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I'm replacing all vacuum tubing on my recently obtained tr6. Replaced flame traps, tubing, rubber l's, etc. I can't seem to find where to make the connection from the flame/fuel trap to the front carb, or the other connection from the "y" fitting from the rear fuel trap to the rear carb. I don't see any place to connect to the carbs. I have been following a diagram from the roadster factory tr6 assembly manual. :cooler:
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TR6 vacuum details 74 tr6
- Thread starter Wike
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poolboy
Yoda
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Taking the front carb first. The nipple for the Vacuum Retard on the distributor is on the bottom of the carb. The hose runs to one of the 2 fuel traps up by the thermostat/ water pump housing. From there to the Thermostayic Vacuum Switch (TVS) on the top radiator hose; from there a single hose to the distributor's Vacuum Retard.
Still on the front carb. From the nipple on top of the Throttle Bypass Valve (TBV)housing to the other fuel trap near the T-stat. From there to the TVS.
Now the rear carb. From the TBV to a "T" joining it to the front carb's TBV hose.
Still on the rear. Fron a nipple on top to a fuel trap to a "Y". Also to a leg or arm of the "Y" a tube from a vacuum breaker switch activated by the carb's idle speed cam.
That leaves 1 leg of the "Y" that leg holds a tube to the top of the EGR valve which is mounted on the cylinder head.
The 74 was unique in it's emission plumbing and in my view the most complicated, most of which can be eliminated or disabled.
Here's a picture of my 74, stipped down as much as I saw fit.
Still on the front carb. From the nipple on top of the Throttle Bypass Valve (TBV)housing to the other fuel trap near the T-stat. From there to the TVS.
Now the rear carb. From the TBV to a "T" joining it to the front carb's TBV hose.
Still on the rear. Fron a nipple on top to a fuel trap to a "Y". Also to a leg or arm of the "Y" a tube from a vacuum breaker switch activated by the carb's idle speed cam.
That leaves 1 leg of the "Y" that leg holds a tube to the top of the EGR valve which is mounted on the cylinder head.
The 74 was unique in it's emission plumbing and in my view the most complicated, most of which can be eliminated or disabled.
Here's a picture of my 74, stipped down as much as I saw fit.
If you look at the Moss catalog under emission control you will see how the different years were set up. I also have a 74 and don't like the look of all those hoses, and the valve at the thermostat housing. I set mine up with the 75-76 diagram and all works fine with much less clutter.
bcbennett
Senior Member
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I also have a '74, and I have none of the thermo switch hoses hooked up, (though the valve is there). I note that the owner's manual states this switch is supposed to rev up the engine when it begins to get hot (say, in heavy traffic) such that the engine will not overheat. Do you guys have problems with overheating?
poolboy
Yoda
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I got curious and tested the switch in a pan of water heated on the stove. Using a thermometer, I observed that the valve started to open when the water started to simmer and was completly open when the water came to an active boil. That would be between between 15 and 25 degrees above the normal operating temperature, but I don't recall the TVS ever activating in use. But then again I don't encounter bumper to bumper city traffic.. Well maybe once in Pidgeon Forge on a Sunday afternoon.
Thanks to all for the info. The picture of the engine differs slightly from mine in so much as my engine has an EGR valve. Also in response to the Moss motor's diagrams: my question in referring to these diagrams for the 1974 application, where does item 88 and 79 connect to? Even in the 1975-76 diagram, would item 105 connect to corresponding diagram 1974 item 79?
The item 88 I'm talking about would be connected to BN31 tube going towards rear carb.It's the one connceted to the "y" fitting. Where on the rear carb does it get connectrd? Also, item 79 is the one connected to tube 98 comming from the fuel trap.Where on the front carb does it get connected?
poolboy
Yoda
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Rear carb.
"Still on the rear. Fron a nipple on top of the carb to a fuel trap to a "Y". Also to a leg or arm of the "Y" a tube from a vacuum breaker switch activated by the carb's idle speed cam." ...Missing that switch ?
Front carb
".... The nipple for the Vacuum Retard on the distributor is on the bottom of the carb. The hose runs to one of the 2 fuel traps up by the thermostat/ water pump housing....."
If you are having trouble finding that nipple on the bottom of the front carb perhaps you have carbs from another year, a pre 74 carb maybe.
"Still on the rear. Fron a nipple on top of the carb to a fuel trap to a "Y". Also to a leg or arm of the "Y" a tube from a vacuum breaker switch activated by the carb's idle speed cam." ...Missing that switch ?
Front carb
".... The nipple for the Vacuum Retard on the distributor is on the bottom of the carb. The hose runs to one of the 2 fuel traps up by the thermostat/ water pump housing....."
If you are having trouble finding that nipple on the bottom of the front carb perhaps you have carbs from another year, a pre 74 carb maybe.
Vacuum breaker switch? Where would it be located...what does it look like? Csn't seem to find any nipples, ports, etc on the bottom of either carbs. There is a small legth of rubber tubing fitted with a screw in the bottom coming off the bottom of front carb. If my tr6 is fitted with carbs other than 1974, what can I do to get this vac problem on track? Thanks for your responses...All have a great new year!
poolboy
Yoda
Offline
That rubber tube with the screw on the bottom of the front carb is what someone did to cap off the nipple for the distributor's Vacuum Retard. A frequently used method of capping off an un used Vacuum line or nipple.
1974 was the only year to have the Vacuum Breaker switch to regulate when the Vacuum from the top of the rear carb opened the EGR valve. It's hard to describe, but it was activated by a cam on the cold start (choke).
You can get some idea of it if you go to Plate BA in The Roadster Factory's Blue Book Catalog. . It's part #ZEB23187.
I sold mine when I got rid of most of that stuff.
You may just have to forget about using it and hook up the EGR in the 75-76 fashon, if you feel the need to make the EGR functional.
1974 was the only year to have the Vacuum Breaker switch to regulate when the Vacuum from the top of the rear carb opened the EGR valve. It's hard to describe, but it was activated by a cam on the cold start (choke).
You can get some idea of it if you go to Plate BA in The Roadster Factory's Blue Book Catalog. . It's part #ZEB23187.
I sold mine when I got rid of most of that stuff.
You may just have to forget about using it and hook up the EGR in the 75-76 fashon, if you feel the need to make the EGR functional.
