Underdrive Pulleys
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=693
Printed Date: November-22-2024 at 3:22am
Topic: Underdrive Pulleys
Posted By: 77stang
Subject: Underdrive Pulleys
Date Posted: August-03-2004 at 1:12pm
Anyone using underdrive pulleys - if so whats your thoughts?
Thanks
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Replies:
Posted By: yellowdog
Date Posted: August-04-2004 at 4:38pm
Okay; 24 looks, no responses. I have to ask, what is an underdrive pulley? Hey, ya never learn if ya don't ask!
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Caretaker of the wife's '78 Ski Nautique
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Posted By: SS 201
Date Posted: August-04-2004 at 7:06pm
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To gain HP by turning all the the add on, water pump, alt, etc lower rpms.
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Posted By: 77stang
Date Posted: August-04-2004 at 11:27pm
here you go yellowdog.
ford motorsports sells them too.
http://www.marchperformance.com/ford_pulleys.html
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Posted By: 79nautique
Date Posted: August-05-2004 at 11:36am
Here's my question would you really want to do it? It seems to me that the alt. wouldn't make a difference the drag would be constant at 600 or 4000 rpm, now the rwp and cir pump does with higher rpm but would it effect cooling at higher sppeeds where you would be drawing less water to circulate? What's your thoughts Bill? I'm sure you must have used them at one point or another with your racing background.
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http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique
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Posted By: SS 201
Date Posted: August-05-2004 at 2:37pm
In a circle race boat never, however we never used alternators,water pumps, etc. These motors were running 7-10,000 RPM.
My opinion would be as 79 Nautique's, not worth the effort. Again if you are going for HP everything matters, however most of these boats turn short of 5250 RPM and are running on torque anyway, over that everything little bit helps.
I don't think they are available for PCM Fords, as the pulleys are different, I could be wrong.
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Posted By: 77stang
Date Posted: September-03-2004 at 4:25pm
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Well after a little investigation and measurements it appears that PCM already underdrove the crank in my 1977 302. Evidenced by the 5 1/2" crank and slightly oversized waterpump pulley.
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Posted By: 64 Skier
Date Posted: September-05-2004 at 8:06pm
For a stock engine, the best place to increase Performance (IMO) is the Prop. We can all change a Prop, pretty easy.
A Water Pump and Alternator don't drain as much HP as a good Tune-Up add to an old engine and for the 302, there's thousands of "bolt on" HP options that are easy and probably safer than figuring out the water flow problem.
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64 Skier
66" HO VTX and 67" HO Triumph
http://www.correctcraftfan.com/diaries/details.asp?ID=1071&sort=&pagenum=3&yrstart=1971&yrend=1975 - 71CC
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