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Fuel Pouring Out of Secondary Boosters

JedIEG

Well-Known Member
Local time
3:26 PM
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Apr 17, 2013
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Location
Columbus IN
My QFT SL-600 has been running like crap so I pulled it off to recalibrate it.

In the mean time I installed a 4175 I rebuilt a while ago. I was lazy and just cranked over until I got fuel in the bowls and checked I didn't have a fuel leak somewhere before starting the car. It started fine, but I had fuel spurting out the air bleeds and pouring out the boosters. I wacked the bowl with a rubber mallet and the fuel stopped spurting out the bleeds, but still lots out the boosters. I am guessing a needle or float problem. Im going to take the rear bowl off to check, but is there anything else I should look at while I'm in there?
 
Yep, a float or needle problem. Of special note, some combinations that use the metering plate as opposed to the larger metering block can have the float rub up against the plate and get stuck. The metal floats all used to be the same, now they are different.
 
Yep. Check fuel pressure.
 
I have an old 4160 that I will swap the rear bowl with and see if that fixes the problem.

I'm not too concerned about fuel pressure since it was running around 6.5psi with the duel feed SL-600. The 4175 is single feed so I can't use the inlet line that has my pressure gauge in it. Also I hate the float bowls since they are not externally adjustable. I would love to fine a set of center hung duel inlet bowls for the 4175. I just want to see if it will run better than the sl-600 has once it's not pouring fuel into the engine.
 
Last edited:
Well I found the problem... Someone forgot to set the float height and the needle was never closing.
 
"Never overlook the obvious." A quote from a tech school instructor from 50 years ago.
 
Yep. Check fuel pressure.
A buddy of mine had a '62 Impala SS with a 327 in it, with a Holley on it. He called me over to have a look at it because it was flooding and fouling his spark plugs. We played around with this carb, but could not get it to run right. It turned out he also had a new Edelbrock carb in the box, so I got it out and installed it. We replumbed the fuel line to it and put new spark plugs in. The motor fired right up and settled into a nice idle. The next day, my friend called to say that his car was running crappy again.
In talking further with him, he said that he had recently had his fuel pump replaced. I told him he should install a fuel pressure regulator and gauge. However, he was certain that fuel pump was OK and that his problem must be crud in his original gas tank. He took it to a local garage that replaced his fuel tank and lines with new pieces. The car continued to run like crap. By this time, my friend was so fed up with the whole experience that he said he was going to sell it. A guy at the garage made him offer for the car, so he sold it. About a month later, the new owner showed up at a cruise night with the SS. It now had a fuel pressure regulator on it.
 
Well setting the float level solved one issue, but the next is a bit unsurmountable- fuel is leaking out from the throttle shafts and I can't get the idle down below 2000 rpm even with the throttle speed screw completely closed. There is visible play in the shafts on the right side. I don't think this carb will work without bushing the shafts... so back to trying to getting the QFT to run right.
 
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