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Old 11-03-2004, 06:53 PM
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Pulleys and Motor plates

Hello, this is my first post here so please bare with me,, I recently bought a 77 Monza Spyder street/strip car ,, it has a motor plate and it has a 3-1/2" crank pulley that runs the alternator and an electric motor that runs the water pump with a belt ,, it turns 2800 rpms always, well the alternator isn't turning enough rpms to keep up with the load of electric fans, feul pumps, water pump , lights,, etc... I have considered a 100 amp alternator but if it isn't turning fast enough I am not sure this would fix the problem,, and I want to make it more streetable, does anyone here run a motor plate and have a pulley setup that runs the alternator and the water pump ,, the motor plate is in the way of the factory pulley system and I would like to find out what pulley system would work best without having to cut up the motor plate too much,,, small block chevy BTW ,, 350,
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Dan

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Old 11-03-2004, 07:32 PM
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You didn't give a name brand on the crank pulley but chances are good whatever it is has different size pulley ratio's to speed up the alternator. Run the alternator at 30% overdriven. Or you can decrease the size of the alt pulley.
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Old 11-03-2004, 08:03 PM
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3 1/2" crank pulley! That is small!

You may need to run a compound pulley arrangement to get some rpm to the alt, can you run a larger crank pulley?

(I'm sure there is a good reason for such a small crank pulley, I had to ask.)
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Old 11-03-2004, 08:31 PM
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pullies

IF you can find a pully to fit the shaft on your alternator, go with one between half to one inch smaller in diameter. This would be the cheapest way out. Scour the junk yards. Going to a smaller pully on your alternater will change the gear ratio between it and the crank pully, and cause your alternater to turn at higher rpm. Same as going with a larger crank pully, but I imagine a lot cheaper. with the smaller alternater pully, you may well have to go with a shorter V belt. Once you install it, put the belt on and see if you have any adjustment left on the belt. If there is still slack in your belt, I would recommend gettng a belt 1 1/2 inches shorter. If your friendly parts man is understanding, get 2-3 different belts from the above mentioned size, to 2 1/2 inches shorter than your stock unit. See which one fits that gives you the most room for adjustment. Return the other one and store the sleeve of the one you do use for future reference.

The alternative to all the trips to the parts house is to take the current belt and cut it down til it will fit your pullies, when the alternater is at its closest adjustment point to the crank pully. That will tell you exactly what belt you need.
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Old 11-03-2004, 10:27 PM
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A stock 30% overdriven alternator spins 2600 rpm. Just right for the bearings and right at the peak output RPM.

A engine turning 9500 spins the alternator at 12350. To many for the alternator to live and way past it's peak output RPM. It's necessary parasitic drag. Running a smaller crank pulley changes the ratio to spin the alt.(same as a blower belt) Slowing it down at race speeds saves power and still get's the job done.

Dan

You never said if the pulley was a gilmore belt or serpentine or V or what. I can find one for you if you like.
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Old 11-04-2004, 06:10 AM
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RE

It is a V belt, Peterson pulley, To let you all know I bought the car like this and it must have been a drag only car for the guy I bought it from that is why it has this problem, the pulley is shimmed with a piece of 3/4" pipe to get it to line up, seems to work fine its not wobbling or anything just turns to slow, my car idles around 1200 rpms and you have to rev the engine to 4000 rpms to see 14 volts from the alternator,,
Thanks for all the replies
Dan
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Old 11-04-2004, 10:57 AM
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A 5" pulley would suit your needs. I assume it was "hand crafted" rather then bolt on. If so finding one will be tricky without buying the entire mandral drive for $400. I see what I can find. I'm thinking a pulley from a Smog Pump would be about theright size and has three holes for mounting that just might fit. Can you post a pic?
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Old 11-04-2004, 03:02 PM
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Is there room for a bigger pulley?
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Old 11-04-2004, 06:19 PM
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RE

Yes there is room for a bigger pulley , it only has the 1 center crank bolt in it,, yes I can post a pic if you guys tell me how, I have a digi cam and have posted before on other sites using the FTP folder is it the same concept on this board, or can I just use the attach file thing and it will post it from my pc,,
Give me a few minutes I will try it,,
Thanks
Dan
I would like to got to a pulley system that would work on the water pump also without having to buy one of the electric 36 GPM type they are costly,, but if it would be easiest I guess that is what I will do
Dan

Okay i can't figure it out , how do you post a pic, I took some and tried the hyperlink to an FTP folder and it didn't work , I also tried just attaching it to the post and it didn't work , Help

Thanks
Dan

BTW at the bottom it says HTML code is off , do i need to turn it on and how if so

Last edited by danarmstrong; 11-04-2004 at 06:19 PM.
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Old 11-05-2004, 05:44 AM
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Re: RE

Quote:
Originally posted by danarmstrong
Yes there is room for a bigger pulley , it only has the 1 center crank bolt in it,, yes I can post a pic if you guys tell me how, I have a digi cam and have posted before on other sites using the FTP folder is it the same concept on this board, or can I just use the attach file thing and it will post it from my pc,,
Give me a few minutes I will try it,,
Thanks
Dan
I would like to got to a pulley system that would work on the water pump also without having to buy one of the electric 36 GPM type they are costly,, but if it would be easiest I guess that is what I will do
Dan

Okay i can't figure it out , how do you post a pic, I took some and tried the hyperlink to an FTP folder and it didn't work , I also tried just attaching it to the post and it didn't work , Help

Thanks
Dan

BTW at the bottom it says HTML code is off , do i need to turn it on and how if so


I put a power master alt that puts out 79 amps at idle and they may have otheres that are bigger and badder and may put out the 100 amp you need at a lower rpm might be worth a check and save a lot of work Ed ke6bnl
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Old 11-05-2004, 06:29 PM
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RE: Pics

I think I figured it out at leat a link not he actual pic,
Dan




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Sory about the double shot,, just figuring this out,,
Thanks for any help/replies / ideas etc........
Dan

Last edited by danarmstrong; 11-05-2004 at 06:26 PM.
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Old 11-06-2004, 02:08 PM
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RE: Posting pics

johnsongrass, I was able to get some pics posted and wonered what you think about it,
Dan
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