Calling all Vacuum Experts

[glemon]

I am putting my TR250 vacuum line system back together, I just figured out I some later TR6 (73 TR6 3508) carbs on the car, it has totally different vacuum connections and is made for a vacuum advance distributor, I have the vacuum advance retard distributor.

At this point I am not swapping out carbs or carb parts, the TR250 vacuum system is a Rube Goldberg like mix of lines and contraptions that as I said doesn't match with the current carbs so should I?

a. plug off all holes except the vacuum advance line and hook that up to an appropriate place on the carb?

b. plug off all lines except the vacuum advance and retard and hook them up to the front and rear carbs respectively ala a 70-81 tr6 as shown on the moss catalof page for emmission controls?

c. Other suggestions???

 

[chappy444]

I have that same vac retard type distributor on my 75 spit.
i disconnected it and plugged the vac port on the carb..i have not noticed any difference better or worse with it connected or disconnected...

keep in mind i am having other issues as well...lol...see my distributor post for details..

good luck with it.
Bill

 

[poolboy]

glemon, the nipple on the bottom of 3508 carbs is for a vacuum RETARD unit. That's the one on the cockpit side of your dizzy.
The thing is, the ports (nipples) on the carbs are not interchangeable as to retard or advance hook ups to the dizzy.
You would need a front carb from 69, 70 or 71 to be able to hook up your vacuum advance.
If you have a good pair of 3150 carbs, I'd cap the nipple on the rear carb, forget about the retard and run the vacuum line from the front carb directly to the dizzy advance.

 

[glemon]

Thanks, that helps, no spare carbs sitting around, is there anyt reason why I can't take the vacuum advance off the intake manifold?, that would be easy for me to hook up without butchering anything.

 

[TR3driver]

If you hook the advance to manifold vacuum, it will be active at idle. Without the vacuum retard, that will give you an idle that is high and unstable.

With the retard, the two will be fighting with each other. I'm not sure which one will win, but I'm guessing it will be the advance.

 

[SkinnedKnuckles]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]If you hook the advance to manifold vacuum, it will be active at idle. Without the vacuum retard, that will give you an idle that is high and unstable.[/QUOTE]

Not so. My dizzy was "converted" to Vacuum advance by switching the module around (the Good Parts mod). It runs fine hooked up to the manifold port on the carb which makes it active at idle.

 

[poolboy]

Here's a link to a Lucas training manual. If you scroll thru it about midway, you'll see how the vacuum advance is supposed to work and when it is supposed to work and when it is not supposed to advance the timing. Clearly in this Manual it's not designed to be a constant.
https://mgaguru.com/mgtech/books/lts_otcc/Session3_CoilIgnition.pdf