Low Speed Alternator Setup - 1971 Cadillac Hearse w/472
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500, 472, 425, 368 Discussion, Low Speed Alternator Setup - 1971 Cadillac Hearse w/472 in Cadillac Engine Technical Discussion; Howdy ALL: First Post. My buddy and I have a 1971 Cadillac Hearse. Once or twice a year, we use ...
  1. #1
    Colonel Monk is offline Cadillac Owners Member
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    Question Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    Howdy ALL:

    First Post. My buddy and I have a 1971 Cadillac Hearse.

    Once or twice a year, we use it in events where the max speed is 5 - 10mph.

    With lights and stereo, etc, we have a real problem keeping the batteries charged. Last year I added an isolator and second battery for the stereo and lighting effects, but we still had the problem.

    Basically, it's running around for hours on idle, and the alternator just isn't producing any power at that speed. We have verified that it does work at higher speeds though.

    Gearing in the caddy seems high as well, so like I said, basically we're riding brakes and never spinning it up enough to charge.

    Now, I'm not sure if the alternator is original or not. I suspect that it's not. I have read elsewhere on here about generator and external voltage regulators and this alt has only a few wires.

    I'd like to say from memory, that it's got just a few wires. Battery charge wire and maybe 1 or 2 small wires.

    I've thought about just using a smaller pulley to turn alt faster, but it's already not very big, I'm not sure we could get a smaller pulley or not.

    The caddy is currently across the country from me, I can try to have my friend get me the details off the badge if necessary.

    Questions:

    Smaller Pulley?

    Suitable Replacement that will have output at idle?

    Bigger Crankshaft Pulley?

    What else?

    Thanks for your help. We love the old caddy it's as bad as they come.

    C. Monk

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    A larger drive pulley at the crank / a smaller pulley at the alternator. The serpentine pulleys are quite small in diameter, compared to the V-belt pulleys. If you change this ratio you have to be cautious if the belt drives another accessory, like the water pump. There are some differences in pulley sizes in relation to some of the different engine sizes. like the 472 versus the 425. Just not sure about the alternator drive pulleys. Most all the alternator pulleys are the same. Moroso makes a larger pulley for the alternators for drag race applications.

  4. #3
    Colonel Monk is offline Cadillac Owners Member
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    I can't remember if it's a v-belt or serpentine pulley.....

    There is alot of room in that engine compartment, one idea I had if all else fails, is to build a braket for a "jackshaft". Basically, mount a double pulley on a shaft, drive one smaller one from crank, then drive alternator with larger pulley from jackshaft... essentially, change the gear ratio to the alternator.

    Would rather not do this, but like you said, I'm not sure if I can get a small enough pulley for alternator to make a difference. Larger pulley on crank if it was possible would speed up other accessories running off the same belt - I'm guessing PS pump and water pump would not appreciate this at highway speed, but who knows?

    The tough nugget is that I didn't take the measurements last year, and I won't be reuniting with the Hearse in Nevada until a few weeks before our event. So I need to figure out what I can remotely and then hopefully just put it together when I get there.

    To explore the jackshaft deal, what other belt driven stuff was mounted to those engines? If this vehicle ever had air conditioning it doesn't have it now.....

    I'm surprised it doesn't charge better, as the hydro pump for the casket had to use quite a bit of juice....... I don't see that it had multiple batteries, but vehicle was modified from stock before I ever saw it.

    CM

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    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    Quote Originally Posted by Colonel Monk
    I can't remember if it's a v-belt or serpentine pulley.....
    There is alot of room in that engine compartment, one idea I had if all else fails, is to build a braket for a "jackshaft". Basically, mount a double pulley on a shaft, drive one smaller one from crank, then drive alternator with larger pulley from jackshaft... essentially, change the gear ratio to the alternator.

    Would rather not do this, but like you said, I'm not sure if I can get a small enough pulley for alternator to make a difference. Larger pulley on crank if it was possible would speed up other accessories running off the same belt - I'm guessing PS pump and water pump would not appreciate this at highway speed, but who knows?

