Re-torquing heads

[bvolcko38]

What is the recommended method of re-torquing heads at 10 and 25 hrs?

[sonex1374]

The AeroVee assembly manual has a section on torquing the heads, and they show the recommended criss-cross pattern to tighten the head stud nuts. Follow the same pattern during the re-torque. You'll need to remove the rocker arm assembly to gain access to the 4 nuts underneath the rocker arm shaft, so don't skip this step. There is no need to loosen any head stud nuts during the re-torque - simply snug up each nut in sequence to the recommended value (18 ft-lbs). They shouldn't move much (if any), and if they do (more than a few pounds light on torque or a half turn or so), you need to investigate why because there is likely something else that is wrong that needs attention.

Make sure you get the pushrods back in their respective cups (not mixed up), and the rocker arm shaft is installed again properly. Reset the valve clearance and you should be pretty much finished.

Pg 62 of the assembly manual has the annual inspection checklist and makes for a handy reference.

Jeff

[mike.smith]

You'll need to remove the rocker arm assembly to gain access to the 4 nuts underneath the rocker arm shaft, so don't skip this step.

Joe Norris posted something at one time about an offset tool he made to get around the rocker arms to get to those 4 nuts, so you don't have to remove the rocker arm shaft.

There is no need to loosen any head stud nuts during the re-torque - simply snug up each nut in sequence to the recommended value (18 ft-lbs).

Yes, and in fact you are never supposed to loosen those nuts before torquing them.

[Sonerai13]

You'll need to remove the rocker arm assembly to gain access to the 4 nuts underneath the rocker arm shaft, so don't skip this step.

Joe Norris posted something at one time about an offset tool he made to get around the rocker arms to get to those 4 nuts, so you don't have to remove the rocker arm shaft.

Yep, I made a "torque extender" out of an open end wrench. Sort of a long "crow foot". Just weld a socket on the handle of the appropriate size open end wrench and you're all set. Make the length at least 4 inches between the center of the socket and the center of open end of the wrench and you'll have enough clearance to slip the wrench down between the head and the intake elbow to torque those two nuts behind the elbow. That way you don't have to disturb the seal on your intake elbow.

If you put the extender at a 90 degree angle to your torque wrench you don't even have to change your torque setting! If you go with the extender straight out, you'll have to do the conversion so you don't over-torque the nut. Here's a site where you can do the calculation:

https://www.mountztorque.com/calculatio ... d-spanners

A quick search of the net will "net" you even more of these sites and related info.

[Darick]

I'm working on a revised condition inspection checklist for myself. In the AeroVee manual it is stated to change the oil and wash the oil screen. On the same page under the time based recommendations, it says change the oil every 25 hours and wash the oil screen every 50 hours. Common sense says if you changed the oil for the 25 hour interval, it makes no sense to change the oil again for the annual, if that was only 5 hours ago. The same applies for the oil screen, and adjusting the valves.

What about torquing the heads? If you haven't flown many hours in a particular time period, why torque the heads and adjust the valves? Seems to me oil changes, valve adjustment and torquing the heads (and a few other things) should be time on the engine not calendar time.

thoughts anybody?

[GraemeSmith]

Oil should be changed every 6 months regardless of time on it.

[sonex1374]

Darick,

The oil gets funky just sitting in the plane, and changing it periodically removes it in favor of fresh oil. Specifically, the oil turns acidic with use and that slightly-more-acidic oil will continue to increase in acidity over time, and that can cause corrosion inside the engine. If you never used the oil at all this might be different, but once it's been run and picked up a good bit of corrosion by-products and blow-by it starts this process and you'll want to change it every so often (3 months is best, but that's kinda up to you).

As for the oil screen, they tend to be pretty resistant to getting clogged under normal use, and could probably go on for a really long time just left in the engine. However, you'll never really know if it's caught something or picked up something that's clogging the mesh unless you periodically remove and inspect it, and if you do that you should clean or replace it while you're at it. I don't think there's a big problem skipping a screen removal every now and then, especially if there isn't much run time on the oil, but you'll want to still give it a look every so often.

For me, If my engine has been sitting over the winter not hardly getting used I still like to change the oil close to the 3-4 month mark to remove any contaminated oil from the engine, but I may skip the oil screen removal until later in the year when the hours start accumulating again. This is a really good reason to have an easy-to-get-to drain plug or a quick drain valve - if it's easy to drain the oil then you're much more likely to go ahead and change it regularly.

