| Subj: Any magic to MA-3SPA carb rebuilding
|
| Date: 3/15/05
Have an MA-3SPA which purchased at Oshkosh that appears to be in good condition but has probably been sitting on a
hangar shelf for 10 or 15 years. I assume you would recommend getting a full rebuild kit for any carb like this one
that is in an unknown state? I rebuilt a few auto carbs back in the old days; if I can build a Corvair engine, is there
any magic to rebuilding an MA? Can't believe they get $600 plus a core for rebuilding one of these.
Thank you.
|
| Rick Holland, Manual #5899, Castle Rock, CO, Building a Piet at 7000 MSL
|
| Reply from WW:
|
| The two most popular certified carbs used on the Corvair are the MA3-SPA and the Stromberg NAS-3. At first glance,
these are very simple, reliable, one-barrel carburetors. But there are other mitigating issues that make their
overhaul cost high if it's done in an FAA certified repair station. First, if you're going to do it yourself, you
should get the necessary parts from Chief Aircraft, and you absolutely must have and read the overhaul manual. Do not
buy the complete overhaul kit, but rather the specific parts that you need. In the case of an MA3, this usually totals
about $150. By doing careful work, you can put together a good carb that will serve you well. This is how we did the MA3
that is on our own 601. When you see $500 or $600 as an overhaul price, it is driven by several factors: The carbs must
be absolutely perfect when they leave a repair station, for they could be installed on a rental 150 the following week in
which somebody's 16-year-old kid is going to solo. Second, the cost of operating a repair station is much higher than most
people think. There's a lot of paperwork involved, training requirements, and in many cases, extremely high price insurance.
Fuel systems on aircraft have been involved in some of the largest lawsuits in aviation - a few fair, most not, but it's
a reality for those in this business. When an MA3 or Stromberg is really worn out and needs things like throttle shaft
bushings, it's time for a really experienced professional. My choice in this is to work directly with a repair station, and
my favorite one is D&G, 1505 N Front St., Niles, Michigan 49120-3933, run by Russ, phone (269) 684-4440. He completely overhauls the carburetor and includes many details
that other shops charge extra for. His price on an MA3, if you're going to have it set up for a Corvair, is $500. The
Stromberg price for a Corvair is $325. Although these may sound expensive in automotive terms, I believe that when you
consider all the factors, they represent a good value. Over the years, I've seen people mess with all types of
alternative carburetors, ground running them for months without ever gaining a lot of confidence in them. In many cases,
builders whose intention is to fly soon would be better served by an aircraft carburetor in which they can have immediate
confidence.
|
| Subj: Oil Temp
|
| Date: 3/11/05
Here are two pictures of my Corvair powered helicopter.
I changed oil and filter fron 20/50 to 10/40. This lowered the cold idle pressure 65+ to about 45 lbs.
The oil temp still goes past 320.
I checked for air blockage (like maybe a rag sucked in) but it is clear. The oil cooler is starting to leak now.
This is the second used oil cooler to blow up on me in less then 15 hours of run time.
Clark's has no new ones at this time.
The cylinder temp stays cool under 300 degrees.
Thanks for your reply. Any suggestions are appreciated.
|
| Bill Gratriex, Susanville, Ca., #5494
|
| Reply from WW:
|
| Thank you for the photos. I prefer 10W30 and 10W40 over thicker oils because the Corvair was designed as a thin oil
system. The oil pressures you have are much, much higher than we use. Our 601 idles at 20 pounds of oil pressure when hot.
The system never goes over 42 pounds. If you have thick oil and high regulator spring pressure, it's possible, as you found
out, to overstress the oil cooler. I don't know what form of instrumentation you're using, but many oil pressure gauges
read low on start up. A mechanical gauge with a long line will not show you how high the pressure actually is. I've tested
a lot of Corvair oil coolers in excess of 100psi. Believe it or not, a high pressure and high volume pump setup with thick
oil can easily exceed this on a cold start without showing it on a mechanical gauge.
The main reason I don't recommend excessive oil pressure is that it is not required and it overstresses the system.
