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MG MGB Technical - Block Preparation

Has anyone got a good sugestion for cleaning the inside of a block before boring. So that is all the oil in the crankcase and all the rust and crud in the water ways. I used to be able to get them hot caustic treated but nobody will do that any more.
I wonder why!!

Colin
Colin Parkinson

Colin,
Try a place doing industrial ultrasonic cleaning.

This immerses the block in water and hits it with high frequency vibrations to loosen all the rubbish.

After that a steam cleaner blasts away whatever remains.

Pete.
Peter Thomas

Colin

Pete is correct. Most shops have a machine that looks like a giant dishwasher. They do a great job. We have ones at our army base that handle tank engines and they come out as nice as the old dip tanks did.

Check with one of your engine machine shops.
Bruce-C

Of more concern is getting all the swarf and crud out of the oilways *after* having any machining!
Paul Hunt

Colin,

Jon at Entune 2000 had mine hot tanked when he did my rebore last year.

They are near Bolton. 01204573548.

David

D Balkwill

I would do it after boring as Paul says. But the m/c shop will probably want it reasonably clean and they may do something like steam it or HP water wash first. Caustic wash will dissolve cam bearings and engine number plate.
I cleaned the swarf out of mine using a large plastic tray to contain the block, and using a 1 litre squeeze bottle hand sprayed Varsol over he internals and through the oilways. Then collect the solvent, filterd it, cleaned the tray and repeated until no more bits came out. It took me 6 repeats. You have to turn the block upside down and right way up to get at all the crannies. When dry, spray it all with WD40 to stop rusting.
Art Pearse

I love WD40

James

Colin-
Since you're doing a rebuild, here's some suggestions:

Have all of your components, including the oil sump, rocker arm cover, crankshaft, engine block, heads, connecting rods, and rocker arms hot tanked in caustic cleaning solution in order to remove the years of accumulated crud that is to be found in all old engines. Prior to this being done, insist that all of the gallery/core/frieze plugs be removed from the engine block so that the chemical solution can get into all of the spaces inside of the engine block. However, be aware that all too often hot tanking alone is insufficient; it is very common to have serious blockages that do not dissolve out. Consequently, it is necessary to remove all of the plugs of the all of the oiling passages inside of the engine block and then clean them out with brushes. Unthreaded plugs can be removed by drilling them and threading them with ¼-20 UNF tap, and then using a socket head cap screw and a socket in order to remove them. Use rifle bore brushes to clean all of the passages. Once you think that you have them clean, do not be surprised if you see more crud remaining in the nooks and crannies. Dig it out, then clean the engine block again. If you don’t, it will come loose and destroy your engine.

Be sure to remove the aluminum Engine Number Tag from the engine block prior to hot tanking, as the caustic chemicals will dissolve it. The engine number plate on MGB engine blocks is held in place by two rivets that are driven into holes in the side of the engine block. Be aware that these rivets have steep wedging threads on their shanks. Simply file a notch on either side of each rivet so that it can be securely gripped, clamp a set of vice-grip pliers onto the rivet, then twist the rivet counterclockwise (anticlockwise). You will find that using this method allows the rivets to come out quite easily. Always discard them and replace them with new ones. If the engine identification plate is missing, there is a way to date the age of the engine block. On the right hand side of the engine block, in the area between distributor and oil filter, there are three numbers that form a circle and that are slightly raised, e.g., 30 12 71, which tells the day, the month, and the year during which it was cast (in this case 30th day of December, 1971). The top one is the day, the left one is the month and the right one is the year. In the early 1970s the month code changed to a letter, thus 12 G 3 would be 12th day of July 1973.

After hot tanking, all of the internal passages should be chased out thoroughly with brushes and flushed. Be sure to tell your machinist that the area around the rear cylinder inside of the coolant jacket of the engine block is commonly a trap for sediment and to be sure that all of it is removed.

