Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Edelbrock 850 performer RPM Q-jet

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1965C-10:
Hi, my name is Mike, first post here.

I bought and read the Cliff Ruggles Q-jet book often, but thought I would double check here before digging in.

I have a 1965 Chevy truck, shortbed, with a 396 big block (#'s decode to a 1968 pickup 310 HP) and a TH400 trans, 3.73 gears, exhaust manifolds.

I bought a slightly used Edelbrock 1910 850 Performer RPM Q-jet in the original box, with owner's manual for 200 bucks as I had a Carter AFB 600 manual choke on the big block from my old 327.

I have been running this carb on the truck almost a year, but it's running rich I think.

First start of the day (if it has not been sitting for a week) just bump the key, no touching the accelerator pedal, it fires right up just fine, then when I take off the higher idle speed comes into play for about 1/2 mile to a mile.

If I drive somewhere like the grocery store, or anywhere, when I come back to start it, it will take about 5-10 seconds of cranking before firing up without hitting the pedal.

Lately I have been cranking it and if it does not fire right away, I hold the pedal to the floor and it will fire up in about 3-5 seconds.

I'm guessing it's running rich on idle, right?

I adjusted the APT screw to one turn counterclockwise, and it does seem the pin is pulling down to the screw when running.

In the last chapter of the book on the 850 Edelbrock, it says you may need to put smaller idle tubes for a more mild engine, this engine sounds like it has a cam, but I don't know what it is.

I was thinking of turning the idles crews in all the way to see what happens, they are about 2 1/2 turns out right now.

Also, when I bought the carb, the guy said it had been sitting in the box about 4 years, and had only been run on his car about a dozen times, it did look pretty new.

Oh yeah, the exhaust stinks, but then again I'm used to fuel injection with cats on my 99 Corvette, so that may just be the way a carbed, no cat engine smells?

1965C-10:


This is when I bought it in 2009, I just put the truck back on the road May 2011 after doing a frontend rebuild, power disc brake swap, power steering swap.

So, it really sat for about 6 years since the previous owner ran it, until I started running it, I did not open it up or anything, just put a new base gasket, and turned the idle screws to 2 1/2 screws CC, and set the idle speed to my liking, and run 12 volts to the choke.

1965C-10:
Also, I'm sure it still has the stock fuel filter in it, but I added and new inline fuel filter to it just to play it safe since I was concerned about the gas in my tank being nasty for sitting a long time, would the 2nd filter be bad for it?

429bbf:
mike, nice carb id like to have it .id start with a by taking it apart and measuring every thing and buy a sr kit from cliff.if the engine is pretty stock id set it up with receipe 1.if cliff chimes in he can tell you just how to get it right the first time.i tuned on quads for 30 years and never got them right till i read cliffs book.now they run like swiss watches .dean

Cliff Ruggles:
Those carburetors have a very generous idle calibration, and the large .149 inlet seat, and a crappy accl pump. 

I would rebuild it with one of our kits, and install smaller idle tubes at the same time, to provide more control of idle fuel for your application.  Unless you have a huge cam in the 396, it's not going to like the calibration of the 1910 unit......Cliff

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