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In previous Open E-mails, we've referred to development work on the details of the 601 firewall forward package. Above is a photo taken in our shop today of the firewall forward development and display stand. This is an actual factory 601 firewall, complete with the tricycle gear mounts. The Motor Mount is one of our production units. This week, we will work up a group of photos showing the installation of the gascolator and fuel pumps, and the remote oil filter housing and instrumentation. Watch for it in Open E-mail. We'll also post the specific dates and stops for our Midwestern Night School Tour.
Have you ever tried using the mixture control on a NAS-3 carburetor on a Corvair engine? If so, how effective is it? I can live without the cutoff feature; a simple fuel value will take care of that. In fact, I prefer this. I will miss the pump feature, but a primer will do. I have some concern about the negative G factor of a MA3-SPA in the event of a departure stall, especially with my 7 1/2 pound wood prop. I have one of each carb. Which one would you prefer in my situation?
|Jack Nelson, Wagabond, Manual #5134, Livingston, Texas|
|Reply from WW:|
|The Stromberg and the MA3 are the two carburetors on which we have the most flight experience. The Pietenpol had
a Stromberg on it for most of its flight hours, and the MA3 is what we use on the 601. It is true
that the MA3 will quit if subjected to a solid negative G maneuver. But I don't think that you really have to be concerned
about it unless you have an extreme airplane like a hand prop Cassutt with a 54" diameter wood prop. 95% of the typical
Corvair applications like KRs and 601s, and certainly Pietenpols and Cub-type airplanes, will never notice this MA3
characteristic. The Stromberg is, by design, slightly more immune to this. You're correct that the Stromberg mixture
control will not idle cutoff the engine, but it can be rigged for effective use and lean the engine through several
hundred degrees, giving you several thousand feet more of altitude capability with correct mixture control. If choosing
between the two carbs, I wouldn't let this characteristic define your choice. I'd probably go with the MA3 because its
accelerator pump makes a priming system unnecessary in everything but the coldest environments.
|Subj: Q Update|
I'm rebuilding a Q200 into a TriQVair. Currently developing the motor-mount. Prototype to be tested soon. I own manual #5206 which I bought from you at your 2002 Oshkosh forum.
Jon M. Swenson, Golden Valley, MN
|Reply from WW:|
|At Corvair College #7, our friend Joseph Snow of Ohio brought his Qvair firewall forward package, including mount and displayed it. At Corvair College #8, QVair builder Larry Koutz of Georgia also brought his motor mount and engine package to share. In attendance also was QVair builder David Posey, Georgia. David is working out a mount for his aircraft based on a Dragonfly design I did several years ago. These builders represent some of the more active QVair people, and I'm interested to see how their unique solutions to the motor mount evolve. We'll keep everyone posted.|
What power loss if I use a standard 110 cam? Best way to straighten bent fins on the heads without breaking them? (Hot or cold?) I have a very low mileage engine and would think all lifters, pushrods should be fine. Valves are like new as are all the engine parts. EXCEPT FOR FLASHING in crankcases and the heads. I have never seen such rough castings on any engine. Crankshaft miced standard and not out of round. Cylinders are very clean but will rebore. Hope I don't sound cheap but I do have to be thrifty. Had crank magnafluxed and polished. Very nice. I watch your comments on Wednesday and Sunday.
I had one other question. Does Clark's regrind your old cam to make the OT-10 cam? Will they leave your cam gear in place? I hate to give up my cam that is already set to the crank.
|Thank you very much, FRIEND BOB|
|Reply from WW:|
|The horsepower difference depends on what rpm you're going to run the engine at. It's about 5 at 2,800rpm, 8 at 3,100 and 11 or 12 at 3,400. If you're looking for an inexpensive alternative to a new OT-10, you can get a reground one from Clark's, part no. C8800R. They do all their grinding with the gear off. My understanding of accurate cam grinding is that it is based on the keyweigh location. I question how accurately it could be done with the gear still on. I'm very cautious about straightening bent fins on cylinder heads. You may want to warm them, but only with a propane torch. Yes, many people comment that the Corvair castings on the heads, especially, are far rougher than aluminum castings made today. But, as many internal inspections of core engines reveal, the quality was in the design and on the inside. We find many engines with virtually no wear inside due to the excellent design of the Corvair's oil system. The Corvair is a book you can't judge by the cover - or the reviews.|
I am starting to clean up my engine and have the pushrod tubes out for painting. After general clean up, I notice that most of the tubes have small dents or deformities caused by pliers or wrenches. Most are very small but I am concerned. What condition are most tubes in that are used in the conversion? I would rather not replace them, but will if the small dents are a problem. They all appear straight and are the same length. Also the O-ring slots are in good condition.
