@@ Line 1: / Line 1: @@
-----
+{{youcanedit}}
 =Introduction=
 This article is written with the intention of informing, guiding and assisting the first-time builder who has never dealt with a carburetor before. It merges detailed, step-by-step directions, complete with images, links to online  and print resources, and a multitude of helpful tips and pointers collected from the members of [http://www.Hotrodders.com Hotrodders] forum, all of them in their own words.
 The article is also meant to complement the rebuild guide books available (Ruggles and the Roe books are the two mentioned most often), shedding extra light on any topic or procedure that may require further explanation. In the future, as time allows for updates, the article will site sections and passages from related books to help the reader follow along with ease.
 Although the article specifically deals with the Rochester Quadrajet 4MV model, the information found here is useful for working on other Rochester 4 barrel models as well.
 At times, the reader may encounter differing viewpoints, especially when dealing with certain repair options. It is up to the reader to decide which method works best. If confusion persists or further advice is needed, it is highly recommended that the reader visit the [http://www.hotrodders.com Hotrodders] forum and ask for assistance from fellow members.
 ----
+=Planning and organization=
+===A. Becoming familiar with the carburetor===
-=Planning and Organization=
-===A. Becoming Familiar with the Carburetor===
 ----
 If you have never dealt with a carburetor in your life, it is important to familiarize yourself with the various components. Please refer to the '''''Books/ Guides/ Websites /Multimedia''''' section below for helpful materials.
+=====Books/guides/websites/multimedia=====
-=====Books/ Guides/ Websites/ Multimedia=====
 :'''''"How to Rebuild and Modify Rochester Quadrajet Carburetors"''''' by Cliff Ruggles is a frequent recommendation by the members of [http://www.hotrodders.com Hotrodders] forum. It is a highly-reviewed book and the author is considered a leading authority on Quadrajet carburetors.
 :In addition to his book, Cliff Ruggles also maintains a website ([http://www.cliffshighperformance.com/ Cliff's High Performance]), with a forum dedicated to discussing carburetors.
 :Another highly reviewed title is '''''"Rochester Carburetors"''''' by Doug Roe / Bill Fisher.
 :Other titles devoted to Rochester Quadrajets are also available from retailers such as [http://www.barnesandnoble.com/ Barnes and Noble], [http://www.amazon.com Amazon], [http://www.ebay.com eBay] and its sister site [http://www.half.com Half.com].
 :If you are a more visual learner, please check out Video series by [http://www.youtube.com/user/alpheus1975 alpheus1975] on [http://www.youtube.com YouTube]. Newer, improved videos may be available by other authors as well so be sure to check for current material.
+=====Carburetor identification: Locations and  decoding=====
-=====Carburetor Identification: Locations and  Decoding=====
 :Once it has been determined that your Rochester Quadrajet carburetor requires a rebuild, the first thing to do is to locate the identification number. The identification number will help with ordering the correct set of parts or a rebuild kit. The number is usually found either as a tag or as a stamping in the body on the driver-side of the carburetor, running vertically up and down.'' ^1'' Should a need arise for decoding, please see the following article for further information and assistance: [[Rochester Quadrajet Carburetors: Identification and Decoding]]
 [[File:Carburetor_Identification_Number.jpg|thumb|center|750x250px|ID Number 17057525 APP 3356]]
 ===B. Parts===
 ----
 *Carburetor Rebuild Kits: Available through various manufacturers. For user experiences, please check out the ''Hotrodders'' forum thread, ''[http://www.hotrodders.com/forum/q-jet-rebuild-kit-210485.html#post1502078 Q-jet rebuild kit]''.
 *Individual Parts: Please refer to the '''''Procedures''''' section.
 *Sellers / Sources: <br  />[http://www.cliffshighperformance.com/index.html Cliff's High Performance] <br  />[http://quadrajetparts.com/index.php QuadrajetParts.com] <br  />[http://www.carburetion.com/index.htm Carbs Unlimited] <br  />[http://www.carbkitsource.com/ The Carburetor Doctor]
@@ Line 65: / Line 41: @@
 ===C. Tools===
-=====Parts Organizer=====
+=====Parts organizer=====
 :The carburetor is held together and in place with fasteners of various sizes. There are also a lot of small parts on the inside of the carburetor body. It is very important to use some sort of a parts organizer to separate everything. It does not have to be anything fancy. You can use things usually found around the house. Egg cartons work well, and the top can be closed to keep the parts in place. Old ice cube trays can also be used.
