Mercedes-Benz Ponton
Gantry Fabrication and Engine Removal

Let's begin with some background for why I started this in the first place: My dad had the engine rebuilt while I was in my undergraduate days. I’m not sure how many miles he actually put on the car since then, but It seems like it’s around maybe 30,000 or so. The real reason for doing this was a failing wiring harness, wherein one of the horns came on all by itself one day, and wouldn’t shut off until I dropped the battery ground on the car. However, as we began to work our way down to the harness in the engine room, removing some pretty deteriorated heater boxes along the way, it became clearer to me that the engine room needed a touch up, and there was peeling paint down along the body rails that needed attention, etc. It seemed like the smartest thing would be to simply remove the engine, check the heater pipes, cores, etc., and do this job right. Also, I’m thinking I may have heard a bottom end knock in the engine the last time it ran – it wasn’t loud, but now’s a chance to get the engine out to my engine shop and have it thoroughly checked – so with the “scope creep” alert sounding loudly in the background, I’m off down that slippery slope that describes every restoration job I’ve done and seen – the problem is that we can’t seem to stop until we get to the bottom of the slope – I’m just not sure how far down the slope actually goes. However, the car deserves it, and I need to make it right now so when I’m through with it someone else, possibly my daughter, can take on the next stewardship role with minimal issues. It’s absolutely past the “in for a penny” stage and we’re about ready to start counting pounds. Seems like a good way for an old guy to entertain himself.

So, the saga continues. Here are some photos of the gantry in assembly and getting loaded into the shop. I had a local fabrication and welding shop get the steel for me, cut it to length and drill the 9/16” holes in the tubing. Then I stuck it together over the weekend and finished the assembly.

Gantry steel laid out

Will it fit in the garage?

This will be used to lift the front of the car high enough to get the engine and sub-frame out. There’s still a fair amount of work to be done to get ready to actually make the lift, but at least now the gantry is in the shop, out of the weather and ready for final touches. 

The plan is to use car dollies to actually move it around the shop, and to do that I’m going to build some jacking plates that bolt onto the base beams of the legs (so they’re removable) and some serious wood blocks to distribute the weight on the dollies. 

Vince at Shade Tree Engineering provided the gantry plans. So far, so good – now it’s on to (for instance) getting the Hydrak clutch servo off the car and out of the way, as well as all the other stuff that still connects the car to the sub-frame.

Update / February 1, 2012

So, the "Great Gantry Exercise" is proceeding apace. The first shot shows some flange plates that I built, attached to a length of 2 ½ inch pipe with a reinforcing gusset, that fit up to my “roller stands” that I’ve been using to elevate the "wire wheel" cars (MG and other British sports cars) while working on them. This is the first undertaking to use wheel studs instead of a wire wheel hub, but the result is I can continue to move the car around in the shop as needed for optimal positioning, yet be able to free up a bay if I need to bring in something else for a running repair.

The second shot shows the “jacking plates” that I can bolt onto the gantry and place it, as shown, on a rollmaster dolly on each side in order to move the gantry around in the shop. I elected in the end to not put casters on the gantry, but to use rollmasters instead, since I can more fully distribute the load on the shop floor without casters, and I have no reason to conclude that my shop floor, poured as a garage floor, is anything other than 4,000 psi concrete with some mesh somewhere in there.

The third shot shows the gantry in position to hoist the back of the car using the jacking sockets. This was necessary to elevate the car onto wheel ramp stands, so I could get under it and remove the exhaust system from the rear (of course) since that was the only readily apparent way to clear the exhaust manifold ports prior to actually lowering the engine out of the car.

The last shot shows one rear wheel up on the ramp stand, as well as the “pin block” I had made, which fits the jacking sockets and connects to the chain fall on each side using a two-ton anchor shackle. I elected to go with two-ton capacity shackles on a one-ton capacity lifting leg (on each side) simply because the shackles are under quite a bit of shear stress at the pins and I just wanted the “headroom.”

At this point I have one more brake hose to undo and I should be ready to try and get the engine and sub-frame, etc. out of the car. Of course, that brake line connects behind the heat shield that protects it from the front pipe, and presently that heat shield isn’t moving – yet. I promise to document the actual engine removal with pictures as it happens.