|Thanks, John Butterfield, 601XL|
|Reply from WW:|
|If the pushrods are as you describe, you have nothing to worry about, it's only cosmetic. It's not a big issue;
when the engine's installed in the plane, you can't really see them anyway. As you point out, the primary concern is that they're
straight, and have nice O-ring grooves. If you have any that are particularly bad, drop us an e-mail. We have about 500
used ones in the shop at any given time.
|Subj: Fuel System|
I've been looking at the new dual-pump system and was wondering why the following scenario wouldn't happen:
1. Primary pump fails
I thought it might work if the plumbing order was primary-switch-secondary. That way the fuel pressure switch would never "see" the pressure output from the secondary pump. But your photos show two pumps in series and then the pressure switch. What am I missing? Also which pump comes first (i.e. is connected to the gascolator): primary or secondary? A schematic (plumbing and electrical) would really help here.
1. Engine stops and oil pressure drops
Now aren't you in the same bad situation the system was designed to avoid - heading for the ground with an active fuel pump?
A few other questions:
Thanks, Craig Payne, Utah, Manual #6154
|Reply from WW:|
|You're confusing two different systems. The original mechanical/electrical system had a fuel pressure switch in
the system. The electric/electric system on the plane now does not. In the photos on the 601
Web pages, the electrical device after the second pump is the sending unit for the electric fuel pressure gauge.
In the electric/electric system, the primary pump is the first one after the gascolator. The system runs on
this pump normally, and the other pump is a backup we only test during the run up and check periodically at cruise
altitude. The primary pump is wired through the oil pressure switch as a safety feature. The secondary pump has no
oil pressure switch in it because the back up system should have the least number of parts in it. The operation of the
pumps is controlled by a 3-position switch labeled auto, off and backup. Notably, if you wanted to use an electric
primer, you could boost the fuel pressure with the pump off with the backup pump at any time, engine running or not.
Additionally, the backup position on the switch can be used to check the integrity of the fuel system during a pre-flight.
We tend to publish wiring diagrams and schematics in Our Corvair Flyer newsletter. The 601
Web page is intended only as a visual guide to our work available to anyone on the Net. We reserve some of the most
technical information for Manual owners, who are our direct customers.
The Facet pumps are available directly from the Aircraft Spruce catalog. They're the model that comes with AN-6 fittings built in. You may have a local supplier who deals with industrial engines and generators, or find a Nason source on the Web. If people have difficulty finding these, we'll make a quantity purchase and keep them in stock. The oil switch is the same make, but is a 15psi model.
In short, neither of the scenarios you're worried about can happen with the current electric/electric installation. Additionally, they didn't happen with the initial installation either, because the output pressure of the Facet pump was below the switch pressure intentionally, so that it would not cycle. Not a concern, just thought you might be curious.
|Subj: Manual Supplement|
I've obtained your Manual, videos, newsletters, etc. and find them to be great help. I was wondering if you have considered a supplement to the Manual that would feature the "latest and greatest" mods and current wisdom? Your lengthy history of research and development spans a great deal of time and modifications. It would be of great help if you summarized a current state of the art recommendation for your conversion in a concise shopping list so that those of us on a budget and buying a piece/part/section at a time can obtain the pieces we need with less confusion as to what is now considered to be the best solution. I realize you are in the business of Corvair conversions and mentoring those of us to do it ourselves, but the additional hints and tips of prepping the airframe/firewall to accept your conversion would be great, i.e. a simple line drawing of fuel line routing through the airframe to the gascolator, battery placement with suggested wire routing and wire size would be very helpful to me at this time in the building process. If some of these items are already addressed in your previous material please accept my apology. I've been reading and watching, but have been buried in trying to get the firewall back portion completed before focusing and learning about firewall forward.
|Regards, Roger Parnow, 601XL taildragger - Corvair powered|
|Reply from WW:|
|We tend to publish the most up to date technical information in The Corvair Flyer. Of
particular interest to 601 builders is this week's shop project: We're working on an exact 601 firewall and
601 Motor Mount on a stand in our shop. We're carefully documenting in notes and photographs every step of the installation.
This particular installation will be built in its entirety in our shop. We'll then deliver and install it to Cleone
Markwell's 601 in mid February. This will allow all 601 builders to follow along and we'll have the drawings you
request available to our customers. We currently have all of them as hand sketches, but they're being updated to