 :Other ideas suggested by [http://www.hotrodders.com Hotrodders] forum members:
 :''<blockquote>"The muffin pans work great. As a technique, I use two pans and label each "bin" and place the old part in one bin and at the same time, I place the new part in the other pan. Most kits are 'generic' so this is the best time to pick out the part that matches the removed part and set the residual parts aside. " ^3'' - '''''trees''''', forum member.</blockquote>
 :''<blockquote>"a cupcake pan works really well for organizing parts ... i also use an old silverware tray for parts" ^'' - '''matts37chev''', forum member.</blockquote>
@@ Line 85: / Line 59: @@
 <br style="clear: both" />
 Having a complete 115 piece drill bit index is a very handy tool to have- it allows making, measuring and gauging holes as well as setting Holley and other float levels where the bit can be fit under the float, or above it when setting the float drop.
 :*Socket wrench set
 :*Open-end wrench set
 :*Screwdrivers - various sizes
 :*Hammer
 :*Parts cleaning tray - Keeps the parts in place and also keeps any chemicals from spilling in undesired places.
 :*Parts cleaning brush - Used for cleaning off most of the grime and gunk off the carburetor parts after dipping them.
 :*Wire brush - Used for scrubbing off the tough spots after dipping the parts.
 :* #7 drill bit ''^4''
 :*Shop towels / rags
 :*Compressed air - For blow-drying carburetor parts after cleaning and washing them.
 :*Carburetor stand - used to keep the carburetor in place while working on it. It is useful for testing out all linkages before re-installation. You can buy one from any performance auto parts supplier or build your own. For ideas, check out this [http://www.forabodiesonly.com/mopar/showpost.php?p=498702&postcount=2 post] on [http://www.forabodiesonly.com/ For A-Bodies Only]
 <blockquote>''"I built a stand to hold the carb body so that I could functionally check all the linkage and clearances on the butterflies. It also makes assembly of the metering rods much easier. You can buy a stand, but hard to justify unless you plan on rebuilding lots of carbs. My Q-Jet book told me how to build the stand and it has been invaluable over the years."'' - '''''trees''''', [http://www.hotrodders.com Hotrodders]forum member.</blockquote>
 =====Chemicals=====
@@ Line 131: / Line 92: @@
 :*Carburetor cleaner spray - A few cans should be kept on hand.
+=====Taking photos=====
-=====Digital Cameras=====
 <blockquote>''"Disassembly tips? Take lots of close up, well lit pictures of the linkages." ^'' - '''''cyclopsblown34''''', [http://www.hotrodders.com Hotrodders] forum member.</blockquote>
 :A digital camera with a good flash will come in very handy. There is no need for a top of the line camera. Even today's cellphones with 5 megapixel or higher rating are more than sufficient. Become familiar with the camera you have and use it to photograph everything, from every angle, every step of the way. If you ever get lost during the rebuild process, you only need to flip through a few pictures to get back on track.
 :The things you will need to keep an eye on are protecting the camera from grease and dip, and the battery life. Battery life varies from camera to camera, as well as the age. Make sure to keep the camera fully charged and as often as possible. If you keep the charger plugged into a socket close to where you are working, charging the battery during down time is a breeze.
+=====Step-by-step documentation tips=====
-=====Step-By-Step Documentation Tips=====
 :Remember, with a digital camera, there are no limitations on how many pictures you can take because you are not using film. And when you upload your pictures, be sure to organize them into folders and sub-folders with useful categories for titles, i.e. ''Removal'', ''Dis-assembly'', etc. Extra effort here will save a lot of time and headache in the future when you have to go through the photos to match up the right parts or bolts.
 [[File:Image Organization.jpg|frame|center|An example of how to organize photos into helpful folders on the computer.]]
