I used 3/8 OD x 1/4 ID bronze bearings to guide the drill bit. 1/4” drill bit is only .002 under the 5/16-18 tap drill size and it worked good for me.
https://www.lowes.com/pd/Hillman-1-Count-1-4-in-Bronze-Machine-Bushing/3024775
I can get you pictures of the results on my EQ heads when I get...
I got a jig that worked well for me. Drilled to 5/16 thread so it keeps the magnum threads and the new smaller size la threads. I live about 2 hours from you I would guess. I'll see if I can dig it out
2.76 open chunk 741 casting, plus a free bonus open carrier. Just pulled out to put in a sure grip one, no issues with it. Save it from the scrap yard.
Local pickup only. Northern California 95709
Thanks! I'm still trying to figure out if I need to send my block in for an overbore... some trash went through cyl 1 and 3, and messed up pistons and cylinder walls. Going to try to hone it out, if I can I'll take a few pistons from you.
Are any of your stock pistons gonna be saveable? I tore down my 5.9 (similar build as yours that kept snowballing as more damage was uncovered) and found 1 damaged piston, so I’m looking to buy 1 or 2 stock pistons from someone.
SOLVED
I threaded a pipe plug into the floor of the intake and now she idles like a kitten. So much smoother, vacuum is up to 19.5 inHg and temperatures are much closer.