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Electric Vacuum Pumps for Brakes.
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Utility8 Offline
#1 Posted : Friday, 15 March 2013 7:46:44 PM(UTC)
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A couple of things lead me fitting an electric vacuum pump to supply my brake booster with sufficient vac to function properly.
Camshaft design & a slightly worn 327 motor that I assembled 20+ years ago, (& 80K hard miles), being the culprits.
Car is fitted an EH with 327/TH700.
Brakes consist of an 8" master vac system with a dual circuit 1" bore master.
Fronts discs are 300mm rotors with BA twin piston callipers.
Rears are HQ drum. (Currently, without more floor mods, rear discs not a feasible option due to shortened diff leaving no room).

Research offered a few solutions:

Replace the camshaft to achieve usable vacuum, but I consider a motor of this age, (& miles), to be a waste of time. Akin to fitting a donor heart to a 90 year old.
Rebuild the motor, which is the preferred option, but costs & car down time dictate that will happen in a few years. Now isn't the time for me.
Fit an electric vacuum pump. Due to cost & ease of fit, this is where I have gone.

Vac pump fitted up quite well & now the braking system has a much better 'feel' throughout all braking requirements.
Low vac gave the car a feeling of limited braking capacity at low rev, low speed driving.

One question I am finding mixed views on is this:
Will an electric vac pump system benefit from fitting an inline vac capacity tank or not?
I do appreciate a vac tank will not increase the level of vac the system is able to produce, but will the volume provided by the tank be of any real value? Given that the eletric pump responds to low vac then operates, whereas the vehicle motor just keeps producing varied amounts of vac.

Thoughts???
Experiences???

Edited by user Saturday, 16 March 2013 7:44:56 PM(UTC)  | Reason: Not specified

utility8
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greenhj Offline
#2 Posted : Sunday, 17 March 2013 7:04:42 AM(UTC)
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my old NA engine was lucky to see 8" of vac at idle and the brakes worked fine, i just had a tank plumbed in with no external assistance via pumps etc.

over run saw it pull more than enough to make the booster work ok, coincidently this was also when i was wanting to slow down so i was happy, at idle speed i was mostly stopped and didnt care anymore.

Edited by user Sunday, 17 March 2013 7:08:06 AM(UTC)  | Reason: Not specified
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greenhj Offline
#3 Posted : Sunday, 17 March 2013 7:07:21 AM(UTC)
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id probably put a tank in it anyway, the greater volume should mean the pump wont need to work as hard.
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wbute Offline
#4 Posted : Sunday, 17 March 2013 7:09:31 AM(UTC)
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I don't think the tank would be necessary as the electric pump should provide constant vacuum. My wb with a 253 has a mild cam. It also makes little vacuum under acceleration. The factory AC vacuum servos stop working and all the air comes out on your feet.
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74HJLS Offline
#5 Posted : Saturday, 23 March 2013 9:40:32 AM(UTC)
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wbute, if the air comes out at your feet, you need to have you booster rebuilt. utility8, the phase III falcons had a vacuum tank for that very reason, it is an easier option than installing an electric pump.
Cheers,
Pete.
Old Holdens never die, they just go faster.
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commodorenut Offline
#6 Posted : Saturday, 23 March 2013 6:20:23 PM(UTC)
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Holden started fitting one-way valves & vacuum reserviors to vacuum controlled A/C systems from VL onwards - this is the little round ball you see under the front guard on a VL-VS.

You can retro-fit this arrangement onto any early vacuum-controlled A/C system (like I've done on several VKs with hot motors). It's simply a matter of fitting a one-way valve between the manifold & the controls, in the vac feed line. You then put a T-piece in after that valve (between the valve & controls) and run a line to the ball that you can mount anywhere.