 :As you organize photos, be sure to delete an "extras" or unusable shots. You can do this either as you are taking pictures or when you upload them to your computer. This will further eliminate clutter and you will only have to go through pictures that are useful. It is also a good idea to use a photo editor for processing images. Quick cropping, sharpening and brightening of photos will turn many mediocre shots into useful images. For a free and easy to use photo editor, [http://www.photoscape.org/ps/main/index.php Photoscape] is recommended. [http://www.gimp.org/ GIMP] is another one, but with more sophisticated features.
 :If you prefer, keep written notes as you go along. A picture is a thousand words, but a handy set of notes can be quite valuable too. If you have printed out this article, use the empty spaces to jot notes as needed. This way, everything you need will always be in on place.
 ===D. Safety===
 ----
 Safety is always a top priority in any project, especially those which require tools and chemicals. Be sure to work in a place that can keep out children and animals. When using chemicals, it is a good idea to warn anyone nearby of fumes. Please refer to [[Health and safety in the shop or garage]] for helpful tips and ideas.
 =====Ventilation=====
 :Ventilation is very important when working with chemicals. For the rebuild, you will be using the Chem-Dip, which has strong fumes. If working inside the garage or other indoor places, be sure to keep the windows and doors fully open. If available, employ a large exhaust fan to suck out the fumes.
 =====Lighting=====
 :Carburetor rebuilds deal with small parts, precise measurements and various tools and chemicals. Proper lighting is key to getting the job done safely without errors or hazardous mistakes.
 =====Protection=====
@@ Line 178: / Line 123: @@
 #Clothing
-----
+==Procedures==
-=Procedures=
 ''The Procedures section is currently under construction. Please refer to the threads and links under  '''Recommended Resources''', which will serve as the basis for this section''
+===A. Before you begin: Preparation===
-===A. Before You Begin: Preparation===
-----
 The following tips will save you time, avoid any unnecessary stress, and keep you working safe.
 #Make sure you are now familiar with carburetor components, as well as the overall process of rebuilding a carburetor. Do not proceed until you are ready.
@@ Line 200: / Line 135: @@
 #If you are a visual learner and can keep a laptop or other computer device with internet access nearby, you can follow along with the video series by [http://www.youtube.com/user/alpheus1975 alpheus1975] on [http://www.youtube.com YouTube], or any other video/multimedia resource you find helpful.
+===B. Prior to removal: Documenting and disconnecting===
-===B. Prior to Removal: Documenting and Disconnecting===
-----
 :Begin by taking pictures of the carburetor as its sits on the engine. Photograph from every possible angle, including:
 :*Front
@@ Line 217: / Line 148: @@
 :*All linkages
 :*All hoses, including where they originate from if possible ''(i.e. hose from vacuum advance canister to carburetor)''.
 :Once the pictures have been taken, using masking tape and a pen or marker, label every hose. Take pictures of every hose, with the label clearly marked and showing in the images.
 [[File:Carburetor Hoses Marked.jpg|center|thumb|750x250px|Hoses marked and labeled.]]
 :At this point, disconnect all hoses and linkages and carefully move them out of the way. Some of the common connections include:
@@ Line 236: / Line 165: @@
 :The carburetor is held in place by two long bolts visible on top of the air horn and either two nuts or two bolts on the back of the carburetor on top of the throttle cable bracket. Loosen these up, remove them, and set them aside in the parts organizer.
 ===C. Removal===
-----
 Try lifting the carburetor up slowly, making sure nothing else needs to be disconnected or removed. Once it clears the intake manifold, take it out of the engine bay and turn it upside down over a container to catch the fuel that will fall out. Skipping this step can result in a large puddle of fuel on the workspace.
 Place the carburetor on a stand if you have one. Keep a couple of shop towels or rags around it in case any more fuel spills out during dis-assembly.
+===D. Dis-assembly===
-===D. Dis-Assembly===
-----
 '''''Note:''''' Be sure to have your parts organizer near by at all times. Also, take the time to match up the new parts with the old ones as soon as you remove them. If something doesn't match up, return it for the right part before beginning re-assembly.
