Temperature compensators

[sujitroy]

I was able to find a Volvo service manual which say they should start to open at 70.F Others have said 125F but no official documents have been referred to. Anyway I adjusted both of mine to start opening around 125. The seals for them are very small. I can't imagine them lasting for more than a few years.

Sujit

[Phil S]

A friend of mine owned a triumph dealers when the stag was on sale, he said they were "off the record" told to disable them by triumph when the cars came back in having problems.

[richardthestag]

Many ZS CD2 Stromberg installations just do not have them at all, at no point in the 16 years (1970-1986) that Land Rover used them on the domestic Rover v8 for Range Rover and Stage 1 did they ever feature! (that I have seen yet) Wonder why?

Grampian stags has a very helpful doc about how to set them up http://www.grampianstags.net/TCs.htm

This chap shows the process for setting them along with explanations about all the other "improvements" to a fairly basic and simple carburettor http://bullfire.net/TR6/TR6-20/TR6-20.html

Page 5 of that link shows how the gent disables both the useless bleed screw and the temp(eramental) compensators in one sweep

I tend to ensure that they both open and close at the same time and worry less about the exact temperature, though I am in the range of 110-140f... ish

Bleed screw, the big one with a spring on it near the temp compensator, I screw right in. That is the start point for tuning anyway, i.e. disabled

The only seal that I can think of is between the temp compensator nose and the hole in the carb body. I cannot see how that is going to suffer any more than the throttle spindle seals?!?

[trunt]

I found that the plungers were not sealing well in the housing, no seal involved. I attempted to make them seal but was unsuccessful. Another pair I had were OK. Idle does seem more consistent since the replacement and setting them with hot water.

[MikeParker]

I had screwed down my temp compensators many years ago, because I didn't like the idle speed increasing when hot. I thought therefore they were out of action. But I'm just looking at my temp compensators now as part of my refurb and there seem to be two O riings one at the bottom of the recess in the carb body and one around the temp compensator body that would seal the outer part of the compensator. Both o-rings have perished, so air has probably been leaking directly into the manifold side of the butterfly for some time. I will fit new o-rings and make sure that the temp compensators are screwed up and firmly closed so that they never open. So my advice is, remove your temp compensators and check the o-rings.
Mike

[sujitroy]

I just found that if you do plan to set the TC's up, the top plastic cover needs to sit flat to avoid unfiltered air to enter the carbs. The air entering the carbs should be about the same.
Correct me if I am wrong, but a leaking TC wont increase idle as the air entering the carb is bypassing the butterfly. I assuming it just makes the mixture weaker.

I definitely want to thank RichardTheStag for his great YouTube videos on rebuilding carbs.

Sujit

[MikeParker]

Sujit,
Yes, a constantly leaking TC will just make the idle mixture weaker. It is only when it increases the air flow with increased temperature (as it is designed to do) that it will increase idle speed and weaken the mixture when hot.

The danger of the constant leak at idle (at all temperatures) is that you adjust the mixture at idle. So you correct the idle mixture by making it richer, but this would make the open throttle mixture too rich. I think this may be the issue with my car.
Mike

[MandM]

Mine were open all the time, adjust using the wife's coffee temperature gauge (don't tell her) to about 110F


P1090862.JPG P1090871 (1).JPG P1090872 (1).JPG

[richardthestag]

Gents you need to look at the temp compensator in it's component parts.

The black nylon plunger that is attached to the bimetalic strip is / should be a snug fit in the temp compensator housing! The temp compensator is also a snug fit into the side of the carb! I would imagine you will have more unfiltered air leaking in around the inlet elbows, throttle or cold start spindles! Not yet had any issues with these devices that I can pinpoint to a slightly warped cover so please don't go gluing them in place

Secondly when the temp compensator opens it allows passage of filtered air via the holes on the end of the round part of the temp compensator body that its inside the carb and through the to hole in the tip of the round part of the compensator inside the carburettor. Look at the plunger and tell me otherwise? This shouldn't impact idle speed as far as I can work out, it is simply allowing more filtered air into exactly the same quantity of fuel i.e. a weaker mixture.

There should be a fibre washer that sits between the temp compensator and the body of the carb, and an o ring in the end of the hole that it sit in.

Back in the good old days when folk used to open their bonnet to do more than just check the screen wash fluid, and owners handbooks did NOT need to remind the owner to avoid drinking the contents of the Lead acid battery, it was not uncommon to give the carbs a tweak for winter running.

What does it mean? well don't worry about the temp compensator, if it is giving you trouble! set it to open at 200f or blank it off. Make a mental note of the season when you tune the carbs up AND if you set them in winter - wind each of them back on mixture 1/2 - 1 turn for summer - or vice versa if you set them up in summer and a rare owner who uses their stag in more inclement weather.

Or buy a weber because it is less aggro...

[jbuckl]

Just an FYI the compensator covers were becoming tricky to find new.
Data for retooling was sent a few weeks back.
Will hopefully soon be available via SOC spares.
Anyone have the screw size handy?
Fwiw I spent hours resetting the compensators to spec… only to find that return to idle dips then recovers when hot.
Thinking it’s best to set to zero compensation.
Also fwiw I did find a rover v8 with strombergs that also had compensators fitted.
No idea what the application was, only saw the engine….

[nigele]

Just an FYI the compensator covers were becoming tricky to find new.
Data for retooling was sent a few weeks back.
Will hopefully soon be available via SOC spares.
Anyone have the screw size handy?;.

I see Moss sell aftermarket replacement covers, no idea what the fit and quality is like, but it might be worth looking at before investing in new tooling.

https://www.moss-europe.co.uk/cover-stromberg-carburetor-temperature-compensator-aftermarket-brand-365-835.html

Nigel

[MandM]

Just ordered couple as seem a good price, some of the zenith ones are £15.84+DEL each, will see what they fit like

[Lingen]

Tooling has been organised, and they will be available in a few weeks for probably around 1/3 of that price if you can wait.
Mike

[jbuckl]

Last time I looked the moss stuff was down to the last few & £££ (on back order now) probably coming to Europe from USA.
Some offerings seemed to be a bit ‘off’ as in smoothed / without ribs to prevent curling.
Thats why we went ahead doing them again in the u.k.
Hopefully it’s worth while.
Anyone got the screw size handy?
measured major dia 0.1185” 40 tpi & 0.36” long round head slotted.
4-40 die did not seem to fit.
sounds like M3 x 0.7 by 9mm long slotted round head