On bare metal, rust forms quickly. It is important to clean off any surface rust and be sure the surface is chemically clean. Some facilities have a second hot tank with an acid-based solution for removing rust. However, should this not be available, you can remove the rust yourself. Under no circumstances should hydrochloric (muriatic) acid be used to remove rust from any of the engine components. It will chemically interact with the rust and impregnate the remaining iron surface with hydrogen, resulting in hydrogen embrittlement of the metal that will lead to cracking. Hydrochloric acid reacts with the iron oxide (rust) to form soluble ferric chloride, thus leaving a clean exposed metal surface. However, it then also reacts vigorously with the iron to form ferric chloride and hydrogen. If you leave an iron engine block in a bath of hydrochloric acid long enough, you will just have a bath of ferric chloride (and enough hydrogen for a Zeppelin!). Instead, use Naval Jelly, which contains phosphoric acid. Being a thick gel, it will cling to the surface being treated instead of running everywhere as would happen with an acid that is in liquid form. Phosphoric acid reacts with the iron to form ferric phosphate, which adheres to the surface. This protects the surface and also slows down the reaction, so it is more or less self-limiting. Phosphoric acid reacts very slowly with iron, thus hydrogen emission is much lower and hydrogen embrittlement of the metal is insufficient to present a significant structural problem that can result in the formation of cracks.

After removing the rust, rinse the naval jelly off thoroughly, then blow the metal dry with compressed air or your wife’s hairdryer (she will not mind you borrowing it for such a noble purpose, of course). Do not be surprised when afterwards you notice a dark-purple-hued, thin passivated layer of ferric chloride where the phosphoric acid has removed the rust. This is a natural result of chemical interaction. Apply a coat of WD-40 to the coolant passages inside of the cylinder head, the coolant jacket, and to all of the oil passages. Once this has been done, take care to prevent machining chips and machining dust from getting into the ports and the passages by blocking them off either with rubber plugs (available at most better hardware stores) or with short lengths of tapered wooden dowel rods. In order to etch the surface for superior paint adhesion, always use a good quality metal conditioner. I use POR-15 Metal Ready, as it removes light surface rust, and etches the surface of the iron in order to create an anchor pattern so that paint can adhere to it, as well as leaves a zinc phosphate coating on the iron metal surface that will inhibit the formation of rust. Being rinsed off with water or wiped with a wet rag, it leaves no residue that needs to be removed prior to paint application, and can be used on aluminum as well. Best of all, being non-toxic, non-corrosive, non-caustic, non-flammable, and bio-degradable, it is very safe to use.

All threads in the engine block should be chamfered so that the uppermost section of the threads will not pull out above their deck surfaces. In each case, the chamfered recess need not be of greater diameter than that of the threads. Dirty or deformed threads in the engine block can reduce clamping force on a gasket in the same manner as dirty or damaged threads on the machine bolts do, so they should be chased with a rethreading tap after chamfering. A rethreading tap and die are designed to clean and straighten thread. Using a regular cutting tap or die can cause a weakness in the threads by causing stress fractures at the point of cutting. This cutting action will damage rolled threads and reduce the maximum amount of torque that the machine bolts can sustain. In addition, all of the untapped machined passageways should be reamed smooth to the diameter recommended by the manufacturer of the plugs that are to be installed in them. The ports of the coolant passages should be lightly chamfered in order to prevent them from shearing the cylinder head gasket, thus preventing gasket material from breaking off and making cylinder head gasket removal into a future headache. Finally, clean all of the passageways in order to remove any debris. Note that no plugs of any kind should be installed until after all machinework on the engine block has been performed and the engine block thoroughly cleaned out to ensure removal of all grit and metal swarf as these passages and chambers can become a repository of such materials. Insist that new oversize bronze plugs be shrink-fitted and pressed in to a depth that is slightly beneath the surface of the engine block so that they will not interfere with proper gasket sealing of the oil sump and the front and back plates. If you wish, you can do this yourself. In order to shrink-fit them into the engine block, the plugs should be sprayed with WD-40 in order to displace any moisture on them, placed into a well-sealed Ziploc bag in order to prevent ice from forming on them, and with the thermostat on the deep freeze set as low as it will go, they should be left in there to chill overnight. That shrinks them to a smaller diameter. When they are ready to be installed, they should be taken out, then immediately seated into the engine block with a flat-nosed punch. When they warm to room temperature, they will be in there good and tight because they will have expanded in place! The only way to get them out will be to drill and tap threads into them and use a puller! Bronze, being an alloy of tin and lead, has a higher coefficient of expansion and contraction than iron. It thus expands more than iron when it gets hot, so there is no way that they will ever come out while driving down the road.

