Friday, March 20, 2015

Overdue Update

It has been a while since the last entry, but some work has continued. Life gets in the way sometimes, and other things have taken priority, mostly family, but also playing the saxophone. Always wanted to learn, so at age 60, I picked it up and started lessons. Fun!! It is never too late.

The engine is still the focus, and most of the major parts have been cleaned, inspected, measured, and at times, replaced.

Oil Scavenge Pump (before)
Pistons and Wrist Pin Caps

Oil Scavenge Pump (after)
Not long after last year’s entry, I cleaned the case (three pieces) in the parts washer and bead blaster. They came out just fine, but the majority of the work has been cleaning up after the bead blasting. It is essential that all blast media is removed and all the oil galleries are free of grit and old sludge. Most of this involves just pressure cleaning with detergent and hot water, followed by thorough rinsing, but there is a procedure for this in the W670 Overhaul Manual, which I followed and hence determined that everything is good.

Accessory Case
Nose Case and Others
Case Center Section


There are many opinions about using a bead blaster for cleaning engine parts and some people get downright emotional about it, but I used this method on a Lycoming engine that I rebuilt for my RV-4, and it has been running fine for 15 years, and I’ve never found any blast media in the oil or anywhere else for that matter. I’ve discussed this with some experts, and read some automotive blogs, and have determined that people who have had problems just didn’t do a good job of cleaning after the blasting. One engine builder stated that he had built many NASCAR engines over the last thirty years using bead-blasted parts and has never had a problem. Good enough for me. Like one friend said, he listens to all the dire warnings then does what he has always done with no ill effects. Once again, good enough for me.
Hand Painted, but They Look Alright

Anyway, all the oil galleries that feed the tappet guides are free and clear, as are all the other passages. All the steel parts have been magna fluxed (with the aforementioned master rod debacle), and a couple coats of engine paint has been applied.

Center Section in Fixture Where Engine Will Be Assembled


Next was the cylinders. With help from Jim Friedline again, we honed the cylinder walls and installed valves. With the cylinder assemblies done, the last item will be to assemble the crank and rods.

Jim Gets Me Started
He's Done This Before!

Here are a series of pictures describing these procedures.

Cylinder Sitting on a Wood Block
Valve Springs Added

Valve Spring
Cap in Place

Valve Spring Compression Tool
Fully Compressed

Adding Keepers (Valve Spring Locks)

Release Tension

Voila, Valve Installed---Thirteen to Go


Next came the crank shaft/rod assembly. Once again, Jim Friedline has all the fixtures and every known apparatus for this chore, so we started in on this procedure with the hope of completing it in one afternoon.

Master Rod Assembly in Place

Other Half of Crank

Where Other Half Goes
The Big Bolt

Crank Halves Joined

Alignment Die
Inserting Big Bolt

Torqued to Half a Million ft-lbs, Check for Stretch

Where Bolt is Pinned

Oh well, not so fast.

 As the crank is assembled in two parts, and clamped one on the other with a giant bolt with the rod assembly in between, the run-out of the shaft is a critical measurement. This requires a fixture that even Jim doesn’t have. I volunteered to make one from wood, since all that is required is something to hold the crank in place while it is rotated while dial indicators on either end measure any wobble in the radial movement of the crank. Simple. Not!

Home-made Fixture with Practice Crank in Place
 This fixture is just not stable enough to hold this very heavy crankshaft assembly while it is rotated. Even a couple thousandths movement is significant since the tolerance is very small. The only person nearby who has a proper fixture lives in another town and has been suffering some health problems of late, so the crankshaft is placed on the back burner for now.


