Topic: Is this voltage regulator correct for a 1970 SCJ?

[Bob Gaines]

All b9s used c8af regulators and had the 4'' alt pulley.  I have never seen or heard of a dotf or a dozf  only the doaf showing up on later 70 and 71 cars with the d2af showing up on the motorcraft regulators.  What i am trying to document is when and why the 15V started showing up stamped in front of the C8  eng # below the autolite stamp.

Ed ,I suspect that the reason that the B9 and the Boss 302 used the C8AF silver stamped regulators instead of the typical C8TF for the 55 amp was because of the 4 inch hipo pulley they both used. The alternator was under driven. The larger diameter pulley decreased the speed that the alternator turned so it could not reach its maximum designed output there by only requiring the the lower capacity C8AF regulator typically coupled with a 38/42 amp alternators. At least that is the most logical explanation I can think of. It is strange that Ford didn't note the exception but I suppose the relative small number of those cars must have had something to do with the decision.

[cobrajet_carl]

Bob,

Thanks. I understand your logical approach. I am also fully aware of the relationship between all aspects of an electrical load, voltage regulators and alternators. My first (of 3) engineering degrees is in electrical & electronics. EG your assumption that a 1970s vintage 55a alternator was designed to output full rated power on a particular engine/ pulley configuration may not be true. The alternator may be intentionally under driven (limited) on a high rpm engine to protect the machine from damage, so necessitating a higher theoretical output. So in this case a 55A rated alt may actually be operating at a lower max power output on its curve at high rpms and adequate output at idle(under driven) which means a 42A voltage regulator is more than adequate. Today, modern designs of alternators have an output curve that is near flat at all speeds, but older designs had a much more linear output in relation to their speed.

Which Ford documents are you referencing?

The load/charging current does not pass through these types of regulators. The regulators themselves do not have a current rating. Well, they do to some degree of course, but not load related to the first order.

[Bob Gaines]

The load/charging current does not pass through these types of regulators. The regulators themselves do not have a current rating. Well, they do to some degree of course, but not load related to the first order.

I use the designation in the same way Ford lists them as being paired to the alternators. It makes for a better understandable comparison for purposes of discussion even if not technically accurate to a regulator.

[cobrajet_carl]

Ed ,I suspect that the reason that the B9 and the Boss 302 used the C8AF silver stamped regulators instead of the typical C8TF for the 55 amp was because of the 4 inch hipo pulley they both used. The alternator was under driven. The larger diameter pulley decreased the speed that the alternator turned so it could not reach its maximum designed output there by only requiring the the lower capacity C8AF regulator typically coupled with a 38/42 amp alternators. At least that is the most logical explanation I can think of. It is strange that Ford didn't note the exception but I suppose the relative small number of those cars must have had something to do with the decision.

The larger pulley will not lower the maximum output of the alternator. It will move it up in RPM but most are putting out full power at 2K engine RPM. The larger pulley reduces the RPMs that the alternator will see for a high revving engine but it won't reduce the maximum output power of the alternator.

[specialed]

 289 hipo 427 boss 302 429 351 429cj scj 351 HO all use a big alt pulley.

[Bob Gaines]

The larger pulley will not lower the maximum output of the alternator. It will move it up in RPM but most are putting out full power at 2K engine RPM. The larger pulley reduces the RPMs that the alternator will see for a high revving engine but it won't reduce the maximum output power of the alternator.

Thank you for sharing your point of view. Your point may well be valid . The Boss 302 and Boss 429 have been observed on many occasions to use the C8AF regulator instead of the C8TF , that is a given .  I find it strange that the C8AF regulator which is not typically paired with the 55 amp alternator as per Ford factory specifications in 69 as well as in other previous years specs yet the one common denominator in the electrical system on both cars is the pulley . That coincidence is the basis for my suspicion. It may or may not be related but it is strangely coincidentally non the less. Since it is typical for Ford to have a reason for everything that they do if the pulley reason does not have anything to do with the regulator difference given the Ford documents then why?

[70cj428]

I checked out the link above where BP says all CJ w/o AC cars got the silver inked C8AF regulator and I'd have to disagree. As I've mentioned above, I've been researching and documenting 70 CJ cars since 1983 when I bought my first one and of all the 70 CJ's I've come across where I had a very high confidence they were unmolested originals, all had the Yellow stamped C8TF regulators, at least 2 dozen cars including 6 428/AC cars ( If it matters, probably 90% were Metuchen cars). It's also mentioned in multiple Ford parts books and even the 70 Shop Manual that silver stamped regulators were used on 38 and 42 amp alternators and yellow stamped regulators were used on 55 amp alternators.
 From an engineering perspective, 55 amp alternators use both a different rotor and stator windings. The difference in the rotor may be just the shaft and bearing sizes (you can't tell because ford didn't service the rotor coil as a separate part) . I'd almost bet that the some or all of the 3 or 4 resistors in the regulator were optimized for the current requirements of the 55 amp alternator stator/rotor. (the 55 amp alternators probably needed more field (rotor) current, but again that's just a guess without reverse engineering a few regulators)

EDIT:  Just found some schematics of a regulator, and it appears that they don't limit the current to the rotor when in full charge mode, so it kinda throws my resistor theory out the window ..... Maybe when I get a chance I'll tear a couple regulators apart and see whats different inside ......