Stainless steel Frieze / core plugs should be used for the same reason. Their high chromium content also means lots of expansion when hot, so once they are properly seated, they will not pop out. Make sure that they have a good concentric seating surface by specifying that an end mill bit be used to clean up their seating surfaces in the engine block. It is not the cheap way to do it, but it always works. If this cannot be performed due to insufficient engine block material thickness, the existing seating surfaces should be power cleaned with a rotary wire brush. When you install the Frieze / core plugs, be advised that their surfaces should be dished inward with a plannishing hammer so that they will be deformed properly into the bore and provide an effective seal. Should the dish be too deep, the plug will shrink and it will come out easily. However, even with the most meticulous preparation, Frieze / core plugs have been know to pop out when the engine experiences detonation. In order to prevent this unhappy experience, thin aluminum flat bar strips can be fabricated to hold in place the three Frieze / core plugs on the side of the engine. Simply use a small cap screw on each end of the strap and a combination of washers to take up the gap behind the bar. If anybody notices this modification, point out to them that the MG Factory Racing Team did this on their works MGAs. The Frieze / core plug at the rear of the engine block can also be secured by using one of the thick machine washers that is used to clamp the intake and exhaust manifolds to the cylinder head and tapping in 3/8” UNF threads or its suitable 9mm metric equivalent. You will also need a matching machine bolt with threads all the way to the cylinder head about 1 inch long. Install the washer with its stepped side facing the rear engine plate, sliding it in until it locates over the hole in the engine backplate, and then insert the machine bolt. Tightening the machine bolt will force the washer against the engine backplate and thus secure the core plug in its recess. This simple design can be further improved by turning a flange into the washer so that it will positively locate in the hole in the engine backplate.

While the engine block is at the machine shop, you may wish to consider having it modified in order to allow the installation of a drain tap (BMC Part # 3H 576). This was a common feature of the earlier B Series engines that was continued into the production of the 18G Series engines that were destined for use in the MGB. Unfortunately, the coolants of that era did a rather poor job of protecting the coolant passages inside of the cast iron engine block from corrosion. As the engine expanded and contracted during heating and cooling, small particles of rust would flake off from the walls of the coolant passages and chest. The primary reason for the provision of a drain tap is that liquid coolant systems can be inadvertently designed in such a configuration that circulating sediment will accumulate in certain ‘dead’ areas of flow. This presents both a potential trouble point, as well as an opportunity to make use of such an area as a collection point so that the sediment so it can be removed. Note that coolant drained from this location will also reveal evidence of an impending disaster, i.e., metal flakes from an eroded impeller of the coolant pump. The sediment tends to settle into the area around the base of the #4 cylinder and the adjacent drain tap, clogging it. This drain tap is located at just such a catch-point in a pocket recessed into the floor of the coolant jacket where the sediment can settle. If that recessed pocket is kept clean, the circulating sediment will keep settling there, and can be gotten out by frequently draining off a bit of coolant. Once the recessed pocket fills, sediment will then settle in other low velocity areas, becoming very hard to remove. That is what coolant system flushing chemicals are supposed to do. Sometimes they work, but sometimes they do not. If the system is drained here periodically, the sediment will be removed and proper circulation can be maintained. If this task is not attended to, then the sediment can build up until it interferes with coolant circulation, in which case you will begin to get either local and / or general overheating problems. Its secondary purpose was to allow coolant to be drained from the cylinder head and the upper sections of the engine block without going to the trouble of draining the coolant system from beneath the car, thus permitting the easy removal of the cylinder head without having coolant run down the sides of the engine block. This permitted a new cylinder head gasket to be installed alongside the road without losing too much coolant. As such, it is a quaint holdover from a bygone age of motoring, much like the micro-adjuster on the Lucas 24D4 distributor. Ultimately, it continued to be fitted until the introduction of the Mark II models in November of 1967. It was fitted to the 5-main-bearing engines "as required" from that point onwards. Just by what criteria the factory determined when it was “required” is as yet obscure. However, modern formula coolants have largely eliminated this silting problem, making the drain tap a viable option. Just be sure to get all of the rust out of the inside of the engine and you should be fine from there on.

