Wednesday, September 24, 2014

How to replace a carburetor

Replacing a tired worn out carburetor can be a easy 15 min swap, that delivers performance and fuel economy you may have lost long ago. If it seems like something better left to professionals, have no fear. Here we'll show you have to remove you old one, put on the new and even get
your starting tune done!

Start by removing the air cleaner and pumping the throttle (either inside the car or at the linkage) to remove the fuel left
in the fuel bowls to minimize the spillage on to your engine. You'll know when its empty when there is no more liquid shooting from the nozzles and rather a mist instead.
Next you need to disconnect the throttle linkage (a rod in our case, but maybe a cable in some) and if attached the throttle return springs. Normally no tools are need up to this point.
The springs are soft and the air cleaner is usually head down by a wing but or bonnet screw. From here forward though you'll need a few basic hand tools.

Next to be removed is the fuel rail. I recommend placing a old shirt or rag under the rail to catch and fuel left in the carburetor or the rail. Typically its a hose attachment at the carburetor on a stock vehicle or in a modified one like ours. It's held on by an fitting which can be removed us in a standard wrench.
With the rail removed. The vacuum lines are next. Ours only had the brake booster, but yours may have additional lines for emissions or gauges. Now that the lines and fuel are gone. The last step is the four bolts securing the carburetor to the manifold. Typically these are a 1/2 bolt. Easily removed by a 1/4 ratchet and a small extension. Them lift the carburetor off the intake manifold. If the gasket between the two is hung up. Gentle pulling by hand can sometimes release it from one or the other with out tear in it. I recommend replacement of that gasket but if money is tight it maybe saved as long as it doesn't rip.

Next reverse this process to this point installing the new carburetor.  Everything should fit the same unless your changing from a two barrel to four barrel. In this case some fuel line modifications
maybe necessary depending on your application.

Basic start up tips...
These days carburetors come nearly start up ready and some will run right out of the box. Rather then chance it here's a simple way to ensure you get a good fire up. Depending on your carburetor, you may have 1, 2 or 4 idle mixture screws. Our carburetor has four, one on each corner. Using a screwdriver turn them into the carburetor until it stops. Don't over tighten them, doing so could damage the seat.
A light turn until it stops is all that's required. Once there turn out 2 full turns. This will give you a nice rich mix for start up. Additionally max sure your idle curb speed screw is opened enough to maintain
an idle. Even if its high.

Advanced tuning tips...
With the car running (neutral for manual trans or park for automatic) attach a vacuum gauge to an open vacuum port on the carburetor. The larger the dial the better. On a stock engine you should get a reading of around 15-20 psi of vacuum. The object is to turn each idle mix screw a even but small amount inward until you reach maximum vacuum. This is your idle/cruise speed fuel mix.