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BUSY BOLTERS Are you one?  The Shop Area
continues to pull in the most views on the Stovebolt. In August alone there were over 22,000 views in those 13 forums.
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| | | Forums66 Topics126,776 Posts1,039,271 Members48,100 | | Most Online2,175
Jul 21st, 2025 | | | | Joined: Sep 2010 Posts: 122 Shop Shark | | Shop Shark Joined: Sep 2010 Posts: 122 | Have a 261 with a 4.3 dia water pump pulley. I also have 2 dampers, one with a 6" dia pulley and the other with a 6.75" pulley. What would be the fan rpm for each pulley at engine speed of 2000 rpm. What is a "typical" fan speed? | | | | | Joined: Jul 2008 Posts: 326 'Bolter | | 'Bolter Joined: Jul 2008 Posts: 326 | Around 2800 vs 3100 RPM
IDK what typical speed/ratio should be. The only steady state RPM would be at highway cruise speeds.
SimS | | | | | Joined: Apr 2014 Posts: 924 Shop Shark | | Shop Shark Joined: Apr 2014 Posts: 924 | DcCrpm= DfFrpm
(Diameter of the crankshaft pulley)(crankshaft pulley/engine RPM) = (Diameter of the fan pulley)(fan RPM)
Both sides of the equation must balance out.
Brad
Wrench Fetcher, PhD | | | | | Joined: Jun 2011 Posts: 1,901 Shop Shark | | Shop Shark Joined: Jun 2011 Posts: 1,901 |
Give me ambiguity
or give me something else
| | | | | Joined: Sep 2010 Posts: 49 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2010 Posts: 49 | I could not go larger than 6" on the damper or the pulley would rub on the motor mount. That's on a 1951 with a 235. Maybe I have a problem some other place. | | | | | Joined: Apr 2014 Posts: 924 Shop Shark | | Shop Shark Joined: Apr 2014 Posts: 924 | ... but talk forum members into hammering out sheet metal into fender patches as opposed to buying replacements? Touché.  Brad
Wrench Fetcher, PhD | | | | | Joined: Dec 2008 Posts: 1,915 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,915 | Far more important: that's also the water pump RPM. Slow it down too much = always runs hot.
Fan speed only matters in traffic, above 35 mph you can remove the fan entirely.
The best fan design: the largest diameter turning at the slowest speed, with a shroud. | | | | | Joined: Jun 2011 Posts: 1,901 Shop Shark | | Shop Shark Joined: Jun 2011 Posts: 1,901 | .... but I never said that!!!
I said if I made one it would be the greatest patch ever and the five layers of bondo were just for enhanced rust protection... our manufacturers have sold us out but I will makes great panels for everyone!
Wheres that LMC catalog?
Give me ambiguity
or give me something else
| | | | | Joined: Apr 2014 Posts: 924 Shop Shark | | Shop Shark Joined: Apr 2014 Posts: 924 |
Wrench Fetcher, PhD | | | | | Joined: Mar 2007 Posts: 4,185 Moderator | | Moderator Joined: Mar 2007 Posts: 4,185 | Ryan, I don't know my fan speed, but I had that 4.3" water pump pulley too, at first. (261 engine) It was very obviously spinning the fan too fast. I simply slipped a larger pulley, about 6" diameter right over the smaller one, using the 4 small fan bolts to hold it in place. I have been running it for 4 years, no issues. | | |
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