Dino DIY - Alternator alternatives + how to connect Alts w/an internal voltage regltr

I've counted 8 Dino guys that have had alternators which had oil drip on them and fry, it would be great to find a low cost alternative and I've done that with a source I discovered in LA.

In addition, the Dino has an external voltage regulator which is a sytem based on mechanical points but there are drawbacks. On my Euro Dino #05082, I wanted to find a solution to connecting a modern alternator with a solid state voltage regulator that isn't prone to these anomalies yet keep the Dino as stock as possible.

I believe I've had success in finding a NOS unit near the $250 mark. Last year, the alternator in my Euro Dino had thje dreaded "oil soak and short out" and the rebuild ame in at 50% over the $250 mark.

Enter the Magneti Marelli 55 Amp alternator for the Fiat 124, p/n 63307400 as pictured on the left, original Dino 60 Amp alternator on the right. Note: I've also seen that the Bosch alternator for the Ferrari 308 series will work too, but they are more expensive.
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The new alternator must fit the same form factor as the old. No changes in the mounting should be necessary and the Magneti Marelli conforms. The pivot bolt span is identical in shape and size as well as the critical offset to the pulley. The tensioning bolt must fit the arc bracket as well as the inset hex notch and again, the Magnetti Marelli conforms exactly.
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The pulley alignment of the alternator contender must be exactly the same distance from mounting bracket as the original to preserve the straight line run of the belt. No run out at all and the Magneti Marelli meets this. The pulley must also fit the standard Dino belt and it does. The difference is that the pulley diameter on the contender is a little smaller which should cause the alternator to turn faster, but I don't see this as a problem.
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Setting up the mounting bracket to the prospective alternator on the work bench shows it mates well and sqaure.
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The rear of the Magneti Marelli has a few differences. The inset unit with the heat dissipation fins at the bottom of the first photo is the solid state voltage regulator.

The spade connector that I'm pointing to in the second photo is the excitation point which requires a constant 12V for the field current to generate properly. This is not normally found in the stock Dino configuration but I found an easy source that does not mar the original wiring.

The large, B+ connector at the top is the same as the original output terminal that provides ouput from power generation.
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The Magneti Marelli unit only requires two wires for operation; the 12v excitation line in and the beefy line out. Note: I'm using a modern 60Amp fuse in Dino 05082 and the beefy output wire terminates at the clear lexan connector in the photos.
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The 12V excitation line is a bit longer than the old unit's field current line so fashion your wire length appropriately. I like to Bundle the wires together in a heat insulation loom (aka "sock") and set it in the heat shield. Now, we're through with the bench work!

Steady man, you're getting excited...

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Install the new alternator and heat shield in the Dino
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While the output path wire is the same (the beefy wire), the only difference is the field excitation wire that must produce a constant 12V. The stock Dino uses a constant 12V into the external voltage regulator and it outputs variable voltage to affect the field current that causes charging.

I propose to use the stock wiring but pass the constant 12V to the new alternator's excitation line by bypassing the external voltage regulator. This will preserve the original wiring lengths and physical mounting but will make it easy to retrofit back to the original configuration.

Dino 05082 is a Euro model and has the voltage regulator (big black box) in the front trunk/bonnet located on the circuit board. USA version Dinos have their Voltage Regulator under the dash next to the ignition switch.
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Verify that the power wire into the voltage regulator is 12 V switched through the ignition key and has continuity to the engine firewall mounted fuse box. Note that it is already supplied power from the standard fusebox so the alternator fusebox is redundant.

Since I'm using a modern 60 Amp fuse for the power output wire, both wires are fuse protected before they meet the Dino alternator fusebox, so I can remove it from the engine firewall with no loss of safety.
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Connect the firewall lines directly to the alternator wiring.
The firewall fusebox is now removed, but each line is fuse protected.
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With safety assured, make a "pig tail" jumper wire with male spade ends. Connect the Voltage Regulator's old 12V power in to the field current output so that the new Voltage regulator will have an ignition switched 12V input excitation line.

Finish off with shrink tube insulation.

Should you ever desire to return to the original configuration, just remove the pigtail and re-attach.
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I attached my voltage meter to the battery terminals with long lines and started the Dino. Pushing the accelerator rail I see the voltage vary and at moderate speeds the output is well above nominal confirming that the alternator is producing charging power.

Success for under $250, using modern solid state voltage regulator and it is fully revertable!

After a test drive I noticed that the Ammeter is showing typical movement direction but is missing the small jitter that it once had. Speculation is that the mechanical points on the old Voltage Regulator caused this jitter.

Note: 05082 is running a 60 Amp MoMa upgraded Ammeter gauge and the increased capacity means decreased needle swing and that for the same current this gauge will display less needle deflection than the standard 40Amp range.
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Dino #05082 is a 1973
The Nov 1975 edition of the Parts Book Table 116 shows 3 possible configurations of the front circuit board/fuse block,
photo below

"...had the solid state relay under the dash"
I never knew there was a ss relay and always thought that USA Dino's had the big red box with 3 wire connection under the dash. Does anyone have aphoto of the solid state unit?
Thanks
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Excellent response. Thank you, its much appreciated as I never knew how the pulley size limits would affect operation and just imagined it would be limited by the "duty cycle" imposed from the Voltage Regulator. I wonder if bearing wear would be affected by the faster turning of a smaller pulley.

Then again, since I have the original alternator so I could easily use the original pulley on the Magneti Marelli alternator.

Agreed, its a common problem.
I've known 8 Dino owners that have had at least one alternator failure, one owner has had multiple failures and they all seem to happen the same way so it can get expensive.
BTW, the alternator issue is not isolated to the Dino and I have F355 friends with the same issue; oil drips down and takes the unit out.

Dang, you read my mind on coming up with a turn key packaging solution. There are only a handful of modern improvements in the Dino design (ignition system, exhaust, alternator) but we can address them. Hence I've bought the last several of these alternator units and have them on the shelf. Most of the projects I'm doing on Euro #05082 are prototyping and fit checking for restoring my USA #05702.

For those that have not seen the difference between the Euro and USA version alternator brackets, attached is a photo of my USA version alternator that Champ mentioned and it is soaked in oil drippings. I conjecture that the waffle canister may be shielding it from some of the oil, but the basic issue is still there.


I also bought a Bosch alternator "core" from a 308 and had it rebuilt at a cost of $300 USD but it looks better than brand new. I've still got some time for winter projects so stay tuned.
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Does anyone need a Marelli alternator?