UNDERDRIVE CRANK PULLEY

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UNDERDRIVE CRANK PULLEY

Post  78 F150 on December 22nd 2013, 2:47 pm

I'm considering buying an aluminum crank pulley from CVF Racing, mostly because I can't find a used factory steel pulley. However, my factory crank pulley measures 8" in diameter and the aluminum pulley measures 5.7" in diameter, which makes it an underdrive pulley.

Question....will using an underdrive pulley on my truck (daily driver; NOT a race truck), which will make the power steering pump and alternator spin faster, cause any issues? Is this not a good idea?

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Re: UNDERDRIVE CRANK PULLEY

Post  schmitty on December 22nd 2013, 3:23 pm

That pulley will turn the accessories slower. It shouldn't be a big issue.
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Re: UNDERDRIVE CRANK PULLEY

Post  78 F150 on December 22nd 2013, 3:44 pm

schmitty wrote:That pulley will turn the accessories slower.  It shouldn't be a big issue.

Thanks for the info....I always get that mixed up whether a smaller pulley makes things spin faster or slower.

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Re: UNDERDRIVE CRANK PULLEY

Post  supervel45 on December 22nd 2013, 4:57 pm

Depends. Power steering should'nt hurt. Charging in stop and go traffic will not be as good. Less water flow also. You will have to try it to see how it work's out I guess. Mine was OK, but missed the charging output in traffic.

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Re: UNDERDRIVE CRANK PULLEY

Post  78 F150 on December 25th 2013, 5:47 pm

supervel45 wrote:Depends. Power steering should'nt hurt. Charging in stop and go traffic will not be as good. Less water flow also. You will have to try it to see how it work's out I guess. Mine was OK, but missed the charging output in traffic.

I would prefer to find a pulley that had the same diameter (8") as the factory pulley, but I can't find anyone who makes one. Do any of you know who makes a factory diameter pulley for a 460? I really don't want to turn the alternator and p/s any slower.

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Re: UNDERDRIVE CRANK PULLEY

Post  LivermoreDave on December 29th 2013, 9:42 pm

There will be about a 30% decrease in operating speed of the accessories the pulley drives. Power steering will suffer during tight turning or heavy load turning and your electrical system will suffer. Electrical components supplied by inadequate power (amps) will overheat and fail.

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Re: UNDERDRIVE CRANK PULLEY

Post  78 F150 on December 30th 2013, 12:25 am

LivermoreDave wrote:There will be about a 30% decrease in operating speed of the accessories the pulley drives. Power steering will suffer during tight turning or heavy load turning and your electrical system will suffer. Electrical components supplied by inadequate power (amps) will overheat and fail.

Dave.

That is exactly what I was worried about....

One of the other guys who commented on here gave me a link to ebay for a pulley a guy was selling. I actually won the bid. Once I get it, I'll clean it up and put it on the motor and pray that it solves my belt slippage problem. I really don't want to have to buy brand new pulleys because I'll not only have to buy a crank pulley, but will have to buy the high flow water pump pulley, alternator and p/s pump pulleys just to keep the pulley ratios close to the same as factory. But you're talking a couple hundred bucks in pulleys vs $25 for this used pulley. So I'm hoping this used pulley works. We'll see what happens when I receive it. Thanks for all your input. I really appreciate it....

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Re: UNDERDRIVE CRANK PULLEY

Post  LivermoreDave on December 30th 2013, 11:30 am

78 F150 wrote:

That is exactly what I was worried about....

One of the other guys who commented on here gave me a link to ebay for a pulley a guy was selling. I actually won the bid. Once I get it, I'll clean it up and put it on the motor and pray that it solves my belt slippage problem. I really don't want to have to buy brand new pulleys because I'll not only have to buy a crank pulley, but will have to buy the high flow water pump pulley, alternator and p/s pump pulleys just to keep the pulley ratios close to the same as factory. But you're talking a couple hundred bucks in pulleys vs $25 for this used pulley. So I'm hoping this used pulley works. We'll see what happens when I receive it. Thanks for all your input. I really appreciate it....

One thing to keep in mind. Coolant flowing through the engine to fast will offer less cooling than coolant flowing at "normal speed" or even a bit lower speed. When the coolant flows to fast through an engine and radiator, the coolant can't absorb the heat from the engine and the heat can not be transfered out through the radiator effectively.

Dave.

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Re: UNDERDRIVE CRANK PULLEY

Post  supervel45 on December 30th 2013, 11:59 am

If you put a smaller water pump pulley, you will be worse off than you started, if the crank pulley is reduced in size, ie same load on belt, and less pulley surface to hold the belt. Deep groove pulleys would be the ideal solution, if the belt is coming off the pulleys. How many RPM are you running? Are all your belts in good condition, and not dried out or twisted, ect, and the correct size? Is your belt alignment strait? Which belt is coming off, or slipping? Hope your new pulley works out, but if you still have problems, check the things I mentioned over, before you spend alot of money.

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Re: UNDERDRIVE CRANK PULLEY

Post  78 F150 on December 30th 2013, 9:27 pm

supervel45 wrote:If you put a smaller water pump pulley, you will be worse off than you started, if the crank pulley is reduced in size, ie same load on belt, and less pulley surface to hold the belt. Deep groove pulleys would be the ideal solution, if the belt is coming off the pulleys. How many RPM are you running? Are all your belts in good condition, and not dried out or twisted, ect, and the correct size? Is your belt alignment strait? Which belt is coming off, or slipping? Hope your new pulley works out, but if you still have problems, check the things I mentioned over, before you spend alot of money.

