@thesamemountainbike, to this day I’m still totally baffled about the main bearing issue. Not only was the thickness different from one half to the other but the width at the center of each thrust bearing half was different by .003 of an inch. The ends of each bearing half were also wider than the center and this effectively gave each bearing shell an hourglass shape. (One half was .001 wider on each end and the other .002.)
The parts house ordered 3 more full bearing sets at the same time and I took the mike with me to check them at the counter. All measured just like the original set; off.
After waving the white flag I ordered a set of Clevites online and those are near dead-on with any discrepancies being in the less than .0002 of an inch category and even that may be due to micrometer feel rather than actual errors.
As you know, I disagree that modern car engines are built to near exact tolerances and I feel that this issue with the main bearings backs my theory up. Federal Mogul supplies bearings (and many other parts) to multiple car manufacturers and they’re building engines with those same bearings. FM also produces connecting rods so one has to wonder if .00251 is acceptable on the bearings would that number also be acceptable on the rod big end bore.
This entire incident with the bearings still has me wondering what in heck is going on and I may go to my grave not ever knowing the answers.
On the issue of torque wrenches, I have only had a 3/8" recently and before this used to tighten the plugs by feel. Since I want to use the torque wrench, I tried it on the bleeder valves on my Mazda. I kept tightening and no click. I think if I wanted to tighten to whatever specs the repair manual stated, I would have stripped everything. And actually in this case there was a range given and I started from the low end. So, I tend to agree that at low end. these torque wrenches might not have much use.
I think it’s generally accepted by tool makers, and even the FAA, that torque wrenches can really only be accurate in the upper 80% of their range and even then there’s a plus/minus. In the bottom 20% of the range that plus/minus is going to be even more exaggerated.
The way I’ve always done mine is to run them down with a piece of vacuum hose until they just touch and then hand tighten from that point.
It’s a pretty safe bet that some mechanics will ram them home with an air tool of some sort…
I too am puzzled. The Clevites are what I’d expect. I can offer no explanation why the FM bearings had such a wide deviation.
I do know that automotive manufacturing in general is far less variant than it used to be, with all the readings being much more tightly grouped around the nominal. Perhaps FM is not one of the industries better suppliers. Or perhaps the aftermarket division hasn’t invested in applied statistics and the OEM division has (they would have been required to).
FYI, my daughter has an 03 Corolla and I have replaced the plugs in it, it is very easy. One bolt holds each COP in place. The COP comes right off after the bolt is removed. The plugs are plated and came out so easy, it was like they were only finger tight, after 117k miles.
As for the torque question, I used to be a very strong advocate for using a torque wrench, not anymore. I much prefer the torque angle approach. The directions on the box of the plugs calls for finger tight plus something like a 1/4 turn. That is the basic torque angle approach. I prefer to use a 3/8" drive breaker bar for this so when I put the plug in finger tight, I can determine the additional tightening more accurately than with a ratchet.
@OK4450 and n2b: I’m not an A&P, but an aircraft owner. I use Champion thread lubricant and a torque wrench when changing plugs on my Piper Seneca’s IO360’s . I’ve never seen an A&P NOT use a torque wrench on a “Lycoming or Continental engine”. My Seneca’s right engine has all helicoils where the plugs go, so I wonder who changed plugs before I owned it.
@tom418, on aircraft engines I’ve always used a torque wrench. However, I’ve also set it on the lower end of the torque spectrum; or even a little below it. Aircraft plugs generally torque at much higher numbers than plugs in automotive aluminum heads; often due to larger shank sizes.
In one specific example on the automotive end of things, the spec given is 7 to 15 Ft. Lbs. Just my 2 cents, but this is hand grenade tolerance. Seven may be fine; 15 may pull every thread on it, and that’s assuming the torque wrench is halfway accurate.
As to your Seneca having Heli-Coils I have no idea what’s behind that but unless something’s changed it’s an approved repair. Maybe an A & P didn’t use a torque wrench when someone wasn’t looking, used a wildly inaccurate torque wrench, or maybe a ham fisted DIY prior owner went overboard with a ratchet. Or an engine or cylinder/head swap at one time. Maybe the plugs were in and out so much over the years that the integrity of the threads was in question.
Sometimes you never know. Some years back while at a small airshow at the local airport near me I got to looking over a single seat, homebuilt that some guy had flown in. It was powered by a 50 Horse air-cooled VW engine.
The bolts holding the prop on were not safety wired. When I asked if that might be of some concern he said that lockwashers and Loc-Tite should hold it…
So far so good I guess, but I had no desire to be around it when he fired it up.
On the issue of whether to use anti sieze on the plugs, I have been using it for years with no issues. It will help when you need to change them again, and it helps when putting them on! Of course the heat burns it up after awhile but main reason to use it is to slow down any corrosion formation on the threads so its easier to take them off.
The last Corolla of that vintage I did had a plastic “rail (tunnel?)” for routing and protecting the primary wires, and that needed to be unattached prior to removing the COPs, even after unplugging them. One of the COPs had its edge just barely under the plastic “rail”. Attempting to remove it without unattaching the rail would have broken the plastic part of the COP that seats to the top of the tube wherein lies the plug. I’ve also broken a few retaining hooks in the past before realizing that they need to be pushed in before being squeezed and pulled out.
Changing plugs isn’t difficult, but it does require some attention to the task. I offered the comments as helpful tips rather than discouraging comments. Perhaps I made it sound harder than it is.