The next engine part is the carburetor. We determined that this engine had a Stromberg NAR 6G installed. The data plate was missing, but the way to tell the difference between the NAR 6D and 6G is the size and shape of the float. Jim supplied me with a new data plate which will be stamped with the correct data plus a serial number from an old unused carb. I disassembled the carb after taking many pictures and dunked the major case parts in a bucket of carburetor cleaner and left them there for a few hours. This stuff is very volatile and SMELLY! It certainly did the job of cleaning and removing old paint, but my clothes had to be washed and my shop smelled of this “stuff” for a month. If you use this method, take my advice and do it outside. And while you’re at it, wear a rubber apron and old shoes.

Old Carb Ready for Dis-assembly

Taking Apart is Easy...Back Together, Not So Much

Beware of This Nasty Stuff; Works Well, Though
 I painted the outside with automotive high temp engine paint, but apparently the surface was a bit too smooth and any little scratch takes it right off. I could have bead blasted this too, which would have given it a much better surface for primer to adhere, but the passageways within the case are so small, I wasn’t sure I could get them cleaned out sufficiently, so cleaning was all I did to prep for paint.

One thing about the 6G carb was that the larger float puts more down pressure on the fuel valve seat. It was designed for use with a fuel pump, thus higher pressure: about 3psi. I had not considered a fuel pump, believing that gravity feed would be sufficient. But after considering the low level of the fuselage tank and its proximity (level) to the carb, I began to re-evaluate this and lean toward a fuel pump. I called Bill Hammond for his expert opinion and he agreed that, at least when the fuel level in the tank gets low, there may not be sufficient pressure to lift the fuel valve off the seat to refill the bowl. He agreed that a fuel pump would be the prudent way to go. So, the search is on for a fuel pump for a Continental W670.

I'm Sure All This Stuff Goes in There

Back Together...WooHoo!
All Safety Wired and Ready for its New Data Plate

Jim is the expert, so after cleaning and re-assembling most of the carb, I took it to his shop to set the float level. He opined that a level about 1/16” higher than book seems to work better. His Stearman was set to a higher level and he didn’t have that engine cough that is so characteristic of this engine when the throttle is advanced from idle. He told me that the old duster guys used to say that if the carb didn’t drip a little when you go to full rich before start, that it was set too low. We set the bowl, seat, valve and float up on his home-made tester and adjusted (by trial and error) the fuel level in the bowl. We set it for 3psi, like what the fuel pump puts out, and after trying a myriad of shim combinations under the seat, finally got the level exactly right. I finished assembling the carb at home with safety wire on all the drilled heads and repainted the scratched areas. So, now the carburetor is finished.

Trim Handle

During lulls in the engine work, I had an opportunity to fabricate an essential control—the trim actuator handle assembly. Luckily, I have a nice set of drawings for this device, with good dimensions, etc. Problem is, when I started practicing my gas welding on the small joints of the 4130 tubing, I got a reminder of how out-of-practice I am on oxy-acetylene  welding. I scoured the internet for advice. I tried stick welding with a 1/16" rod. Not much good. Then I looked at MIG welding on 4130. As usual, there was a plethora of experts warning about the impossibility of MIG welding this very touchy alloy. "Can't be done!," said one. "No way to stress relieve," said another. This is not a structural part. I got a couple of pieces of scraps and gave it a try. Wow! Those guys were WRONG! It welded beautifully! Good penetration, good flow out, and a very strong joint. I let the scraps cool and tried to break them. Couldn't. So, I decided to go ahead and build the trim actuator using this method. It came out just fine. Good advice is hard to find sometimes, especially on the internet. There are self-proclaimed experts everywhere who have no clue of what they speak. I love the internet as a source of reference material; you just have to be careful to whom you listen.

The hardest part was finding a proper spring to fit in the tube and provide the right tension. Ace Hardware had a couple of drawer fulls of springs. Cheap, too. This mechanism will be mounted on a piece of oak that runs under the pilot's seat and forward under the throttle. There are two of these oak pieces, one on either side of the cockpit. They were originally meant to hold up the pilot's seat, but my fuselage has steel tubing for that, so the oak will be just for the appearance of originality.