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SU carb problems


Guest Anonymous

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If the float is "sunk" then it could be one of two things. The fuel inlet needle valve could be stuck or your float has a leak. Pull the float and see if fuel drains from the float. Try submerging it under water and look for bubbles. While you have everything apart, clean clean clean. Put the top half of the float chamber back together(exactly) and flip it upside down. Blow air(with your mouth) through the overflow tube and move the float down(since it's upside down) and when the float stops the flow of air, hold float and measure the distance from the top of the float(remember, your upside down) to the seating edge of the lid. This measurement should be 1/2". If it's not, bend tab until you get it precisely 1/2". That should set the float properly. Put back together and see how it goes. Email me or post back here. I'll be back on tomorrow.

This may be alittle brief, but it should get you going. Go to go now. I think I typed this in about 20 secs.

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Guest Anonymous

well i think the needle had some varnish or something on it cause it all of a sudden went away...now all i need is one of those carb synco thingys to check the carbs out...and the 2nd and 3rd gear on my 5 spd is whinning really bad....i have a 4spd tranny but are the drive shafts the same between them....and of course the electrical system is pretty fried...mostly the turn signals and brake lights....man what a project car....i know i paid to much for it (700) but its a 73 so its smog exempt....thanks and ill be back soon im sure...lol

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Guest Anonymous

ok i just bought a POS 73 240 that will be a daily driver as soon as i can get it running right....but the rear carb seems like is out of adjustment and has a sunk float...here are the symptoms...the bowl vent hose that goes to the aircleaner assy. is pouring fuel out of it (but not all the time)..and i dont have a carb syncro thingy....lol...but the front carb is pulling more air than the rear by feeling with my hand...both have enough oil in the tops and both sliders have about the same feel to them when lifting them up....never messed with the SU's much at all...mostly have V8 experiance so anything i maybe overlooking will help out. thanks

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Cheap carb sync tool, a length of small dia. hose(vacuum hose works great) and your ear.

Pull your air filter and put one end of the hose in a hand with about 1" sticking out. Put the other end up to your ear. While the car is running, put the 1" into the bore of the a carb, using your hand to set up a specific distance your inserting the hose. Now move to the other carb using the same distance into the bore of the carb. You may have to adjust the distance inserted depending on your vacuum/idle, but always use the same distance for each carb. By listening to the hiss from each carb you can tell which one is pulling more air then the other. Adjust to make the same hissing noise from each carb, while at the same time keeping your idle at a good level. Set balance adjustment with your head between the carbs, listening for the opening point of each and your good to go. Setting the mixture is about as easy. Ask and I'll fill you in.

I do believe I got my unisync from MSA. Was about $30. Sad part is, I prefer previously described method. Hope it helps.

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When I did the 4 speed to 5 speed swap on my '74 I used the 5 speed drive shaft because the ujoints on the other shaft needed replacement and this one wasn't that bad. The difference in length is about 1/4-3/8" if I remember correctly. I plan to replace the bad joints and swap it out, one of these days. Probably soon since I have a tranny leak somewhere.

Glad to hear the carb issue was resolved. I would atleast pull the domes and piston(carefully, not to bend the needles) and clean everything thoroughly. Could give you alittle more responsiveness and gas mileage. Not that we worry about gas mileage these days. icon_wink.gif

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Guest Anonymous

yea ..i think ill wait to do that project for another day...i need to get ahold of a carb syncro so i can make sure they are adjusted right...and i have a bad brake booster so im gonna swap that out swap in the 4spd...take out the A/C and the smog pump crap...try to clean the engine bay up alittle...any other ideas....know where i can get the carb syncro from?

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