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internal volt reg alt

Old January 10th, 2019, 07:26 PM
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internal volt reg alt

Just now getting to my project 1970 Cutlass SX that was purchased a while back. Unfortunately, the original 455 eng was replaced by a 72 350 which has an internal volt reg alternator.
Question i have is- was my wiring harness modified for this or was the internal reg alt correct for the 455 SX cars as it was for the 442 in 70
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Old January 10th, 2019, 09:05 PM
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The 1970 Chassis Service Manual says the internally regulated alt (ie- "transistorized ignition) was used "on all 442 models"....that's all it says and doesn't mention any other big block equipped models.

I assume the first three digits of your VIN are "342" which means it's a "4200 Series" car. 442's are "4400" series cars (VIN begins with "344"). The reason I mention that is the PIM (Assembly Manual) seems to confirm the Chassis Service Manual b/c the PIM shows ONLY the 4400 Series getting the "AY" coded alternator on any 455-equipped cars. "AY" was the internally regulated open face alt in 1970 based on what I have seen.

However, I can't say I've ever seen a super original '70 SX and paid attention to the alternator setup....I could be wrong.

Last edited by 70Post; January 10th, 2019 at 09:07 PM.
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Old January 11th, 2019, 07:54 AM
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Originally Posted by lunaboy View Post
...was my wiring harness modified for this...
If the external regulator and its harness are still on your car, wiring modifications that were required to accommodate the internally-regulated alternator are simple and easily reversed (as long as the job were not done with a machete).
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Old January 11th, 2019, 02:11 PM
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the external regulator is not there but the holes on the firewall are.
could this sx convertible with 455 and 4 core rad have the Code Y72 option that required an internal reg alternator?
" y72 option was ... "
the Heavy Duty Radiator Code ED part number 3017108, 4 core – not available with the VO1, VO2 options, not available with W30 or W31, not available with 3.91 or 3.42 axles. Mandatory with W33 (police use). Available with or without C60."
anyone else have an sx with factory internal reg alternator? and car not being a 4400 series car ?
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Old January 11th, 2019, 03:15 PM
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Is the pigtail and the 4 wires/ or 4 pin connector there for the olf VR?
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Old January 11th, 2019, 03:34 PM
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This might be more anecdotal, but several years ago I looked at a 1970 SX that was a survivor condition car. It did have the 4 row radiator and also had the voltage regulator mounted to the firewall. I've got some photos of the engine compartment I can post if it would help. John
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Old January 11th, 2019, 03:40 PM
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I found the thread when I was sharing about the car. I posted a bunch of photos so you might find something else that would help. It was an elderly couple who owned it. John

https://classicoldsmobile.com/forums...-survivor.html
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Old January 12th, 2019, 06:48 AM
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The 1970 PIM calls out different alternators for 4400 series and all other A-body cars.

Standard alt:

1100879 (code AS) - non-4400
1100880 (code AT) - 4400 only

HD alt:

1100777 (code AJ) - non-4400
1100890 (code AY) - 4400 only
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Old January 12th, 2019, 08:31 PM
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well it looks like the only correct alternator for my 70 sx conv would be the 1100777 55 amp

by any chance is that an internally regulated unit.

i have looked at my harness and there is no pig-tail where the wires would go to the v reg on the firewall.

maybe the harness was swapped out, who knows.

thanks for your help anyway.

Last edited by lunaboy; January 12th, 2019 at 08:44 PM.
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Old January 12th, 2019, 09:54 PM
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1100777 55 amp is a externally regulated alternator.
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