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Carb Woes and Vacuum hoses?

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Norton47

Jedi Warrior
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Where does the vacuum line connect to the intake system for a retard type distributor?
I have a port on the intake manifold that also has the brake assist port on it.
I have another port on the aft carb on the topside of the carb body right by the flange area, just before the isolator pad.
I also have a port on the forward carb, on the bottom of the carb body right by the flange area.
All unused ports are plugged or capped off.

I looked at various cars at the show and there did not seem to be a consistent attachment point.

The port that comes off the intake manifold seems to have vacuum all the time, and it seemed like I remembering trying it and I did not see the distributor advance when connected there and the engine was revved.

The one on the aft carb only pulls a vacuum when the engine is revved up, and so does not retart the distributor to 4 ATDC at idle. Is this indicating some other problem?
The forward carb port does have vacuum at idle, does pull the distributor to 4 ATDC and allows the distributor to advance when revved. Seems like the right one. However it was blocked off when I bought the car. When I took off the cap to try it, fuel dripped out. Just a few drops.
Is this indicating a incorrect fuel bowl level?
I used some clear tubing and can see that this happens.

I have been running the car with it connected here, but I can't seem to get a consistent smooth take off from a stop sign. The engine wants to hesitate or stumble. It seems to do this with the carbs set lean or rich, according to the plugs.
Seems like I might be chasing my tail so I wanted to confirm where to connect the distributor vacuum at?
Thanks
 
vacuum retard on these engines should be hooked up to manifold vacuum.

Manifold vacuum will read highest at idle. When you open the throttle the vacuum will lessen/disappear. This is what you want on retard. So your distributor advances on acceleration.

Vacuum advance is usually, (I'm talking basic engine design now, not just 6's) ported vacuum. No vacuum at idle, but when the throttle is opened vacuum occurs.

So go get an inexpensive vacuum gauge(or a good one as it can be a very useful diagnostic tool, once you learn how to use it) and hook it up to the various nipples on the carburetors to determine which gives you vacuum when.

The Moss catalog vacuum diagrams in their catalogs are helpful.
 
FJA
Thanks for the link. Looking at those pictures, I would be most like the 1972 and 1973. My engine head does not have the air ports nor all the other stuff on the 1974 diagram. It has the vapor cannister and the anti run on valve, which is not connected vacuum wise.
The manufacture date of the car is Nov 1974
 
The port under the front carb is correct for the vacuum retard. The retard should only get vacuum with the throttle closed. The bottom port was used on all TR6, except the very early ones where there was a mechanically-operated valve to cut off the vacuum to the retard when the throttle was opened.

Fuel dripping out the port probably indicates a problem with fuel level in the float bowl.

Your rear carb apparently has an advance port, which would indicate the carb didn't originally come from a 74 TR6. The advance was deleted for the 72 model year and onwards. Some early carbs might have had a plug in the port, but by 73 they simply weren't drilled.

However, 'service' carbs may have had the port, so the carb isn't necessarily "wrong" for your engine.

Originally on a 74, the retard line would have been routed through the Thermal Vacuum Switch (TVS) on the radiator and a vapor/flame trap. You can ignore the TVS if you want, it's only function was to disable the retard (raising idle rpm) when the engine started to overheat. But the trap is a good idea IMO as it helps keep that dripping fuel out of the retard unit; where it might damage the diaphragm.

Personally, my approach would be to simply disable the retard and cap off it's port. It wastes fuel and increases CO2 emissions. The only operational effect of not having it is that you might have trouble getting the idle rpm down where it belongs. If you do, check the linkage to the float bowl vent valves.
 
Randal
Flame trap must equal Fuel trap on the Moss page (part 108)
interesting thought on removing the retard entirely. Jeff at Advanced Distributors also advocates that approach. However, a local guru advocates the retard in place approach. He explained it as getting more or quicker advance using the retard, I guess advancing from 4 ATDC to about 8 BTDC when you step on the throttle then having the mechanical advance kick in. Where as without the retard, you would set the timing to 8 BTDC and then have only the last little bit of mechanical advance.
I don't know enough yet to even know if I am repeating it all correctly. So I am trying to keep every thing stock until I can be sure of what I am doing.
With out the retard connected what would the starting timing position be? 8 degree's BTDC?
Thanks
 
I use a recurved distributor from Jeff, with the retard in place, timed as you said above. I feel that it gives me the best performance, after trying it without the retard unit connected.
 
Norton47 said:
Flame trap must equal Fuel trap on the Moss page (part 108)
Click to expand...
Yeah, that's the gizmo I was talking about.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I guess advancing from 4 ATDC to about 8 BTDC when you step on the throttle then having the mechanical advance kick in. Where as without the retard, you would set the timing to 8 BTDC and then have only the last little bit of mechanical advance.
I don't know enough yet to even know if I am repeating it all correctly.[/QUOTE]Sounds like you have a grasp on the situation, all except why going from 4 ATDC to 8 BTDC is better than starting out at 8 BTDC.
Oh, and I wouldn't call it "the last little bit" ... the mechanical advance will add quite a bit at higher rpm. Don't have a book handy, but should be at least another 12-15 degrees for over 20 total at high rpm.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]With out the retard connected what would the starting timing position be? 8 degree's BTDC?[/QUOTE]Whatever the book gives as "static" timing. Was 10 BTDC in 73, but maybe it was lowered in 74.

Of course you can experiment from there, to see what works best for you, but that's the place to start.
 
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