Just installed my 'one off' fabricated clutch fan and thought I'd post the fabrication dimensions, parts used and my reasons for bothering with this.
First, a little project background. After fabbing all the pieces to remount the alternator at the pass side and mount the compressor on the driver side in my Kadett, I found I could not drive both the alternator and water pump off the crank dual rear pulley as is normally done with the alternator on the driver side . . . WP belt path clearance issues with pass side alternator.
Solved this by only driving pass side alternator from crank rear pulley and driving WP and compressor from the crank larger front pulley and using .550" to space WP standard pulley and fan blade forward for crank pulley and compressor clutch fan blade clearance and WP belt path alignment with crank front pulley.
All of this worked fine for my stock, solid mounted, 5-bladed fan. Since front crank pulley is ~13% larger than the stock pulley, the WP and fan are driven ~13% faster. Not necessarily detrimental as far as the WP is concerned, especially down here in Texas, but not a real good solution where the fan is concerned . . . additional drag from higher driven speeds.
Decided to look into mounting a clutch fan to negate the additional drag from the solid mounted fan. Anything you can do to reduce loading on the engine is beneficial from all points of view and especially so with a completely stock engine like my Kadett's. Another consideration was that I wanted to be able to use any stock '68-'74 water pump, not the special '75 'clutch fan' pump with its fixed position, non-removeable drive pulley.
Had a
fan clutch (any 3.0 engined '72-'79 BMW) from a previous 'U-Pick' used parts emporium foray, an ~'80s Opel CIH clutch fan adapter WP pulley and an asymetric five-bladed black plastic fan blade from Germany and a stock WP pulley. These are the four items I used to fabricate my Kadett clutch fan assembly to use with a standard '68-'74 CIH water pump since belt path is altered.
Took three tries to get all clearances right, so I won't bore you with details of the first two attempts. Here's my final version in detail:
1.
Machined the outer fins off the BMW fan clutch to fit inside the Opel CIH fan blade mounting recess. Without those fins, everything fits exactly!
2. Mounted machined clutch to asymetric 5-bladed Opel fan assembly with eight 1mm washers to space fan blade backwards on clutch by 2mm.
3.
Machined entire pulley assembly spot welded to the rear of the Opel clutch fan adapter/pulley off the adapter.
4.
Machined .200" off nose and stepped shoulder of clutch fan adapter for clutch face to radiator clearance.
5.
Enlarged center hole of stock WP pulley to fit around adapter shoulder.
6.
Machined .355" thick spacer to fit around adapter shoulder and adapt pulley to altered belt path.
7.
Mounted spacer and WP pulley on adapter with bolts and welded pulley to adapter mounting flange.
8. Removed bolts and
machined .455" from front of pulley mounting face, pulley mounting face sheet metal is .100" thick.
Mounted
finished clutch fan assembly and road tested it. Initial results very positive . . . woohoo!!
And now for some 'seat of the pants' observations: my stock 1.9 automatic with 3.18 gear . . . floored standing start over same distance end speed:
1. Original stock single crank pulley, fixed 5-blade fan on water pump and stock alternator -
44 MPH
2. Dual crank pulley with alternator drive at same speed as stock and WP and fixed 5-blade fan overdriven by ~13% from larger front crank pulley -
42 MPH
3. Dual crank pulley with alternator drive at same speed as stock and WP and 5-blade asymetric clutch fan overdriven by ~13% from larger front crank pulley -
47 MPH