GM Proportioning Valves investigation for compatibility

[scottswatches]

I'ved just ordered two new 3/35 nova valves that i will modify to fit my original spring into, which make them 3/15's. Hopefully they will be here this weekend so i can spend my birthday under the car getting it back on the road.

I will report the success/failure story here first.

[saska]

I'ved just ordered two new 3/35 nova valves that i will modify to fit my original spring into, which make them 3/15's. Hopefully they will be here this weekend so i can spend my birthday under the car getting it back on the road. I will report the success/failure story here first.

Do you have 2 valves per side or just one per side?
The problem with the Nova valve is it fits directly into the master cylinder so is missing an end piece to fit the brake line. Whether or not the end pieces from your current valves will fit I couldn't say.
If you do the 3/15s, In the first instance I'd get it to an MOT station and see if the rear brake force is 100 and the fronts are 300 or greater. If the rears are more than 100 and the fronts are around 300 then you should probably test for rear brakes locking before the fronts.
The standard method is to have 3 things:
1. A piece of white chalk
2. An observer
3. A straight, quiet section of road
Proceed as follows:
1. Position the observer with a good view of the braking zone.
2. On the observer's side mark the front & rear tyres at 3,6,9,12 o'clock with good thick chalk marks. (They'll wipe off after)
3. Do hard stops (try to induce lockup) from 20, 40, 60 and have observer note whether front or rears lock first -- it will be very obvious with the chalk marks.
Please note if at the lower speeds the rears are locking first then you should not proceed to the higher speeds since if the rears lock first at lower speeds they will almost certainly lock first at higher speeds.

Alternatively:
Today I ordered a rake of the large & small O-rings in EPDM to rebuild the present valves. I'd expect them to be here sometime next week.
Was also investigating replacement springs to BobB's dimensions. Bob noted that removing the spring to replace the O-rings may damage it though Mark Hooper didn't note any difficulty in his rebuild article.
Thought the best way to do a rebuild kit would be to do both O-rings, the spring and a seal washer (don't have dimensions for this yet).
If you do replace yours with the Nova 3/15 valves I'd really appreciate the seal dimensions -- Internal Diam, Outside Diam. & Thickness.
If you want to do the o-rings email me an address and I'll send a set out to you first class as soon as I get them so you can get the car back on the road. We can sort out pennies later -- should only be a quid or 2 for 4 o-rings.
Think it will take a few weeks to get a full kit together but Mark did his just with replacing the o-rings.

[RayD]

Jay's (2/15 Valves)
Front 330 350
Rear 100 100
Handbrake 120 130

Ray's (2/15 Valves)
Front 300 300
Rear 100 100
Handbrake 200 200

Dave Speck (Failed due to imbalance at the front)
Front 234 315
Rear 63 73
Handbrake 140 147

Dave Speck Passed (Front calipers replaced)
Front 310 315
Rear 70 73
Handbrake 145 147

[scottswatches]

I'ved just ordered two new 3/35 nova valves that i will modify to fit my original spring into, which make them 3/15's. Hopefully they will be here this weekend so i can spend my birthday under the car getting it back on the road.

I will report the success/failure story here first.

Success!

RichyP came round this weekend and we had a few hours working on rear brakes - we first got the tricky seal on his piston using Bob Browns tool (and a couple of lengths of 40mm plastc drain - one about 12" long to push the seal down evenly and one about 3/4" at the bottom of the piston to make sure we didn't push it down too far. Again.

Then came the proportioning valve. It came apart easily and while it did look pretty clean I think someone had tried to fix this before - the internals of the valve were anodised purple, which didn't look like factory spec to us! We took the spring out of the old unit and put it in a 3/45 new valve sourced from Vauxhall and rebuilt it and brled the brakes using RichyP's Gunson EeziBleed kit (now on my shopping list!). A quick run to my friendly MOT centre and I was getting 310 on the fronts and about 80 on the rear, with the handbrake at just over 100. Importantly, everything was balanced.

