Underdrive pulley kit no-charge at idle...ideas?

[MoparDealer1971]

I have a Mopar (March) pulley set on my 318.  I recently replaced the Alt, regulator, and battery in an effort to improve the charging situation.  Turns out my old alt was junk (low charging at any RPM), but other than that...still the same real issues.  The battery does not charge at idle.  At night with lights on this can be a problem at a light when everything dims down to nothing and my amp gauge is pegged on D.  March says this is sorta normal for an old Mopar and my options are limited.  They have a 25% larger pulley but by my figuring that really isn't enough.  Is there a conversion to put a better or more modern alternator on that might fix this issue?  I idle 500-750RPM and I don't get the amp gauge above center with lights on until 1200.  No load it comes up around 1000.  Is it dangerous to let it bounce back and forth between D and C with the loads on and off throttle?  I was thinking maybe just getting a deep-cycle battery and letting it take the heat.  Thoughts?

[MEK-Dangerfield]

My apologies for my ignorance on March setups, but you aren't the first to have trouble.

This pulley that they have that is 25% larger, is it located on the alternator? It seems to me you would want a smaller pulley so it spins faster and keeps the revs up on the alternator, thus more output.   

[MoparDealer1971]

My apologies for my ignorance on March setups, but you aren't the first to have trouble.

This pulley that they have that is 25% larger, is it located on the alternator? It seems to me you would want a smaller pulley so it spins faster and keeps the revs up on the alternator, thus more output.

Yes you are correct.  You would want a smaller alt pulley.  The 25% larger is for the crank.  I want to keep the underdrive advantage though so I don't really want to change the pulleys unless I have to.

[johannes]

The electrical system is maybe the weakest part of our cars...

I run MARCH myself on a 440.
Yes, I have had ALL sorts of problems,...but they were NOT related to pulley diameter..

In anycase, a larger pulley ON THE ALTERNATOR will SLOW IT DOWN, and make things worse...
....large pulleys on alternators and PS will reduce HP loss at high RPM....


Poor connections, damaged Volt regulator, poorly grounded Volt regulator, etc, etc... is more likely your problem.

May I suggest you check the following;

1) Is your Volt regulator properly bolted to the chassis? (Two bolts and serrated washers to "bite" a proper contact)

2) Connect a Volt meter between alternator output= thich cable, and your battery +.
    What is the Voltage reading at idle, and at say 1300 RPM? (Lights on, fan on, everything switched ON)
.....This reading shows the voltage drop across bulkhead connectors, amp-meter, etc...and should be as low as possible...in the order of say 0.5 Volt..

[Chryco Psycho]

This is normal as stated above , Mopars barely charge at idle stock ,  so slowing down the RPM to increase power is a bad idea  . Mancini has a Denso alt conversion that will help giving you more charge at idle .

[ntstlgl1970]

If you want it to charge at idle, get a newer style alternator of another car. That's the only real solution. Denso, ford, Gm. The old style chrysler alternators don't do anything at idle. Even the 100A versions of the old style alt barely put out 20A at idle with a small pulley.

[MTS-Challenger]

Here is a web sight that may help. I'm in the process of rewiring my charging system and headlights to get the full advantage of more direct voltage.  Hope this helps.
 http://www.madelectrical.com/electrical-tech.shtml

[ShelbyDogg]

I've tried to fit the later model Dodge altenators (denso style) on the original stock style brackets. The longer alternators hit the power stud right on the head. There really isn't any way to use the newere style alternator without changing the brackets to a later model setup.  Later model A/C and alternator, small block setups, require a different manifold that locates the themostat housing closer to the driver's side.  Lots of work to fix the idle-charging problem. What we need is a newer style "skinny" alternator.

[ntstlgl1970]

I think GoodysGotaCuda did a write up on how to swap a late model alternator onto a 318. He had it on his website too. Or the Mancini kit that CP mentinoed, but I'm pretty sure that one uses non-stock brackets.

[Chryco Psycho]

440 Source has a conversion kit also 

[MoparDealer1971]

440 Source has a conversion kit also

I only see a kit on their site for big block (go figure...lol)  Where can I find GoodysGotaCuda's write up?  I like rigging things up on my own so if I had a few pointers from someone who has done it I am sure I can knock it out.

[ShelbyDogg]

Make a new bracket to hold your top alternator mount point out farther to clear the block. Then make a smaller bracket to bolt to the 2 holes in the head to match the new front bracket's new alternator mounting point.  I'll be doing the same thing for my newer alternator soon.      I was at Woodward Dream Cruise last year, idling for 4 hours and driving about 1 to 2 miles an hour for the same time. My battery voltage dropped down so low that the fuel injection finally quit after 9.5 volts.  I decided to put a newer alternator in when I change my engine next week. I'll take pictures.