This gives the A/C system enough vacuum reserve so it maintains it's settings under all conditions.
Cheers,

Mick
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the eh Offline
#7 Posted : Sunday, 24 March 2013 2:46:48 AM(UTC)
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I run a Summit vacuum pump (rebadged CVR) and a vacuum tank that has a volume of about 1.5 litres. I have 6 piston front and 4 piston rear calipers controlled by a VT master cylinder on a XE booster. I have plenty of vacuum and never feel as though the pedal is getting hard. HOWEVER these pumps are as noisy as hell and I hate it. If I could find another solution I would go with it immediately..
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mmazz30 Offline
#8 Posted : Monday, 25 March 2013 7:15:44 AM(UTC)
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You could try fitting a vacuum pump off the series 2 VE SIDI
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wbute Offline
#9 Posted : Monday, 25 March 2013 7:28:03 PM(UTC)
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Ah this all reminds me of 1950's trucks with vacuum assisted brakes. They had big vacuum tanks on them. Everything old is new again.
Sounds like the one way valve would fix my problem.
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HK1837 Offline
#10 Posted : Monday, 25 March 2013 9:19:28 PM(UTC)
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Didin't the diesel MQ Patrols have an alternator with a vacuum pump on the back?
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Utility8 Offline
#11 Posted : Monday, 25 March 2013 10:19:07 PM(UTC)
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Thanks for your replies.
The jury is in.
Firstly, to confirm a few things, I have already fitted the electric vacuum pump as the motor does not, & will not, produce a sufficient level of vacuum. 18" hg is realistically required as a minimum. My motor only ever produced 15" hg.
My electric vac pump is not connected to the motor in any way, it works independently.
Also, a vacuum tank can only ever hold what the motor can produce. What a vacuum tank will do, when connected to the motor, is allow effective brake pedal applications, more often, while the motor is not producing good vacuum. Typically at low rev or idle as greenhj mentioned. As mine is a street car, I really needed constant, reliable vacuum.

After using the electric vacuum pump with a capacity tank & without one, it really makes no difference to the braking system. The vac pump simply comes on until 18" hg is achieved then shuts off. When vac gets down to around 15" hg, it comes on again. The tank will effectively slow down the on/off cycle, but run for longer time between. At the end of the day, the pump will always supply sufficient vac on it's own...no tank required. Which is what wbute suggested.
I do agree with the eh, they are noisy. One thing that I have found quietens mine is to fit rubber tubbing to the exhaust side of the pump. It tends to work as a baffle taking the sharpness out of the sound.

Again, thanks for the replies, it's always good to see how other people approach different situations.

Edited by user Monday, 25 March 2013 10:23:03 PM(UTC)  | Reason: Not specified

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Dr Terry Offline
#12 Posted : Tuesday, 26 March 2013 12:13:11 AM(UTC)
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You quote figures of 15" & 18" hg, but this is only at idle. When you accelerate it will drop markedly & when you back off it goes the other way.

If you attach a vacuum gauge & look at what happens when you simply rev the engine & back it off, the vacuum will max out at 27"-28". This how the vacuum tank worked on Phase IIIs. One or two revs & the vacuum tank was full. This assumes that the one-way valves are set-up correctly. The combination of the volume of the booster plus the reserve was enough for 3 or 4 brake applications, even if the motor stalled. These things idled at around 10"-12" & without a vacuum tank the brakes were awful, but the vacuum tank returned them to normal.

Dr Terry
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Utility8 Offline
#13 Posted : Tuesday, 26 March 2013 1:13:27 AM(UTC)
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quote:
Originally posted by Dr Terry
You quote figures of 15" & 18" hg, but this is only at idle. When you accelerate it will drop markedly & when you back off it goes the other way.

If you attach a vacuum gauge & look at what happens when you simply rev the engine & back it off, the vacuum will max out at 27"-28". This how the vacuum tank worked on Phase IIIs. One or two revs & the vacuum tank was full. This assumes that the one-way valves are set-up correctly. The combination of the volume of the booster plus the reserve was enough for 3 or 4 brake applications, even if the motor stalled. These things idled at around 10"-12" & without a vacuum tank the brakes were awful, but the vacuum tank returned them to normal.

Dr Terry
I will make a correction to my figures after fitting a vac gauge to the electric vac pump system. It runs up to 24" hg then stops. It will start again when the vac hits 16" hg. The figures I mentioned were sent with the paperwork for the vac pump. Sorry for the error.
The figures of 15" & 18" hg have absolutely no relevance to idle.
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Dr Terry Offline
#14 Posted : Tuesday, 26 March 2013 2:08:48 AM(UTC)
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quote:
Originally posted by Utility8
The figures of 15" & 18" hg have absolutely no relevance to idle.

I don't quite understand, if not idle, when are they measured ? You stated your motor only ever produced 15" of vacuum.

Any engine, no matter how lumpy the cam, will pull 26"+ on deceleration.

Dr Terry
If at first you don't succeed, just call it Version 1.0
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