Just more fuel for the Fire ....   John

[cobrajet_carl]

I checked out the link above where BP says all CJ w/o AC cars got the silver inked C8AF regulator and I'd have to disagree. As I've mentioned above, I've been researching and documenting 70 CJ cars since 1983 when I bought my first one and of all the 70 CJ's I've come across where I had a very high confidence they were unmolested originals, all had the Yellow stamped C8TF regulators, at least 2 dozen cars including 6 428/AC cars ( If it matters, probably 90% were Metuchen cars). It's also mentioned in multiple Ford parts books and even the 70 Shop Manual that silver stamped regulators were used on 38 and 42 amp alternators and yellow stamped regulators were used on 55 amp alternators.
 From an engineering perspective, 55 amp alternators use both a different rotor and stator windings. The difference in the rotor may be just the shaft and bearing sizes (you can't tell because ford didn't service the rotor coil as a separate part) . I'd almost bet that the some or all of the 3 or 4 resistors in the regulator were optimized for the current requirements of the 55 amp alternator stator/rotor. (the 55 amp alternators probably needed more field (rotor) current, but again that's just a guess without reverse engineering a few regulators)

EDIT:  Just found some schematics of a regulator, and it appears that they don't limit the current to the rotor when in full charge mode, so it kinda throws my resistor theory out the window ..... Maybe when I get a chance I'll tear a couple regulators apart and see whats different inside ......

Just more fuel for the Fire ....   John

I suspect the only differences are the voltage settings. The pic Bob posted would seem to confirm that.

[specialed]

Interesting john  (70cj428) about your research on 70 cjs having c8tf (yellow) v-regs  and i dont remember now which v-reg i put on the 70 cjs i restored and worked on in the past but the red  low mile 70 mach 1  cj i bought from canada original owner  back 20 years ago was unmolested and i used that car for reference in the past and jeff s. has many photos of it also he uses in his post for 70 reference. So maybe jeff has a photo of the v-reg area as i dont know where my photos arent handy buried smewhere in the 1000s of reference photos i got since that was in late 90s when we bought that car out of canada.  The 1970 mustang cars had a dozf altenator vs c9zf on 69s yet they used the same pulleys and the 70 cars had a totally different wiring setup and 70 cjs had many changes from 69 cjs including a rev-limiter on 4-speeds and dual point distributors. Also the dual altenator pulley used on 70 cjs with factory a/c is another factor to figure in.

[cobrajet_carl]

Interesting john  (70cj428) about your research on 70 cjs having c8tf (yellow) v-regs  and i don't remember now which v-reg i put on the 70 cjs i restored and worked on in the past but the red  low mile 70 mach 1  cj i bought from canada original owner  back 20 years ago was unmolested and i used that car for reference in the past and jeff s. has many photos of it also he uses in his post for 70 reference. So maybe jeff has a photo of the v-reg area as i don't know where my photos aren't handy buried somewhere in the 1000s of reference photos i got since that was in late 90s when we bought that car out of canada.  The 1970 mustang cars had a dozf alternator vs c9zf on 69s yet they used the same pulleys and the 70 cars had a totally different wiring setup and 70 cjs had many changes from 69 cjs including a rev-limiter on 4-speeds and dual point distributors. Also the dual alternator pulley used on 70 cjs with factory a/c is another factor to figure in.

From the pics of that car it looks to me like yellow stamping. Interesting that Ford didn't use a large pulley on any of the 428CJs.

[J_Speegle]

Question-  Do we want to change the discussion to include non SCJ cars?  All 70's or just expand it to all Cobra Jets?

Just asking before I collect what I can have and trying to stay between the lines

[cobrajet_carl]

Question-  Do we want to change the discussion to include non SCJ cars?  All 70's or just expand it to all Cobra Jets?

Just asking before I collect what I can have and trying to stay between the lines

Well it would be nice to know for sure which ones came with what engines and options...

[J_Speegle]

Well it would be nice to know for sure which ones came with what engines and options...

Here is what I have to offer to the discussion. Of course any of these could have been replaced but the condition appears to match the rest of the parts in these examples. Will list options and details of each as best I can. Sorry there are not more but keeping with SCJ and CJ Mustangs

As I usually try cars are listed by assembly plant grouping and in production order from earliest to last within those groups. Hope this helps

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0F05R1188xx - silver markings. Options: SCJ engine/Drag Pak, 4 speed, P/Disc. Completed Oct 20 1969




0F03R1230xx. Difficult to make out. Believe it might be a silver version only due to a possible lower outline from the ink stamp in the lower left in the picture of the cover. Options: Drum brakes, 421 eng code, automatic, PS, Calif emissions, power top.




0F05R1291xx - maybe yellow markings. Options: Unknown




0F05R1631xx - yellow markings. Car that Ed was referring to and in the unrestored picture thread section of this site. Options: Automatic transmission, PS, Tach. Completed Feb 24 1970




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0T05R1362xx - appears to me a it's silver markings.Options: Automatic transmission, P/Disc, PS

[cobrajet_carl]

Last pic looks yellow to me Reality is that any of the regulators would work with any of the alternators. Perhaps there was an intended pattern but ended up being what was used was what was available.

[Bob Gaines]

I posted a picture of a 69 Service specifications (small book) previously which is part of the shop manual series of books.  65 Mustang on have them. I don't have a 70 version . Does anyone have one to see what is in the 70 manual on the subject?