Now I just have to get them to finish the MOT and she'll be back on the road! Many thanks for all contributions on here and to RichyP's help at the weekend.

A couple of things to note. The vauxhall dealer had 3/35 valves, but when I expalined that I would be stripping them him sent a picture of the 3/35 and the 3/45, because you couldn't strip the 3/35's he had. Also, the 3/45's I did have had different thread for different sized brake pipe ends. We think they may be sided, with the larger thread on the OSR but this will be confirmed when I change this one. First it will past the MOT, then it will not stand still all summer!

[ashm]

the internals of the valve were anodised purple, which didn't look like factory spec to us!

I remember thinking it was a bit odd when I was changing the brake lines on my old car and I noticed bits of the prop valves were anodised purple! They may have been this way from day one, strangely.

Adam

[saska]

the internals of the valve were anodised purple, which didn't look like factory spec to us!

I remember thinking it was a bit odd when I was changing the brake lines on my old car and I noticed bits of the prop valves were anodised purple! They may have been this way from day one, strangely.

I agree -- Mark's article on rebuilding them shows a pink/purple piston too

Scott

A quick run to my friendly MOT centre and I was getting 310 on the fronts and about 80 on the rear, with the handbrake at just over 100. Importantly, everything was balanced.

These figures look fine for front/rear balance -- nice job!
When you get a chance can you please measure the single valve body seal from your old valve. ID OD and thickness. I've already got the o-ring dimensions.
Also was there any problem getting the spring out of either valve?

[DeeAitch]

Success!

We took the spring out of the old unit and put it in a 3/45 new valve sourced from Vauxhall and rebuilt it and bled the brakes using RichyP's Gunson EeziBleed kit (now on my shopping list!). A quick run to my friendly MOT centre and I was getting 310 on the fronts and about 80 on the rear, with the handbrake at just over 100. Importantly, everything was balanced.

Do you have a part number for the 3/45 valve? Recent MOT had both my rears at 30ish Handbrake was something like 120 each side so the calipers would appear to be fine.
Time for a valve rebuild me thinks

[Specky]

and the price...

TTFN

[bobbrown]

try here http://www.atozmotorspares.co.uk/index. ... 9674_21696

[scottswatches]

I paid £35 for the pair for Vauxhall Green Spares, but they were the last ones they had so Bob's referal looks good to me

[scottswatches]

I have an MOT! I'm going for a long overdue drive tomorrow!!!

[scottswatches]

the internals of the valve were anodised purple, which didn't look like factory spec to us!

I remember thinking it was a bit odd when I was changing the brake lines on my old car and I noticed bits of the prop valves were anodised purple! They may have been this way from day one, strangely.

I agree -- Mark's article on rebuilding them shows a pink/purple piston too

Scott

A quick run to my friendly MOT centre and I was getting 310 on the fronts and about 80 on the rear, with the handbrake at just over 100. Importantly, everything was balanced.

These figures look fine for front/rear balance -- nice job!
When you get a chance can you please measure the single valve body seal from your old valve. ID OD and thickness. I've already got the o-ring dimensions.
Also was there any problem getting the spring out of either valve?

HI Saska.

The springs came out easily - in fact the whole job was pretty straightforward. Here are a couple of pic's to demonstrate the differences. I'll get you the body seal dims soon but i can't find my verniers and a ruler just isn't going to be accurate.

[bobbrown]

3/15 valve spring dimensions

33mm long
14.1 od
10.9 id
16 gauge wire diameter
7 coils ground ends

would check the spring you have fitted is to these dimensions to convert a Vauxhall 3/what ever to 3/15 as it is the spring that sets the 15bar.

[saska]

The springs came out easily - in fact the whole job was pretty straightforward. Here are a couple of pic's to demonstrate the differences. I'll get you the body seal dims soon but i can't find my verniers and a ruler just isn't going to be accurate.

