This is just a quick writeup of parts I used for doing the turnbuckle method for tensioning my quest alternator. I had a welded bracket but the sweep angle was really off and my belt would squeal because I could not tension it any more. Saw this idea on here and gave it a shot. Hope it saves some people a bit of time. No pics, sorry. it's really straightforward once you have the parts in hand.
FYI I am using the 4pk845 belt. RB25 water pump and crank pulleys on a 26 motor. But basically this should work for all RBs (I hope. at least it worked on mine). Total parts price was $41.xx shipped from mcmaster. over $13 was spent on the jam nuts, which you're forced to buy too many of. I've got 4 extra sets if anybody wants them. part numbers are below, and I have some spare jam nuts due to ordering quantity restrictions. I measured my tensioned length to be approximately 4" from the top bolt of the water pump. If your tensioned length is not this length, dont buy the parts below. the parts below allow an adjustment up to about 5" total length according to what i calculated.
1 94450A260 18-8 SS LEFT-HAND THREADED THIN HEX NUT, 3/8"-24 THREAD SIZE, 9/16" WIDTH, 7/32" @ $5.04 (5 pack)
2 94805A217 TYPE 316 STAINLESS STEEL THIN HEX NUT, 3/8"-24 THREAD SIZE, 9/16" WIDTH, 7/32" @ $8.25 (25 pack, ugh)
3 60645K141 HIGH-STRENGTH BALL JOINT ROD END, 3/8"-24 RIGHT-HAND MALE SHANK @ $4.32
4 60645K142 HIGH-STRENGTH BALL JOINT ROD END, 3/8"-24 LEFT-HAND MALE SHANK @ $4.32
5 8419K13 EASY-ADJUST THREADED CONNECTING ROD, 2" OVERALL LENGTH, 3/8"-24 THREADED FEMALE ENDS @ $15.03 (aluminum only, ugh)
Here's what I did (stupid steps that anyone can figure out without reading below. just buy the parts and do it.)
1) remove the original tensioner and set aside. in order to take out the two M10 water pump bolts, you need to remove the water pump pulley.
2) put the lower bolt back in to the block and tighten it down. I took the washer off the top bolt and stacked it onto the lower bolt (2 washers now) so the lower bolt doesnt go too far into the block. Also the thickness of the heim makes the top bolt a close call in terms of available length if you are reusing the existing water pump bolt... so best to get rid of the washer for the top bolt. Personal preference. or get new bolts. i was lazy but it still worked.
3) take one of your heim joints and dremel out the inside using a sanding drum. The 3/8 rod end is too small to put the M10 water pump bolt through it. The other heim joint needs no modification for the M8 bolt on the alternator side. why didn't I buy a metric turnbuckle? mcmaster doesn't sell the LH/RH threaded rod for it.
4) assemble your turnbuckle with the jam nuts and adjust it all the way down to the shortest length.
5) attach turnbuckle (enlarged heim goes on water pump side, duh). Smaller side goes into alternator. On the alternator side I used a washer on either side of the ball joint. On the water pump side I used no washers due to bolt length.
6) tighten everything up.