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Dismantling

 

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Some enthusiasts like to do as much work on their cars as possible themselves. However, vintage engine work is not something to be rushed - you may end up creating more work if you do not follow a few essential guidelines. 

Dismantling is a very important stage, because it is when initial inspection takes place, obvious faults are identified, and on rare engines, when records are made of how components fit in relation to each other -  (although nothing can be taken for granted as correct).

Rule number 1 "Do not throw anything away until you have its replacement and you are sure it fits"

   

Dismantling / cleaning & initial inspection

NB: The following is very general and will vary considerably from one engine to another

Before dismantling it is advisable to thoroughly clean the external surfaces. Steam cleaning is ideal, but this may force water into the engine, so dismantle as soon as possible after to avoid rusting.

 

An Aston Martin DB2/4 (left) and Meadows 4.5lLready for external clean

Photograph the engine before and during the strip down to record how parts fit together ( this is especially important on rare engines, as it may not be possible to look at another engine for reference or find documented guidance).  Visually check everything as you remove it, looking for obvious signs of wear, damage and bodged jobs from previous repairs. Assume that all bushes, bearings, seals etc. are worn out until you have checked them thoroughly.  

  

Example of an "obvious fault" on a 1923 Cadillac V63 - Left - Broken con rod Right - its damaged partner

When you have a reasonably clean exterior, remove all ancillary parts, ie: Dynamo , Magneto or Distributor, Water pump, Manifolds and Carburetors, externally fitted oil pumps etc., and place in safe containers, together with their nuts & bolts etc, all labeled and photographed as necessary. This should leave you with the engine block, head, with flywheel and front pulley still attached. With the spark plugs still in place loosen the starter dog / front pulley nut. Next undo the flywheel bolts and tap the flywheel free from using a soft hammer. Keep turning the flywheel to avoid jamming it, then if detachable remove the flywheel housing. Remove the previously loosened starter dog / front pulley nut, followed by the pulley, and engine damper etc., if fitted, (a puller may be necessary for this).

Ancillary components removed ready for further attention

Take off the timing cover, but before removing the timing chains / gears check to see what valve timing you have - it may not be correct or the best that can be achieved, but may give some valuable clues later.  

Valve timing diagram for 1932 Rover 10/25 h.p. - if you have this information for your engine (and your engine has not been modified for competition etc) then checking valve timing may not be essential at this stage.

To check the Valve Timing:

Turn the engine to no.1 TDC compression (inlet & exhaust valves shut). This is most accurately found by using a dial test indicator through no.1 plug hole onto the piston (On side valve engines the head can be removed first). Remember there will be a small distance around TDC through which the crankshaft will move without a corresponding piston movement. This is when the con rod stops and moves across ready for the downward stroke. The centre of this movement is true TDC. If it is not possible to reach the piston through the plug hole, temporarily remove the cylinder head to give direct access to the piston. On an engine with a one piece head / block you may have to gain access from underneath, ie: by removing the sump

Degree disc attached to flywheel - and pointer

Attach (either by bolting or sticking) a degree disc to the front or rear of the crankshaft as convenient. Sharpen one end of a piece of 1/8th welding wire or wire coat hanger, or similar, find a convenient bolt hole or stud, and twist the other end of the wire into a loop through which the bolt will pass. Secure the wire to the engine and bend the sharp end so that it lines up with the 0 or 360 on the degree disc. Check / set no.1 valve clearances, and set the DTI on top of no.1 exhaust valve spring seat.  

Use DTI to determine valve opening / closing

Turn the crankshaft in the direction of normal running (usually clockwise from the front)  until the DTI needle just moves, indicating exhaust valve opening. Record the reading on the degree disc. (NB: if you accidentally move too far past the point where the needle just moves, keep turning in the same direction until the valve closes, then re-opens. (If the engine is turned against rotation, slack in the timing chains will give a false reading). Continue turning the crank until the exhaust valve closes, ie: when the DTI needle just stops moving, and record the new reading on the degree disc. Repeat the procedure for the inlet valve.

Continue dismantling: Mark the timing gears in relation to each other and undo the timing chain/s spring clips (roller type) or remove a pin (silent type). Remove the chains (these will probably be replaced, but keep them as patterns). If roller timing chains have no spring clips a link extractor will be needed. If clips cannot be seen to the front, check the back run of the chain before using the link extractor, in case they are fitted this way around. Using pullers or pry bars at the centre of the timing gears, remove them taking care not to damage the teeth, in case they are serviceable.

      

 

Silent chain (Morse type) - remove washer to "break" chain (note direction of rotation)

    

Link extractor on roller chain       Puller may be needed to remove sprockets

Some engines (like this Bentley) use all gears for timing etc

 

Now turn your attention to the cylinder head (if separate). Unbolt the rocker shaft evenly - if overhead cam, mark any bearing caps and remove. Remove the cam/s and replace any caps etc. to keep safe. 

Singer Le Mans - cam and rocker arrangement

If overhead valve lift out and number the push rods. Slacken and remove all the cylinder head nuts / bolts. Use pry bars under the external edges between the head and block. If the head will not move, undo all the head studs and try again (these will need removing anyway, once the head is off). If the head will still not free, you may have to resort to carefully driving wedges into the head gasket. With the head off, turn your attention to the bottom end. 

          

2 views of Morris Isis internals - showing oil pipe positioning

Remove the sump, oil pump, pipes etc., and ensure that once removed you will be able to rematch the big end and main bearing caps. Number stamps, or centre punch dots are commonly used for this. Also check to see if piston tops are marked to indicate the front of the engine, If not, mark with paint. Once you are happy that you will be able to remarry all parts, remove a big end cap, and if the big end will come up through the bore, push it and the piston out, and refit its cap. If the big end is too big, it has to be withdrawn through the crankcases, so for the moment just push the piston up to through the bore and remove the piston rings for withdrawal later . Repeat the procedure for the other rod / piston assemblies. 

Split mains:      Left - Hudson and Right Hillman 14 (note the shim plates - keep all shims in original position)

    

Riley's: 2 bearing Riley 9             Centre cheese from a 12/4 (before machining) 

With the rods free of the crank, and if you have split main bearings, undo the caps, and remove the crankshaft. If the engine is fitted with cylindrical type main bearings, then the front or rear (or both) will be fitted in a housing that is removable, giving just enough space for the crankshaft to fit through. If the engine has a centre main/s, it will probably be held in a circular housing, also just large enough for the crank shaft to pass through. Undo the centre mains housing retaining bolts, and those retaining the removable front or rear housing, and carefully remove the crankshaft. The centre bearing may need to be separated once clear of its location in the crank cases, before the crank can be completely removed. If the cylinder block and crank cases are two items, separate them and remove the camshaft, and tappets. Clean and wipe dry all components ready for detailed inspection. 

 

Further Details of engine work can be found on the following pages

White Metaling

Engine Specifications

 

 

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Email: Enquiries@formhalls.com 
Formhalls Vintage & Racing Ltd. Greycott, Lower Densome Wood, Woodgreen, 
New Forest, Hampshire, SP6 2BE England

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