Is this broken pipe important? (Chim 500)

[Oldwolf]

Swapping the plug leads I noticed a broken pipe, should I do something about it?
The reason for swapping the plug leads is that the old ones were very old ones with the extenders and at 30MPH in 3rd and 40MPH in 4th there was a slight hesitation so this seemed a logical first step to cure. I only took it for a quick install run after fitting them and it was raining so I couldn't tell if the new leads had improved things (obviously it felt like they are worth another 20HP! )

The broken pipe ends up just below the dizzy as in this image


The other end goes to the plenum



As with any question I ask I take no offence if it's obvious and welcome people pointing and laughing - as it might save another poster from similar embarrassment

Thanks

Ben

[bobfather]

Vacuum advance & retard. It alters the spark timing depending on how much fuel demand the engine generates. The engine will run happily without it but it's best to have it connected

[J-2]

Yes you should replace it. It is the vacuum advance pipe.
I replaced mine a few months ago, you can get a kit from Racing Green parts for a few £ it is a 5 min job to do.

John

[Oldwolf]

Thanks both, appreciate the quick responses.

Ordered.

[nzflash]

From experience I wound also check the advance unit is functioning. One easy check is to suck on the pipe when connected to the advance unit. If you can suck air through the pipe your vacuum diaphragm is perforated.

Sucking on the pipe when the engine is idling should cause the idle revs to increase slightly.

[RochdaleGT]

completely un-important.---> thats why rover and tvr has fitted it....just for fun and for un-importantness....

[Classic Chim]

RochdaleGT said:

completely un-important.---> thats why rover and tvr has fitted it....just for fun and for un-importantness....

Doesn’t it effectively speed up the time it takes for the dizzy to advance so increasing power sooner.
Sort of tells the dizzy the engines under load so without it the timing will lag behind crucially loosing power probably when you want it most.
I have coil packs so long since forgot to learn about these ancient items.
They work ok though

[Oldwolf]

nzflash said:

From experience I wound also check the advance unit is functioning. One easy check is to suck on the pipe when connected to the advance unit. If you can suck air through the pipe your vacuum diaphragm is perforated.

Sucking on the pipe when the engine is idling should cause the idle revs to increase slightly.

OK... so my neighbours already think I'm a little odd, when they see me sucking my car I'm not sure what they'll think.

I also am reading that and remembering when I was in my first job and the apprentice would be sent for a long stand or tartan paint etc.....

The part should be here today / tomorrow so I'll give it a go, thanks!

[rev-erend]

Just a note that the pipe to the engine needs to be blocked, if the dizzy end is not connected. OK its only a small air leak but
it will affect if more at small throttle openings and tickover more.

[Oldwolf]

rev-erend said:

Just a note that the pipe to the engine needs to be blocked, if the dizzy end is not connected. OK its only a small air leak but
it will affect if more at small throttle openings and tickover more.

I strongly suspect then that this was the original issue that I replaced the plug leads for. On gentle throttle openings there was a hesitation, it was only slight (my passenger couldn't feel it but I could).

The leads and extenders really did need replacing though so I don't mind that - 2 of them came apart pulling them off.

Just need some sunshine to test the beast out

[Zener]

Its fitted to advance ign timing at small throttle openings cruise etc to light off the leaner fuel air mix sooner , and yes its worth having functioning correctly , the exhaust manifolds will give off less heat too in the above circumstances due to that small advance boost

Edited by Zener on Tuesday 22 June 10:58

[Steve_D]

Oldwolf said:

............I also am reading that and remembering when I was in my first job and the apprentice would be sent for a long stand or tartan paint etc.....

As an apprentice I was sent to the stores to get a 'Glass Hammer'.
When it came to my turn I told the storeman that both he and I knew I was on a fool’s errand but I had no choice but to ask.
Storeman’s eyes lit up as he said 'I've got one, stay right there while I lock up'.
He, and I, plus the remainder of the stores queue then went back to my tormentor to see what he wanted it for.

The hammer was made by the storeman’s brother who is a glass blower. It was a work of art and everything you would expect a large ball pein hammer to look like.

Steve

[rev-erend]

Oldwolf said:

The broken pipe ends up just below the dizzy as in this image


The other end goes to the plenum


Thanks

Ben

The part on the distributor should just price off.. you can just run a rubber pipe from the plenum to the dizzy ..
The existing pipe may already have been blocked with a self tapping screw..