Not that I'm breaking any new ground here, but I thought I'd bring it up for posterity. Here are my recent attempts to make underdrive pullies work on my '91 Fox 5.0. I used a centech infrared thermometer aimed at the thermostat housing as my gauge. The IR thermometer is a cheap $30-ish model that reads 203* (off by 9*) when aimed at boiling water. So, it reads a bit low. All future references will be given in gauge readings.
Relevant car setup as purchased: Ron Davis radiator w/o blockage and clean 50/50 coolant, GT40X/GT40/E-303 cam @ 14* base timing. Stock fan & shroud. 180* t-stat. Idle RPM appears to be in the 800-900 range. If you want more info about the car, ask or check out my "new hatchback" thread.
The ASP pullies product description on LRS:
- 2.5" alternator pulley (stock is 2.1" for a 16% difference).
- 15% Water pump under drive (stock is 4.6". This one measured 16.5" circumference so ~5.25" diameter)
- 25% Crank under drive (stock is 5.8" so probably sized 4.375")
Combined, the crank and water pump pullies, as described above, reduce fan and water pump speeds to 63% of stock. If the car is idling at 900 RPM, the adjusted RPM to reach the same fan and water pump speeds would be ~1400 RPM.
I bought the car this way 6 days ago, and drove it for 9 hours without issue. The car averaged 22mpg, despite the 4.10 gears. Temps stayed just above the 2nd white line on the guage while driving, but crept up the gauge in traffic and when idling. I never stopped long enough for it to overheat. I let the car idle on the first day home to see how warm it would get. As a stress test, I put the A/C, which still works wonderfully, on full blast (max) and let it idle in the driveway. The car went right up to 240*, which is my absolute limit with aluminum heads, before I shut it off.
I attempted to fix the problem and retested after each adjustment. First I replaced the fan, which was cracked anyways. With it, I replaced the fan-clutch. No change. Then, I swapped in a 195* T-stat. No change. Finally, today I swapped the water pump with a basic autozone unit.
Today, tests were conducted in 56* ambient temps on a humid overcast day in Xenia, OH. While idling with the A/C off, the car came up to 220*. It's unclear whether this represents an improvement, as the weather today is noticeably cooler than it was several days ago when I initially tested it. Manually raising rpm to 1500RPM -- 1400 RPM was problematic because the computer fought to adjust -- brought temps down to 199* within 5 minutes. With A/C on blast again, the Tstat housing went up to 238*. Concerned, I brought RPM up to 3000, which dropped temps back to 203* within 3 minutes and dropped A/C vent temps down by ~10* immediately.
Despite the fact that I appreciate the looks, extra power and fuel economy, I just can't bring myself to leave these pullies on. A friend of mine already gave me the stock pullies for the alt/WP/crank, and I'm going to put them back on. If/when I upgrade to a 3G alternator & E-fan, I'll give the pullies another chance. Like I said at the beginning, I'm sure I'm not impressing any experienced mustang guys, but it's a bit more scientific a test than I've seen before. I'll follow up with an edit when I swap the pullies over.
- Stock size reference (not sure if correct): Mustang Factory Style Steel Pulley Kit Black (79-93)
- March's pulley kit (for similar sizing information that I couldn't find on ASP pullies): March's Power & Amp Series, with a 4.375-inch crank pulley, a 5.5-inch water pump pulley
Read more: Performance Mustang Underdrive Pulley Test - 5.0 Mustang & Super Fords Magazine
Follow us: @ModMustangs on Twitter | ModMustangsandFords on Facebook
Relevant car setup as purchased: Ron Davis radiator w/o blockage and clean 50/50 coolant, GT40X/GT40/E-303 cam @ 14* base timing. Stock fan & shroud. 180* t-stat. Idle RPM appears to be in the 800-900 range. If you want more info about the car, ask or check out my "new hatchback" thread.
The ASP pullies product description on LRS:
- 2.5" alternator pulley (stock is 2.1" for a 16% difference).
- 15% Water pump under drive (stock is 4.6". This one measured 16.5" circumference so ~5.25" diameter)
- 25% Crank under drive (stock is 5.8" so probably sized 4.375")
Combined, the crank and water pump pullies, as described above, reduce fan and water pump speeds to 63% of stock. If the car is idling at 900 RPM, the adjusted RPM to reach the same fan and water pump speeds would be ~1400 RPM.
I bought the car this way 6 days ago, and drove it for 9 hours without issue. The car averaged 22mpg, despite the 4.10 gears. Temps stayed just above the 2nd white line on the guage while driving, but crept up the gauge in traffic and when idling. I never stopped long enough for it to overheat. I let the car idle on the first day home to see how warm it would get. As a stress test, I put the A/C, which still works wonderfully, on full blast (max) and let it idle in the driveway. The car went right up to 240*, which is my absolute limit with aluminum heads, before I shut it off.
I attempted to fix the problem and retested after each adjustment. First I replaced the fan, which was cracked anyways. With it, I replaced the fan-clutch. No change. Then, I swapped in a 195* T-stat. No change. Finally, today I swapped the water pump with a basic autozone unit.
Today, tests were conducted in 56* ambient temps on a humid overcast day in Xenia, OH. While idling with the A/C off, the car came up to 220*. It's unclear whether this represents an improvement, as the weather today is noticeably cooler than it was several days ago when I initially tested it. Manually raising rpm to 1500RPM -- 1400 RPM was problematic because the computer fought to adjust -- brought temps down to 199* within 5 minutes. With A/C on blast again, the Tstat housing went up to 238*. Concerned, I brought RPM up to 3000, which dropped temps back to 203* within 3 minutes and dropped A/C vent temps down by ~10* immediately.
Despite the fact that I appreciate the looks, extra power and fuel economy, I just can't bring myself to leave these pullies on. A friend of mine already gave me the stock pullies for the alt/WP/crank, and I'm going to put them back on. If/when I upgrade to a 3G alternator & E-fan, I'll give the pullies another chance. Like I said at the beginning, I'm sure I'm not impressing any experienced mustang guys, but it's a bit more scientific a test than I've seen before. I'll follow up with an edit when I swap the pullies over.
- Stock size reference (not sure if correct): Mustang Factory Style Steel Pulley Kit Black (79-93)
- March's pulley kit (for similar sizing information that I couldn't find on ASP pullies): March's Power & Amp Series, with a 4.375-inch crank pulley, a 5.5-inch water pump pulley
Read more: Performance Mustang Underdrive Pulley Test - 5.0 Mustang & Super Fords Magazine
Follow us: @ModMustangs on Twitter | ModMustangsandFords on Facebook
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