+====Accelerator pump actuator====
-====Accelerator Pump Actuator====
 <blockquote>''"Something you'll need to know for disassembly, on the driver side front, the accelerator pump, there is a fulcrum the actuator arm rocks on, there are I think two holes in it, note where the throttle linkage attaches to it. The instruction sheet will probably tell you where to attach it depending on which engine too. To remove the lever, just use a small diameter punch and push the roll pin out of the fulcrum point and lift the lever off. I did several Q-jet rebuilds, all the while cursing the way I had to twist the top of the carb to remove it, once I realized there was a removable pin, it made disassembly and reassembly a breeze." ^'' - '''''cyclopsblown34''''', ''[http://www.hotrodders.com Hotrodders] forum member.''</blockquote>
+====Choke and linkage====
-''More Coming Soon.''
-====Choke and Linkage====
 '''''Cautionary Note:''''' It is very important to take good, well-lit, close-up pictures of the linkages before dis-assembly. The choke linkage has several parts that must line up in a specific way during re-assembly or they will not work.
-''Coming soon.''
 ====Air Horn and Metering Rods====
-''Coming soon.''
-====Float/ Fuel Bowl====
+====Float/fuel bowl====
 *Accelerator pump and spring
 *Gasket
@@ Line 287: / Line 192: @@
 *Fuel Filter Housing
+====Base/throttle body====
-====Base/ Throttle Body====
 *Idle mixture screws
 *Gasket
+====Trouble spots====
-====Trouble Spots====
 Please keep an eye on the following areas during dis-assembly and rebuild.
@@ Line 303: / Line 204: @@
 [http://www.cliffshighperformance.com/services.html Ruggles] and [http://quadrajetparts.com/rochester-quadrajet-parts-quadrajet-inlet-fittings-service-fuel-inlet-thread-repair-heli-coil-installation-inlet-carburetors-pr-356.html Gessler] will do this operation, cost varies. If using a helicoil repair is not possible for whatever reason, there are self tapping fuel inlets available, like from [http://www.gesslerheadporting.com/gesslerheadporting/ghp.nsf/822dcaaaa26c6da985256dd80023623d/a661ef84a4b8f9f6852574fd005f54f8!OpenDocument Gessler].
-=====Loose Power Piston Retainer Cap=====
+=====Loose power piston retainer=====
 According to Hotrodders forum member '''''TommyK''''':
 <blockquote>''"It is not uncommon for the retainer to fail to positively secure the PP in its hole in and of itself. The solution is to take a chisel and gently stake the edge of the hole in one or two spots against the retainer." ^''</blockquote>
@@ Line 313: / Line 214: @@
 [[File:GHP-Q3622-PP RETAINER BUSHING SPLIT.jpg|thumb|250px|center|Replacement power piston retainer bushing; split type.]] <br style="clear: both"/>
+=====Leaking float bowl well plugs=====
-=====Leaking Plugs / Main Wells=====
 A common problem on the early Q-jets especially, is leaky main wells. The 'cure' for this has long been to use JB Weld, etc. to seal them over. This is just a stop-gap measure, I have seen personally how the epoxy will degrade over time and quit sealing as it did at first.
@@ Line 323: / Line 223: @@
 [[File:Quadrajet- Detriorated Epoxy on Wells.jpg|thumb|center|450px|Deteriorated epoxy on a Quadrajet 4MV]]Please see Post #76-78 and #90 on [http://www.hotrodders.com/forum/1977-chevy-k20-engine-suffers-hesitation-power-loss-when-drive-213757-6.html page 6] of the thread [http://www.hotrodders.com/forum/1977-chevy-k20-engine-suffers-hesitation-power-loss-when-drive-213757-6.html ''"1977 Chevy K20: Engine Suffers from Hesitation/Power Loss When In Drive"'']
+=====Shaft bushings=====
-=====Worn Shaft Bushings=====
 The primary bore of the aluminum throttle plate is where the majority of wear is going to be. The shaft has an anti friction coating (the green colored material seen on the shaft and some linkages) but even so, the shaft wears directly on the aluminum of the throttle plate, so the primary shaft will also show some wear- but being steel on aluminum, the shaft wear is going to be much less than seen in the bore. There are bushing kits to fix this if it's worn too much.
@@ Line 348: / Line 247: @@
 The secondary throttle shaft do not need bushings. If the secondary shaft/throttle plate bore is that bad, the rest of the carb is likely worn badly; another core or at a least another throttle plate should be considered.
