TECHNICAL TIPS - ENGINE

OIL PRESSURE: If you’ve lost oil pressure after a service and have tried all the obvious culprits – pump, drive gear, woodruff key, pressure relief valve and pressure gauge, here’s one you may not think of.  There are 2 types of rear camshaft bushes!  If you fit the wrong one for your crankcase, you can finish up with no oil pressure.  So check the rear bush to ensure it is a good running fit on the camshaft and a close fit within the crankcase avoiding oil by-passing the bush altogether.  For 3-bearing engines, check the oil feed pipe to the centre main is seated well and not fractured.
OIL PRESSURE: The "spit and hope" type lubrication of the Seven makes it most important to keep a watchful eye on your oil pressure gauge. You will soon see that when the engine is cold it swings off the scale but, as the oil gets hot and thins, the pressure drops back to less than 5 lbs under normal driving conditions. This is quite normal. However, when hot, should it uncharacteristically rise dramatically, immediate measures need to be taken. One of the most important items to carry at all times is a length of 1/16th rod or stiff wire about 6-8 inches long. A sudden rise in oil pressure usually means that there is a blockage in one of the oil jets supplying the big ends and, if left unattended, this would cause starvation and big-end failure. These jets are covered by 2 small brass bolts on the offside of the engine crankcase either side of the oil filler tube. To clear a blockage, turn the crankshaft 1/4 turn on the starting handle, undo the bolts and carefully poke the wire down through each of the jets—it should go down about 3 inches plus, (it may take a few attempts to get the feel of it and locate the holes, why not have a dry run at home as practice?) This will ensure each jet is free of obstruction. Replace the bolts and start her up and check the gauge. Hopefully this will avoid an expensive engine rebuild!! Gary Munn
RE-FITTING PISTONS: When re-fitting pistons—confused about the thrust side?  Always re-fit pistons with the split skirt nearest the camshaft—sorted!
GUDGEON PIN:Probably the worst disaster that can happen on your engine is to have a gudgeon pin clamp bolt work loose and come out. On its way out it will probably bend the con rod, score the bore and break the piston.  It will drop on the gauze filter, be picked up by the crankshaft and smash a star-like crack in the side of the crankcase. The answer to this is not to use locking tabs but to ensure that you have new high tensile bolts fitted with spring washers and do them up really tight using ‘Loctite’ etc. on perfectly clean threads.
OIL JETS:Jack French recommends turning the little oil jets that squirt oil down onto the troughs in the crankshaft 20 deg towards the crank centre-line (Mike Forrest says 30 deg, so take your choice!) to increase the period during which the oil is squirting into the troughs.  I use a piece of hollow rod which fits over the jet and bend it slowly.  First clean up the ends of the jets where previous owners will have walloped them trying to remove the crank and after a gentle bending, test them by inserting a suitable piece of thin straight wire to check alignment.
CLEANING: For cleaning the waterways you can use a mild acid as found in brick cleaner or patio cleaners found at builders merchants.
REMOVING CYLINDER HEAD: When removing A7 low compression, 18mm, cylinder heads, to save hammering a screwdriver or chisel between the joint, try using the hook end of a Ruby boot key into the plug holes of numbers 1 and 4 alternately.  Even better, get 2 boot keys and make it even easier.  This dodge does not work for 14mm heads.
SUMP NUTS: In replacing the sump, I’d fitted new set screws – those nice long-headed ones with the oval washers. What I had forgotten, was that for the centre rear one, you have to use a short one – otherwise, yes you’ve got it, the tip just catches on the starter ring……
TIMING GEARS: Before undoing the timing gears, remove the fuel pump entirely from the crankcase and don’t replace it until after the new gears have been firmly installed. If you don’t do this, the camshaft may move backwards once the timing gears have been removed allowing the petrol pump cam-follower (lever-thing) to slip to one side of the pump-drive cam and jam things up! Even after re-fitting the pump it will be judicious to check things are where they ought to be by gently turning the crank by hand. If the cam follower has been displaced, a firm ‘clunk’ can be felt as the crank hits the obstruction.
ALUMINIUM PULLEY: To release the large aluminium pulley at the end of the camshaft, hit it sharply sideways against the edge of one of the holes so as to try to rotate the pulley on its shaft rather than trying to hit it from behind along the length of its shaft.
CAMSHAFT BUSHES: Should you be building a 2-bearing engine from spare parts, make sure you have the correct camshaft bushes fitted at the front and back of the crankcase as there are two different sizes: the earlier crankcases (with the starter inside the car) have a smaller outside diameter for both front and rear bushes than later engines (with the starter under the bonnet) and the front bush is also slightly shorter. It is important not to confuse these with the ones fitted to the later crankcases as they look the same to the naked eye. Should the earlier ones be fitted in a later crankcase by mistake, there would be no oil pressure as the oil would simply flow down the sides of the bush. The inside diameters are the same on both crankcases. If in doubt, the bushes should be a snug fit in the crankcase in both instances usually requiring a light tap. Also check that you have the bushes the right way round as the oil holes must align with the holes in the crankcase. Another useful tip is to replace the square peg bolt that secures the front bush with a 3/16 inch Whitworth bolt of exactly the same length, and then tap a 3/16 inch Whitworth thread into the larger peg hole in the bush. This allows the bush to be bolted up tight after assembly. Bolt the rear bush into the crankcase first, making sure that you line up the oil holes, fit the front bush on to the camshaft then “glue” the 9 centre rollers into their slot in the shaft with grease and lower the assembly through the front of the crankcase taking care not to dislodge the rollers, carefully lining up the front bush as you lower it in so that the bolt holes line up. If you are lucky, the rollers will slide into their cage first time but it could take several attempts! Screw the new bolt and a fibre washer into the front bush - job done, simple. If you are building the later 2 bearing engine, you will need the camshaft with the extra cam to drive the mechanical petrol pump. The 3-bearing engine is different again, but that’s another story. Glyn Llewellyn
OIL FILLER TUBE: So how does one remove that thin-walled oil filler tube without collapsing it and rendering it useless? I managed to find a piece of heavy gauge pipe which just fitted inside and after making sure nothing nasty could drop into the engine and with pipe in place I was able to unscrew the tube with an oil filter remover without crushing the tube. Richard Bishop
CORE PLUGS: If you are having problems getting your core plugs to seal the following clever solution was offered to me the other day. Soak some strands of string in Hylotyte Red (replacement for Red Hermetite which is no longer available) and roll into a sausage shape. Clean the recess in the head thoroughly and allow it to dry. Line the inside edge of the recess with the wetted string where the new core plug will bear and fit the core plug in the normal manner. Tap it down with a suitable drift (suitable being about the same size as the plug) until the domed surface is flat. Leave for 24 hours before refilling or topping up engine with water. It should now be watertight. Hylotyte Red remains flexible and is easier to remove than Red Hermetite. With many thanks to ‘Bumbling’ of the A7OC”.
THE CASTLEMAN CLIP:  When I saw a trickle of oil from one of the oil jet plugs I just thought that the plug had loosened as part of the settling-down process. But . . . you can imagine my horror when I found that the thread in the crankcase was very worn and quickly became non-existent after my attempts to tighten the plug. The prospect of dismantling the engine passed in front of my horrified eyes as this thread is (virtually) impossible to get at with the cylinder block in place, and any swarf that dropped into the oil gallery would have to be removed.  So, after much head scratching, wailing and gnashing of teeth I hit upon the idea of making a small clip that fits under the adjacent cylinder block holding down nut and presses down on the top of the plug to stop it from being pushed out by oil pressure. It might leak, but the plug would still be in place.  This was not difficult to make from a piece of flat steel, and I incorporated a refinement into the basic idea by putting a small set screw and nut in the outer end and allows adjustment of the force the clip applies to the plug. In honour of the occasion, I call it The Castleman Clip.  I inserted plug into the crankcase using Loctite 2700 high strength thread locker, fitted the Castleman Clip under the block bolt and tightened it down. Then I left it overnight and, next day, started the engine with some trepidation. I need not have worried! No leaks, engine running normally and oil pressure its normal lofty self.  Roger Bateman
CRANKCASE/BLOCK REAR NUTS:  I always seemed to have difficulty getting the back nut to the Crankcase/Block really tight, there seems to be so little room to get a spanner on and or to move round. So my solution was to use one of the 'long' nuts from the tappet area (OK - I actually bought some more) to take the top of the nut into an area where there was more room around the nut to get a 1/4" W - 5/16" BS ring spanner on.  However, even then I had to thin down the outside of the ring to ensure it went on OK. The photos show the difference in height.  With thanks to Sandy Croall (Cornwall A7C)
OIL PUMP: When you assemble your oil pump don't forget: radiused shoulders to the top, no gasket under the cover plate.

