DusterIdiotís Distributor Rebuild/Recurve Tutorial
by Zach "Halfafish" Thomas and Rob "Dusteridiot" Armstrong
The following is a step-by-step description on how to rebuild and re-curve your slant six distributor. The example used for this document is a super-six distributor. The tag number on it is 3874876. This one was made for two years for the super six, in 1977-1978, and two more years for Federal Package 225s in 1979-1980. In many photos a pointer was used to try to show a detail of interest, however some of these arenít as clear as desired so colored arrows were added for better identification.
A tip before starting this project. Donít throw anything away until the project is completed, and maybe not even then. Some parts can be hard to find in any condition and may be worth saving or refurbishing if necessary.† Disassembled parts will be needed to match up to replacement parts. You will need to refer to the original parts to determine your starting point, so adjustments can be made to re-curve for your particular needs. This tutorial is a guide to take the distributor apart, clean, and reassemble it. It does not address theory on how to select parts for your specific build.
The first step is taking out the distributor. Either remove all the plug wires or just remove the entire cap, then remove the vacuum line. Remove the bolt sitting at about 3:00. Donít lose the horse-shoe shaped hold-down bracket. Lift the unit out of the block. Pre-1978 hold-down clamps look different, like a slotted plate. These plates are attached to the distributor, just remove clamp bolt at the block and lift out the assembly.
Note: I find re-installation easier if, before you remove the distributor, you rotate the engine until the rotor is pointing just past 12 o'clock as you are looking at it over the fender. That way you don't have to remember where the rotor was pointing when you put it back in. (Chuck)
Once the unit has been removed from the car, the first step is to pull the wiring harness (green arrow) out of the recess in the dizzy housing (red arrow).
The reluctor (red arrow) is a tight fit on the mainshaft. It needs to be pried off with a pair of flat-blade screwdrivers to remove it. Watch out for the little locator pin (hiding inside) that locks the reluctor to the shaft Ė you will need it for reassembly.
Next out is the advance plate assembly (yellow arrow) with the pickup plate and pickup (green arrows) mounted on it. Before the plate will come out, the vacuum advance pod (red arrow) has to come out. To remove the vacuum pod, remove the two screws going through the housing from the outside. Then lower and rotate the pod until the little round locator pin (blue arrow) pops out of the base plate. Then remove the last two screws from the outside of the housing which frees up the advance plate for removal by lifting it off the main shaft. One of these screws will likely hold a tag with the dizzyís part number. Save this for reassembly.
If necessary, a flat blade screwdriver or other flat pry bar can be stuck into the vacuum advance pod slot, and persuade the advance plate to pop out.
To disassemble the advance plate from the pickup plate, turn the unit upside down and slide off the star spring clip (red arrow). The two plates will now separate.
This is the vacuum advance pod after itís out. Save this to match up the shape and length of the arm on the new pod, as well as for the ID info stamped on the reverse side of the arm. Note the pin (red arrow) that will have to go back into the hole in the advance plate during reassembly.
The drive gear on the bottom of the shaft is pinned in place. Support the end of the shaft on a block and, using a 1/8Ē flat nose punch, drive the pin out.
If the pin is stubborn and wonít drift out (as was the case for this unit), there is a plan B. Set the dizzy on the floor while supporting and protecting the body from the floor with your hand, then whack the gear with a smallish hammer. Donít get heavy-handed with this step as bending or marring the main drive shaft will be the end of this project, forcing you to replace the distributor. A smart rap with the hammer shown did the job nicely.
Remove the bolt holding the mounting plate using a 7/16Ē wrench.
Remove the small flat washer on the mainshaft, right next to the dizzy body.
At this point the main shaft should slide out of the housing. If it is stubborn you may need to drive it out with a punch. In this case the main shaft had a few burrs on it, requiring a light application with a fine-tooth file to clean up the shaft so it would slide out.
Then the shaft was driven out using a 3/8Ē flat nose punch. This shaft was stubborn from being 40 years old and thoroughly gummed up with old grease, varnish, and crud.
The main shaft removed from the housing. Note the little round felt button (red arrow). It came out of the hollow top of the governor (green arrow). Save this for later.
Remove the OEM phenolic washer from the bottom of the housing and save it for later.
