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BT-7 Choke Question

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B

Blonde Healey Girl

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I have a 60 BT-7 that has a solenoid between the carbs. (Car has been sitting for 22 yrs. drained the tank, cleaned the bowls, messed with the pump, installed cheap inline filter) Anyways, I have no idea how the proper operation of this choke should work. It seems to draw fuel from the back carb, then has this solenoid that clicks when I flip a switch under the dash. Has three rubber lines that flow directly to the intake manifold. Today I pressurized the fuel system for the first time. The bowls were not overflowing through the overflow tubes but the pump never fully quit pumping ( click every 5-6 seconds) but after 2-3 minutes the maniflold drain was dripping and one of the 3 barrels in the solenoid choke thing was dripping. I tapped the floating solenoid with my finger and that seemed to stop the dripping?Is this correct operation? I never flipped the switch nor did I try to start the engine yet . Thought it might be wise to consult someone who has "been there done all that" Thanks for any advice!!! noticed Healey did away with this design in 61, is the old pull choke a better way to go?
 
BHG

This seems normal. The thermo carb is incredibly simple. I almost never use mine but decided that the cost of new carburators and a choke assembly was way more than just rebuilding the AUC935s. I actually had a manual choke cable at one point of time and realized there is nowhere to use them on the thermo carb setup.

T
 
I sent the info to yer mail. Also get a shop manual it describes them in there as well.
 
BigHly, Thanks so much for sending that JPEG. My manual didn't mention anything about it. Looking at your photo, Mine does not have that triangle looking flat piece. You can look down all three barrels. Wonder if that matters? Funny, while purchasing the car, I asked the previous owner what it was and how to work it. He shook his head and said, beats me, but keep an eye on it while starting, its spits and barks!!!
Thanks again.
 
BigHly, Thanks so much for sending that JPEG. My manual didn't mention anything about it. Looking at your photo, Mine does not have that triangle looking flat piece. You can look down all three barrels. Wonder if that matters? Funny, while purchasing the car, I asked the previous owner what it was and how to work it. He shook his head and said, beats me, but keep an eye on it while starting, its spits and barks!!!
Thanks again.
 
BHG: Your thermocarb will probably work just fine, if you are careful about its use. Originally, the thermocarb was wired to a sensor in the engine block that operated it automatically. These sensors commonly stuck, and a common modification at the time was to just remove the wire from the sensor and substitute a toggle switch on the dash somewhere. Yours has apparently been modified in this manner. The thermocarb essentially sprays raw gasoline into the cyllinders for cold starting assistance. This abundance of raw gasoline is why you reported seeing the gasoline dripping out of the overflows on your car when you operated it before.

If you are careful with the use of the thermocarb and remember to turn it off after starting and when the engine approaches something close to normal operating temperature, it will do just great. Yes, they do hiss and puff some when in operation. You could even replace the sensor on your engine block and return the thermocarb to automatic operation, if you choose to do so.

Healeys only used the thermocarbs for a couple of years, but Jaguars used them for a long time before and after Healeys! AL Bradley, longtime BT-7 owner.
 
BGH,

I will fess up. When I first tried to start my engine I found that the builder had put the lower distriutor 180 degrees out. What was happening was the thing would fire on a down stroke and backfire violently and escape through the intake valve and out through the carbs. On these thremo jobbies I guess the center hole is the path of least resistance since thats where it would seeming come from. So I understand the barking discription all too well. Because of the prolonged running of the fuel pump I also experienced the fuel dripping out the manifold overflow (much better than flooding the cylinder!).

I toyed with removing the triangle aluminium plate until it "barked" during my early efforts of starting the car (actually ran the new battery dead then). I would recommend making ip a plate and putting it on. It's function is to keep fuel from flying all over creation IF it does bark and also to keep little bits from falling down inside the center (intake?) hole.
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s_101-0129_img.jpg
 
Wow!!! Thank you guys. This right here proves how valuable this forum is. Bradal you are right about the sensor being disconnected. That was going to be another question I was going to post. That sensor is sitting up front on the block with no wires connected. I didn't have a clue. And yes Bighly I will fab a plate thanks to your awesome picture. Might try to start it today if it warms up. OAT of 39F at the moment. Thought it best if I roll it out of the garage. In an attempt not to burn the house down.
 
BTW my head is missing a place to put the thermo carb connections. I have it wired to a switch which I only use if I want a cheap thrill listening to the very pronounced hissing noise it makes. It is a great conversation piece at gatherings.

I would cease to turn on electrics until I was ready to start it up. Keep a fire extinguisher handy if you can't help yourself. It will just pump gas where you don't want it anyway.
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by bighly:
BTW my head is missing a place to put the thermo carb connections. <hr></blockquote>

The thermocarb switch goes in a triangular well on top of the left front corner of the head. You may have a triangular plate there if it was taken out.

cheers.gif

John
 
Bighly,

I don't have one of those "contraptions" on my BJ8, but it's been interesting to follow this discssion thread. For those unfamiliar with this type of choke, the added pictures sure help us understand it.

Slider
 
Thanks again guys, the engine started (first time in 5-6 years) after a little popping and snappin, Yea!!!!. Bighly, I made a plate like yours (glad I put a Roto-zip on my christmas list, great for that sort of stuff). Warmed it up to SOT and drove up and down the driveway a few times (Neighbors think I'm crazy, now they have proof.....)
 
BHG,

You must be pumped to have the thing running. When mine first ran I was excited and nervous running about the garage like a giddy kid, checking pressures, listening for noises. Congratulations!!!! Did you turn on the thermo carb and get that cool hissing? hehehehehehe
thumbsup.gif

Tracy
 
Yes Bighly I was jumping all around!!! Having the engine running changes your whole perspective. Up until I got it running all the other work made me feel like I was arranging deck chairs on the Titanic........The thermo carb helped a whole bunch. I tried starting with out (put my hand over each carb while cranking, air cleaners off) and it only ran on 2 or 3 cylinders. Hit that dash switch and everything smoothed out. Oh, Yes, that thing makes all kinds of hissing noise, also spits like a snake every now and then...... Healey Cobra???
 
Hello BHG,

some further info on your thermo starter, the small central nut is used to adjust the mixture.
(This is the one the jet sits in, between the two screws that hold the aluminium deflector plate. This plate, incidentally should be flat on the sloping section)
Start the car and warm it up, bring in the thermo starter by shorting the sensor or acivating via the manual switch. The aim is to get the engine running noticeably rich, screw the nut up to richen and down to lean.
I seem to remeber that my Jaguar manual says that you should pump the throttle to activate the unit when doing a cold start as the air flow sucks down the needle.

regards,
Alec
 
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