of FV432 luddites will be welcome.

Perhaps not so much on the 432 itself, but the B81 is very familiar indeed.

Right now we have them running after a fashion... real problems with developing any power.

There is a procedure for using the auto box in the appropriate range and they are rather gutless with the B81 which needs to be on the boil continuously.

On the B81 do the two barrels of the carb each serve four cylinders? If so it might explain some of the low power problems we are having.

No. The carb is a twin choke device with a shared float chamber simply to flow enough gas without having one huge and uncontrollable choke tube with its inherent difficulties of low Reynolds numbers.

The manifold below the carb is just one big oval hole.

I suspect one set of points are fouled if four cylinders have gone AWOL, in fact I'll stick my neck our and guarantee it. Generally the distributors completely fox the UK as we don't historically have twin point systems domestically and the US too where it was commonplace on the early, 6V multi-cylinder cars, but the B81 distributor operates in a totally different way to your historical norm.

You must consider the distributor as two, four cylinder devices sharing a common cam, and surprise, when you pop the top off you'll find a FOUR lobe cam firing EIGHT cylinders. Plus. . . . . .take one set of points out and use "Numbers in circles" as you will see moulded in the cap and you have a B40 distributor - common parts.

The points take turn and turn about at both firing their four pots and doing the dwell angle extension for the other set.

By pulling one plug lead you will immediately know which four are firing and (in firing order) cyls 1, 2, 8 and 7 are served by the "fixed" points - the set furthest from the engine, while 6, 5, 3 and 4 are fired by the "moveable" set nearest to the rocker cover. To put it another way for contact sets A - fixed and B - moveable:
A....1 2 8 7
B.....6 5 3 4
Thus a firing order of 1, 6, 2, 5, 8, 3, 7, 4


It is also important that the angular sync between the point sets is spot-on or one half of the motor can be mis-timed. This is a bench job only with a home-built jig and fraught with possibilities for problems, the process can be fiddly as both the gapping and angular displacement interact. If you're thinking about pulling the distributor best mail me first.

Let me know what you would like for the diaphrams and I'll get you an address to send them to in Bristol. I'll be in touch about the other bits. Due to temperature extremes here right now we are cutting back on outdoor work in an effort to preserve flesh from frostbite. We can still pull a carbie and work on it indoors, tho'.

They're so light I may well be able to send them direct and I do have some economy (A misnomer if there ever was one) jet diaphragms too.

I do not know about Canadian fuel, but the American stuff with added alcohol does play merry hell with older diaphragm material and often needs an extra jet size to account for the alcohol content.

Carb icing is a problem here also; more accurately idle air bleed icing and a function of EU spec high volatility fuel, un-heated inlet air and damp English days. I can guarantee it here below 13ºC unless its a very dry day.

Plugs too can be problematical, we have had no end of trouble with the platinum RSN13P, even a new set out of the wrapping beginning to mis-fire in 100 yards. If you dis-assemble to clean do not ever uses any metallic brush as the centre insulator will become "plated" and shorted immediately. The mica insulating tube in the bore also gets chafed and causes HT shorts. You may well have 1/2" of spark at the lead but the nature of the 13P is a weedy yellow-white pin-prick of spark at the electrode.

We find the RSN12Y (24V LR) a much better bet.

Tracking rotor arms, distributor caps and broken ballast resistors are also known to lead you on a merry dance too.

R.