The engines we build use stock pumps, and only bump the oil pressure from a stock 37psi to 40-42psi. My primary thought
on an engine which has normal CHT but high oil temperature is that the oil cooler bypass is not seating. We test this
specifically when we rework builders' Oil Accessory Cases. If this doesn't seat, the engine
will bypass the cooler at all temperatures, and the oil will run hot. Your oil cooler should be a stock 12-plate cooler
in the stock location. We've had the best results with this simple setup. The mechanical work of raising the oil pressure
may contribute to its high temperature, and I suspect the high pressure is a factor in making some of your oil system
components function poorly. Your oil system cover could be removed and tested by us, but this is a far easier job before
the engine's built and installed. To field test your cooler bypass without major disassembly, you can make a block off plate
where the cooler's mount was bolted to the case. Get two mechanical oil pressure gauges, and put them into each of the
outlets from the case. Remove the distributor and run the oil pump with an electric drill driving an old distributor shaft.
If the cooler bypass is in good condition, there will be 7-8psi difference on the two gauges. On a complex issue like this,
feel free to call me on the hangar line, (386) 478-0396. We're there from 9 a.m. till 10 p.m. while we're prepping for the
beginning of airshow season.
|
| Subj: Safety Shaft
|
| Date: 3/10/05
Have finally found a good 110 engine, good crank (std.) and rebuildable
heads.
I am putting together all the mod. parts and kits. I have Clark's W.W.
gasket kit.
Have your Engine Assembly Video # 1. I have 2 questons: I see in The Corvair
Flyer that you
are using 7075 aluminum Safety Shafts now. Is it the same price, and also same thread (1-14)?
Is there a particular reason for using 1-14 thread?
Harold Davis, Manual #6361
|
| Reply from WW:
|
| After some experimentation, we have shifted to filling orders with 7075 aluminum Safety Shafts. For people plans
building this part, I still recommend using the 4130 specified in the Conversion Manual. The aluminum
is half the weight, but this is only a few ounces. The aluminum has to be 7075, as all other available grades are nowhere
near strong enough. The introductory price on this part is the same as the steel safety shaft. The 1-14 thread is our
flight proven choice for thread patterns.
|
| Subj: Replacing valve guides
|
| Date: 3/7/05
On a typical valve job, is it necessary to replace the factory valve
guides? Or for a flight motor is it best to pull out the factory steel
guides (regardless of condition) and replace them with manganese bronze?
|
| Craig Payne, Utah, Manual #6154
|
| Reply from WW:
|
| Most Corvairs that we use as cores in the shop still have good valve guides. We have flown the vast majority of
our hours on the standard factory valve guides. In a standard valve job, we leave the guides alone. If the guides are
excessively loose, I prefer to replace them with bronze guides. This work is best done by one of the shops that
specialize in doing this for Corvairs. We frequently use Wheelerizing in Brea, Calif.
|
| Subj: Removed head - cylinders too
|
| Date: 3/6/05
Hello again from Minnesota. I was working on the Corvair this weekend and found myself removing one of the heads.
Two questions: How can I be sure the studs didn't rotate in the case? I tried to watch for movement but I'm just not
confident that I didn't miss any minor movement. The other question: When I pulled the head from the case, the cylinders
remained attached and the whole assembly came off with the baffles attached too. Any harm in this? Maybe this is
somewhat normal but I had to take a rubber mallet and give the cylinders quite a few whacks to unseat them from the head.
Other comments: After I got the head and cylinders off, I thought I should remove the pistons, however the inner
rod bolts seem very difficult to reach. Maybe with the other side off it's easier, but I could only get a socket on to
break it loose, then the rachet just spun and spun (about 1/8" at a time). Any suggestions? It appears the engine has
been rebuilt as there is some signs of wrench slippage on the rod nuts.
Tom Brant, Brooklyn Park, MN
|
| Reply from WW:
|
| Occassionally, Corvair heads come off with the cylinders still attached. This is not a big deal. Kroil and light
taps with a rubber mallet can usually work them free. If the nuts came off the studs, they probably unscrewed without
turning the studs. I would not be overly concerned if you did not see any sign of movement. Generally, the studs that
unscrew have the nuts frozen on them.
You can reach any rod nut in the engine by rotating the crank to a favorable position and using a fine tooth ratchet
and a 12-point socket. It may take a little work to loosen them, but if you study the issue with the socket in your hand,
you'll see how it's done. To take rod nuts on and off, I find that the best socket length is part of the way between deep
and standard. The socket we use is 1 3/8" long.
|
| Subj: Oil pressure and Exhaust
|
| Date: 3/6/05
I have 2 questions:
1. Can I use an Earl's T fitting to mount the stock Corvair oil pressure
switch and a VDO oil pressure sensor to the stock switch mounting location?
