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I had a high output 100 amp 12SI alternator for years but the gen light would flicker at idle with my Hella Euro Halogen headlights (100 watt highs) so I switched to the much more modern and efficient GM CS-144 (140 amp stock charging rate) a few years ago. Generally its not a great idea to up the amps in the Stock 10/12SI alternator housings since the fan will not sufficiently cool the alternator at high amp loads, will not provide high amps at idle (they require some revs for high output) and were never designed for high amp output (my stock 12Si was rated at 63 amps). I went with the CS-144 140 amp alternator since it has a much bigger housing for cooling, was designed for stock OEM 140 amps, has a much bigger cooling fan, Charges like a champ at idle (I believe, not sure now, but 60 amps at idle), and fits perfectly in the stock location. You will need an adapter wire to go from the CS-144 to the stock wiring plug (easy and cheap). I did not upgrade the wire from the alternator to the battery since my total draw is only about 80 amps but you should with your setup. I paid $170 for the CS-144 new..not rebuilt.
I was planning on buying a recored 12si with 105 amps, but now you have me worrying.
I would have gone with a 130 or 144 CS but apparently when running tall valve covers and such, these will not fit.
I look at it this way. More than is needed may buy you some insurance in that the alternator is working far below it's capacity and therefore creating less heat than it is capable of.
If the cost difference is reasonable to you then go with the higher capacity and more expensive alternator.
There may be other considerations as well as Belgian has pointed out.
What I considered was the charging amps available at idle. That is where the system usually fails to meet the need.
So If 60 amps at idle is sufficient and total requirement is far below the optimal output of the alternator then go with the idle output needs first. Then ensure that the total output requirement is also met.
I kind of wonder if heat related failures have more to do with header proximity/type and whether coated or not and under hood temps rather than an alternator failure due to heat created due to the alternator output requirement.
I just got mine from skip white. Looks very well built! I wanted to replace mine since installing a dual fan setup. Hope to have reports in about a week.
I look at it this way. More than is needed may buy you some insurance in that the alternator is working far below it's capacity and therefore creating less heat than it is capable of.
If the cost difference is reasonable to you then go with the higher capacity and more expensive alternator.
There may be other considerations as well as Belgian has pointed out.
What I considered was the charging amps available at idle. That is where the system usually fails to meet the need.
So If 60 amps at idle is sufficient and total requirement is far below the optimal output of the alternator then go with the idle output needs first. Then ensure that the total output requirement is also met.
I kind of wonder if heat related failures have more to do with header proximity/type and whether coated or not and under hood temps rather than an alternator failure due to heat created due to the alternator output requirement.
I run tall covers and the stock alternator is close. I gave the dimension to a US based alternator shop that someone over here gave me and they told me the CS144 wouldn't fit. I can still pull it outward, but then the belt will hit the power steering pump below.
Guess, my only option would have been the Si12 upgrade or none at all.
I can just about squeeze by with all of the extra's I have on her right now (efi + vacuum pump) but I was planning on a alu rad + fans (mostly because it's the only way to solve my cai) but with the stock alternator this is out of the question unfortunately.
Anyone now on which models the CS130 or CS144 is normally fitted ?
Last edited by Belgian1979vette; Oct 14, 2014 at 01:24 AM.
I always grab the CS144s off of late 90s Chevy/GMC trucks/Suburbans. It was the optional high output alternator. That is the easiest one to find them on, but I have seen them in mid 90s Caddilacs (can't remember the model I saw it on), too. SC130 was used in almost everything else in the late 80s through mid 90s. TBI trucks, Caprices and F-bodies are where I would find them.
