Been gone for a while, haven't had my truck so I haven't been doing much until now. Drove her from STL to Cleveland, made it just fine with the exception of a front wheel bearing going out in the last 50 miles. (Replaced with Timiken, bearing turned out to be original w/ 235,000 miles on it. -- oh well)
Anyway, more to the point. I followed these instructions (with some modifications of my own) For a B2600i pickup. The swap is relatively similar with a few key differences to note:
For one, the m10 x 80 bolt is too short. B2600s use a drill block and a sliding bracket for the alternator adjustment instead of just a bracket. For the 2600, both the block and the bracket need to be reamed out.
Drill bits I used were 13/32 for a tighter fit, could go to 27/64 for a little looser feel.
Bolt I used was a 3/8ths inch (VERY SIMILAR TO M10) with coarse Threads, 4 Inches long. (need to compensate length because of the block). Instead of using a dremel to adjust the bracket, all I needed was a flat file, however there was some serious filing involved.
The upper bracket for the B2600 needed to be taken off completely, and given a small (one or two washer) shim away from the engine to fit right with the GM unit. Don't go more than this or else thhe bolt isn't threaded into the block right. If you need more shim, I suggest you bend the bracket, or get a longer bolt into the block (Which I intend on doing soon)
Also, the lower bracket on the B2600 is slightly different, I had to file the outer casing of my alternator a little and adjust the drilled out hole to be a little looser (27/64ths) so that it would fit on all the way.
Do Note: I noticed that the fan on the GM unit comes VERY close to the horizontal bracket of the 2600. For me, it seems to clear the bracket with about 3mm to spare, however I strongly recommend that anyone doing this swap check to make sure none of their alternator blades are bent out or are too long. The tolerance is a little tight, and I sure wouldn't want to see anyone whacking their alternator blades off into their engine doing this.
Other than that, the retrofitting is roughly the same. The original alternator is still the mitsubitchie 55 amp unit, with the same two wire connector on the back. My findings were that White/red Stripe was 12 Volt constant, White/Black Stripe was with ignition.
Oh, and if you are wondering. The alternator I used was from an 83 Citation, I made it work, however I noticed that unlike the one used above, this one had the connector near the back of the alternator, right in line with the hole for the lower tab. I made this work OK with a small ammount of difficulty, however for future ease of use: TRY TO FIND A GM ALTERNATOR WITH THE CONNECTOR NOT IN LINE WITH THE BOLT.
Final words: It seems that the GM units want to be spun a little faster than the Mitsu. I haven't had any problems yet, however I am only getting 12.3 at idle, 14v comes at around 2000-2500 rpm. Any suggestions?
Oh and the Duralast Belt mentioned is a *litttle* short, but its okay. Works well.
Pictures of stuff below:
The drill Block
The Horizontal Bracket
Choose Alternators Wisely: DO NOT LET THIS HAPPEN TO YOU
Reamed and Filed so it can go around the B2600i lower bracket nice and smooth. (Stupid cast iron parting lines...)
Fitting it in: NOTE SHIM WASHERS
All fitted in nice: note close fit between blades and bracket. Just be careful.