1098 Vacuum Pipe

[kingsley]

Mine has the metal vacuum pipe with the integrated cylindrical chamber.
As a matter of interest what is the chamber for - moisture? anti-flashback?
I really don't like the aesthetics of it and I would like to replace it with a black rubber or silicone vacuum hose.
Am I OK cutting the metal tube at the dissy to leave a short length to attach the new hose to?

[philthehill]

The cylinder in the vacuum advance tube is there to reduce the possibility of a fire if the vacuum advance unit failed and fuel mixture got into the distributer and was ignited by the contact breaker spark.
The cylinder should be kept vertical with the pipe from the carb entering at the bottom.
Later cars did not have the cylinder but did have a different carb and distributor vacuum advance.
You can cut the metal pipe either side of the cylinder and fit a rubber pipe in its place. The pipe must be a good fit and be rigid enough to resist collapse when a vacuum is created in the pipe.
Personally I would leave well alone.

[myoldjalopy]

Good advice....

[kingsley]

The cylinder in the vacuum advance tube is there to reduce the possibility of a fire if the vacuum advance unit failed and fuel mixture got into the distributer and was ignited by the contact breaker spark.
The cylinder should be kept vertical with the pipe from the carb entering at the bottom.
Later cars did not have the cylinder but did have a different carb and distributor vacuum advance.
You can cut the metal pipe either side of the cylinder and fit a rubber pipe in its place. The pipe must be a good fit and be rigid enough to resist collapse when a vacuum is created in the pipe.
Personally I would leave well alone.

Many thanks for the explanation Phil, particularly the part about the cylinder being kept vertical - as mine isn't
Now that I know the cylinder's purpose I will leave it as it is

[JOWETTJAVELIN]

Other later cars in the BMC/BL range had a flexible plastic pipe with rubber ends which pushed on. No flame trap. Agree it should be left alone though.

[philthehill]

I do not know how well the vacuum advance diaphragm is able to cope with modern fuels. It may be that we have to go back to fitting a fuel/fuel vapour trap.

[jagnut66]

I do not know how well the vacuum advance diaphragm is able to cope with modern fuels. It may be that we have to go back to fitting a fuel/fuel vapour trap.

This subject may well be worth an article in the magazine Phil.
Allot of us thought the original pipe was just an untidy mess when we bought our cars and far better (and neater) replaced by a (suitable) plastic or rubber hose / pipe.
That is if it was even still on the car and hadn't been replaced already.
Certainly I have done it on mine and never had an issue yet but given what you've said I think someone with the knowledge should write a piece and submit it. Including suggestions for what to use as / where to obtain a vapour trap, plus the best type of hose / pipe to use and a source for this also.
Thus bringing the issue to the attention of a wider audience than we might get on this site these days.
Best wishes,
Mike.

[JOWETTJAVELIN]

I have never heard of a case where the distributor has exploded or contained explosions because a spark has ignited a fuel/air mixture from the carburettor. Not only is the suction from the engine pulling air in away from the distributor and up the tube, there is a diaphragm in the way which even if broken would still be extremely restrictive. The chances are slim to none.