Delta Blower Drive Idler Arm & Accessories

 Delta Blower Drive Idler Arms

The Delta blower drives haven’t been made in about 50 years. There are two different style arms that I am aware of and both were castings. The arm shown to the left was originally used for a 2″ blower pulley. The one to the right, being billet, is more than sufficient for a 3″ setup as well.

The original arm utilized a 9/16 bolt for mounting the idler pulley.

The arm on the right was reproduced from billet stock and is dimensionally close to the original. I say close because the casting has draft angles that makes an exact reproduction almost impossible. This difference can be seen in the small lightening pockets. The standing ribs appear to be narrower compared to the billet. Well, they are at the top and then taper down to the thickness I provide with the billet.

I machine these on a Bridgeport vertical mill with a rotary table – no CNC here. It is time consuming and therefore more expensive than a production run but you will be happy with the results.

I also offer the following options:

  1. Pulley end tapped for your size idler bolt – no extra cost.
  2. Offset arm – If you need the arm offset out to allow for proper belt alignment, I can accommodate. Call
  3. Length of arm – I recently machined a 1” longer arm for a special application. Call
  4. Narrower ribs – If you want the standing ribs in the small pockets to look more like the casting, I can provide whatever you like. The ribs are presently .400 thick – no extra cost.

If you’ve been looking for an idler arm and can’t find one, give me a call.   P/N  Delta   $295


Print this “Word” document and follow the machining steps. Good luck!

Delta Idler Arm machining 


Adapter – Standard Blower Pulley to Delta shaft

Have you noticed Delta blower pulleys are getting harder to find? I’d say so! If you’re into a static display, one pulley will suffice. But, if you’re like me and actually run in competition or on the street, you need a selection of pulleys. To make the selection easier, I offer an adapter to use a standard off the shelf blower pulley with a Delta-like split collar to accommodate the 1.375 shaft. Most of the Delta pulleys were 7/8″ thick at the back. With the modern 1/2″ pulley thickness + my 3/8″ locator, the pulley will move forward 3/8″ but the collar will remain in the same position on the shaft.

The adapter is 3.500” in diameter compared to 2.800” for a Delta split collar. Given the larger diameter there is a limitation on the inside diameter of your pulley in order to tighten the split collar. I am including a long handle 5/16” box wrench and short hex driver for this purpose. Based upon Good Vibrations Motorsports measurements, a 35-tooth pulley (or 4.875” I.D.) is the smallest diameter that can be used and still have room to insert the box wrench and hex driver. By choosing combinations on the Good Vibrations site, the supercharger can be over-driven 23% (35 top / 43 bottom). When choosing a combination of pulleys with this adapter, it would be better to have a larger top pulley for 5/16 wrench clearance purposes. For example, if you were running a ratio of 1:1 you could use either a 35 tooth top and bottom or a 37 tooth top and bottom. In this example, a 37 tooth would provide more wrench clearance since it is larger in diameter  $215

Bottom pulley spacers available in .100 increments from Good Vibrations Motorsports for adjusting belt alignment.


Variation – If you prefer a split collar that more closely resembles the 3-hole Delta, I can omit three holes. It would look like the touched-up photo below. $200


Note on machining: In 2020 a potential customer asked why the adapter was so expensive. As a result, when making another one in 2021, I documented the steps shown in these Word documents. If you would like to make your own, here are the steps. After reading, you may want to order one from me as I will take responsibility for any mistakes.


Standard blower pulley to Delta shaft adapter – Lathe Operation


Standard blower pulley to Delta shaft adapter -Bridgeport


Modification of Standard Blower Pulley to fit Delta Shaft

I can modify any aluminum blower pulley to fit the 1.373 Delta shaft including broaching the 5/16″ key-way.  The shortage of Delta pulleys has necessitated the need for this modification in order to keep the entire setup looking “Delta”.

You can either send me your pulley or I can supply one for the price of the pulley plus an additional $25.

Modification only – $175


Delta Split Collar

How about a split collar for your Delta pulley? There are two configurations.

Split collars also came in a variety of thicknesses, diameters and bolt size for tightening to the shaft.

Early collars utilized a 5/16-18 bolt where the later configuration utilized a 3/8-16 bolt. Note: For nostalgia reasons I use a 2″ wide pulley. The Delta configuration (idler pushes inboard) provides more belt/pulley contact reducing the chances of stripping the cogs off the belt. I’ve run 25% over with the 2″ setup without belt failure.

A dimensional check of the tapped holes on both the .280 and .410 pulleys shows a considerable difference. Neither bolt patterns are on a concentric bolt circle. Thus, the split collar I supply will be an exact duplicate of the original. Or, as an option, send me your pulley(s) and I’ll provide the correct collar. $145

BTW – The early configuration (we’ll call it the 2″ setup) has a shorter 1.373 drive shaft. Before ordering, check the length from the seal in the Delta cover to the end of the shaft. Early = 1.950, Late = 2.400. The early configuration may require a thinner (1″) collar to avoid overhanging the end of the 1.373 shaft.

Run-out: Each collar is checked for both radial and lateral run-out prior to shipping. As assembled with a blower pulley, I am attempting to provide less than .005 at the outer edge of the pulley with my setup which has “0” shaft run-out. It should be noted that if you find excessive run-out, use calipers to check the dimension from the 1.377 bore in the pulley to the outside of the blower pulley tooth in several places. I have found as much as .008 difference on my pulleys. Given a split collar does not center perfectly, you may experience as much as .012 radial run-out. Until recently, I have never checked for run-out and never had a problem on the track so functionally it will still work. Another area to check is shaft run-out. I have seen .005. To eliminate this run-out, the mounting surface to the supercharger will need to be machined. Not a bad idea here since run-out affects the load on the bearing.

If you find your pulley has a different key-way offset than shown above, I can custom make your split collar to fit. Your pulley will be required for this modification to ensure key-way is in the correct position.


Delta Front Cover Bearing and Seal

Call for availability

New bearing for Delta front cover – $72.50 + shipping

New seal – $29 + shipping


PLEASE NOTE – All pieces are fabricated one at a time. The good news – I can customize any order to meet your requirements at little or no additional cost. The bad news – “one offs” cost more than a production run.


Check “For Sale” section for used Delta items