Should I use the Teflon paste on the
NPT fittings? Then, is it kosher to drill and tap a 1/8NPT fitting on the
bottom of the oil pan to mount the oil temperature sensor there?
2. I think I've found a cheap, repeatable, off-the-shelf exhaust
system. You mount the stock iron logs, then you buy a 180 exhaust tube
from Clark's, and cut it off at the point where the
straight part makes the second bend in the wrong direction. Weld the
cut-off bend in the opposite direction, and you have changed the U into an
S that seems to fit the Dragonfly firewall pretty well perfectly.
See any problems with that? How far should the exhaust
pipe be kept away from the fiberglass bottom of the canard to prevent heat
damage?
|
| Dave Morris, Dragonfly, Texas
|
| Reply from WW:
|
| I've studied your photos carefully. The 1/8" pipe plug will not tolerate having that kind of weight
supported off of it if the sensors are allowed to vibrate in any way. It will work if you make a bracket
that supports the mass of the sending unit and does not allow it to vibrate. (That has to be one of the
larger sending units I've seen.) While you can put the temp sender in the pan, I prefer to have them in
the oil stream, reading the temperature of the flowing oil. However, I understand the space constraints of
your conversion.
As for your exhaust system, I would make sure that the pipes pointed down at something like a 15 degree angle
and were several inches below the canard. As I'm sure you're aware, room temperature cured composites do not like
heat. In your favor, the prop blast will help to keep the area cool. The Clark's u-bend you have is a typical
automotive bend which has necked down sections and is galvanized. This will make it hard to weld, and flow less
than a mandrel bent pipe (like the tubing sold by Magnum Force racing). With a Dragonfly, pay special attention to
isolating the gascolator from heat radiated by the exhaust.
Bonus Photos
|
In the photo above, right, is Ivan Carlson, Corvair/Super Pulsar builder from Louisiana, and myself, standing in front
of his running 2,900cc Corvair. Ivan started this engine at our shop during Corvair College #8,
and returned last week to finish it off and give it a test run on the dyno. This engine was particularly challenging
to build. Kevin worked directly with Ivan, and had a lot of days in bringing it all together. The engine is based
on 90.5mm VW cylinders. It has roller rockers, which required modifying the valve covers and getting custom pushrods
made. It has 140 exhaust stacks in 95 heads. This modification required extensive reworking of the stud holes in the heads,
the exhaust stacks and the pushrod tubes, which additionally had to be ceramic coated. For those with sharp eyes, you'll
notice that the engine is also reverse rotation. It has one of our Front Starter Kits installed with
a special starter. The prop it is turning is the 72x48 Sensenich from Grace's Taylorcraft.
(This is an extreme cruise prop for Grace's C-85 engine.) The Corvair turned it substantially more RPM static, despite
the fact that this prop is designed to operate well below the Corvair's torque peak. The main reason why I do not
recommend highly modified engines like this is that they are much harder to build than standard engines and offer only
modest power increases over standard engines. Ivan's a very determined builder who's willing to travel to our shop and
do what it takes to resolve technical issues in a first class manner. (At times, this means being patient while
spending money.) His unique position allows him to have one of the nicest Corvair engines we've built in our shop lately.
|
John Locke, above right, flew in from Texas to work on his Corvair engine for his own Super Pulsar. John made some
really good progress, and got a preview of how his own engine will run. Gus flew both builders in the 601 on long
familiarization flights. This way, they'll be well acquainted with normal, smooth Corvair operation when their own
airplanes are ready to take flight. His friend Linda, in the foreground, came along to lend a hand with the engine. She
got along great with the hangar gang and did some flying with Gus in the 601.
|
| Subj: Dual Alternators
|
| Date: 3/4/05
Have you thought at all about how to install dual alternators on the
Corvair engine? This would seem to be a useful option (with dual
batteries and regulators) in an all-electric, non-magneto system.
My engines are all torn apart but it would seem to be possible to
install your new front alternator brackets on both the right and
(flipped over) on the left side of the engine and run a single belt over
all three pulleys. This would not be the optimal set-up as the belt
would be a potential single point of failure and might not have enough
contact with the pulley on the crank. Instead it would appear that
there is plenty of room between the existing Pulley
and the Prop Hub to
install another Pulley. This would allow the use of two independent belts.
|
| Craig Payne, Utah, Manual #6154
|
| Reply from WW:
|
| With the existing single alternator, battery, ignition system we have, you could start the engine,
take the generator offline, and operate the ignition system and the electric fuel pump for hours off battery
power alone. This is one of the great advantages of a points-based ignition system. They have very low power
consumption, and will operate at greatly reduced voltages. Conversely, electronic ignitions are big power
consumers, and many of them refuse to operate below 10 volts. In all of our years of flying John Deere
generators, we've never had any type of a failure, including losing a belt or regulator. If we were ever to
experience such a failure, our current system would provide a great amount of time to select an airport, fly to
it and repair the problem. Additionally, if you had some type of problem with the battery, we have test flown
our ignition system operating straight off the John Deere without the battery in the circuit.