+=====Cleaning orifices=====
-=====Cleaning Float Bowl Orifices=====
 Please see posts numbers 23 through 28 on page 2 in the thread ''[http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558-2.html Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level)]''.
+=====Throttle blades=====
-=====Throttle Blades=====
 Check the base plate to be sure the throttle blades are exactly 90° when wide open. There are some who believe having the secondary throttle blades go "over center" helps with A/F distribution in some cases using certain intake manifolds. While this may be true, until you have a good grasp on the engine tune, and unless the plug readings indicate a need for this, keep them at 90°.
 The linkage adjustment is fairly easy to do, it only takes a pair of pliers and a bit of patience to get them set perfectly.
+=====Airhorn warpage=====
-=====Airhorn Warpage=====
 The warpage of the air horn is discussed in Ruggles' book. For additional discussion, please see posts 49 through 53 in the thread, ''[http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558-4.html "Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level)"]''
+=====Cleaning idle tubes=====
-=====Clogged Idle Tubes=====
 The procedure for removal, cleaning and re-installation is covered in Ruggles' book (chapter 5, "Rebuilding the Carb", pages 77-78). It is also discussed on the thread ''[http://www.hotrodders.com/forum/1977-chevy-k20-engine-suffers-hesitation-power-loss-when-drive-213757.html "1977 Chevy K20: Engine Suffers from Hesitation/Power Loss When In Drive"]''  ([http://www.hotrodders.com/forum/1977-chevy-k20-engine-suffers-hesitation-power-loss-when-drive-213757-5.html page 5], post # 53, 58, 59).
 ===E. Cleaning===
 ----
+=====Soaking the parts=====
-=====Soaking the Parts=====
 '''Cautionary Note:''' According to [http://www.hotrodders.com Hotrodders] forum member '''''trees''''':
 <blockquote>''"Soaking all metallic parts is the way to go but using small brushes lightly is a good ideal. Do not soak non-metallic items." ^''</blockquote>
+=====Cleaning with brushes and wires=====
-=====Cleaning with Brushes and Wires=====
 '''Cautionary Note:''' According to [http://www.hotrodders.com Hotrodders] forum member '''''trees''''':
 <blockquote>''"You also need to use the correct size wire to run through all the jets and orifices. Be careful not to force the wire and score the surface." ^''</blockquote>
 ====="White Stuff" Build Up=====
 For information on the ''"white stuff"'' that can build up on carburetor castings, please see the discussion on the ''Hotrodders'' thread, [http://www.hotrodders.com/forum/quadrajet-211629-3.html '''''Quadrajet'''''].
+=====Drying the parts=====
-=====Drying Off All the Parts=====
 '''Cautionary Note:''' According to [http://www.hotrodders.com Hotrodders] forum member '''''trees''''':
 <blockquote>''"One last rinse with the cleaner and blow dry everything. Make sure you use eye protection for this because the solvent can do serious damage!" ^''</blockquote>
-''More Coming soon.''
 ===F. Rebuilding===
 ----
 Before beginning the rebuild, be sure all potential issues listed in the '''''Trouble Spots''''' section have been inspected and addressed.
-=====Base/ Throttle Plate=====
+=====Base/throttle plate=====
 '''Note:''' Sometimes the Q-jet base plate may be missing a screw or two (there are only two on most carbs; three at the most). While the base plate is "helped" being held on by the two long front intake manifold mounting bolts and the two long screws at the rear of the carb, it's still a good idea to replace the missing screws. Just be sure to not over tighten these long bolts. If they're over tightened, it can warp the carb permanently.
+=====Float/fuel bowl=====
-=====Float/ Fuel Bowl=====
 :# Ball
 :# Seat and Needle
@@ Line 418: / Line 292: @@
 :# Power Piston and Rods
 :# Accelerator Pump
 '''Note:''' When removing the accelerator pump arm roll pin, place a ~0.050" feeler gauge (or similar thickness material) behind the accelerator pump lever pin, so when you drive the pin towards the air horn lip it doesn't butt tightly against it; instead there's room to get a thin straight blade screwdriver in behind it to lever the pin back into position.
