Anyone have any knowledge of brake vacuums?

[jaguartvr]

I have an old 5.3 V12 jag running 6 weber carbs, my problem is that they do not provide enough vacuum to operate the brakes. Ferraris of the 70's suffered the same problem so they had a vacuum pump running off the end of the camshaft.

The webers only have the front 2 carb intakes tapped to take the vacuum pipe, individually they draw about 3 hmg of vacuum, with a y splitter and one way valve thepull about 5hmg. I need at least 29 hmg. Would drilling and tapping the other 4 carbs increase the vacuum if they were all connected together?

I have tried fitting an electrical vacuum pump but it is very noisy, seems to be on too much and runs so hot that you would burn your hand if you touched it.

In desperation, I have bought a set of 4 SU carbs from an E-type and had started to fit them when I wondered if daisy chaing the webers up together would be better.

Any one have any bright ideas?

Thanks

 

[NZ00Z3]

The math is simple.

2.5hmg per carb x 6 carb's = 15hmg.

Well short of the 29hmg you need

 

[jaguartvr]

Not the answer I wanted but makes perfect sense. So I need to remove the 6 webers and replace with 4 SU's or fit a vacuum pump.
The vacuum pump that I had fitted was loud and I didn't think would last. I have found a rotary pump kit in the US that is far quieter and perforns better than the normal piston pumps, but expensive. Black Bandit brake booster pump, about $600 by the time you have added shipping and import duty.

 

[Pingu]

Can you increase the size of the vacuum holes on the Webers?

It would mean butchering your carbs, but I'd rather have 6 Webers than 4 SUs any day of the week.

 

[jaguartvr]

Current vacuum pipes have an I/D of 9mm.
The connection going onto the servo is also 8mm so would increasing the pip diameter on the carb make much differece>

 

[Pingu]

Current vacuum pipes have an I/D of 9mm.
The connection going onto the servo is also 8mm so would increasing the pip diameter on the carb make much differece>

You are quite right that if the orifice at the carburettor is 8mm, there would be no benefit.

It would depend what the narrowest diameter is all the way to the carburettor. I'd have a look at the carburettor and see what the diameter is the vacuum take-off.

If you do increase the size on the carb, you will probably need to add a one-way valve.

I've just had a look at a DCOE (I don't know if that's what you have), but it looks like the vacuum take-off must be on the manifold.

https://classiccarbs.co.uk/product/...-newgenuine-twin-40-weber-jetted-to-your-spec

V12 jag with 6 Webers must be awesome if properly set-up

 

[D R Oldfield]

the majority of 1980s Peugeots diesels had a a belt driven vacuum of the end of the camshaft it was only a small unit could this system be adapted ?

 

[jaguartvr]

The webers are 40idf

Pardon our interruption...

A mere snip at £3900! Obviously, I didn't pay that as they were fitted to the car when I bought it. I have been onto the weber supplier explaining the problem but they can't help. If I had paid for the carbs myself I would be pretty p***** off with that level of customer service.

Hunted through eBay for a Peugeot pump but can only find direct drive ones, I also have no spare engine pully and very little room.

I have however had a stroke of luck, found a bandit vacuum pump kit on eBay UK with no bids on it and managed to get it for £58 inc delivery, the seller had ordered it in from the US for an EV project that wasn't completed.\

The V12 engine with the webers is turbine smooth when running. It has no chokes so you turn on the ignition and wait for 30 seconds for the float bowls to fill (1/2 gallon), then press the accelerator 3 times (another 1/2 gallon). It will then burst into life straight away but with a very lumpy idle and coughing, farting and backfiring through the carbs (another 1/2 gallon), you need to let it warm before moving off as it is an auto.
At this point you will need to take it for a quick spin to the nearest petrol station.

It then drives beautifully and very smooth but doesn't have that slam you in the seat power, personally I would prefer a V8 and if money was no object a TVR 5.0 with a manual box would be my preference. The car is however a Daytona 365 spyder replica which originally had a V12. hence the reason for using a Jag V12.

I will update when I have fitted the pump.

 

[Delk]

Not sure if it would be an option but you may look at an alternator from a diesel. Since a diesel doesn't provide a vacuum source some have a small vacuum pump on the back of the alternator just for the power brakes.

 

[jaguartvr]

Any idea of what model uses them?

 

[Delk]

I am pretty sure my old Ford Ranger had one on the back of the alternator. Did a quick google and Discovery's came up with one on the front.

ALTERNATOR GENERATOR 90A 12V WITH VACUUM PUMP + INTEGRATED REGULATOR | eBay

Find many great new & used options and get the best deals for ALTERNATOR GENERATOR 90A 12V WITH VACUUM PUMP + INTEGRATED REGULATOR at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

 

[jaguartvr]

Thanks, I do like that solution, I didn't know they existed. If my pump doesn't work then this will be plan B.

 

[jaguartvr]

Alternator fits VAUXHALL ASTRA F 1.7D 91 to 98 CORSA 1.5D 1.7TD VECTRA ISUZU 609843366269 | eBay

Top quality Remanufactured part, in original box.

www.ebay.co.uk

This looks ideal and cheap as chips, it is also for a V belt. If I can get this to fit I think it will be a better option.

Thanks for the advice.

 

[D R Oldfield]

I had one of these alternators on a Bedford Midi diesel i had for what i can remember they had to have an oil feed and drain as well and were prone to filling the alternator with oil , just talking to friend of mine he has had a similar problem with his kit car and said use one from a BMW i3 cheap enough on Ebay and just need a electric supply

 

[jaguartvr]

So the Corsa pump on the back of the alternator needs an oil supply? That's going to be a problem. Does anyone know of an alternator with a vacuum pump attached that doesn't need an oil supply?

The great thing about the alternator driven pump is that it isn't e;ectric.

 

[jaguartvr]

Looks like the Corsa alternator with vacuum pup is going to be my best bet.

Alternator fits VAUXHALL ASTRA F 1.7D 91 to 98 CORSA 1.5D 1.7TD VECTRA ISUZU 609843366269 | eBay

Top quality Remanufactured part, in original box.

www.ebay.co.uk

It looks as if the vacuum pump on the back has 3 connections, one for vacuum take of and 2 for oil flow and return, please correct me if I'm wrong.

The oil flow and return, I don't have any take off points that I can use, I presume that the oil is for lubrication and not for cooling. Do you think I could get away with a loop of rubber pipe filled with oil to provide the lubrication?

Why is nothing ever simple?

 

[Delk]

Just doing some googling and it appears the Corsa had an electric one also.

2014-18 Vauxhall Corsa Brake Booster Electric Vaccum Pump 13431921 | eBay

Vaccum Pump. 2014-18 Vauxhall Corsa. ElectricBrake Booster. All of our electrical parts are been run and checked to make sure they are running correctly.

www.ebay.co.uk

 

[jaguartvr]

I currently have an electric vacuum pump from an Audi fitted, it is very noisy, louder than the engine at tickover and it runs very hot so I was hoping the pump on the alternator would be quieter and more trouble free.

 

[D R Oldfield]

From what i can remember the bedford midi the oil lubricated and cooled the vacuum pump if they got to hot (which they did frequently ) they used to fill the alternator full of oil