    The tough nugget is that I didn't take the measurements last year, and I won't be reuniting with the Hearse in Nevada until a few weeks before our event. So I need to figure out what I can remotely and then hopefully just put it together when I get there.

    To explore the jackshaft deal, what other belt driven stuff was mounted to those engines? If this vehicle ever had air conditioning it doesn't have it now.....

    I'm surprised it doesn't charge better, as the hydro pump for the casket had to use quite a bit of juice....... I don't see that it had multiple batteries, but vehicle was modified from stock before I ever saw it.
    CM
    A 71 uses V belts. The extra battery only extends the time before they are dead; you want
    to boost the charging current to keep up almost all the time. And the isolator decreases the
    efficiency of the system. The 71 uses an external voltage regulator; I think performance
    would be better with a 75 or later internally regulated alternator. Certainly this would give
    the option of far larger alternators now available. Alt pulleys do vary in dia somewhat,
    measure it. Don't be in a hurry to use a smaller one, because you are asking for a bad
    slipping belt problem. The jackshaft idea is a great way to go. In 81 Olds adapted this
    method: a larger pulley was attached to the water pump and used to drive only the alt.
    This allowed more rpm while maintaining alt pulley dia. And there was more belt wrap
    around both pulleys (near 180 degrees), reducing belt slip. Bruce Roe

  6. #5
    the APEMAN is offline Cadillac Owners Fanatic
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    I'd skip the older Cadillac alternators all together. Alternator stator core metallurgy has come a long way since the 60s (when your alternator was designed).

    Same for alternator rotor winding enamel. This leads up to alternators that make more power for a given size.

    The 1971 Cadillac may already have a step-up in shaft speed to the alternator. Many did. If it has the A.I.R. system the air pump shares a common shaft pulley at the water pump with the alternator. The alternator pulley is larger diameter giving extra speed to the alternator.

    That system is often deleted by folks expecting great power gains from "losing all that emissions stuff".

    Any number of things could have been changed over the years too.

    Time to check under the hood and maybe post some pictures.

    The good news is there are many modern inexpensive alternators that easily out perform what you have.

    Say goodbye to the external regulator.

    One thing to avoid is modified alternators advertising extra current from a given case size. They are all over ebay and similar places aimed at kids with large audio systems. Those alternators actually put out less power at idle.

    Another thing to avoid is anyone who can write a full page essay on unnamed "new technology" solutions for automobiles.

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    Colonel Monk is offline Cadillac Owners Member
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    Howdy Guys:

    I'm working on getting some pics. The poster that mentioned the Alt being driven from water pump pulley gave me an idea.....

    Can anyone confirm if the alternator is driven off from a waterpump "double pulley"? That seems like it would be the best solution for changing just the ratio for the alternator....

    AS I recall, the alternator on this Hearse is mounted on passenger side of engine. I believe that it has already been "swapped out" with the original, I say that because when I worked on it last summer there was no external voltage regulator. Seemed like a 1 or two wire alt setup - Might have been one wire. Can't remember.

    If I can get my buddy to take a few pics and give me the info on the alt's badge we'll be on the way to solving the problem.

    In the meantime, can anyone verify it's usually driven off that waterpump pulley, and if so, is it possible to increase the size of the pulley driving the alt?

    Thanks.

    CM

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    A change in the size of the water pump pulley will have no effect on the speed of the alternator, just the water pump. The speed of the belt will only change due to the ratio of the drive pulley to the driven pulley.

  9. #8
    Colonel Monk is offline Cadillac Owners Member
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    Well, not necessarily.... Remember, what I'm talking about is a motor with a double pulley on the water pump, which in turn drives the alternator.

    I can't change the speed of the water pump pulley, that's true. But if the water pump pulley was a double, and I increased the size of the second pulley in the double that goes to the alternator, I'd be changing the ratio of the pulley to the alternator.