+=====Air horn=====
-=====Air Horn=====
 :# Metering Rods
-''More Coming soon.''
 =====Linkages=====
@@ Line 435: / Line 302: @@
 ::Installing the ''"three hole"'' key will prove challenging. ''"Fishing"'' method works best. be sure that the accelerator pump has already been installed before installing the linkage and key.
 :*Throttle linkage
-''More coming soon.''
+===G. Re-installation===
-===G. Re-Installation===
 ----
-''Coming soon.''
 '''Cautionary Note:''' Tighten the carb to the thick insulator-type gasket evenly but not too tightly. Because the gasket of that type has a lot of give to it, it can cause the base plate to warp- sometimes enough to cause the throttle shafts/blades to bind.
 '''Cautionary Note:''' According to [http://www.hotrodders.com Hotrodders] forum member '''''cyclopsblown34''''':
 <blockquote>''"That nut on the backside of the carburetor base plate, do not overtighten it. Use a thread sealant tape or paste on it and don't wrench down hard on it, the casting is thin and will crack if over torqued. you can pretty much get it tight by feel, the sealant allows you to tighten it with less torque and still have a good seal." ^''</blockquote>
-===H. Tuning===
+==Tuning==
-----
+===Idle discharge ports===
-''Coming soon.''
+The idle discharge ports that are controlled by the idle mixture screws can be anywhere from around 0.050" to 0.080" diameter. If you find a lean idle condition that doesn't seem to respond to turning the screws CCW, you can gauge the port size using your small numbered drill bit index, then enlarge it one size at a time until you regain control w/the screws.
+This is providing that the throttle plates are not open too far due to a large cam- which will over-expose the transfer slot, just like on a Holley. The cure for that is the same as you'd do w/a Holley- start by using more ignition advance. This allows the primary throttle blades to be closed down some to lower the idle speed, which increases due to the advanced timing. Often, this is all that's needed, so be sure to do this FIRST, then enlarge the ports only if still needed. Normally, going larger than 0.0100" isn't needed and if the idle screws are still not responsive at this size, the problem lies elsewhere- like needing idle bypass air (or more bypass air).
-'''Tuning Tip:''' The idle discharge ports that are controlled by the idle mixture screws can be anywhere from around 0.050" to 0.080" diameter. If you find a lean idle condition that doesn't seem to respond to turning the screws CCW, you can gauge the port size using your small numbered drill bit index, then enlarge it one size at a time until you regain control w/the screws.
+===Power piston springs===
+A power piston spring allows the power piston (aka "PP") to behave like a Holley power valve (or "PV"), that is, the enrichening system is controlled by the amount of vacuum the engine is producing- which is also an indication of how much load the engine is under. More load = less vacuum. Less vacuum = more enrichment, all else being equal. PP springs are seldom mentioned when Q-Jet tuning is being discussed, but need to be addressed just like if it were a Holley PV. The same principals apply, as far as tuning for low vacuum cams, etc.
-This is providing that the throttle plates are not open too far due to a large cam- which will over-expose the transfer slot, just like on a Holley. The cure for that is the same as you'd do w/a Holley- start by using more ignition advance. This allows the primary throttle blades to be closed down some to lower the idle speed, which increases due to the advanced timing. Often, this is all that's needed, so be sure to do this FIRST, then enlarge the ports only if still needed. Normally, going larger than 0.0100" isn't needed and if the idle screws are still not responsive at this size, the problem lies elsewhere- like needing idle bypass air (or more bypass air).
+At high vacuum, the vacuum exceeds the PP spring rate and the needles are pulled down into the main jets, leaning the fuel/air mixture. Conversely, when vacuum drops, like when under a load or the accelerator pedal is whacked WFO, the PP spring rate exceeds the pull from the engine vacuum, which allows the spring to lift the needles up to their smaller diameter, or "rich" position.
+If a “medium” PP spring = a Holley 6.5 in/Hg, a "soft" PP spring (allows enrichening to come in at a lower vacuum) would be like a 3.5 Holley PV; a “stiff” PP spring = a Holley PV of, say, 8.5 in/Hg. Longer duration cams will “like” a softer PP spring.