Many homebuilders go through a phase where they want to incorporate complex redundant systems. Keep in mind
that your plane only has one set of control cables, one main wing spar, one prop, etc. Many homebuilders forget that
redundant systems on military aircraft serve an entirely different philosophy than sport airplanes: The redundant
systems on military aircraft are there to increase the chances that the aircraft can get through to its target.
With their philosophy, the mission will continue no matter what damage is suffered or which systems fail. The
target is the goal, and the plane and crew are expendable. Conversely, our goal is to simply have fun and enjoy
ourselves. This means simple, reliable, proven systems, and in the highly unlikely event of a failure, simply
flying to the nearest airport and fixing it.
|
| Subj: Tachometer
|
| Date: 3/4/05
What was the name & type of tach that counted flywheel teeth?
Tim, Manual # 6113, East Central Ohio
|
| Reply from WW:
|
| We use a Stewart Warner tach. The one we have installed in our 601 is a 0-3,500rpm unit, which has a full
sweep, allowing you to clearly see a 25rpm difference. Because it works by counting flywheel teeth, it is
entirely divorced from the ignition system. The Stewart Warner part no. is 82636. If you look at our
601 Web Page, you'll see the tooth counter attached to the front alternator bracket. I've used this
tach in many Corvair powered airplanes over the years. I like it because it has very smooth operation, and it is
extremely accurate when checked against our digital optical tachometer.
|
| Subj: Corvair and Sport Aerobatics
|
| Date: 3/3/05
You have made several statements regarding your considering the Corvair to be unsuitable for aerobatics,
citing crankshaft design and inverted system complexity.
If aerobatics are limited to positive 4.5 and momentary 0 to negative G loadings, do you still consider the engine
to be unsuitable for this use? Considering installation for Cassutt. Engine would be built with no electrics or starter
for weight and simplicity. I don't mind being restricted from outside and sharp snap manuevers.
Thank you. Your web site is very professional and informative.
|
| Regards, Thomas A. Berthe
|
| Reply from WW:
|
| Thank you for the nice comments about the Web site. Grace Ellen puts a lot of hard work into it. The two most
popular engines of all time in the Cassutt would certainly be the C-85 and the O-200. Neither of these engines in
their common forms are considered aerobatic. The Continentals use a wet sump oil system, just like the Corvair, and
any time you subject these systems to negative G, they're going to suck air instead of oil. I suspect in routine flight
that a lot of Cassutt guys did this, but technically, you can understand why it's a bad idea with any wet sump engine.
As you understand, aerobatic maneuvers put enormous loads on the crankshaft, far beyond what most people estimate.
While the Corvair has a very strong forged steel crankshaft, I'd be reluctant to encourage anyone to fly aerobatics
because the long history of flying Corvair engines was done in normal maneuvers. There isn't a lot of flight time
done using them for aerobatic applications. I strongly suspect that Rotax, Jabbiru, and the VW suppliers would give
you the same perspective on their engines.
|
| Subj: Engine Assembly
|
| Date: 3/3/05
I have a couple of questions. First, what are your thoughts on builders who want to build the engine but are not able
to attend a Corvair College, do you advise against this? Second, is there any type of package for
someone wanting to order all the Assembly Videos?
Thank you for your accessibility.
|
| Chris Barrow, NC, Christavia MKI
|
| Reply from WW:
|
| Over the years, we've sold several thousand Conversion Manuals. In the first eight
Corvair Colleges, we've had perhaps 400 builders attend to learn and work on their engines. In between Colleges,
we've hosted perhaps 400-500 more builders who came to do the same. These visits vary from a builder stopping by to
have us inspect his core engine before he started the rebuilding process, straight through people who purchased a
complete engine from us but wished to spend several days in the shop while it was assembled so they'd know the engine far
better than most homebuilders know their powerplants. Even with all these visitors added up, the great majority of
our active customers have never been to a College or visited our hangar in person. Our Manual, Videos and instruction
style assume no prior experience with engines, nor do we assume that most builders will have the opportunity to
attend a College. I purposely selected the Corvair as one of the few engines that met the flight requirements, but
additionally had the characteristics of simplicity and ruggedness that would allow us to teach builders in remote
locations how to complete and operate their own engines.