    For ease of discussion, let's assume that all the pulleys are the same diameter, so ratio is 1:1.

    If I had crank at 1000 rpm, the water pump would also be 1000, as would the alternator.

    If I increase the size of the pulley driving the alternator , I decrease the ratio and thus the rpm of the alternator.

    Now, I'm talking about leaving the diameter of the pulley driving the water pump alone, and just increasing the diameter of the pulley on the DOUBLE that goes to the alternator. So the waterpump would stay the same rpm.

    None of this means anything unless the belts are actually laid out like described above. I was looking at the V8 in my old wood boat, and it has this kind of arrangement. Automotive water pump is driven off the crank pulley, and the generator is driven off the waterpump. I don't know if the caddy is set up like that or not.

    CM

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    The dual belt arrangement on the Cadillac engines is for those that had the AIR pumps. I forget what years, but I believe they were California cars. The second belt did not around the alternator, but to the pump.

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    jayoldschool is offline GM RWD V8 addict
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    Use a later alternator from a overdrive trans equipped car. GM designed them for higher output at low rpm. I suggest the 140amp unit from the 94-96 full size GM RWD cars. Swap the serpentine pulley to your V belt pulley, and splice your two alternator wires onto a later connector, available at any parts store.
    the APEMAN likes this.

  12. #11
    the APEMAN is offline Cadillac Owners Fanatic
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    Don't forget to upgrade the alternator to battery positive lead if it is skinny.

  13. #12
    Colonel Monk is offline Cadillac Owners Member
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    Thanks Guys.

    I got a little info from my friend, but he hasn't snapped any pics yet.

    He said, that the ALT is driven off the water pump, but I reiterated with him, whether or not it's off the water pump direct, or driven by crank AROUND the water pump.

    It's a Delco Remy 7135M Alternator.

    I googled it for specs, but I'm not finding anything. I had suspected that the ALT was replaced already, and wanted to know what this one is. Can anyone comment is this original or ???

    Last summer I upgraded the charge wire to about a 2 gauge wire (I was making the cables and that's what I had) so it's plenty big!!

    JayOldSchool: I have had others suggest that those mid-90s alternators are good as well - do you know, would it be a direct replacement or would mods need to be made? I won't have alot of time for mods, and though there is welding equipment, there's no machine shop and we'll be 120 miles in the desert north of Reno - the closest city. So at the most, we might be able to make a single trip to Reno for parts but I'd like to have this sewn up before I get there if possible.

    So, if anyone has done this please let me know.

    Thanks.

    CM

    ----------

    BTW, does anybody know if the alternator that Jay was talking about is the GM CS130? I think this is the one I've heard being used in these Art Vehicles in the desert.

    Thanks.

    CM

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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    I'm talking about the CS144. The CS130 would be good, the 144 would be better.

    This should help:

    http://temp.corvetteforum.net/c3/zma...ternator01.htm

    https://www.youtube.com/watch?v=Z70844woBXo

  15. #14
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    From what I've heard, you don't want a single wire alternator. Without a starting circuit,
    you need to rev them up to get them started. If you didn't do that last time, you will be
    getting no charge current. Bruce Roe

  16. #15
    Colonel Monk is offline Cadillac Owners Member
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    Re: Low Speed Alternator Setup - 1971 Cadillac Hearse w/472

    OK, I have some pics finally.

    ALT1a.jpg

    ALT2a.jpg

    So, the alt is driven off the water pump alone. Water pump is driven off crank and also around PS pump.

    Changing the size of the drive pulley on water pump should be possible, but:

    Is it? I mean, what is the size of the pulley and is a larger one available?

    The fan is also mounted to that pulley - can't see from pics, is it just thru bolted to water pump hub?

    Thanks for the correction on the alternate alt - This could be the easiest solution, but the big question there, is it a bolt-in replacement or will the existing mounting need changing?

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