Growing a Grumman
- Part 2
writing part 1 of this story - which was written a mere 8 years after
starting the project! - have we been busy or have we been busy?
When writing Part
1, the airframe was substantially complete and the Chev V6 motor had been
rebuilt, but was lacking most of it's ancillaries, such as intake manifold,
carbs, fuel pump, alternator, starter,flywheel exhausts etc.,etc.
Leaving the airframe
to attend to the engine, the best idea seemed to be to build a stand on
which to mount the engine - one on which it could also be test run. With
a will we got to work fabricating this from steel sections, and since
I did not have a decent welding set it was simply bolted together. Worked
out okay, but towards the end of the process it dawned that, in effect,
all of this work was soon to be redone - inasmuch as a mount was going
to be built to fix the engine to the airframe! Duh - why not use that
as the test stand?
quickly to Plan B, the test stand was abandoned and some mild steel tube
purchased - real cheap is mild steel tubing , I think I paid something
like R130 ($20) for enough to fabricate a tubular engine mount, which
is fortunate, since after all the rough cutting and welding of this it
looks pretty awful. However it will never be required to fly - or even
to taxi - so I am not too concerned as it is after all the FIRST prototype
- emphasis on first - since I suspect that we will go through at least
one further iteration before #3 becomes the finished engine mount. People
( and many writers on the subject of building engine mounts) told me that
I should use wooden dowels or PVC conduit to make the prototype or pattern
of my mount - but since I need, for my own peace of mind and satisfaction,
to see this engine run - and run well - before proceeding to other, yet
more costly but essential components, it seemed that steel was the way
to go - wouldn't like to run an engine hanging on wooden or plastic tubing!
The other thing that
needed doing was a hefty modification to the inlet manifold. I might mention
here that the engine as obtained in "rebuildable" condition
some years ago, had the GM TBI (Throttle Body Injection). This TBI unit
was totally beat-up and most of the electrics that controlled it were
missing anyway, so the decision to ditch it and use some other carburation
system was not difficult. However the Holley that I would have preferred
to use is simply not stocked in SA by any of the specialist speed shops,
who all offer the 600 cfm or bigger unit. The one needed for the V6 to
run happily at 4500 rpm and less would be no more than 400 cfm - and that
Holley carb is enormously expensive, even in the USA.
After looking at a
friends motor car, a Rover 3.5 ltr V8, which runs twin SU carbs and revs
happily to 6000 rpm, giving maybe 160hp, I figured that those same carbs
could be adapted to the Chev manifold - and with a but of luck and some
re-jetting if necessary, would do the trick.
of SU carbs is that they are, to some extent, self-compensating for altitude,
having for mixture control, a tapered needle and jet arrangement controlled
by vacuum. Well, that's the theory anyway. For US visitors, you may be
more familiar with this Rover engine under the guise of the Buick 215
around soon found a set of carbs in good nick, complete with manifold
from a Rover V8 for the reasonable sum of R 1100 ($150).
Now this is where
the story takes a rather expensive - and painful - turn. Since the first
necessity was to cut up the Rover manifold to remove the plinth on which
the dual carbs are mounted, this plinth then to be welded to the Chev
aluminium manifold, out came the trusty angle grinder. Mounting the manifold
in the bench vice we fired up this demon device, even installing a new
cutting disc for good measure!
It was only a few
short minutes later that we were destined for hospital treatment, after
the blade had jammed in the soft ally and in so doing twisted the grinder
violently out of my grasp, allowing said blade, still turning at a zillion
revs, to contact my index finger, just above the fingernail! Gadzooks!!
Of course at the time,
hospital did not seem necessary - and a dab of antiseptic and a bandage
was all this medical expert deemed necessary. A week later however the
excruciating pain from the finger said that something needed attention
- medically speaking.
To cut a very long,
expensive and stupid story very short, the operation (on one index finger
yet!) to remove the infection that had set in, involved two days in a
hospital bed, an operation under general anaesthetic which took a max
of 15 minutes and an eye-watering R12 000 ($ 2000)! Makes airplanes look
Moral of the story
- angle grinders have their uses - maybe cutting manifolds is not one
of them - but like all power tools they can cause severe damage to the
Having suffered this
setback, in terms of time lost, enthusiasm waned and much needed cash
wasted, a month or so later saw work resume. The manifold was finally
modified, not without further complications, in that the manifold height
once the Rover carb mounting was added was too great for the standard
top cowling. This meant that the Chev manifold TBI mount plate had to
be milled down by some 1.5 ins before adding the Rover adaptor.
But eventually we
had a manifold that looked like it should do the job and could accept
the SU carbs - and importantly would fit under the cowlings without unsightly
lumps and bumps being added for clearance.(Note - this did not work out
as planned as you will see from the pics later)
the airframe and the engine were residing 50 kms apart - the aircraft
still at the airfield and the engine in my garage at home - time to bring
said airframe to the garage - which itself required a major clean out
before to make space for it! Managed to borrow a trailer again for this
job and relinquished my lease on the hangar as I could see no point in
paying to keep it empty!
Another week of cutting
and welding tubes created Protoype Engine Mount #2 and the whole catastrophe
could then be assembled to the airframe - quite a moment as one steps
back from the labours to view an aircraft with a purposeful-looking V6
lump hanging in the right place on the airframe!
Fortunately the Christmas
season had by now descended on SA and holidays were the order of the day.
Since my own business depends on at least some of my clients and prospective
clients being around to talk to - and they weren't - the work could proceed
apace through December and into January 2004, without such irritating
matters like work interfering!
