Prime time: Priming the gearbox castings

Having given the gearbox castings a final cleaning with an aviation surface prepping agent, they received what we hope to be the final masking to get them ready for paint.

It has been a long road to get to this point and we are starting to see the light at the end of the tunnel. First up though is a coat of super strong epoxy primer applied nice and thin so as to not hide the texture of the cast aluminum.

We started by mixing the primer using our milling machine to stir the contents at low speed for about 10 minutes and followed up with painting in a makeshift spray area we set up. With primer on we will soon move to putting on colour which will be the subject of a future and hopefully final post on the gearbox castings.

All kinds of resistance: Restoring the ignition coil resistor

The resistor block located on the backup ignition coil gave us quite a few challenges along the way of what we thought would be a simple task. Of course it was stripped and painted like other parts we have done. Likewise all of the hardware was stripped and re-plated to original finishes. When we thought we were all finished we discovered that the resistor came with a stamping on top. Again artwork needed doing and another painting stencil was made to replicate the marking. In the end it was a massive amount of work for a part that will spend its life behind a cover in the trunk.

The following photos show the process of restoration followed by an incriminating photo of a practice attempt that is likely to end up having me spend a night on the couch. All necessary sacrifices when restoring an old Italian car.

Carb Re-build #4: Putting it all together

With the three carburetors re-assembled now came the fun task of bolting everything together on the intake manifold. This included all new gaskets, hardware, and hoses the latter of which was treated to a special stencil that allowed us to paint an exact replica of the original CAVIS brand that would have been on there new (CAVIS is period correct as the more commonly known CAVIS BENZ came after the Dino ceased production).

Included in the assembly is a calibration of the throttle linkage to ensure that all of the cabruetors open in sync and have full throttle as it is common for one carb to open a little less than another.

With the assembly finally completed we are very pleased and proud of the result.

Carb re-build #3: choke mechanism, float height, and final assembly

With the throttle butterflies installed the rest of the install is fairly straightforward. It is impossible to install anything in the wrong spot and the only two places were you can run into issues is on the choke mechanism and float height.

First up is the choke or rather fuel enrichment system. This acts like a little carb within the carb and is activated by means of a pull wire that transfers its motion to a gear system (seen below). This gear system operates the fuel enrichment valves that allow the engine to get extra fuel when it is cold. When assembling this component it is important to note the little marks on the gears. The valley of one gear is to fit in the peak of another to have the correct alignment. It is a small and simple detail but one that is critical for the proper operation of the system. Also it is important to remember to grease everything well during assembly to ensure a long life for the parts.

Next up is the float mechanism. This is the only part on the carburetor that requires setting during assembly (ignoring needle valve settings of course which are done externally). Inside the carb are a number of tubes and passages that need to operate inside of a pre-determined height of fuel. Too much or too little and the passages are either flooded or starved and the mixing of air and petrol does not take place as it should.

The procedure for setting the float height is very simple. It involves taking measurements with the top of the carburetor horizontal (achieved easily by laying it flat on a table with the float hanging off the edge) or vertical which (as seen below) is done by using a square to hold the carb top upright on a flat surface. If the float height is off, all you do is bend the stops as needed so that the upper and lower settings are correct.

The float height is an important setting and it is critical to check all measurements when you are finished to make sure that they correspond with the correct specifications. DO NOT assume that a previous measurement will be correct after you make a float height adjustment. Normally making one adjustment will knock the other one out a little so you need to be sure that both the open and closed measurements are correct after all setting is done and before the carburetor is closed up.

We have already posted images of the finished carbs and the next step is to mount everything on the intake manifold with the completed linkage. Keep reading as we will profile that in a future post.

Carb re-build #2: New bearings and getting things aligned

With all of your parts clean, laid out, and ready to install, the first step is to fit the main throttle shaft and butterflies in our fresh carburetor body.

