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Necoa #: 8721
Location: 13(TX)
Joined: Dec 22, 2006
Posts: 333
Year: 1983
Model: El Camino
Posted: Fri Jun 13, 2008 11:12 am Post subject: Dual Jet tuning specs and loose throttlr rod.
I have gone through the paper by Lars Grimsrud on tuning the Q-Jet using the information on the primarys to tune my Dual-Jet. Everything is set up the way it should be but I am not sure the jet/metering rod set up is optimal.
Does anyone run a Dual Jet on a 229 V6? If so what setup do you run??
When I started I had a Q-Jet with the Secondaries blocked it had a 72/46 Jet/rod setup. It ran fine but after a year it developed a lumpieness. When I changed to the Dual Jet it initially had a 72/50 Jet/rod setup (came with the carb) and I could not start the car unless I dumped fuel into the intake. So I changed the rods to the 46s that came out of the Q-Jet. Then the car will start and run but its still lumpy and accelerates poorly. This was an increase in jet area of about 12%. But now my mileage has gone from 19 mpg to just 10 mpg!!! I am considering going to a set of 42 rods to see if that works but dont want to increase the fuel consumption.
BUT as I was working on the thing this morning I noticed that the throttle shaft going through the bottom of the carb seems to have a lot of play in it. Can this be a cause of an extreme lean condition that I am trying to correct with metering rods?
If so, what is the fix for a loosely fitting throttle shaft?
Or do I just have to buy a new carb? _________________ Jim
1983 El Camino
You will need to have bushings installed in the carb . This is a normal procedure for carburetor shops. I have seen kits for DIYS bushings, but I believe I would have it done by a pro. It's just like a vacuum leak when the throttle shaft has a lot of play in the carb.
Doug _________________ 85 El Camino 305, TH350, K&N, dual exhausts
87 El Camino 305, 2004R, K&N, dual exhausts
1964-1/2 Mustang conv, 260 V8, dual exhausts
2002 Jaguar XJ8, 2000 Harley Road King
Lakewood, CO
Necoa #: 8721
Location: 13(TX)
Joined: Dec 22, 2006
Posts: 333
Year: 1983
Model: El Camino
Posted: Fri Jun 13, 2008 11:40 pm Post subject:
I just did some extensive research on this and I am now convinced that the problem is, indeed, a need for rebushing the throttle shaft. I checked the old Q-Jet and it has a loose throttle shaft also so that was the original problem and then the "new" used Dual-Jet also has a loose shaft. The other symptoms were intermittent rough running and a sticking throttle. That explains why changing the carbs didnt help, they were both leaking. Now I need to find a source for some bushings. I will probably be able to go back to the leaner 50th metering rods after I rebush the throttle shaft. _________________ Jim
1983 El Camino
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