12 replies to this topic

[Howie1000]

Hi,

I have a metro 1275 engine in my mini, originally it had a vacuum pipe going from the dizzy to the SU carburettor. I now have a Weber carburettor, it has no where to put the vacuum pipe.

Any ideas as to what I should do? Is it needed? I have the engine running, but due to other work going on with the car, it's not ready for the road yet so I can't comment on the drive of it without the pipe.

Many thanks in advance 👍

[Ethel]

It is, if you want any sort of fuel economy and you'd have to compromise on part or full throttle performance as with one input it can only be right under one condition..

[timmy850]

The Australian Cooper S never had vacuum advance and they went pretty well on the road. There is a bit in the article here about the vacuum signal with Webers:

 

http://www.minimania...tyle_Carburetor

Edited by timmy850, 30 March 2016 - 12:43 AM.

[nicklouse]

Hi,

I have a metro 1275 engine in my mini, originally it had a vacuum pipe going from the dizzy to the SU carburettor. I now have a Weber carburettor, it has no where to put the vacuum pipe.

Any ideas as to what I should do? Is it needed? I have the engine running, but due to other work going on with the car, it's not ready for the road yet so I can't comment on the drive of it without the pipe.

Many thanks in advance

if your Dizzy has one you should use it.

 

if you don't then you need to lock out the base plate and modify the bob weights to give a suitable advance curve etc.

 

or change out to one that have been modded to your spec or fit a mappable ignition set up.

[gazza82]

It is, if you want any sort of fuel economy and you'd have to compromise on part or full throttle performance as with one input it can only be right under one condition..

Fuel economy ... With a DCOE? Unlikely ...

[dklawson]

Fuel economy ... With a DCOE? Unlikely ...

 

 

Good point.

[MRA]

10mpg is better than 8mpg ..... fuel economy is relative.

 

The distributor has a vacuum advance therefore it will be subject to atmospheric pressure, the advance curve will not be suitable for your application, you have a Weber carb, therefore the chances are you also have a lot of other mods so you need to get either an ECU, a re mappable distributor or a modified dizzy with suitable curve.

[Howie1000]

Many Thanks for the replies guys.

This engine is a standard metro 1275, the dizzy is original to the engine,mit doesn't have points, the vacuum ran from the dizzy to a standard 1 3/4 SU carb, the only mods now are a Weber carb, K&N, LCB and RC40. The car itself is fairly sorted as its meant to be my MED1380 engine living under the bonnet, however that is now stripped and a project on its own, so for now, just to get the car back on the road, it's a 1275 metro engine.

I'm not running a servo, so there's a blanking bolt on the inlet, I suppose I could modify that to house the other end of the vacuum pipe if required??

[timmy850]

Manifold vacuum is different to carb vacuum. Manifold vacuum is present at idle as the engine is consuming air, but the carb vacuum port is on the other side of the throttle butterfly so at idle you have no vacuum.

Some distributors are designed for carb vacuum, others for manifold vacuum and others for none. You should really keep the advance on the distributor as it was designed for.

[Howie1000]

Actually........ The original,pipe ran from the carb,Minot he inlet manifold, that might cause more problems??

[Ethel]

The carb vac advance is placed so it doesn't see full manifold depression with the throttle shut, it idles better with less extra advance. 

[KernowCooper]

At one stage they ran the MG Metro with inlet manifold vacuum, just to clean up the immissions if my memory serves me correctly, why not just run the HIF44 on the 1275 until your other engine is ready

[Icey]

why not just run the HIF44 on the 1275 until your other engine is ready

I was thinking the same assuming the OP has one to hand. The Weber won't be adding anything.

Edited by Icey, 30 March 2016 - 11:12 PM.