The next step, removing the governor (red arrow), is the most difficult due to tight clearance inside the top of the governor. A better photo was attempted several times, but due to the small parts and tight clearance inside the governor, they would not come out in better focus Ė sorry! The following photo shows very clearly how these parts fit, as shown after disassembly. If you look carefully inside the governor, you can see it is secured to the main shaft by a funny looking hairpin c-clip (green arrow). The clip secures the governor to the shaft by compression. Using a pair of needle-nose pliers, grab one of the vertical legs on the c-clip and pull it up and out to remove it. Try not to bend it, as it can be re-used during assembly.
With the parts separated, you can better see how the governor (red arrow) is secured to the main shaft by the c-clip (green arrow). (In this photo there is a spare clip shown, but your dizzy will have just one clip.) The c-clip seats in the groove at the top of the main shaft (blue arrow).
Remove the flat washer (red arrow) from the bottom side of the main shaft, saving it for reassembly later.
Next is removing the weights. Note the difference in the two advance springs. The one on the left is lighter, the one on the right is heavier. If using different weight springs, it makes a difference which way the governor is mounted during reassembly. There is a slot (red arrow) in the base collar of the governor for the rotor that should be installed toward the heavier spring side. If using the same weight springs, clocking of the slot makes no difference.
Lift the weight off the pivot shaft (red arrow) and rotate it to remove the spring from the shaft on the base plate (green arrow). If the spring is stubborn, a dental pick can help wiggle it off the shaft. Remove the advance springs from the weights.
The last piece to remove is the white or orange nylon spacer (red arrow).
All the parts except the vacuum advance pod and the pickup need to go in the parts washer for a good soak. 10-15 minutes should do it. After soaking, each part needs to be cleaned with a wire brush to clean off all the accumulated crud and start the rebuild. Holes need to be scrubbed with a bottle-brush style wire brush (red arrow).
To start the assembly process, make sure your main shaft is in good condition. The first step is to chuck the lower part of the shaft in a drill, then spin it to see if the top of the shaft wobbles. If the shaft isnít arrow straight it will need to be replaced. While the shaft is spinning, also check the base plate (red arrow) to make sure it isnít bent or wobbling.
Next, check the tolerance on the main shaft and the bushing inside the housing. While a dial caliper can be used for both measurements, better accuracy is obtained using a micrometer on the shaft and an inside gauge on the bushing. Measuring at both top and bottom, the shaft is typically between 0.497Ē and 0.499Ē. The shaft should not be unevenly worn. The bushing in the body should measure no more than 0.002 larger than the shaft. Measure the bushing at both the top and bottom of the housing, as it can wear unevenly. If either part is out of spec it will need to be replaced.
This is an inside gauge for measuring the inside of the bushing.
Clean up and polish the surface of the shaft by chucking the top in a drill and spinning the bottom against either fine emery cloth (400-600 grit) or a piece of Scotch-Brite pad.
The inside of the bushing in the housing can be cleaned and polished by wrapping the same fine emery cloth backwards around a pencil, and gently clean the crud off the inside of the bushing. Make sure to clean both the top and bottom bushings.
To start reassembly, lube up the base plate using general purpose grease. Synthetic grease is the best choice.
Part of the re-curve process is to change springs to suit your build. Shown are the three spring weights Ė light, medium (two are shown in the photo), and heavy. Again, sorry for the somewhat fuzzy photo Ė these little buggers would not cooperate with the focusing process.
Install the white nylon spacer (red arrow), then the weights and springs. The easiest way to install the spring is to attach it to the stud on the weight, then hook the other end on the stud on the base plate. Rotate the weight around and slip it on the pivot pin (green arrow). Grease the upper pivot pins for the governor (blue arrows). For this re-curve two medium weight springs were selected.
Install the governor of your choice, and remember, if using springs of different weights, the slot in the base collar should face the heavier spring.
Now comes the fun part. The funny-shaped hairpin c-clip (red arrow) needs to be re-installed on the groove at the top of the main shaft to lock the governor in place. This is done inside the top of the governor, which again is a nuisance due to tight clearance. You will have to finagle the clip over the top of the shaft until it snaps into place in the groove, securing the governor. A couple of very small, thin-bladed screwdrivers, scratch awls or very thin needle-nosed pliers can help with this task.
Reinstall the phenolic washer to the bottom of the housing.
Grease the bottom side of the base plate, and reinstall the metal washer (red arrow) to the bottom side of the main shaft, up against the base plate.
Slide the shaft back inside the housing, and give it a few finger spins to make sure there are no hang-ups or stiff spots.
