Editing How to rebuild automotive carburetors

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==Introduction==
Sooner or later, every hotrodder runs into the steps of making induction and carburetion choices while building a performance engine.

For some, it's a tough choice whether to buy a brand-new carburetor, or to find an old dirty one and rebuild it. While buying a new carburetor may be convenient, at $200 and up, the cost can be prohibitive for the budget-minded hotrodder.

On the other hand, a brand-name carburetor rebuild kit may cost as little as $15, and the rebuilt carb, (if rebuilt correctly), will last many years to come.

==Where to start==
Things to consider when choosing your first rebuild victim...

*CFM (cubic feet per minute of air or air/fuel mixture flow), and how much do I '''need'''?  
*[http://www.4secondsflat.com/Carb_CFM_Calculator.html Handy CFM Calculator]
*Spreadbore vs. squarebore -- which one to use?
*Parts and rebuild kit availability

==Holley squarebore carb==
The squarebore 4bbl Holley is a very flexible carb. The design of the model 4150 and 4160 squarebore Holley 4 barrel carburetor has changed very little since its introduction in 1957, and the design and tuning techniques remain basically unchanged as well. They are easy to rebuild, tune, and they have great aftermarket support- in fact a "Holley" carb can be assembled without using any Holley parts. 

[[Image:Holley.jpg‎]] <br style="clear:both"/>

===Fuel transfer tube===
Holley redesigned the fuel bowl transfer tubes and seals used on the 4160, 4150/4175, and 4165 carbs. The old style used a simple rubber O-ring on a transfer tube that had a collar on both ends to secure/locate the O-ring. This design was leak prone and somewhat troublesome.

The new design has a straight tube without the collar and a new type of seal. Details are shown in the photos below. 
{|
|[[File:New seal transfer.jpg|thumb|center|230px]]
|[[File:New tube w seals.jpg|thumb|center|400px]]
|}

===Power valve===
The Holley carb uses a power valve to supply additional fuel when the engine vacuum drops (and presumably the engine load increases). The amount of fuel it supplies is equal to about 7-8 jet numbers. If the rear power valve (if present) is removed, the threaded hole it was in has to be plugged. The jets have to be enlarged 7-8 jet sizes to compensate for the loss of fuel flow it provided.

[[File:Holley pv stamping1 id.jpg|thumb|left|400px| Holley power valve vacuum rating]] <br style="clear:both"/>
 
===Transfer slot===
Baseline the throttle blades to give a transfer slot to look like the image below.

[[File:Holley transferslot.jpg]] <br style="clear:both"/>


==Rochester Quadrajet carb==

[[Image:Rochester.jpg‎]] <br style="clear:both"/>

The Rochester Quadrajet- if properly tuned- is one of the best carburetors available on the market. 

It does have its restrictions though. If you are running a fairly healthy cam profile that has a tendency to limit your vacuum level, the Q-jet power piston spring needs to be selected carefully- just as you would do a Holley power valve. Several companies make different power piston springs for this and jets and metering rods are also available. 

With it's centrally located fuel bowl and the aforementioned power piston, the Quadrajet is a great all-'round carb for street machines and if your doing a restoration on a 60's or 70's muscle car, the carb just can't be beaten. Once tuned, it stays that way, with very little need for upgrades or maintenance. It's true, that it is a little more difficult to rebuild because of it's varied tuning characteristics, but that is the beauty of the beast, you can make it work on just about any engine design. With it's small primaries, you can cruise and get reasonable fuel mileage, or you can kick in those monster secondaries, forget about fuel mileage, and fly.

Most rebuild kits come complete with instructions and application charts for whatever engine your working with, and you can always hold on to the parts you didn't use and use them on your next rebuild or experiment. Several companies make everything you need to tune the Q-jet to fit your needs, or you can buy a new carb from Edelbrock. [http://www.jetchip.com/ Jet Performance] also sells Q-jets in several stages to meet your application. If your running a nice little street engine with a little thump, you can't find a better carb, but if your getting into that monster pro street stuff, you need to look at carburetors that can handle the needs of these engines and/or have a very good understanding of the tuning requirements needed to allow the Q-jet to work well under these conditions.


==See also:== 
*[[How to Rebuild a Rochester Quadrajet 4MV Carburetor]]


===Quadrajet Tuning and Repair Parts===
*[http://www.cliffshighperformance.com/index.html Cliff's High Performance] 
*[http://quadrajetparts.com/index.php QuadrajetParts.com] 
*[http://www.carburetion.com/index.htm Carbs Unlimited] 
*[http://www.carbkitsource.com/ The Carburetor Doctor]  
*[http://www.edelbrock.com/ Edelbrock]

==Carter Carb specifics==

[[Image:Thermoquad.jpg‎]]

==Stromberg Carb specifics==

[[Image:Stromberg.jpg‎]]


==Actual rebuild procedure==
The overall steps are the same no matter what type of carburetor you are rebuilding.
* Identifying what you have
* Purchasing the right kit
* Purchasing some sort of cleaning media
* Rebuilding the carb.

To keep from losing small parts, work over a clean, well lit work space. An old cake pan works well for holding larger parts as the carb is disassembled. Small parts like the check balls, needle and seat, metering rods and springs, etc. can be stored in pill bottles, for example. It is a good idea to take some pictures as you go through the disassembly process, they could come in handy for reference later. Most rebuild kits will have an exploded view of the carb to help with the reassembly as well.

Usually the top (air horn) comes off first, after any linkages are removed like the accelerator pump link on the Q-jet. 

Next remove the float and needle so they don't fall out when the carb is inverted to remove the base plate. Once off you can turn the carburetor over and remove the base plate. It is a good idea to look at the instruction sheet that comes with the kit so you know where all the check balls and other small parts that may fall out go. On Holley style carburetors with removable metering plates and fuel bowls these also need to be removed. Remove all needle valves and rubber parts from the outside of the carburetor.

Try to preserve the gaskets if you can. A lot of the kits come with gaskets for several models of the same carburetor and using the correct gasket is critical. You can use the old ones to match the correct new ones.

Once you have it torn down, all the parts need to soak in your carburetor cleaning solution. Follow the directions for the cleaner that's being used. It's best to not over soak the carb parts that have a dichromate finish so the finish isn't removed. While the parts are soaking, it's a good time to go over the instructions that came with the kit. They will include the adjustments that will need to be performed. A good kit will also have a good exploded view to use as a guide.

Check all the parts to identify what you will be replacing. At a minimum all gaskets, needle and seat and the accelerator pump need to be replaced. Some kits will have additional parts as well. Once the carburetor has soaked, rinse it clean with water and blow out all passages with compressed air.

Re-assemble using the kit instructions and your pictures as a guide.


[[Category:Carburetors]]
[[Category:Engine]]
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