Looking back I can't believe it's been almost a month and half since I posted to the blog. I've been busy waiting on some stuff I ordered to take the next steps on the motor rebuild and some travel to visit family in Ann Arbor Michigan took up a bunch of time as well. Well worth it though, we needed a quick family get-away to recharge.
Since my last post, I took my engine block into the machine shop to fix the snapped stud issue. They have a highly accurate CNC milling machine which will make short work of the snapped stud. The process will remove the remnants of the broken stud but this will also mean sacraficing the hole threads. I've now got the TimeSert install kit that I ordered which will repair the damage and create a new set of threads to insert the studs into.
Until I get the block back from the machinist early next week, I got some of the prep work needed for the studs done. The original short (lower) head studs from my core engines are in decent shape, but typically very dirty with some light surface rust. The push rod tubes are similar. Here is the before pic:
The perfect tool to clean these is the bench grinder. This one is a beautiful old school one. I prefer old tools that are made to last:
The wire wheel makes short work of cleaning of the decades of old grime and rust and is excellent for cleaning up the stud threads:
The push rod tubes from the core are really dirty. Under the grime, the tube was manufactured with two coatings on top of the bare metal, as shown in this picture from Google:
I had a go with the wire wheel on one of my tubes and this was the result:
I'm happy with how they cleaned up, particularly around the o-ring area. However, after seeing the picture from Google that I found for tonight's blog entry, I'm not sure if I've just removed the grime, or removed the zinc coating as well. Removing the zinc coating and getting down to the bare steel is what I want to do as this will allow me to paint (or maybe powdercoat) them white as described in the conversion manual. I'll have another look next time I'm in the shop. These may require a bit more work. The one in the picture I copied was sandlasted, perhaps that's what I'll end up doing.
Overall, the first twelve studs all came out really nice and clean - they should paint up real nice. There are some minor tool marks on each. I have a bunch more in the inventory, so I'll clean those up too and choose the best ones for the build:
The other task I've been pondering is cutting new threads on the end of those studs being inserted into the TimeSert holes of the block.
The studs on Corvair engines are made from a very high tensile steel alloy. The original threads at the block end are a proprietary GM thread called 38-16 NC5. These will not fit the TimeSert which are the more common 3/8-16 NC. So, for those holes that I'm installing TimeSerts, I'll have to use a die cutter and rework the threads to be 3/8-16 NC. The head end doesn't need to be altered.
I had a bit of time today, so I took one of the old long (upper) studs that are being replaced with new ones due to corrosion and experimented cutting new threads on it. Best case, I see how easy or difficult it is, worst case I ruin an old stud that I won't be using anyhow.
I clamped the stud tightly in the vise. When I do the good ones, I'll have to remember to put something in the jaws of the vise to prevent clamping damage marks. Here is a picture of the tools I used. I couldn't find where ron keeps his cutting oil (if there even is any), so I substituted a little 3-in-1.
There ins't a huge difference in the GM thread and the 3/8-16 I need to use with the TimeSerts. Carefully starting the die on the threads and using a fair amount of oil, I managed to cut or reshape the threads about under half way down. This involved the time proven method of turning the die down a little bit at a time, and backing off numerous times but it went marvelously well. Here's a close up:
When I got home, I test fitted this stud in a TimeSert and it threaded in real nice. I bit of LocTite 620 should make the repair as good or better than the factory fit. I've been worried about this process for a long time, but I think with a little attention and time, it's going to work out fine.
Next up, prepping the block for stud install.
Time until takeoff
Husband, father and 911 dispatcher. Long time pilot with a licence that burns a hole in my pocket where my student loan money used to be. First time aircraft builder. Looking to fly my own airplane.