Need to boost the RPMs on alternator

[jims6t6]

On my 66 I'm running a 16 inch Spal Fan. In parades everything is fine if I keep the RPM's at 900-1000 to avoid draining the battery. With a C4 Trans this means that I have to shift to neutral often. Is there a smaller diameter pulley for stock alternator that will increase the RPMs of the Alternator? If so what the possibility of damaging the alternator at normal highway speeds?

 

[AzPete]

With an electric fan, you really need to upgrade to a larger alt. that puts out at low speeds.

 

[jims6t6]

With an electric fan, you really need to upgrade to a larger alt. that puts out at low speeds.

I know that's one answer but I would like to avoid it.

 

[AzPete]

Spinning an original type alt. faster MAY cause internal damage at faster engine speeds. I have seen one personally...as a friend had done the same and the alt. did come apart internally. It also becomes an issue as to what the alt. can put out amperage wise. If at the max all the time, it will run hotter also, load the engine more, and shorten the alt. life all the way around. Older ones were 40 amps....pretty light weight.

 

[Jonk67]

Do you know what amp your current alt. is? the stockers came from 35A-65A in the same case TMK, you may have a 45A and can switch it to a 65A that looks identical if that suffices for the electric fan. I would measure your pulley size and compare to those a your local parts stores. If you know the counter guys, they take in cores and may let you measure/swap pulleys, I used to. The HiPo ones are larger so that won't help you. Can't say what it'll do to the alt. at high rpm's or durability.

I bit the bullet and went to a larger alt. (100A) but didn't want to pull the VR, wiring, etc. so I swapped to a large case 1G. It looks similar to the stock one, just larger and uses the same VR and wires but I did have to splice for the different alt. connections. It came from mid 70's full size Ford/Linc./Merc. and I only needed a ~1" longer belt. I can post pics if you like.

I also looked into the stock small case 1G that have the internals swapped out for ~90-100A but spoke on the phone with a couple of personal rebuilders and they stated they didn't do that since the case wasn't large enough to vent all the heat and they would fail sooner.
Jon

 

[jims6t6]

Do you know what amp your current alt. is?
Jon

I have an original 65 amp which has been rewound to a 95 amp. Would appreciate a picture. of the 70's alt. Do you know if it charges at low rpm's?

If at the max all the time, it will run hotter also, load the engine more, and shorten the alt. life all the way around.

Pete, doesn't the alternator have continuous output and the VR stops it from going to the Battery? (I flunked electrical in school)

 

[AzPete]

Pete, doesn't the alternator have continuous output and the VR stops it from going to the Battery? (I flunked electrical in school)

Woops......been out in the heat today......who took elec, in school anyway? Once into the output speed, I believe you are correct. 95 amp in a stock case is going to run warmer than planned also. You can always try it and give us a report.....

 

[jims6t6]

Woops......been out in the heat today......who took elec, in school anyway? Once into the output speed, I believe you are correct. 95 amp in a stock case is going to run warmer than planned also. You can always try it and give us a report.....

The longest trip I've taken in it since upgrading to the 95 amp is around 300 miles at once. I'll check and see if the case is exceptionally hot the next time I'm out with it. Meanwhile, I'll try looking for a smaller pulley..

 

[Jonk67]

Here's some pics for comparison, please excuse the untidyness, it was all going to be pulled anyway.
Yes it charges at low RPM's, the headlights are the same brightness at idle as they are at 2K+ so no lag or need to 'excite' the alt. from first idle.

As mentioned I used the same 4 hookups from my 65A - (+), (-), FLD and STA (hooked my electric choke up here). Worked flawlessly for the yr. I drove it. I use a coil wire cap over the + post so I don't ground it with a wrench by accident.

I was out by Fort Loudoun Lake off Northshore Dr. in Knoxville this weekend but not in my '67 (I wish it was running now..)
Jon

 

[jims6t6]

Thanks Jon