Growing a Grumman - Part 2
Since 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 ancilliaries, 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?
Moving 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.
Another advantage 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 cu. in.
Scouting 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 cheap!
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 user!
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)
Meanwhile 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 research.
Promises, promises! - 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.
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 position.
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 going? 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!
Now 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 Chev V6.
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!