Here are the results of my testing of Scott's new reduced diameter (4.9") water pump pulley.
Both tests were conducted with the engine at idle, radiator fans cycled on, and A/C off.
Front deck lid closed, rear deck lid open, trunk out, engine bulkhead cover removed.
Test vehicle was a '72 Pantera
Engine: '72 351C, 43920 miles (never rebuilt), original cam.
Water pump: rebuilt stock, installed late 80's (more on this later)
Temp. sensor location: front of swirl tank (stock)
Temp. readings also (laser)taken at top water pump outlet pipe, indicated in photos below with red dots.
Temp. gauge:stock Veglia, pictured and marked below.
Radiator: stock '72 original, original position.
Fans: stock (650cfms?)
Factory timing and idle specs: 16*BTDC, 700rpm.
Pulley: 5.5" (stock)
Belt contact w/pulley: unk
Duration: 30 minutes.
Ambient temp:Start: 78.8*F, End:79.8*F
Relative humidity:Start: 37%; End 37%
RPM: 700; w/fans on and A/C off: 700
Max Temp: 192*F
Pulley: 4.9" (reduced diameter)
Belt contact with pulley: unk
Duration: 30 minutes.
Ambient temp: Start:80.1*F; End 85.1*F
Relative humidity: Start: 33%; End: 32%
RPM: no load: 700; with fans on and A/C off: 700
Max Temp: 185*F
Summary of these tests:
The start, with stock '72 everything.......
The red dot at top left is where the temps were laser read, and the miss aligned pulley it had been running with since the rebuilt pump was installed in the '80's
And sure enough, when first installed, the new pulley repeated the same miss alignment.
The fix?.......This .1350 thick fan spacer installed behind the pulley worked great to.....
Bring the pulley out to perfect alignment......ymmv
The Finish, and ready for the second test.
I used the slightly smaller (13/32"x 40-5/8OC)NAPA #7400 belt,and the different (closer) alternator position on it's bracket can be seen
The Gauge, in red is where the stock pulley was indicating when the max temp. was 192*F (Test #1) and in green was where the smaller pulley was indicating when the max temp was 185*F (Test #2)
Overall impression.........This pulley is a lot of bang for the bucks...... I'll take 7 degrees any day at idle, and tomorrow afternoon/evening I'm taking it out for a ride around the valley, ending at a car show and I will have lots of time to watch the temps under all conditions then.