The belt isn't coming off the pulley, it's just slipping and it only slips when I hit 4000 rpm or higher. The belts are brand new and are the correct size. The alignment is perfect. The belt that's slipping is the power steering pump / water pump belt. The p/s pump is the same pump I had in the truck when I had the 400 in it. I pulled the 400 and replaced it with a 460. Ever since I've had the 460 in it, the belt slips and squeals. It never did this with the 400, so I'm presuming it's slipping at the crank pulley and I've had others tell me the same thing.

The p/s belt is the same belt that runs the water pump, which runs off the crank. The p/s groove on the stock crank measures 7.75 (7 3/4"); the p/s pulley measures 5.875 (5 7/8"); the water pump pulley measures 6.25 (6 1/4"), which gives me a p/s pulley ratio of 1.32 and a water pump pulley ratio of 1.24.

The aftermarket crank pulley from CVF Racing measures 5.7". If I run it with my stock water pump pulley (6.25"), I get a ratio of .91. The guy at CVF racing told me he's running the same crank pulley (5.7) with their high flow water pump pulley (5.2"), which comes out to be a 1.09 ratio. He mentioned that his 521 ci Ford doesn't get above 180* with this setup. The standard size water pump pulley they offer measures 5.9", which comes out to a .97 ratio. Their p/s pump pulley measures 5.4", which comes out to a 1.05 ratio (with their 5.7" crank pulley).

So if I can't find a factory crank pulley that will work without slipping, I'll have to buy all new pulleys  Sad

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Re: UNDERDRIVE CRANK PULLEY

Post  supervel45 on December 30th 2013, 10:35 pm

One thing that I thought about that was not mentioned yet, what kind of fan are you running? It can put alot of load on your belts also. You might want to try a lighter flex type fan if you are not using one allready. I run stock pulleys on my 429 to 6,000 rpm and have not had this problem. Pulley's do wear out though, and cause this kind of problem sometimes. What happens is the groove is not strait, and the belt does not have a good contact surface to grab on. You can run your finger tip in the groove, and if it feels rounded in the center, then it is pretty worn out. On commerical A/C units, we would have this happen, and get noise complaints, and sometimes had to replace pulleys. Do you have an A/C compressor on the engine? My A/C belt also went around the waterpump pulley, and helped with the waterpump load?

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Re: UNDERDRIVE CRANK PULLEY

Post  466cj on December 31st 2013, 1:33 pm

Keep in mind new belts will stretch and require more tension. May want to get a gauge to properly tension your belts. As far as the pulleys go only issue is if the surface the belts ride on are glazed. Some sand paper or bead blast them will deglaze them. Need be you can use some belt dressing on the belts too.

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Re: UNDERDRIVE CRANK PULLEY

Post  78 F150 on December 31st 2013, 8:17 pm

supervel45 wrote:One thing that I thought about that was not mentioned yet, what kind of fan are you running? It can put alot of load on your belts also. You might want to try a lighter flex type fan if you are not using one allready. I run stock pulleys on my 429 to 6,000 rpm and have not had this problem. Pulley's do wear out though, and cause this kind of problem sometimes. What happens is the groove is not strait, and the belt does not have a good contact surface to grab on. You can run your finger tip in the groove, and if it feels rounded in the center, then it is pretty worn out. On commerical A/C units, we would have this happen, and get noise complaints, and sometimes had to replace pulleys. Do you have an A/C compressor on the engine? My A/C belt also went around the waterpump pulley, and helped with the waterpump load?

I'm running the stock fan that was on it when I had the 400 in the truck. No problem with belt slippage with the 400 and the same fan. It's a solid fan, not a clutch fan. No, I don't have A/C on this engine, unfortunately.

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Re: UNDERDRIVE CRANK PULLEY

Post  78 F150 on December 31st 2013, 8:24 pm

466cj wrote:Keep in mind new belts will stretch and require more tension. May want to get a gauge to properly tension your belts. As far as the pulleys go only issue is if the surface the belts ride on are glazed. Some sand paper or bead blast them will deglaze them. Need be you can use some belt dressing on the belts too.

To get the belt to stop slipping at lower rpm's, I have to tighten the belt. As it is, the belt is way too tight; tight enough to ruin the bearings in the p/s pump. But as the belt has stretched, it starts slipping at lower rpm's. I believe the belt surface on the pulley might be glazed. The surface is pretty shinny. That's the only explanation I can come up with. And I tried the belt dressing. It stopped the squealing for a short period of time until it wore off. And it also made a huge mess!

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Re: UNDERDRIVE CRANK PULLEY

Post  466cj on January 1st 2014, 2:14 pm

78 F150 wrote:
466cj wrote:Keep in mind new belts will stretch and require more tension. May want to get a gauge to properly tension your belts. As far as the pulleys go only issue is if the surface the belts ride on are glazed. Some sand paper or bead blast them will deglaze them. Need be you can use some belt dressing on the belts too.

To get the belt to stop slipping at lower rpm's, I have to tighten the belt. As it is, the belt is way too tight; tight enough to ruin the bearings in the p/s pump. But as the belt has stretched, it starts slipping at lower rpm's. I believe the belt surface on the pulley might be glazed. The surface is pretty shinny. That's the only explanation I can come up with. And I tried the belt dressing. It stopped the squealing for a short period of time until it wore off. And it also made a huge mess!

Get some 220 sand paper and deglaze the pulleys. Belt tightening unless you use a gauge to measure how tight they are you are just assuming what is too tight or not. Make sure you have the right belts too. They should sit in the V, not bottom out in it.

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