I wish to replace my current 2G alternator with a 3G unit but I have run into some road blocks regarding the mounting bolt spacing and possible tensioning issues with the V-Belt pully configuration. These alternators come in both 7" and 8.250" center to center mounting bolt spacing. My current OEM 2G unit is 7" C-C spacing. It seems to reason that I need a replacement 3G unit with 7" C-C spacing, however I'm reading conflicting things. Can anyone confirm the correct needed spacing for an upgraded 3G alternator for my 351 HO engine? If you've done this on an engine like mine, feel free to recommend an alternator and anything else you might add? Thanks!

 

well if its too hard to get to it to measure what you have, I'd go to like advance auto parts website, put in your truck specs and look up to see specs on a replacement to confirm it is 7" cc. As far as tensioning and idle cycles, when I did my 3G upgrade I just pulled the wheel off the original and used that on the new alternator. I have a 4.9 L6 not a 351 but i'm not sure if that actually makes a difference or not.

 

If I was doing the 3G upgrade, I would find the 95 amp version, not the 130 amp version. A single groove v-belt will not support 130 amp output.

 

well this is what i'm running: I havent had any issues. Should I be? Oh, its been a couple years but I think I have a double vbelt on the alternator. Its dark and snowing otherwise I'd go look. But that is what is sticking in my brain for some reason

 

Thing is not all truck motors had 2 belts on the ALT.
I think the non AC 300 motors had 2 belts on the ALT but the AC trucks only used 1.
You would think it would be the other way around?
Dave ----

 

Doesn't the second belt drive the smog pump ? Just checked my photo's, I have two grove pulley on my alternator, but I removed the smog pump.

 

On the AC trucks I think that other groove was for the air pump
I forget how the pump was driven on the non AC trucks?

Then again I could be totally wrong on all this
Dave ----

 

I agree with using the 95 amp with a single v belt. I put a 130 on my 86 5.0L which only had one belt and it would squeal on start up. Put on a soft start regulator which had a time delay so the amperage would come on slowly and that cured it. Just mention it in case someone really need a higher amp unit.

 

I have factory ac and my fog pump is still intact. Two belt on alternator. I will mention that I leave my defrost on with motor on low all winter and it does squeek a split second when I turn it on. It doesnt squeak if the defrost is off, but the lever moves so slow in the cold I just leave it on lol

 

If you have your truck tuned up and a good battery, you will never really need a lot from the alternator. But if for some reason your battery has drained, the 130a alternator is going to throw it to it, and that is when you will get belt slippage. Most factory 3G 130a alternator setups have a serpentine belt.

 

Well, after much research with no absolute answers in regards to my particular engine in the above opening query, I said screw it and went to AZ and got a 3G alternator for a 93 Taurus with a 3.8 engine. Alternator is 130 amps. I bolted it up yesterday and it appears to fit. I've not done the wiring yet as I have some things I still need to work out. It does not appear that I will be able to run dual belts, so I am going to go with a soft start relay with a 10 sec delay. Would rather have a 95 amp alternator but finding one with a 8.25" C-C spacing seems to be impossible. I'll keep this thread posted as to how it all works out.

 

In my previous post I wasn't referring to a time delay relay. There are different regulators for the 3G series alternator depending on the application. The Ford part # for the regulator with a 2.5 second delay is GR814. These are also available in aftermarket and are white instead of gray. I used one on my 86 with a single belt and it worked fine.