Having finally mounted
the engine to the aircraft, now all the other bits and pieces needed to
make it run had to be obtained. First off, flywheel and starter - since
I am hoping to use a chain drive - like Fred Geschwender(Note - plan changed
and used a belt eventually) - and am always open to advice and Fred's
advice is to use, not a flexplate, but a full sized flywheel, I hunted
breaker's yards for such items - eventually ending up with a flywheel
from a Nissan 3.0 V6 4x4, but no starter to match was available from the
same source. Nothing daunted, the flywheel was dropped off at a local
engineering shop for new bolt holes to be drilled, matching the pattern
of the Chev crankshaft. Incidentally I looked at many flywheels which
had the right diameter and weight - but many already had little "meat"
remaining at the centre boss for 6 new holes to be drilled - luckily the
Nissan had plenty of metal in the centre for the new holes and is very
close in size and weight to the original Chev flywheel, according to my
- when I dropped the flywheel off for redrilling, the engineers shop said
they would be closing in a few days, but that I would get my stuff back
before they went off for their vacation - all lies! I eventually got the
flywheel back only early January.
Meanwhile over December
there was till plenty to be getting on with. following the example of
Jess Myers of BAP (Belted Air Power) I made up and installed baffles which
will direct incoming cooling air to the firewall mounted radiator under
pressure. This baffle system creates a plenum chamber when the top cowling
is installed and according to JM works extremely well with a compact radiator
mounted at the firewall. I have yet to have the rad made up - that comes
later - but for the moment am using a temporary radiator of unknown origin.
Exhausts had to be
fabricated for test run purposes - since I was not sure whether the engine
mount layout would remain as per Prototype #2 (likely won't) I used the
existing exhausts that were on the engine. Strangely, one was a nice unit
of tubular steel - and the other a great ugly cast iron thing. So the
tubular exhaust was chopped and bent and re-welded to suit and a new "log"
manifold made up of mild steel tube for the other side. Some bits of scrap
tubing from the local exhaust shop finished this temporary setup, dumping
the exhaust gases out of what would be the bottom of the cowling.
V6 motor is believed to have lived in one of these in the USA -
a 1987 Chev S10 Pickup.
Now came the thorny
problem of what to do about the water pump. The Chev water pump being
cast iron is very heavy, and in any case the one I have rotates the "wrong"
way, since this engine used an elaborate serpentine belt system for water
pump, alternator, aircon and power steering. I could replace the water
pump with an aluminium unit, but this would have to be specially imported,
enquiries showed. The other severe drawback to the Chev water pump is
that it extends rather far forward of the engine block, using valuable
space which I needed, to position the engine real close to the firewall
for Cg reasons.
I remembered that
the pump on a Ford V6 Essex engine (had a few of these in the past) is
a super lightweight unit, very compact, commonly available and real cheap.
Could this do the job of circulating water in a Chev engine? Why not -
it does fine on the Ford, but of course the entire mounting methodology
is different. Just going to have to make a plan - and that's what we did,
mounting the unit on a sturdy fabricated bracket to the left (looking
from the front of the engine, as in a car) and below the fuel pump mounting
Using an old radiator
which was on hand, I fabricated piping for the cooling water. This had
to bring the water out of the block to the new pump arrangement, using
the two holes in the Chev block. Quite simple to do, and eventually, if
testing shows that it works well, neat alloy piping will be made up. One
concern is the ratio now created using the Chev crank pulley, which is
a large diameter, and the pulley on the pump. What size crank pulley did
the Ford have? - probably smaller than the Chev, which would mean that
the pump rotation speed may not be right. We will know more about this
in due course - and whilst the Chev crankshaft front pulley cannot easily
be changed in diameter due to the existence of the large diameter external
damper, the pump pulley probably can be altered.
On the other side
of the block, low down and out of the way I installed the alternator,
fabricating brackets as needed. Right now everything is driven off one
single vee belt, which is not the acme of perfection - we'll have to work
out how to build in redundancy here. It seems to this writer that dual
belts running side-by-side on double pulleys are not in fact the answer
- experience has shown that when one belt goes, flailing bits of broken
belt often take out the remaining good belt. Whilst a non-functioning
alternator probably won't create a serious problem - a stationary water
pump most certainly will!
Happily then, both
the water pump (not too heavy) and the alternator (quite heavy) are now
located right at the "back" of the engine, as close to the firewall
as they can be - I am happy with that positioning, as the Grumman being
so short coupled, there is little leeway to easily adjust CG by moving
things around - and in any case what things? The only thing that I can
use for weight repositioning is the battery - and that has already been
repositioned to live behind the rear baggage compartment bulkhead. I have
even modified the seat runners to allow for an additional 3/4 inch rearward
travel of the seats, and the backsides sitting in them!
With the purchase
of 5 litres of engine oil and an oil filter, we were now clearly getting
serious about making noise with this engine! But before pouring the oil
into the engine let's fill the radiator and check for leaks - after fixing
a few of those the radiator water level kept dropping - odd, no leaks
where can the water be? In the damned cylinders, that's where! Oh boy
- the modified intake manifold was clearly leaking through from the internal
water jacket - off with the manifold, but nothing obvious or visible of
course. Had to again cut up the manifold, (hacksaw and lot's of elbow
grease this time) to find cracks in the welds - maddening!
This time around I
used a different welder - there are those who claim to be able to weld
aluminium and there are those who can actually do it right!
How for the final
piece of the puzzle - at least for test run purposes - a starter motor.
After again searching breakers yards to no avail, bought a new starter
(R1000/$140) for the Nissan 3.0 and made up a bracket on which to mount
it. Conveniently GM mounts the starter to the engine block with 3 bolts,
rather than to the gearbox bellhousing. The starter is a 1.4kw unit and
is a geared unit for improved torque, and it appears to work well on the
Being now at
the point of incipient engine running, I am now about totally exhausted
as a result of some intensive mechaniking over the past several
weeks. Next instalment once we have run the beast!