sick 454 carb

[thirstycanadian]

I recently bought a 1985 GMC K-35 with a 454.  It has been stored for the past 5 years or so and as can be expected it is running pretty rough after sitting that long.  I've replaced the plugs and wires, but not the distributor cap or rotor or any other ignition components.  Timing has been checked and it is fine.  Aside from a rough idle it seems alright until I place any kind of real load on the engine (like going up a hill, or shifting into 3rd at what would normally be a reasonable RPM).  Once a little load is applied it sputters and stalls out if I keep on the gas.  I think it is drowning itself (it has a very rich mixture - the spark plugs that came out were caked with carbon). Everything is original equipment, Rochester 4 barrel.

I think the carburetor is at fault, but I guess it could be something else in the fuel delivery.  I am trying to decide whether to have the carb rebuilt (rebuilding it myself is a little out of my league at this point), order a new Rochester, or order an Edelbrock (they have a 750cfm that should work).  I was also considering a new intake manifold while I am at it, probably from Edelbrock, but if I go with another Rochester I do not know how well that will work, if I will need an adapter or something.  

This is a daily driver for me (it will be at least, when it is running a little stronger) and I am looking for driveablility and as many mpg as possible (I will consider myself very lucky if I can get 9 or 10).  

I figure you guys will be able to give a little advice on this to point me in the right direction.  I am lacking in the expertise department, but am trying to learn.  I am pretty new to this stuff, but am loving it so far.  

Thanks a lot for any advice.

[Lt.Del]

two words:  fuel pump

The diaphram has dried out.  Your accelerator pump on the carb could also have dried...you can get those very cheap.

Another thing to check is the bowl float and needle.  The valve which allows gas into the bowl could have tarnished in 5 years and may need to be cleaned.  If this is the case it would stick in the up position even though the float is all the way down, indicating an empty bowl of gas. A stuck valve will allow very little gas to come in...therefore, going up hill or under a load, she'll bog down. Same symptoms of a bad fuel pump.   Clogged fuel filter perhaps...i'd change that regardless due to the 5 yr slumber.

You are correct in that it could be the fuel delivery system.


SgtDel

[VileZambonie]

Why did you decide not to replace the cap, rotor and wires? Checking the fuel pump is easy, just pop the line off of the carb and route it into a jar. Crank the engine and measure the volume. 5 years is a long time to sit with old gas. Just rebuild the Qjet, it's pretty easy to do and you'll probably find about a hundred websites that can help walk you through a rebuild. I would never spend $3-400 on a reman q-jet. The Edlebrocks are fine and will run out of the box but usually have a very generic fuel curve. Fuel economy surely won't be there unless you buy a metering and jet kit...

[Lt.Del]

When I threw a new 383 stroker in my 79, i bought a brand new edelbrock qjet for $470 from PAW.  I am glad I did that.  It needed no adjustment and has been "right on" ever since. Choke, cold idle, air mix, low idle, etc all works perfectly.  All I did was bolt it on, hook up the vacuum lines, gas line, throttle linkage, kickdown cable---and she runs great.


Which carb looks better?






SgtDel
   

Edited by: SgtDel at: 4/8/06 9:42 am

[VileZambonie]

Which carb looks better?


Obviously the first one!  

[thirstycanadian]

Thanks a lot for the input.  Much appreciated.

I am going to replace the cap and rotor, haven't had the time lately, and have not yet decided on whether to go with an OE Delco or something else like an Accel.  I will definitely check out the fuel pump and filter.  I am leaning toward the rebuild for the carb, but will likely shop around for a reman or Edelbrock, just to see exactly what is available around here.

Thanks again.