Update / February 4, 2012

First of all, the engine and sub-frame rolled out “almost” as planned today. The lift pin blocks worked as designed, the gantry was the perfect tool for the lift, and I adapted Bruce Bristow’s design for a tail wheel, which did the job for me. The only thing I forgot was to undo the choke cable where the sheath attaches to the rear carb. Yep, I did disconnect the cable, but I missed disconnecting the sheath. I’ll see if I can collapse the stretched out sheath, but if not I may need a new(er) cable. One thing I did do, which was very helpful, was to put the front wheels on rollmasters. That let me move the engine and sub-frame assembly from side to side, or cock it at an angle as needed. I also put the body back on a variant of the roller platform stands, so with the rear wheels on rollmasters and the front supported on rolling stands I still have the flexibility to move the body around in the shop so as to get it out of the way, or put it in a prime working location as needed. 

"Stand Caps"

Here are a few more photos. The first shows the variation in “stand caps” between the earlier design for the wire wheel cars and the newer “crutch” design sized to just fit the frame rails under the car. I have these positioned at the same point as the jacking socket locations at the front, and the doors open and close with no strikes when the car is supported on the rear wheels and the rolling crutch stands. 

The second shot shows the engine and sub-frame, etc. mid way out from under the car. This also shows the rollmaster platforms under the front wheels. 

The third shot shows one of the lifting legs connected to the gantry. The critical issue here is ensuring that the lifting leg doesn’t touch the trim or finish as the car is lifted. I used grade 5/8 inch washers to space the pin block out a little farther – three seemed to do it, and the gap shown is the gap under strain (this was taken during a dead hang exercise prior to actually removing the flange plates and putting the front wheels back on in preparation for the lift. 

Finally, the last shot is the engine and sub-frame out of the car. I figured this was a good place to stop for the day, but now I’m staged for more work to do. 

If it fits, the fifth shot is a close-up of the crutch box fitted to the top of one of the roller stands. This is no more than a section of ¼ inch plate bent to a U, with a flat plate used to clamp it on the top of the stand, and then another U welded to a piece of flat-bar, also welded to the box that clamps onto the stand. The car feels pretty safe sitting on these stands since the weight of the frame rails actually rests on the underside of the top of the clamp box, which then carries the weight down to the rollmaster and on to the casters. Not much to give.

For anyone thinking about using this technique themselves, I can’t emphasize enough the importance of doing static hangs prior to actually doing any lifting. I typically waited about ½ an hour for the static hang to prove itself, and after each static hang I pulled the pin blocks back out of the sockets and checked for any deformation of the pins. This is particularly important when using washers to space the blocks farther away from the car, since it creates a longer section that could bend rather than emphasize shear stresses, and bending is a sign of weakness and thus a “failed test”, which should prohibit the car from actually being lifted until the equipment can prove itself strong enough not to bend. Also, in my case it’s serendipitous, since I didn’t actually plan it this way, but when lifting the tendency of the top of the pin block is to roll away from the car rather than towards it – also a healthy approach to mitigating any bending action, which might result in the pin block or the shackle touching the paint or trim.

One other point I should make – with the Triumph, which is a roadster, we found a lot more body flex when lifting the car, particularly when putting it up on ramp stands at both ends, one corner at a time. It was necessary to keep the doors closed when lifting, I felt, to control that flex. With this car, granted it’s a sedan, but nonetheless although the car has a little flex when I start lifting at one jacking socket and then run around to the other chain fall to catch up on that side, this body is SOLID – the word “tank” comes to mind. It’s a real pleasure working on a car so well thought out for servicing, even if the methods are a little unconventional – at least to someone used to working on the English cars. The gantry approach to lifting has also been gratifying. In the back of my mind, I want to, in the future, fabricate some wheel slings that will let me use the gantry to lift one end of a car (both sides) at a time, similar to what I’ve done on this job but for a car that doesn’t have jacking sockets in place. I’ll seek to try that when I get to the MGB and Austin Healey waiting patiently for me in the barn.

More to come...