Be sure that all bearing support surfaces are line-reamed and then line-honed afterwards, plus all of their oiling holes carefully deburred. If possible, it would be wise to have the rocker arms, heads, engine block, crankshaft, and connecting rods either magnafluxed or, better yet, x-rayed in order to be certain that there are no cracks. All of the rocker arm faces should be resurfaced on a contour grinder and rehardened to 54-56 ROC if they are not to be replaced by new ones. Because the depth of hardening on the external layer of the original working surfaces of the rocker arms is only a few thousandths of an inch thick, this rehardening after resurfacing is an absolute necessity in order to attain a durable working surface.

After the machinework on the engine block has been completed and the interior and the oil passages have been cleaned out thoroughly, be sure to paint the inside of the crankcase area of the engine block as well as the interior of the oil sump with Glyptal, a coating that is highly resistant to oil. This is recommended to seal the pores of the iron, thus preventing any deposits or metallic machining dust remaining in the pores of the iron after cleaning from leaching into the oil. This is what the factory did. It will also promote drainage of the oil down the inside of the engine block and out of the oil sump as a deterrent to the buildup of carbon and sludge. Likewise, the interior of the rocker arm cover and the tappet chest covers should also be coated with Glyptal for the same reason. However, their flanges should be left unpainted so that they will form a more effective seal with their gaskets.

Prior to painting the exterior of the engine components, be sure to mask off the outer walls of the cylinders, all bearing mounting surfaces, the crankshaft main bearing cap seating surfaces, and the gasket areas, and then apply a coat of thermoconductive enamel engine paint onto the exterior surfaces of the engine block before it has a chance to rust again. There is something that you can do in advance that will turn your engine rebuild into an easier experience that will also produce a more satisfying finished product. Purchase all of your seals and gaskets well in advance before you start the reassembly rather than waiting until just before you start (as most people do). Using the gaskets and seals as templates, draw around them on wax paper in order to make cheap cut-out silhouette copies of all of them. Why go to the effort of making cheap silhouette copies? Because the copies can be used to precisely mask off all of the sealing surfaces prior to painting the engine block. Tape or glue stiff tabs onto the edges of each of them so that they can be easily peeled off of the surface immediately after the painting of the engine block. While it is true that many people simply spray paint the entire surface of the engine block, including the gasket sealing areas, in reality this is a bad practice. Such engines tend to ooze oil around their gaskets because the gaskets cannot achieve an effective seal against a smooth, glossy surface. Gaskets do a much better job of sealing when applied to bare metal surfaces that are machine-finished to the proper surface texture that is achieved during manufacture at the factory. Instead, all gasket areas of the engine should be masked off prior to painting so that the gaskets will have a metallic surface to seal upon. Failure to take this extra step will likely result in oil oozing out from under the gaskets. Simply smear a coat of petroleum jelly to one side of the copy and place it over its sealing area on the engine block, and then apply the paint. After applying the paint, remove the gasket and allow the paint to dry thoroughly, and then remove the remaining film of petroleum jelly with alcohol. Getting this detail of the rebuild prepared in advance will make for a more oil-tight engine. Unfortunately, few commercial shops will take the time to make this extra effort, despite the fact that they know full well that factories do not paint an engine until after it is assembled. Most owners who are faced with doing the reassembly themselves usually omit this step of advance preparation in ignorance of proper procedure, and simply paint the entire engine block and cylinder head prior to any assembly work being done, only to end up with the disappointment of living with an engine that oozes and leaks. Do not allow paint to get into any of the threaded holes.

