Conflicted4WD
04-27-2008, 03:42 PM
Well, this is my first post so I'll say hi to all. I live in Colorado Springs (Ft. Carson) and am in the process of building a 1975 Jeep CJ-6. I was all planned out to do a Chevy swap until I started reading this forum and some of the posts over on Pirate 4x4. Went to the junkyard and poked around a bit and on the first trip came across a 401/TH400 in a 74 Jeep J10 (Camper Special).
I tore the motor down this morning and the crank and rods look good- very good- but I'm worried about the cylinder bores. The motor appears to have been sitting for a while and the rings were rusted to the bores pretty well. I was C-A-R-E-F-U-L getting them out, soaked in penetrating oil, super-gentle removal, etc., so the damage to the bores is minimal. What has me worried is the ".030" on the piston crowns. I remember reading a while back about issues with overbored blocks but can't find the thread/article where I saw it. There's no ridge at all and I don't have a dial bore gauge anymore so I haven't measured taper, but I doubt the rebuild was all that long ago. .010" would probably take care of anything a hone can't. I was hoping (still am) that things'll clean up with a good hone job, but if they don't, how much can you safely overbore a 401?
I'm sure this is just the first of many questions I'll have- built more than a couple motors in the past but this is my first AMC. Lot of good ideas in the design, but different from what I'm used to.
Thanks, all-
Adam
EDIT: P.S.- anybody know a good machine shop in the Colorado Springs/Denver area?
I tore the motor down this morning and the crank and rods look good- very good- but I'm worried about the cylinder bores. The motor appears to have been sitting for a while and the rings were rusted to the bores pretty well. I was C-A-R-E-F-U-L getting them out, soaked in penetrating oil, super-gentle removal, etc., so the damage to the bores is minimal. What has me worried is the ".030" on the piston crowns. I remember reading a while back about issues with overbored blocks but can't find the thread/article where I saw it. There's no ridge at all and I don't have a dial bore gauge anymore so I haven't measured taper, but I doubt the rebuild was all that long ago. .010" would probably take care of anything a hone can't. I was hoping (still am) that things'll clean up with a good hone job, but if they don't, how much can you safely overbore a 401?
I'm sure this is just the first of many questions I'll have- built more than a couple motors in the past but this is my first AMC. Lot of good ideas in the design, but different from what I'm used to.
Thanks, all-
Adam
EDIT: P.S.- anybody know a good machine shop in the Colorado Springs/Denver area?