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05-30-2015, 01:19 AM | #501 | |
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Re: Ford vs Chevy Build-up
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The set-up as run... Just grasping at straws here. I did not have any 10 gauge wire on hand so I paralleled two 12 gauge wires to the battery positive and a short 10 gauge ground from the alternator case to a head. Edit: Just re-read the instructions and it states no Jegs alternators are designed to to be spun beyond 15,000rpm (6000 engine rpm). I can try it one more time with a large crank pulley or purchase another brand alternator. At this juncture I just want one that works without worry.
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Rich Taylor I/SA - 321 Last edited by HandOverFist; 05-30-2015 at 01:48 AM. |
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05-30-2015, 04:03 AM | #502 | |
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Re: Ford vs Chevy Build-up
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I think that you have it backwards.... Big crank pulley & small alternator pulley = overdrive Small crank pulley & large alternator pulley = under-drive 4" crank pulley with 2" alt pulley at 7,000 rpm engine RPM = 14,000 alternator RPM 2" crank pulley with 4" alt pulley at 7,000 rpm engine RPM = 3,500 alternator RPM Hope this makes sense to you and helps...... Bob
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Bob Mulry 7516 STK A & M Motorsports |
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05-30-2015, 08:24 AM | #503 |
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Re: Ford vs Chevy Build-up
As stated above, the small crank pulley slows it down.
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05-30-2015, 08:42 AM | #504 |
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Re: Ford vs Chevy Build-up
You know, that is what I thought as well but I let someone talk me into that one lol. With that out of the way I can see no reason for two failures in a row other than these alternators are junk.
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Rich Taylor I/SA - 321 |
05-30-2015, 11:10 AM | #505 | |
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Re: Ford vs Chevy Build-up
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Dale
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Dale Shearon 68 Mustang 6394 |
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05-30-2015, 01:25 PM | #506 |
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Re: Ford vs Chevy Build-up
Rich a one wire alt. has to turn around 2000 rpm to excite it for it to start charging. Once it starts charging it stays until you shut off the engine
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05-30-2015, 04:47 PM | #507 | |
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Re: Ford vs Chevy Build-up
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Rich Taylor I/SA - 321 |
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05-30-2015, 09:48 PM | #508 |
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Re: Ford vs Chevy Build-up
Bob is right on. That crank pulley has to be close to 3.5", if the alt pulley is 2", that calculates to 12,250 at 7000 RPM. At 1000 RPM the alt is only at 1750 RPM.
Will the alt produce any voltage if you increase the engine RPM to 2000 or 3000? Sean
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Sean Marconette 84 Mustang 5060 SS/N |
05-30-2015, 10:22 PM | #509 |
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Re: Ford vs Chevy Build-up
From the beginning both alternators worked fine, even at idle. I guess they lasted part of one stint each at the track when I realized they were no longer charging. You can wing it to six grand if you like...it aint happening. Something inside the alternator is just not holding up it's end of the bargain.
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Rich Taylor I/SA - 321 |
05-31-2015, 09:41 AM | #510 |
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Re: Ford vs Chevy Build-up
Just went through a similar issue. The one wire alternator didn't excite until 2500 alternator rpm. With the combination of a large alternator pulley and small crank pulley, there wasn't a lot of time that the alternator was putting anything back into the battery. To make things worse, the alternator had a bad diode and rectifier so it was only putting out 15 amps when it was charging. Had it rebuilt and now it works fine.
Changed the charging system to a larger 74 amp constant output alternator with a 6" crank pulley. The excite power wire runs through a heavy duty toggle switch on the dash so the alternator can be turned off during a run. -Al
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