The outer walls of the cylinders should then be prevented from rusting by smearing their surfaces with WD40, and then covering them with WD40-soaked paper until the time arrives for reassembly of the engine. Because the electric starter motor needs a solid electrical ground (earth) in order to work properly, do not paint either the gasket area of the rear of the engine backplate where the starter motor mounts or to the area of the front face of the engine backplate where it mates up with the gasket on the backside of the engine block.

Remember that machine resurfacing of a gasket area does not necessarily guarantee either flatness or the proper surface finish. That is why the flatness and surface finish should always be checked before installing a new gasket. When using a resin-impregnated cylinder head gasket the surface finish for both the mating surface of the cast iron cylinder head and that of the deck of the cast iron engine block should be 80 to 100 RA microinches. When using a steel-reinforced cylinder head gasket that combines either a fiber composite or expanded graphite layers, the surface finish should be 60 to 100 RA microinches. If a rubber-faced multilayered steel cylinder head gasket is used, then the surface finish should be 30 RA microinches maximum, but there is no minimum. The smoother it is, the better its seal will be. When the mating surfaces of a cylinder head (aluminum alloy as well as cast iron), intake manifold, or exhaust manifold are resurfaced for use with a resin cylinder head gasket, the surface finish should be 50 to 60 RA microinches. When using a copper cylinder head gasket the surface finish should be 60 RA microinches for a cast iron cylinder head and 40-50 RA microinches for an aluminum cylinder head. In all cases the surface finish should be fairly uniform across the entire face of the cylinder head and deck of the engine block, not varying more than 20% from one area to another. In addition, there should be no more than +/- .001” (.0254mm) of out-of-flat across for 3” (76.2mm) in any direction. Pay particular attention to the areas between the cylinders on the engine block, between the combustion chambers on the cylinder head, and where the cylinder head gasket seats around the cylinders on both of these surfaces, as these are the most highly stressed sealing areas. Any surface flaws that are found should be eliminated by resurfacing.

As a general rule, the smoother the surface finish is, the better it is. When the surface finish is rougher than about 100 RA microinches, there are too many peaks and valleys on the metal’s surface to permit a proper seal to be achieved. The cylinder head gasket may not cold seal and could leak coolant, oil, and / or combustion gases. Using a thicker cylinder head gasket that has increased conformability and / or a thicker soft facing can compensate somewhat for a rougher surface, but such cylinder head gaskets do not retain torque well and are less durable. Too rough a surface finish has more ‘bite’, digging into the cylinder head gasket more aggressively, increasing the scuffing and shearing that the cylinder head gasket undergoes as the engine expands and contracts. In bimetal engines that pair cast iron engine blocks and aluminum alloy cylinder heads, this can be especially hard on the cylinder head gasket because of the difference between aluminum alloy and iron in the coefficients of expansion and contraction. Too smooth a finish may not provide enough bite to seal the cylinder head gasket securely. There can also be movement between the gasket and metal, causing the cylinder head gasket to abrade and leak.

Steve S.

Steve
Nice one- Willy
WilliamRevit

Steve, thanks for (all) that!!

When is the next book due out?

Colin
Colin Parkinson

This thread was discussed between 29/04/2009 and 04/05/2009

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