Good to know about the springs and let us know when you've got dimensions for the main seal -- verniers are good :) I've already got 250 of both the O-rings and have found a firm that will do the springs for about £3 each. Only thing lacking for a full rebuild kit is the main seal dimensions. Would be looking to do a rebuild kit for both valves for £10 or maybe less.



I note the Lotus one has 3 channels in the centre of the piston the Vauxhall one only has 2, the third one on the Lotus piston appears deeper than the other 2 on either piston -- don't know why this is?



Good photo of the original springs and shows that BobB's measurement was correct (not everyone knows how to measure a spring particularly when the spring is closed & ground flat).

[bobbrown]

It is important to note the spring dimension for the 3/15 valve are NOT the same as those for the 2/15 valve.
Also the O ring size for the larger piston on a 2/15 valve is not the same as a 3/15 valve

[saska]

It is important to note the spring dimension for the 3/15 valve are NOT the same as those for the 2/15 valve.

I don't understand why this would be so; the spring seats look identical and they're both 15 bar and the photos Scott posted look diameter-wise the same but thicker wire diameter/fewer coils on the 3/45. Still, I'll take your word for it.
If anyone can measure a 2/15 valve (which is what most of us have) for O-rings, seal and spring. Or equally if anyone has a 2/15 valve I can borrow for a week or 2 I'll measure everything and get the springs measured professionally. I'll then either return it immediately or if I can organise a kit, I'll rebuild it for free and then return it -- your choice.
I'll probably end up removing one from a car but am loathe to do so as have just done stock rear disk/hub, caliper rebuild on the SE and BobB's excellent Hi-Spec kit on the S2 so would prefer not to mess with either but c'est la vie.

[bobbrown]

I don't understand why this would be so; the spring seats look identical and they're both 15 bar and the photos Scott posted look diameter-wise the same but thicker wire diameter/fewer coils on the 3/45. Still, I'll take your word for it.

The 2/15 and the 3/15 valves are 15bar due to the different springs hence a 3/45 valve has a stronger spring.
Easy when you think about it, the 2/15 has a larger piston differential area (big piston – little piston) than the 3/15 valve, It has to be like this to get the ratio, if you then need the valve to start to operate at 15bar the spring needs to be stronger or else it will operate at a lower pressure. Conversely if you fit the spring from a 2/15 valve to a 3/xxx valve then the valve will start to work at a higher pressure.

[Jackonicko]

While I don't pretend to follow this, it sounds to me as though Bob Brown knows what he's talking about, and that it would be in all of our interests (we'll all need these, sooner or later) if he was involved and paid heed to.

His re-emergence on the thread, after a frustrated sounding "I'm dropping this and not doing any more work on it" ought surely to be welcomed and encouraged.

Not least because he is 'Mr Brakes' - to the extent that my wife refers to him as Bob Brown Brake Boy (B4 for short?). Just don't let him torque your nuts........

I'm puzzled at all the figures being bandied around - unless you can simultaneously measure the effectiveness fronts and rears, don't things like tyres and condition of the drum on the machine make such measurements of brake balance at least slightly problematic?

[saska]

The 2/15 and the 3/15 valves are 15bar due to the different springs hence a 3/45 valve has a stronger spring.

So for clarity; you're saying a 2/15 spring is different to a 3/15 spring?
If so for which spring did you provide measurements earlier in the thread?
And which valve did the O-ring measurements come from?

[RayD]

I'm puzzled at all the figures

Please let me know if anyone is enlightened ...

A 2/15 valve has a ratio of 0.2 to 1, and 1 divided by 0.2 = 5
A 3/15 valve has a ratio of 0.3 to 1, and 1 divided by 0.3 = 3 (ish)

A 2/15 valve has 5 times more tendency to close, were it not for the spring.
A 3/15 valve has 3 times more tendency to close, were it not for the spring.

For them to start operating at the same pressure – 15bar - the spring on the 2/15 valve needs to be stronger by about .... 100 x 3/5 = 60 .... 100 - 60 = 40%

Ray