The throttle shaft runs on ball bearings and these should be replaced for new sealed units for 2 reasons:

1. The bearings in there are likely the original ones and over 40 years old. I was told that the bearings never go bad and this advice was NONSENSE! Every one of the bearings we removed were rough and not nearly as smooth as a new one. New bearings are less than $10 each with every carb using 2 so this is not the time to cheap out for so little money.

2. The original bearings were of an open cage design. Weber tried their best to seal out air by using a number of flat and spring washers but they are still prone to leak a little. This air leakage leans out the mixture at different throttle openings and takes away a little precision from the assembly in addition to causing noticeable irregularities in how the engine runs. New bearings (again from www.piercemanifolds.com ) are of a sealed design, are maintenance free, and keep the air out.

With new bearings in the next step is to fit the throttle shaft. Be sure to use some oil or grease on the shaft at all of its operating points.

Next come the throttle butterflies. They need to be fitted with care as their fit is very tight in the bores. DO NOT FORCE ANYTHING! If something is stuck find the reason. It could be a tiny burr of metal or a mis-alignment. Everything should fit together nicely and force will only damage the brass plates or soft aluminum carb body.

With the throttle plates in the closed position then fit the throttle plate screws. There are two tricks here:

1. Use red Loctite on these screws. You want all the insurance you can that they will not fall into the engine.

2. Tighten them so they are 'just' snug. Tight enough so that the plates do not move easily but not so tight that they are fixed in place.

The next step is to build all of the outboard components of the throttle shaft and tighten them down well. At this stage the shaft will have shifted a little bit and, having left the plates loose enough to move, then you can loosen the butterfly screws a little to allow them to really settle into a finished position.

With the screws loose & the butterflies in the closed position hold the carburetor up to a bright light and look down the inlet barrel. You should see just a faint bit of light around the perimeter of the butterfly. What you are looking for is uneven light which indicates a butterfly that is off to one side. Once you have a nice even light pattern, fully torque the screws.

With the screws tightened check the operation of the assembly to make sure that it is smooth with no tight spots. When assembled the movement for the shaft should be almost Swiss watch like precise. This is all a function of good assembly of clean straight components and will make a noticeable difference in the operation of your engine.

Carb re-build #1: Disassembly, cleaning, & inspection

The first thing to do when re-building the carburetor is to strip it down. Take lots of photos of it if you feel you will be unsure of how it goes back together but in reality it is hard to get it wrong as no part can really go into the wrong place.

The first thing to do is find a large clean and steady table. You will be dealing with a lot of tiny parts so you want to make sure you have a surface with a nice light colour so you can't misplace anything.

While disassembling the carb it is a good idea to lay all the parts out on your table grouping like items together.

In our case we re-plated every metal piece back to the original yellow zinc finish and all metal parts were cleaned in a chemical bath of carburetor cleaner. This fluid is fantastic at removing old deposits as it is essential that everything be surgically clean before re-assembly. To do a proper job you must have a source of compressed air to test that all passages are clear. If you do not have a compressor, a can of pressurized air (used to clean computer keyboards and available at any office supply shop) works well.

You will also require a re-build kit. There are many on the market and by far the best is the one from Pierce Manifolds www.piercemanifolds.com . It is very complete and reasonably priced at less than $50 per carb. Other kits cost less but have much fewer parts so this is worth the extra expense. Do not be afraid of having left over parts as the kit is very comprehensive and has pieces for multiple carb models.

With all of your pieces clean it is time to inspect everything. Using a straight ruler check to make sure that all machined surfaces are flat. There is no magic here and all it takes is patience. Also look for anything that appears off and check to make sure that the throttle shafts are straight by rolling them on a flat surface. If they roll easily then they are straight.

Extensive cleaning is not about being obsessive. The time spent with a part during cleaning gives you a chance to really have a close look at it to try and locate damage, cracks, and faults that can cause problems later on.

An essential tool when working on the carbs is a magnifying loop. With this simple tool you can magnify the tiny holes in the carb passages and ensure that they are clean and clear. At this time it is also a good idea to record the markings on all of the jets and tubes in the carb. Your re-build kit will come with a parts diagram which will name all of the parts.

