I have a 1970 small block with AC - the alternator is old and I
expect it will go sometime soon. So, I want to be prepared.

In the catalogs I see alternators from 42,60,61,63,85,140, plus -
I'm thinking I need a 60 amp 3-wire internally regulated - is this
correct and -- can you have too much alternator (hurting the
battery) , and is the price range in the $75 area?

Also - door skins are much cheaper than the entire door. How much
of a problem putting on?

Thanks in advance. I have learned so much on the Corvette Forum
and I just want to thank all you experts!!!

 

I might be able to answer part of this... alternators are sized according to the anticipated load. If you plan on adding electrical loads beyond the factory's you might require a larger unit. A properly working alternator won't affect the battery.

My '72 came with a 60 amp unit stock.

 

I agree, doesn't matter what size alt you get, it will only put out current based on the load. Stock is fine if your not going to add fans or thumper stereo.
Door skins are pretty easy, use a good heat gun to soften up the glue on the frame and work a thin putty knife in there to get the skin to peel off. Is the existing skin that trashed? it is pretty easy to fix.

 

My recommendation is to allow the parts counter to look up the correct OEM alternator. Autozone says 63 amps: A link won't work for autozone since they store and use cookies for the vehicle selection...but you can find it at http://www.autozone.com

Kragen/Checker/Schucks also says 63 amps:
Kragen/Checker/Schucks

The price is about $45 with a $15 core...so around $60.

One important thing to realize when selecting an alternator involves comparing the alternator in the electrical system to the engine in the drive-train. In this comparison let's assume that the drive-train was designed like the electrical system in that all the components were designed to handle the OEM power. The drive-train in the 1970 was designed to handle the 435HP engine and the 63AMP alternator. If you were to install the 140AMP alternator then it would be equivalent to installing a 967HP engine. The difference in this comparison is that with the engine you have a throttle pedal so that you don't have to use the full output of the engine. But, with the alternator is will kick into high output just after starting and when you have the headlights on...it would be equivalent to flooring the 967HP engine and dropping the clutch.

So...if you want to get a higher power alternator then you need to replace the wiring as well. For 140 AMPS you would need a 000 gage wire to run from alternator to battery...a 00 would do for a short distance, but the alternator to battery line is very long; thus, a thicker wire gage is needed. You are correct about the battery perhaps getting damaged as well as the wiring. I installed a 140AMP alternator in my auto/RV so I can run appliances...I used a short 00 gage wire and I used TWO deep cycle batteries in parallel to help reduce the current load on the batteries (my first setup had just one battery and it died after just a month). Even with two batteries I had problems...one day I smelled something like melting wire and checked the batteries. The batteries were fine, but the terminal melted...it was one of those heavy duty terminals made out of lead and steel. I replaced it with stainless steel and it didn't melt any more, but the 00 gage wire got awfully hot.

Anyway...if you don't have anything like a huge stereo system or want to run power tools out of your vette then you don't need anything larger than the 63AMP model. Most cars have a 40AMP alternator so vettes have a larger one to begin with. So...if I was able to melt terminals with a 140AMP alternator then just think what it would do to your stock wiring...your vette would probably get burnt to the ground...don't play around with this stuff...I'm glad you posted your question, and I hope you stay safe.

 

Thank you for the input. I have printed these to add to my
Vette files.

Re; The door skins - I really don't know much about these other
then a lot cheaper than door panels. Do you mean you have to
"peel off" the current skin then glue on the new? How difficult
to change the hardware?
Tnx Peter

 

yes its basically a peel and stick kinda thing. There will be glue around the edge and on the horizontal beam in the middle of the door. Hardware is not to bad, especially with the skin off. I have to do mine dureing the rebuild, found rust flakes in the bottom of the door when I was putting on new panels.

 

Used doors are easy to find and usually run around $100
Just another suggestion

 

Good Point Bob.

 

If you get a rebuilt alternator keep your original pulley. On my 71 the diameter of the pulley was smaller than the pulley on the reman unit. The smaller pulley allows the alternator to turn faster at idle and keep up with load at idle. Using the wrong pulley will make a difference. While I'm not sure of the pulley size on your 70, you should be aware of the difference and look out for it.

 

Would you need more amps when using and MSD Ignition?

 

Just get an alternator that is shiny chrome and you'll be fine

 

I don't know the requirements for MSD ignitions, but I believe that some of them are about double the current that standard ignitions require. But, I think the average current (RMS) being drawn is about 2 amps on a standard ignition set, so I'm thinking there's nothing to worry about. Actually, I'm looking at the msdpromag.com site and they have a 44amp ignition which is the "mother of all magnetos", but the next step down is a 12 amp unit. And, these are for racing. For street/track like most of us then there's like the MSD 6A which is a 6amp product. The only ignition that you might want to think about routing a fresh line would be the 44 amp ignition system.