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Vacuum control valve

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Vacuum control valve
#1
  This topic is about my 1968 Triumph TR250
06nine Silver Member Craig F
San Antonio, FL, USA   USA
How are they disassembled? Before I ruin something so rare, I thought it best to ask first...
Thanks in advance!
Craig

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Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Craig, you talking about the little vacuum valve down on the throttle plate just below the carbs? That's the only extremely rare little valve I think you are talking about. Mine still works on my TR250 so I haven't dissected mine yet, kind of looking forward to having it fail so I can take it apart. I have designed a replacement on my CAD system but have been waiting for mine to quit working so I can confirm what I think the innards look like. Maybe someone else here has taken theirs apart. I eventually want to make one out of aluminum. Most people just take the valve out of their system. They come up on Ebay every once in a while for crazy money.

06nine Silver Member Craig F
San Antonio, FL, USA   USA
Yes, Brian, that is it's location. So rare and expensive, I am baffled as to why "those that have gone before us" haven't come up with a solution for repair/replacement. I read that some '80's XJ6 Jags had these in their hvac system, but any time you mention Jaguar the cost goes up drastically-please don't ask me how I know this...
It really is a simple valve. And I like what it does for our timing. But my preliminary research on the internet indicates it is way over-priced. When you can find it.

You may be our best opportunity, Brian!

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Bpt70gt Brian T
Westmoreland, NH, USA   USA
That little valve does intrigue me a lot, it’s one of the very few things I haven't totally taken apart on my TR250. Almost hope mine fails so I can take it apart and duplicate it out of brass or delrin. I agree, it lets the idle settle down nicely with that little bit of retard. I've been tempted to buy one off ebay on that rare occasion one shows up just so I could take it apart and dissect it. As I mentioned, I have one drawn up but was waiting for an excuse to take mine apart. Since its winter up here in NH, maybe I'll head out to my little machine shop and start making up the components for the fun of it. It would be an interesting little project. I think most just don't mind bypassing it and forgetting about it instead of solving the issue. Basically a little body, with a piston, O-ring, spring and retaining clip. Damn, talking myself into a new little project. I've had my TR250 for over 20 years and every spring figuring the little valve will have died and I'd finally have to get into it. Maybe now's the time. I too have researched the internet and it's a very rare little bugger and hardly any information on it. Only ones I've ever seen have been on ebay but for $60.00 plus. Crazy. But that's why most owners just take them out of the loop. It evidently is a very durable little valve. As far as I know, on my car it's the original one.

Brian

TR250Guy Avatar
TR250Guy Tim Moore
Dayton, Ohio, USA   USA
1968 Triumph TR250 "TRminator"
I believe this Jaguar vacuum valve is the same as whats on our TR250. But at 121 euros its pricey. Its part 16 https://www.limora.com/en/british-cars/jaguar/jaguar-xj12-and-daimler-double-six-series-i-iii-1972-1992/electrics-ignition-system-heating-air-conditioning-and-dashboard/heater-and-air-condition-control-unit-series-ii-and-iii.html#16



1968 TR250 "TRminator"
Owned since 1980
Frame off rotisserie restoration completed in 11-2014 by myself and my brother

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Hard to see in the picture but certainly looks like it. Nice link. Figured one of the other British Cars would use the valve. Some early GT6's used them also but my 70 GT6+ didn't. Crazy money. Guess I'm going to have to do some shop time. Needed something to do.
Beautiful 250 Tim, I completed mine over 20 years ago but it's now due for a new paint job. Mechanically it's fine. Just have to finish my GT restoration before I repaint the 250.


Attachments:
TR and Pool repair 068.JPG    68.1 KB
TR and Pool repair 068.JPG

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1436681 by 06nine And I like what it does for our timing.
I'm just curious, what's to like about vacuum retard ?

It wastes fuel, increases heat, and by today's standards actually increases CO2 pollution, while being only marginally effective at reducing HC.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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06nine Silver Member Craig F
San Antonio, FL, USA   USA
I understand that one of the benefits of vacuum retard is at idle; the result is a leaner mixture-but please correct me if I am in error!

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Nope, doesn't change the mixture. Just makes the engine less efficient, so the throttle can be open farther (hence increasing peak cylinder pressure) without having the idle rpm ridiculously high.

The idle trim screw and the temperature compensator lean out the idle, but not the vacuum retard.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Agee, doesn't change the mixture, just retards timing at idle. But I do like it just for that reason. My TR idles smooth at 800 all afternoon. Plug it and idle goes up 200 rpm. Efficiency on a 49yr old car is a bit debatable but I've been to LA and seen the air and smog efficiency is very important for sure. Got more cars there than in my entire state.

06nine Silver Member Craig F
San Antonio, FL, USA   USA
Thank you for the clarification-and the education!

carpecursusII Drew H
Oklahoma City, Oklahoma, USA   USA
The Jag part is the same part as what we have on our cars, I've never purchased a new one so I don't know what you would get but the originally were the same.
As for construction, the "foot" is crimped on to the shaft that goes through the body of the valve. The bottom of them valve is just a pressed in plate to retain a spring, it is easily pried out with a dental pick. The spring will fall out and you will see a small shoulder on the shaft. There is an o-ring or other rubber type seal that is retained by the shoulder, this is what seals against the body of the valve to prevent vacuum from getting through. I have never fully dissembled one because I didn't want to cut off the brass "foot". If you could reproduce the foot then any valve could be overhauled.

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Hi Drew, yes it's evident that the foot is crimped on. My thought when I have to rebuild mine was to have the foot screw on. I have some micro taps and dies so that isn't a problem. That way the valve becomes more serviceable. I guess I'm going to wait until mine fails to totally take it apart. It's been on there for at least the 20 years I've owned the car. It's bad when I want something to fail just so I can fiddle with it. Too bad I couldn't find one that someone didn't want anymore, that would give me a good reason to dig into it. Sure it's easy to just not have it on the car anymore and bypass it but a little challenge is fun sometimes too in rebuilding some of these little items.

tirebiter Jeff Garber
Dighton, MA, USA   USA
I've had a lot of experience using an exhaust gas analyzer to adjust the idle speed mixture. Retarding the ignition timing actually does effect the mixture.

Retarding the idle speed timing yields a richer exhuast gas analyzer reading. Not leaner. You need to manually lean out the mixture (if you want) to maintain the recommended mixture.

This end result of the retarded idle timing and manually leaned out mixture setting, affects the mixture at all other conditions of throttle opening and RPM. Effectively leaning out the overall mixture, except only at idle.

This fact is often overlooked by many experienced mechanics and DYIers.

2ml2us2 Avatar
2ml2us2 Tom Brocke
Haymarket, Virginia, USA   USA
Ok guys, I have been monitoring this thread. I am one of those rare people owning an ONS vaccuum retard valve. And you guys are correct they go for stupid money on ebay, or elsewhere for that matter. I have weber down drafts on my '250 and was keeping it for the time I might choose to go back to ZS. That time might not ever happen, so here is what I am willing to do ...

Brian, if you decide to take on the project you spoke of, and make up this valve in your shop, I will supply you with my valve as your mule. My condition is if you are able to bring the project to fruition and can supply a few of these valves. I want the first 2. One for me. And one for me to offer on ebay (or other LBC forums) to recoop my expense on my original. Capitalistic? Yes. Fair? Maybe ..but I am willing to take the risk if you are.

Let me know what you think.

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