In our next post we will get started on the re-assembly of the carburetor.

Fueling progress: The first carburetor is built

Over the next few days we will post once daily our progress on the assembly of the carburetors. Putting these together is not hard but does require a clean workspace and an attention to detail. It is something that the hobbyist can do at home and in the next few blog postings we will outline some of the tips and tricks in getting the carbs right. Hopefully it will give the reader the confidence to try this procedure on their own.

Before getting into the guts of the work we thought we would start with finished images of the first carburetor we got done. It was a lot of work to get it looking like this but, seeing as this is a main showpiece in the engine bay, we thought it worth the extra effort.

All charged up: Re-building the alternator

One part that worked well but looked tired was our alternator. Despite doing its job well, it just did not look up to the standard of the rest of the engine. To correct this we took the alternator apart and gave it a complete test and mechanical re-build.

This included bench testing all of the components, re-insulating the main windings with Glyptal (a product that was originally developed for this purpose), replacing the bearings for new Italian made SKF parts, and replacing the brush box.

In addition every part was detailed with all fasteners receiving the correct plating. The result is an as new alternator that should deliver all the voltage we need to keep our Dino running its best.

The value of planning: A simple trick when prepping the intake manifold

As we prepare to re-build the carburettors we first turned our attention to the intake manifold. It is a wonderful cast aluminum piece that was looking a little tired and dirty. To really get it nice we immersed it in carburettor cleaner and then scrubbed it clean with a soft plastic bristle brush. The result is a factory fresh looking part.

As always we got it ready to accept the carbs by pre-assembling it with all of the nuts, washers, and gaskets it would need. It is a good tip to do this at this stage because your brain has the whole assembly all fresh in its head and it is double the work to have to come back to at build time to figure out what fasteners go where. This way it is ready to assemble with the minimum of ramp up time.

Lastly we fitted the 4 long bolts that fix the manifold to the engine block as these cannot be installed once the carbs are on. It would be a real shame to have to take everything apart because we overlooked this little detail.

Going in reverse is the slow way to move forwards: Cleaning and sealing the gearbox castings

In previous posts we showed our efforts to restore damage on the gearbox castings and explained how Ferrari painted some of their castings in part to seal their porous nature from oil leakage.

For those who missed it here are some of the old links:

Discovering the finishes Ferrari used

Restoring damage on the castings

Ferrari originally cast the gearbox housings, primed and painted them, and then machined the final surfaces.With only a finished casting to work with we learned how slow it can be to do things in reverse as with each step the machined surfaces needed to be protected as we aimed to clean and prep them for sealant.

Once the first major wash was done the first step was to mask off every surface we did not want media blasted. Sounds easier than it looks as the main gearbox housing took a full 8 hours to prep and mask for blasting. Then it was into the blast cabinet where medium grit media was used in varying pressures to clean away all old primers and finishes keying the surface just enough for final paint without being so aggressive as to damage the original look of the aluminum. It was as much art as skill and it took many hours to get this right.

After blasting all the tape was removed and the parts were washed over and over again until they were surgically clean. Then came heating to outgass the aluminum and later a cleaning with Xylene to really get the last bit of contaminants off. It is critical to have a perfectly prepped surface as a failure of the sealer could be disastrous in the gearbox and engine.

With everything clean we needed to mask the edges again and then apply the sealer. For this task we chose a product called 'Glyptal'. Used in all industries from NASA to the US Military Glyptal is a very durable chemical resistant coating that applies on bare aluminum and has exceptional wear properties. It is the coating of choice in high end vintage engine re-builds and has proven itself as a reliable finish for this application.

Glyptal can be applied by spray, dip, or (as we chose) brush as it offered us the most control over the application and film thickness. Once applied the parts were baked to fully cure the finish.

Next comes exterior painting but that will be another day. Now for some photos. As you will see the casing was pretty dirty to start with.