Chris

Update / February 18, 2012

I pulled the engine off the sub-frame this week and broke it down to the point that it’s ready to go out to the engine shop. The first photo shows the car over in the far bay of the shop, where it will likely stay while we get the engine bay cleaned up, painted, etc. Depending on how the engine work goes and what the engine really needs, we may be able to start laying in the new harness before we put the sub-frame back under the car again – but I don’t want to get too far ahead of myself. I should point out that the car remains completely mobile even in this state, so I have the option to swing it out sideways in the shop and clear space on both sides if needed. Strike a blow for roller platforms, to be sure.

The second photo shows the engine and sub-frame, etc. positioned to start stripping the engine down in preparation for getting it out to the shop. In this photo I’m using the gantry and one of the chain falls as an aid to help support the back of the transmission, so all of the weight isn’t left on the tail wheel. I dithered a bit about whether to send the engine out or not, but there were a couple of considerations that convinced me it makes sense. When I hand-roll an engine I consider to be healthy, I normally hear hissing and gurgling sounds as the engine turns. This one manifests none of that. Further, with the plugs out and thus no compression, it turns really easily – much more so than the freshly rebuilt Triumph engine did when it came back as a long block. So, I think at a minimum I need to have the shop go through this engine in detail and assess what it needs. Are, for example, the big ends of the connecting rods “ovaled” as they were on the Triumph? Are the main and rod bearings good enough to go back in for another 50,000 miles or so? How’s the end play on the crankshaft? Are the rings worn to the point we should replace them, or are the bores ovaled enough that we need to address that? This would be the time, while the engine is out, to be sure, so the journey down the slippery slope continues.

The third photo (apologize for the slight blurriness – didn’t realize it was fuzzy until too late) shows the unique flywheel configuration of a Hydrak car. There’s a lightweight flywheel for the torque converter, then a much heavier plate / flywheel attached to the converter, which in turn hosts the mechanical clutch. I was surprised at how much rust was on the mechanical clutch when I took it apart. I think some of this may have started when the car was stored in a working garage during a Wisconsin winter, and another vehicle was coming and going in that garage in the snow and salt. Looking at the Hydrak bellhousing, it’s well ventilated to ensure the torque converter doesn’t overheat, but that also exposes the workings to humidity much more than a normal, closed bellhousing. I will likely have the clutch disc relined and will also have the pressure plate and cover assembly checked out while I have them on the ground. There was and hopefully still is a good shop in town that can do that work.

Photo 4 shows the engine clear of the sub-frame and stripped of accessories, etc. and ready to go out to the shop on Monday, which is supposed to be a dry day. The engine needs to ride in the back of a pickup, so weather is a consideration. I’m using nylon lifting slings and my leveling bar to move the engine at this point. I couldn’t find any sling points I was comfortable with for use in lifting, so I opted for some fabric slings so as to not risk marking the engine, oil pan or valve cover. The leveling bar simply lets me keep the engine level, so the fabric slings don’t slip from their intended locations. The center of gravity of the engine as shown is somewhat forward of center, which makes sense considering the weight of the timing chain, sprockets, harmonic balancer, etc.

Finally, photo 5 shows the now empty sub-frame ready to get cleaned up and painted. There is surprisingly little rust on the sub-frame – none really that I can see. I need to pretty much get the accumulated road grime and grease off, check the engine mounts and get it out of the way until I’m ready for it again. One interesting aspect to all of this was that as I began pulling the transmission, then the mechanical clutch, then the torque converter, etc. off the back of the engine, the center of gravity for the remaining engine and sub-frame was quietly shifting forward – to the point that the sub-frame came really close to simply flipping itself and the engine over frontwards. I needed to stop and get another jack stand under the front to keep it from doing that, and in the end I supported it on two jack stands, one in front and one in back, while I undid the engine mounting bolts and lifted the engine off the sub-frame.

So far, so good. I’m probably not going to like what the engine shop has to say, but we need to do this. I do know, from my father telling me, that the crank has been ground twice and the engine bored once, so if we need to replace components there could be an availability issue for the correct sizes. Yup – there are ways of course to compensate, but never as easily as simply putting in the correct parts if they’re available. Still, as someone remarked, the car deserves it, so we’re off to make it better. I am beginning to think fondly of the day I can actually start hanging things back on the car, as opposed to taking them off.

