Alternator Amperage

I am thinking about switching my alternator. My headlights kind of flicker a little bit at night. I don't know what I have in there right now. It"s either a 60 or 70 amp alternator. Would a PowerMaster 90 amp be too much? I am running a MSD Dist and MSD 6AL box.

Put relays on the lights. There are a number of posts covering the way to do it. Cheap and easy. and cures the flicker issue as well as brightens them some.

If the headlights are flickering, I would guess you have another issue that should be addressed,
A higher amp alternator may "MASK" the root cause of the problem, But I will wait for the other board experts to chime in,

I'm not changing the alternator because of the flickering issue. I need a new alternator and don't know which one to use. Also did it come with a round back or square back for 1970?

Relays on the headlights is still a good idea for our old cars.

In the bay area the first thing I would check for the flickering is the head light grounds on both sides of the headlamp harnesses that are grounded to the radiator core support

Some headlight flickering, or at least dimming, was pretty much as designed for 1970. Low voltage and some discharge at idle and make it up when rolling. As original.

1970 was a transition year from single field to dual field roundbacks. I think the squarebacks came a year or two later. A later dual field squareback should bolt right in.

If your car is set up with single field regulator, you will need to ground one of the two alternator terminals. Hook up the VR to the other.

Either the later 78 A unit as reman or a 90 amp aftermarket squreback unit will work. An upgraded charge wire and bypass of the bulkhead connector is highly recommended if you run a higher amp alternator.

on the supply side an electromechanical reg (which you don't have I'm assuming) and or a worn alt (brushes etc) can cause flickering. do you have the early mechanical box reg/single field terminal alt or later flat reg/2 field terminal alt system? As said any later 2 field terminal alt will work & agreed on cleaning ALL terminals/connections on the power and the ground side. all that is left is what alt do you think is best (Mopar regular 2 field or Denso (which has good feedback)

Mine is a dual field round back alternator. I don't know if is suppose to be round back or square back. Like said I'm not changing it because of the flickering. I think this light flickering is normal. I just don't know which amp to get.

other than the early electromechanical reg setup, any flickering ain't normal. any 70's alt new or used is fine & if getting new or rebuilt I'd just get the highest amp unit offered which they have the std thick stator (in between the alt cases) other than the big heavy high output Leese Neville beast with the fan behind the pulley & it is good but requires its special bracketry so I dont think that is an option here. the 78 amp one for an 85 M body is the highest but has a thin stator & needs slight fore/aft/swing arm adjustments. reportedly some of the higher amp ones have a problem with lower output at lower speed (not good)

AS RR stated the flickering is not normal and the cause needs to be diagnosed and corrected before a bigger problem develops. It is a direct indicator of a bad alternator/ regulator or a connection issue somewhere in the wiring that is appearing under higher electrical load conditions. Failing to address the connection issue ( if it is due to that) can result in an electrical meltdown.
I also agree with his suggestion on a replacement alternator and will caution that going with a higher amp output than the factory used will require additional changes to the wiring to handle the additional capacity

I do have a bad alternator. I know that. I just want to get a good brand. What do you suggest? This is the alternator I'm using now but don' know what amp it is.

The alt will only put out what the system draws.So if you have lots of add on ut will put out more.As for the flickker if you have the old points reg thats one problem.They make one that replaces it and is solid circuit.had one in the 62 and 66 and they charged great even with the old single field alt.The 62 had a big amp and never had a problem in 12 yeays and tons of street miles.My 65 i changed to new style reg and run a Summit chrome dual field alt.Its been in at least 10 years no problems.Rocky

I want to get a 60 or 70 amp round back single pulley dual feed alternator but can't find one.

How about the Powermaster #7018?
95a, roundback, single or dual wire, single groove pulley.

https://www.summitracing.com/parts/pwm-7018

http://www.powermastermotorsports.com/mopar2.html

Your Photobucket is private, I can't see it.

Let's get back to basics: The alternator if properly regulated will not put out any more amps than the load it is feeding requires. So what do you have? MSD box needs 1 amp per 1000 rpm, so let's say 6 max. Headlights high beams usually about 55 watts means 4.5 amps times 2 equals 9. Radio unless you're using an external amp usually about 1 amp. All the other lights on probably no more than 2 amps. Heater motor I guess 20 amps. Air conditioning clutch 4 amps. That's 39 amps.

As far as brand of alternators, I would use a remanufactured unit from AC Delco or Remy (or a new one from either). I would also look at Bosch. No Cardone or other no-name alternators for me. NipponDenso also made alternators for Chrysler products and they are very good. The above brands are available at Rockauto.
I guess Powermaster has been a successful product for board members.

Really, a 65 amp alternator is all you need, but if it makes you feel better, you can go as high as 100amps with no issues.

All the above comments about cleaning the bulkhead connector, putting headlights on relays, etc are good advice. A larger alternator will put more amps into the fire if you have a short circuit.

R.

I saw that but wondering if 95 amp is too much.

I have a ToughStuff 100amp dual field square back (replaced an autozone 60amp dual field which was putting out squat at idle), externally regulated. The tag that came with it said 15 amps at idle. I have bypassed the bulked feed by doing a home run from the alt to the starter relay. I intend to go strait to the starter in the future. I've put relays on the headlights and AC clutch.

All that done, I still had flickering from the dome lights, tail lights and turn signals. I cleaned the connectors in all the lighting circuits and the bulkhead connector with electrical degreaser and AL oxide (silica sandpaper may be a better idea) sandpaper, then cleaned the contacts again with electrical degreaser and packed everyting with dielectric grease. No more flicker.

At night with all the electrical load I can put on it, the voltage is steady between 12 and 13 at idle and no flickering anywhere. I have a 45w x4 channel JVC head unit, and had it cranking for my little test. I figure I now have headroom for electric fans.

I think ToughStuff hardware is worth considering.

Resized my bad alternator. Don't know what amp is.

50Amps

95 is definitely not too big with upgraded wiring. You don't want to run a 95 amp alternator on stock wiring.

That's what I thought. I replaced the old engine harness about 15 years ago with the one that Yearone sells. Dash harness is still original.