-----
+Below is an image showing a variety of different springs, another shot shows three different types of power piston. The springs vary in length, coil diameter and wire diameter (0.012"- 0.020" in the collection below, as an example).
+{|
+|[[File:Power piston springs 002.jpg|400px]]
+|[[File:Power piston springs pistons.jpg|400px]]
+|}
+Edelbrock has some Q-Jet tuning parts; they show only 4 different PP springs, but they only come in a "Race Calibration Kit" that contains a selection of main jets and rods, secondary rods, hangars, PP springs, high flow needle and seat and an accelerator pump. There are also other suppliers of PP springs and other various tune up and repair parts; see the links below this section.
+*GM power piston spring p/n 7037305 is set for a tip in point of ~6 in/Hg, and would work well w/a high vacuum, smooth idling and/or wide LSA-type cam.
+*GM PP spring p/n 7036019 has a tip in of about 8 in/Hg.
+*GM part #7029922 is a rather weak spring that was OE for HO Pontiac engines from the early ‘70s. It delays enrichment until vacuum drops to ~3 in/Hg. This spring will work with durations >/= 230 degrees @ 0.050” lift.
+GM/Delco PP springs come in packs of 10 springs unless you can talk your way into buying less.
+Another seldom-mentioned adjustment that can be made to a Q-Jet, is the travel limiter for the PP. It can be adjusted (screwed) up or down to allow the primary needles to sit higher or lower at max vacuum, and is another tuning aid when dealing w/long duration or overlap cams. This adjustment is referred to as the APT or "adjustable part throttle" setting.
-=Recommended Resources=
+It is shown w/a red arrow pointing to it, below.
+[[File:Pp adj 001.jp]] <br style="clear:both"/>
-===A. Wiki Articles and Knowledge Base Links===
+===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]
+==Recommended Resources==
+===A. Wiki articles and Hotrodders Knowledge Base links===
 ----
 ;[http://www.crankshaftcoalition.com/wiki/How_to_rebuild_automotive_carburetors '''''How to rebuild automotive carburetors''''']
 :Wiki article intended to provide information on rebuilding a carburetor. ''(Article remains under construction as of June 22, 2011)''.
 ;[http://www.crankshaftcoalition.com/wiki/Quadrajet '''''Quadrajet''''']
 :Wiki articles that provides background information, history, and variants of the Quadrajet carburetors, as well as the pros and cons of using one.
 ;[http://www.hotrodders.com/kb/carburetor-articles-2 '''''Carburetor Articles''''']
 :Selection of articles linked to on Hotrodders' Knowledge Base.
+===B. Hotrodders forum threads===
-===B. Hotrodders Forum Threads===
 ----
 ;[http://www.hotrodders.com/forum/rochester-quadrajet-4mv-carburetor-removal-disassembly-rebuild-rookie-level-190558.html '''''Rochester Quadrajet 4MV Carburetor: Removal, Dis-Assembly, Rebuild (Rookie Level)''''']
 :The thread discusses the removal, complete tear-down, cleaning, rebuild kits, rebuild process, re-installation, and tuning of a Quadrajet 4MV model. The discussion includes detailed, step-by-step pictures, various links to online resources, and lots of helpful advice from forum members.
 ;[http://www.hotrodders.com/forum/restoring-tuning-quadrajet-201455.html?highlight=quadrajet+4mv '''''Restoring and tuning a quadrajet''''']
 :Covers base plate-mounted APT adjustment. Also see article below.
 ;[http://www.hotrodders.com/forum/quadrajet-flooding-bad-200583.html?highlight=quadrajet+4mv '''''Quadrajet flooding - BAD''''']
 :Discusses sudden flooding and float issues.
 ;[http://www.hotrodders.com/forum/q-jet-power-piston-springs-160724.html '''''Q-Jet Power Piston Springs''''']
 :Thread offers information on power piston springs in relation to tuning a Rochester Quadrajet. Information provided on spring ratings, manufacturers and part numbers*.