- Chris

Update / February 29, 2012

I’m still in the hunt, although we are at the point where the glamour is elsewhere. This is just the grind-it-out part of a restoration that enable glory days ahead — at least that’s the plan. The work recently has been to look at a stuck heat riser valve on the rear exhaust manifold. The first task was to separate the intake and exhaust manifolds. I rebuilt and re-bedded the carburetors not too long before the car was laid up, so elected to leave them in place and break the assembly at the joint between the exhaust and intake manifolds. The first photo is the work of separation in progress.

Photo 2 is the rear manifold ensconced in the bench vise. The heat riser valve can be clearly seen inside the chamber that bolts up to the bottom of the intake manifold. Fortunately or unfortunately, this valve is stuck in the closed position. The thermostatic operating springs are both missing, probably rusted off, although it looks as though there should be two – one on each side. My initial thought was to gently remove the asbestos gaskets from the top of the chamber, and soak the manifold in the parts washer until the valve came free or I ran out of patience – whichever came first.

As someone once remarked, it’s always good to have a Plan B. The gaskets seem to be well and truly stuck to the manifold, and it doesn’t help to have the two studs still stuck in the manifold. The third photo is of a heat shield I made out of a scrap piece of galvanized that had been serving as a dust magnet for several years. I heated one of the studs red hot, triple nutted it and it still won’t turn. I also tried heating the manifold, to no avail. Long story short, I’m now soaking the pivot points of the heat riser valve from both sides with penetrating oil to see if that will free it up. I’m pretty sure the asbestos gaskets are difficult to replace, and so I’m reluctant to do anything that might damage them. I can be very patient.

Finally, while I’m entertaining myself fooling around with heat riser valves, my bride Eileen, a.k.a. the "Queen of Clean", has been working in the engine room attacking 54 years worth of road grime, oil weeps and the all important chassis grease that blows up into the engine room after an enthusiastic greasing. Photo 4 shows her standing in the middle of the engine room with the tools of her trade. We both like "Goo Gone" to help cut the grime. I’ve also been working on the sub-frame getting it cleaned up and on the way to getting painted. It looks much better so far – photo to follow when it’s painted and “nice.”

Yup – it’s still a journey

Update / May 3, 2012

Apologies for not having written something a little sooner. Spring happened in western New York state, and I took the opportunity to catch up on a little yard work, including cutting up some trees that I dropped into a gulch a few years ago to open up a hedgerow a bit, and taking out a couple of other good size limbs that were a threat to anyone standing under them in any sort of wind. The fresh cut ends represent pieces newly cut to length, most of which will need to be split when they dry out a tich.

And the "chip me" pile of stuff too small to be worth using for firewood grew substantially as a result of this exercise.

However - the weather turned cold again, and while I did do a couple of things like replace the rear springs and add a front sway bar to the MG Midget, and replace the wiper motor and a worn clutch linkage pin on the Triumph, I've also made some progress on the Mercedes-Benz Ponton sub-frame. The first thing I did was clean and paint the upper side as it sat in the shop. Then, with the upper side at least coated with a rust encapsulator, I hung it from the gantry and turned it over so the underside was facing up. This was done by hoisting the sub-frame vertical, then "dead hanging" it off the gantry so I could "change hooks" to the chain fall on the other side of the gantry, and then using the original chain fall to hoist the bottom up, hold the sub-frame horizontal and gently lower it back down, one end at a time, to the stands again. Nylon sling straps are invaluable for lifting the sub-frame, since they won't scratch the paint or ding the metal. The picture below shows the sub-frame in the air, just prior to dead hanging it and switching hooks.

Following the Service Manual (see Job 32-4), I got the shocks out. Of course, one was bad and the other wasn't great, so now I have two new shocks on hand to use when reassembling the sub-frame. Next, I set out to remove one of the front springs to gain access to the inside of the spring tower, which looked pretty rusty. The Service Manual shows a special tool being used that compresses the spring between the upper and lower control arms. The sub-frame is shown in the inverted, or "upside down" position in the next photo. I didn't have the tool, but I did have an axial spring compressor, which goes through the center of the spring (as opposed to the more common "side by side" compressors), and although I could have adapted the axial compressor by extending it with long Grade 8 bolts and a couple of nuts welded together, the hole in the top of the shock tower is only 12 mm, which is less than half an inch - a little narrow for my taste and smaller than the threaded rod of the spring compressor. I didn't feel like trusting the run of the mill threaded rod available from the home stores, so I elected to grab the spring just "below" the spring tower in the sub-frame, and compress it against the lower control arm. That's the top of the spring compressor, with one of the compressor's hooks visible in the spring, in the next picture. I also used a piece of ¼" bar stock to span the hole in the lower control arm where the shock mounts up, since the compressor "almost" fit through the hole in the lower control arm, and I was pretty sure I could get the compressor well and truly stuck in that hole if I didn't make the base of the compressor bigger somehow. The bend in the bar stock attests to the strength in the front springs.

