Author Topic: Crank pulleys, which way to slow everything down  (Read 778 times)

Offline dodge freak 2

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Crank pulleys, which way to slow everything down
« on: April 26, 2009 - 05:39:47 PM »
Help! My P.S-Fan belt is being thrown off at 6500 rpms, not every time but twice in one day stinks. Pulleys are pretty straight and I seen no wobble as I spin them...this car had 2.45 gears when new so likely its set up for low rpms.

March pulleys seem a bit $$$ but I seen a smaller 3 groove crank pulley at Summit for my SB....but would that speed up everything or slow everything down...getting a headache thinking about it. It do something for sure being an inch smaller but what  ???




Offline GoodysGotaCuda

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Re: Crank pulleys, which way to slow everything down
« Reply #1 on: April 26, 2009 - 05:45:20 PM »
Have you tried a different brand of belt? Or putting some more tension? I, and MANY other cars run stock pulleys and have seen 6500rpm without belt tossing.
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Offline Chryco Psycho

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Re: Crank pulleys, which way to slow everything down
« Reply #2 on: April 26, 2009 - 06:07:15 PM »
smaller crank pulley will slow everything down , oe larger pulleys on the driven accessories

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Offline GoodysGotaCuda

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Re: Crank pulleys, which way to slow everything down
« Reply #3 on: April 26, 2009 - 10:36:08 PM »
You mentioned the problem started with the flex fan. What about moving to a clutch fan? You dont need the fan spinning at 100% rpm at that high of speed. May be better as far as a clutch fan goes? Just a thought.
Build Page: Goody's 'Cuda Build Page
1976 Dodge Warlock
1972 Barracuda - 5.7 Hemi + T56 Magnum

Wheel & Tire Specs:Link

Offline dodge freak 2

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Re: Crank pulleys, which way to slow everything down
« Reply #4 on: April 26, 2009 - 11:28:47 PM »
True, I really don't even "need" it around here since I am stop just for traffic lights...no traffic jams. Got a brand new one off E-bay for $15 total, a Derale. Its nice being small since I can slip the little belt that drives the water pump from the crank right over the fan. Because there is no clutch I can turn the fan and pop the belt on in under 1 min (taking it off I need to unbolt the fan and spacer...the spacer is from a 1964 car (I love Ebay, lol) its made of metal not plastic. But then no PS but I can drive it back home.

But I am hoping to go on a long road trip in to Canada in one month, that means going past Customs and there is always line up at the border...so I trying it out now...really aren't going to rev it past 4,000 on the trip (I better not, they impound your car for a week for 50 kmh-35 mph over the limit in Ontario CA).

I notice now that my little bracket is crack that goes on the bottom of the PS pump and the block...so if I take it off my exhaust shop would weld it and I could get the belt even tighter but it seems pretty tight now.

Just was looking at that smaller crank pulley and could not figure out what a smaller crank pulley did, now I know...March has all the stuff, larger PS pulley, smaller water pulley (to prevent over heating with the smaller crank pulley) but I wanna have fun and not spend much money on my ride right now. Got new tires and police rims just last month and then needed a brake valve. Oh yeah, and MSD gauges, a tach, water and fuel gauge (ebay again, $150 for all three brand new, I "had" to buy it, lol).

Again, no Cuda..a ST Regis...so no sweat cutting and modify everything..but it could run with some of yours here and lots of stuff is pretty much the same. Plus I feel safer leaving it park outside theft wise..will unhook the battery at night and chain the hood down thou on holiday at night.
« Last Edit: April 26, 2009 - 11:36:07 PM by dodge freak 2 »

Offline HP2

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Re: Crank pulleys, which way to slow everything down
« Reply #5 on: April 27, 2009 - 12:21:33 PM »
You could try a narrower belt so it would sit further down in the pulley.

Might have to try a parts store that has a better selction of belts than one of the chain stores.

Offline Chryco Psycho

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Re: Crank pulleys, which way to slow everything down
« Reply #6 on: April 27, 2009 - 01:43:54 PM »
there are 11-13-or15 series belts  that # is the width of the belt  try a tinner belt , 11 is thinner

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Offline dodge freak 2

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Re: Crank pulleys, which way to slow everything down
« Reply #7 on: April 27, 2009 - 08:17:28 PM »
The belt number starts with 15...maybe that is the problem right there, I'm getting the next size narrower belt  tomorrow...Cool.