During the year, we offer special deals on products to
active builders through our newsletter, The Corvair Flyer. Subscriptions to the Flyer cost $20
a year for U.S. builders, $25 for international builders. Over the year, we offer multiple opportunities to recoup the
subscription price. In The Flyer, we occassionally offer discounts on video purchases.
|
| Subj: Carburetors
|
| Date: 3/2/05
I ran across this information on the MA* - SPA carburetors. You already know all this information but I thought
you might want to pass it along to your customers: http://www.kellyaerospace.com/articles/Accessory_AMT.pdf
Also I was looking at the Ellison site and they recommend that you install a priming system when using the EFS-3A.
Is this needed on the Corvair engine, and if so do you recommend the manual primer or the electric one?
|
| Larry Kyle, New Palestine, IN (I met you at Casey, IL)
|
| Reply from WW:
|
| Thank you for the link. Kelly Aerospace makes a lot of parts for certified aircraft.
An Ellison is an excellent carburetor, but you're correct, it does require a primer for clean starting. An MA3-SPA
with an accelerator pump does not.
The two options on primers are the traditional hand pump or an electric primer. We've flown and used both types. If
I were installing an Ellison in a 601, which would use our dual electric fuel pump system, I'd opt for the electric
primer because you already have the rest of the system to run it.
|
| Subj: Engine Cleaning
|
| Date: 3/2/05
This is a really dumb question, but could you provide a step by
step on how you get the case and heads so clean? With all the parts you
sell, the Vair engine is almost an "assembly kit" with the exception of
teardown and cleaning the core (future video maybe?). So far this has been
the most time consuming/hardest part of the conversion. I'm ready to
assemble the lower end but I'm not convinced the case is really clean
enough to hold paint. I'm working on the heads now. They have been
degreased but now what? Glass bead, walnut, plastic? I know you've said
don't glass bead, but then it seems like a lot of people are glass beading
and all of the shops I've talked to glass bead their aluminum parts. I
want them as shiny as those on the fantastic looking engines you just
delivered on your Midwest Tour, so if glass beading is definitely out, it
looks like I'll have to get them cleaned up myself before I take them in
for the valve job.
Also I have a set of the grooved rocker balls from Clark's. I noticed
Clark's sells mated pairs of rocker arms and balls. I'm planning to use my
original rocker arms with these new grooved balls. Do I need to "mate these
up" or just let them "mate up" in operation?
Thanks, Gunther Zion, Manual 5086, Greenfield, IN
|
| Reply from WW:
|
| While automotive shops may use glass beads on aluminum parts, you will not find a practice like this in
the aviation industry. Every now and then, somebody will bring a case by our shop that has clearly been glass beaded.
It takes but a few moments to show people a little corner or a passageway that has half a thimble full of beads waiting
to destroy the engine upon startup. Even if the case is really clean, the lifter bores and bearing seats are ruined by this
type of procedure. The heads are less critical, but still intolerant of glass beading. While we now own an environmentally
friendly high pressure wash tank, we traditionally cleaned cases with bristle brushes and a regular wash tank, filled
with mineral spirits. We used to figure about 2-3 man hours to clean a case with a stiff bristle brush and fresh
mineral spirits. You will not be able to remove all the stains in the cases, but you should be able to have it clean
enough that a regular white piece of paper, when pinched against any surface on the case, will not pick up any dirt.
We finish off heads in our walnut blaster. Both heads and cases are cleaned to the point where they may have stains
or discolorations, but they are completely free from any type of dirt particles. In our shop, all the cases are painted
to improve their looks. The Plastikote paint we use is impervious to flight temperatures, and will stick tenaciously
without primer on the cases. It has the additional plus of drying in half an hour. The heads on the engine you saw on
the trip were very lightly painted on their exterior surfaces only with a color called Cast Alumninum. Under absolutely
no circumstances should any interior surface of the engine have paint on it. It all takes time, but there are no special
tricks or shortcuts to a good looking and clean engine.
Engines built in our shop utilize reconditioned GM rocker arms with grooved balls from Clark's. If the rocker arm is
not damaged in the pivot area, I've found that they will work with new balls and mate in operation.
|