With the spring pressure eliminated to the point that I could get a little independent movement of either the upper or lower control arm, I undid two of the bolts holding the inboard end of the lower arm, per the manual, and inserted my guide rods. These are nothing more than 12 mm rod, threaded on the end to the same thread as the bolts. I took a bolt over to my local fabrication and machine shop so they could match thread and size exactly. With the guide rods in place, I removed the last two bolts holding the lower arm, and then slowly backed off on the spring compressor.

Just like the Service Manual said, the inboard end of the lower control arm rode the guide rods upwards until the spring tension was completely released. At that point I removed the guide rods, swung the inboard end of the lower control arm straight up and sure enough — there was the spring in all its rusty glory.

Note that I'm using one of the chain falls on the gantry and a nylon strap to support the weight of the wheel hub, brake drum, etc. The underside of the sub-frame can best be described as "a mess." There are 50 years of road grime, excess chassis grease and just general dirt caked in all kinds of places. The inside of the spring towers isn't exactly pristine, either. This morning I spent time cleaning up the driver's side of the sub-frame on the bottom side, which is now facing up since I turned it over. It's still resting on roller stands, so I can continue to move it around the shop to get the best light, or to shoot caked gunk towards the door and not the toolboxes when using a wire brush in a die grinder to get the hardest caked masses someplace other than on the sub-frame. I can personally attest to the fact that a wire brush in a die grinder can shoot caked gunk a good 15 feet across the shop. For more liquidity add "Goo Gone."

The sub-frame steel continues to look really good. There's a fair amount of surface rust, and some of it has been running under an old undercoat my dad applied years ago. It's not deep, though, and structurally the sub-frame, springs and control arms are very sound. One issue I discovered is movement at the upper control arm outer end, where there shouldn't be any. This is a critical location, since this is the point where the cam bolts are located that adjust the kingpin inclination. This has to be solid, and precise. I took this joint apart, by first removing the clamp that holds the cam bolt in rotational position, then removing the nut from the end of the cam bolt and gently driving the bolt out of the threaded bushing that fits into the kingpin. There is play between the bushing and the cam bolt, so I've ordered an "upper control arm kit - outer", which will provide the cam bolt, the bushing, seals and washers necessary to put this back on spec. I also put a punch mark on the clamp that aligns with where the strike on the cam bolt was when I started disassembly. I won't by any means testify that this will allow me to get the kingpin inclination precisely correct, but it will allow me to get the adjustment "roughly right" enough that I can safely drive the car (some day) to a shop and have a complete front end alignment done. The photo below shows the cam bolt partially inserted in the bushing, which is partially threaded into the kingpin. The clamp, not shown, is nothing more than a bat-wing shaped plate that clamps down on the flange of the cam bolt facing us, and prevents the cam bolt from rotating. The strike on the cam bolt, which is used to re-gain alignment, is shown running from the top of the bolt in the picture into approximately the center. The outer end of the upper control arm, still upside down, is shown at the bottom right of the photo.

I talked with the engine shop last week. They haven't started on the engine yet - their bread and butter is what are termed "race motors" in this part of the world, and spring is a busy season for them. It's just as well, though, since as I get deeper into the sub-frame and suspension I'm effectively pushing out the date when I'll be able to put the engine back in the car, and that's OK. I still think of myself as the steward of the car for the next generation, and that means I need to make it as perfect as I can so the next steward may have less to do. It continues to be a journey. I've got the spring over to a shop in town for bead blasting. Once it's back, and I've installed the new cam bolt and bushing it on the side I'm working on, I'll reassemble that side, including the shock, and do the other side, replacing any obviously worn parts there in the process. Then, hopefully, I can move the sub-frame out of the shop along with the gantry and concentrate on the body. There are, as the saying goes, some things to do there. More as progress happens.