Reassembly can be made easier by using a junk dizzy housing (red arrow) as a third hand. Set it on the bench upside down, and stick the bottom of the main shaft inside. This holds the unit you are building so you have both hands free.
Lube the bottom side of the pickup plate (red arrow), and set it back into the advance plate (green arrow).
Reinstall the spring clip (red arrow) to secure the two plates together. It only fits one way.
Install the new pickup (red arrow) on the plate. Note there are two slots in the plate (green and blue arrows). The green arrow slot near the pickup is used for proper orientation into the housing. It will slide over a pin inside the housing.
The green-arrow slot in the previous photo is shown here in the correct orientation of the slot onto the pin in the housing. Make sure to get this clocked properly when assembling.
With the plate in place, both screws can be re-installed through the outside of the housing to secure the plate assembly.
Select the new vacuum advance pod of your choice and re-install it into the housing. Grease the pin (red arrow) and, using the same wiggle/twist process used to remove it, slip the advance pod arm through the slot in the body of the dizzy, making sure to get the pin back into the locator hole in the advance plate (green arrow).
Secure the vacuum advance pod with the two screws through the outside of the housing.
Next is to install the reluctor (red arrow). Put the locator pin (green arrow) back into the slot in the reluctor (a blip of grease in the reluctor slot will help hold the pin in place so it doesnít slide out during assembly). When the reluctor is installed, the pin will lock it to the governor by sliding into the recess in the base of the governor (blue arrow).
Using a properly sized deep socket that will clear the governor shaft, start tapping the reluctor into place, checking for proper orientation of the pin (red arrow) into the governor slot.
Seat the reluctor fully, then check that the pin (red arrow) is flush with the bottom of the groove in the reluctor. If not, tap it fully flush using a small flat-face punch.
Check the clearance from the reluctor to the pickup using ONLY a brass gauge (red arrow). Clearance should be .008-.010Ē. Adjust as necessary. Check the clearance at all six lobes; they can be irregular.†
Slide the felt button (red arrow) back into the top of the governor shaft and give a few drops some light oil.
Itís show time! If you are lucky enough to have a dizzy testing machine, give the rebuilt unit a spin and see how your planned advance curves work out for both the mechanical and vacuum advance. Once you are satisfied with your curve, the drive gear can be re-installed. For those re-curving without a testing machine, a process of trial-and-error is needed with your fully assembled dizzy going back into the car, then checking both advances on the dampener timing mark.
The final step is to re-install the drive gear. This rebuild kit was from Dorman, part # 90450, which includes the gear, roll pin, and new washer circled below. Note: the four screws in the photo were already used to secure the vacuum advance pod and the advance plate into the housing. If they need to be replaced they will have to be purchased separately. They do not come in the kit.
The first step to installing the new drive gear is to set the end play of the gear to the bottom of the housing. This is done by installing the new aluminum washer (red arrow) from the kit, along with a cleaned up original washer (green arrow) to set the end play. Note the shaft hole (blue arrow) as it will be referenced in the next step.
When you open your parts kit, the gear will have a single indexing hole (red arrow) already drilled in it. Line this up with the shaft hole (shown in the previous photo). You canít see the shaft hole at the moment because the indexing hole is directly above it. Note the location of the index hole to the shaft hole in terms of length down the shaft. It is likely a new hole will need to be drilled in the gear to EXACTLY match the location of the shaft hole. With a Sharpie, mark the center of the shaft hole, relative to the index hole (shown in the next photo).
Here is the index hole (outlined in black and shown with the red arrow) with the Sharpie tic-mark (green arrow) showing the location of the center of the new shaft hole that will need to be drilled out. Rotate the gear 90 degrees and copy the length of the Sharpie mark of the shaft hole center to the new location (blue arrow) using another Sharpie mark. Drill an undersized pilot hole at the new location, and after confirming the shaft hole is properly lined up, drill the gear to full diameter of the shaft hole.
Remove the extra spacer washer under the gear, leaving the new washer from the Dorman kit in place then replace the gear and drive the new roll pin into the gear and shaft.†
Replace the mounting plant and 7/16Ē bolt.
Re-install the dizzy into your block with your original or new O-Ring, indexing it properly for rotation and secure with the horse-shoe shaped hold-down and bolt (or the older style slotted plate). For those who DO NOT have access to a distributor testing machine, itís time to check your timing advance using a timing light. Adjustments may need to be made with spring size, governor choice, and vacuum advance pod selection to achieve the best curve for your engine.