The valve adjustments are driven more by the hours running the engine and the temps of the heads while running. I tend to only do them at the 25-hr mark unless there has been a trend of needing more frequent adjustment (which in that case something else is going wrong and you need to figure that out).

Torquing the heads is a pain because you need to remove the rocker assembly from the head to get access to the nuts inside the valve chamber. If you have a specialty tool (something custom or maybe a good crowsfoot adapter) that allows you to access these nuts without removing anything, so much the better - torque each time you adjust the valves. However, I wouldn't be too eager to constantly remove the rocker shaft every 25 hrs and chance wearing something out or messing something up in the process. Check it a few times in accordance with the manual, then when the torque is consistently staying put, you can scale back to once a year or so. If the torque never settles down, that's indicating a problem you need to address.

Jeff

[Darick]

thanks guys for all the info. Jeff thanks for the annual condition inspection you posted some time ago which I am using as a template.

[Bryan Cotton]

I'm doing my 10 hour torque right now. It's a bit of a pain but I'm working tooling to made it easier. Here are my torque wrench adapter details.

First I turned down some crappy sockets on the lathe, so only the 3/8" square drive part was left. I turned off the chrome first, for welding purposes.

I cut a 15mm combination wrench in half, and welded those parts on.

Here I am using it set at 90 degrees.

For the back top nuts, they are a pain even with the adapter. So I drilled a hole for socket access. This will allow me to torque this without removing the intake next time.

To locate the hole, I used the long nuts that hold the rocker shaft down and that the valve cover bolts screw into. I slipped a socket on, screwed the nut out, and was able to mark where the hole goes more or less.

For those building their aerovee, I'd recommend two things:
1) Cut down the studs. Makes it easier to get the box end on, and lets you use a normal socket with an extension rather than a long socket. That can be helpful especially for the top back corners.
2) Punch a hole in line with the top back corners, and figure out a removable plug, so you can sneak a socket in there with the intakes still on.

When I get the intakes back on I'll see if my open end adapter can get in there like Joe mentions.

[mike.smith]

My own personal preferences based on 8 years and 560 hours on the engine:

- For the first 2 years I did everything by the book. That would be my first recommendation. Do it, see what happens, and get to know the engine.
- The first couple of years of flying, I re-torqued the heads every 50 hours. During the first year, there was a little movement in some of the nuts, so it was the right thing to do. After that, the nuts have never moved. So I made the decision to re-torque them during the condition inspection, instead of every 50 hours. The engine is already half-apart during the inspection, so it's a good time to do it. The nuts have never since budged against the torque wrench, so it makes sense to my brain.
- The caveat to the previous comment, is that if you remove the head for any reason, and reinstall it, definitely recheck the torque at 50 hours max, or even at 25 hours.
- Since the beginning I have taken oil samples for analysis at each oil change. I get the ones from Lab One Aviation, available from Aircraft Spruce. They are the least expensive, and give back all the information you need for a VW. Oil analysis saved me and the engine when the samples showed high levels of nickel and aluminum, indicating my Nickasil cylinders were failing.
- I have never found anything in the screen, even when I had the high nickel and aluminum. The screen is so porous, if it catches something, you'll have seen the issue in the oil analysis long before that.
- So I only check the screen at my condition inspection, unless I see any metals trending upward in the oil samples. The less you mess with those nuts holding the sump plate on, the better! The studs are not well secured in the relatively soft metal of the case, and are easy to move (rotate) with the nuts. My studs finally rotated and stripped the case. So I took them out (except the one holding the sump pickup in place), tapped the case, and have used small allen-head bolts instead. You still have to be really careful not to strip the threads in the case when tightening them.
- If you don't have a quick-drain valve in your oil sump plate, add one. You will be more inclined to do your oil change on time if it's not a messy PITA. Use a clear plastic section of hose from the hardware store, to drain from the valve to your container of choice. I tapped a second hole in my plate, so the center hole has the quick drain valve, and the second hole has the oil temperature sender.
- I change my oil every 25 hours. I fly around 80 hours per year. If you do the math you'll see I don't change the oil 4 times a year (every 3 months). I think it's over kill if you fly the airplane. If you don't fly much, then it's probably not a bad idea.

These are just personal preferences. I'm not saying any of it is "right," but it's worked for me.