 ;[http://www.hotrodders.com/forum/4mv-quadrajet-4bbl-choke-linkage-missing-need-diagram-showing-how-188110.html '''''4MV Quadrajet :4bbl choke linkage missing need diagram showing how to mount on carb''''']
 ;[http://www.hotrodders.com/forum/rockester-quadrajet-tuning-tips-200058.html?highlight=quadrajet+4mv '''''Rockester QuadraJet Tuning Tips''''']
 :Covers adjusting carburetor and timing settings for optimal performance.
 ;[http://www.hotrodders.com/forum/quadrajet-high-idle-warm-engine-197099.html?highlight=quadrajet '''''Quadrajet, high idle with warm engine''''']
 :Throttle return springs and choke unloader issues.
+===C. Other online resources and digital media===
-===C. Other Online Resources and Digital Media===
 ----
 ;[http://www.scribd.com/doc/49167713/Rochester-carb Delco Carburetor Models 4M, 4MC, 4MV Service Manual]
 :Complete factory service manual.
 ;[http://vetteprojects.com/kstyer/quadrajet.htm '''''Rebuilding and adjusting the Quadra-Jet Carburetor'''''] by Ken Styer.
 :A step-by-step article with photos on rebuilding a Quadrajet. Covers electric chokes and tamper-resistant plugs.
 ;[http://vetteworks.tripod.com/qjet.htm '''''Rochester 4MC, 4MV, M4MC, and E4ME Carburetors''''']
 :Article provides information on rebuild process and carburetor adjustments.
 ;[http://www.digitalcorvettes.com/forums/showthread.php?t=88376 '''''Quadrajet Info by Lars''''']
 :A detailed document written by Lars Grimsrud on troubleshooting and tuning Quadrajet carburetors.
 ;[http://www.newagemetal.com/pages/Chevrolet/75/index.htm '''''1975 Chevrolet Carburetor Parts List Sheets''''']
 :Offers exploded view of Rochester Quadrajet carburetors.
 ;[http://home.earthlink.net/~quadrajets/quadrajet_airflow_ratings.htm '''''Quadrajet Air Flow Ratings'''''] by GRZ
 :Discusses the Quadrajet's air flow ratings from factory, and tips on modifying or replacing the air valve shaft, the secondary metering rods and hangar, and the cam follower for maximum air flow.
 ;Video series by [http://www.youtube.com/user/alpheus1975 alpheus1975] on [http://www.youtube.com YouTube]
 :Gives a detailed, step-by-step demonstration of disassembling and rebuild a Quadrajet carburetor. Although the carburetor he uses is a marine application, the procedure is the same.
-=====Online Sources for Identification and Decoding=====
+===Online sources for identification and decoding===
 :''[http://www.cliffshighperformance.com/tech_carb_ID_2.html Carburetor Designation/Identification]'' - Covers casting designations and identification numbers. From Cliff Ruggles' [http://www.cliffshighperformance.com/index.html Cliff's High Performance].
 :''[http://www.recarbco.com/technical/rochester/qjet.html Recarbo Fuel Systems]'' - ''"This guide is just that: a guide. It is not set in stone, because it is a documented fact that Rochester didn't follow these rules 100%."''
 :''[http://www.carbkitsource.com/carbs/numbers/Rochester/Quadrajet/index.html Rochester Quadrajet Carburetor Numerical Index]'' - From [http://www.carbkitsource.com/ "The Carburetor Doctor"].
+==References==
-----
-=Reference=
 ''^1'' [http://www.recarbco.com/technical/rochester/qjet.html Recarbo Fuel Systems]
-----
 ''*Manufacturers and/or part numbers may no longer be current. Members are urged to add updated information if and when they come across it.''
 ''**For current availability, edition and pricing, please visit an online book retailer such as [http://www.amazon.com Amazon],[http://www.ebay.com eBay], or [http://www.half.com Half.com]. This title is also available through Ruggles' website.''
-=Photos to be used if and where needed=
+===Photos to be used if and where needed===
 [[File:Q-JET BANJO FUEL INLET FITTING ON CARB.jpg|thumb|300px|left|"Banjo" fitting used to make a straight fuel inlet into a 90 degree inlet]]
 [[File:Qjet banjo inlet.jpg|thumb|300px|left|Banjo fitting closeup]]

How to rebuild a Rochester Quadrajet 4MV carburetor

Revision as of 22:30, 16 May 2012

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