CYLINDER HEAD NUTS: Use three or four steel washers under each nut on the A7 cylinder head. With the washers in place, if a thread does strip all you have to do is to remove the washers and use a new nut on the undamaged part of the thread which had been covered by the washers. Presumably the reverse is possible using washers to cover stripped thread so that a nut can be placed higher up the stud on good thread.  Bart Walsh Essex A7C

CHECKING COMPRESSIONS:  Here is a simple test if you suspect your engine is low on compression which will determine if it's your rings or valves, without having to take the head off.  First remove the spark plugs and check the compression with a compression gauge and take a reading, then put about a teaspoon full of oil down the bore you wish to test, then put your compression gauge over the spark plug hole crank the engine and take another reading. If the compression increases, your rings are worn, if it doesn't it's your valves. What the oil does is to form a seal around the top of the piston so that compression is not lost down the sides. Do the same test on the other three cylinders.

CRANKSHAFT BEARINGS: The dual-purpose races at the front end of the crankshaft should be assem­bled with the faces marked " thrust " towards each other. When the centre members of the races are tightened on the crankshaft, the effect should be to hold the outer members together.  A method of testing is to grip the centre members in a vice, when the outer members or tracks should be free; when wear has occurred, it may be possible to pass a feeler gauge of .002 in. thickness each side between the outer members. Should a feeler gauge .003 in. be accepted each side the races should be renewed.  The sketch shows correct fitting.

MODERN LIP SEALS: fitting one of the modern lip seals with matching cover plate, available from our usual suppliers, it will be noticed that comparing the new cover with the old, there is no cut-away for the oil return to the crankcase which, if you look with the cover off, is rear of the rear main bearing outer at about 5 o’clock. Carefully mark the new cover plate and file or grind the ridge on the plate to align with the oil hole in the case - this will encourage return of the oil to the sump when fitted. We always retain the oil dish thrower (outer dish towards you). Do not over-paste the cover with sealant or the goo can creep and block the oil return hole which, of course, you have previously ensured is clear. Try the seal on the flywheel boss before fitting to ensure you have the correct one and the boss is smooth. Apply a tad of grease where the lip will seal. Gary Munn “Munwellyns”