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Researched and contributed by Eric North from the original “Modern Motor - February, 1958
This article deals primarily with the 1934-36 Buick Series 40, but much of the data applies also to later models.
The 8-cylinder engine has a 3 3-32 in: bore and 3 7-8in. stroke, giving a piston displacement of 233 cub.in and' a horsepower rating of 30.63.
To remove the engine on models up to 1938, take off the bonnet, radiator, and all necessary sheet metal, including bonnet side panels, engine side pans, etc.. Disconnect the distributor, headlamps, horns, generator and ignition coil, heat indicator and battery cables; unscrew the fuel lines from the pump and carburettor, and disconnect the exhaust pipe from the manifold, then remove the rocker shaft arms, support bolts and oil fittings.
Unfasten the engine mountings and disconnect the torque tube and universal joint from the gearbox. When disconnecting the rear mountings keep the shims separate and "tag" them to ensure that they will be returned to their original positions.
Before lifting out the engine assembly, have a good look round the units to see that there is nothing which would foul or prevent the engine from being swung out of its position in the frame.
The same procedure can be followed for the 1939-40 models, except that the radiator and front guards are removed as a unit, and that you MUST NOT loosen the mountings from the frame as full realignment with the rear axle will then be re-quired. When removing the gearbox support and steadying rod keep separate the shims, at each end of the support so that the original installation is maintained.
When replacing the engine, centre it in the frame at the flywheel housing, and install the original quantity of shims. These are inserted between engine mountings and flywheel housing, on 1940 models only. On 1936 models the engine should be centred in the chassis, using the centre hole in the front cross-member as the datum point, and held in this position until the rear engine mounting bolts are tightened.
On earlier cars, and also on 1937 models, before bolting the torque tube to the universal-joint flange, loosen the rear spring U-clips to prevent any undue strain on the torque tube when the gearbox support is fastened to the frame cross-member. On all models, bolt gearbox support to frame cross-member, adding shims as required to obtain the central position.
On 1938 cars assemble the gearbox steadying rod, but do not fasten it to the cross-member until after the rod is secured to the lower plate at the centre of the frame cross-member. To avoid any strain on the member, one of the nuts which fasten the member to the brace rod has a shake-proof washer and should be tightened first. On 1940 models, when connecting the engine to the rear mountings,
Install the bolts and place .a jack under the gearbox to raise the engine until both supports are-clear of the mountings. Then lower the engine slowly until one support just rests on its mounting, measure the clearance at the opposite support, and insert the required amount of shims.
Assemble the gearbox steadying red, leaving the nuts which attach the rod to the cross-member loose while fastening the rod to the lower plate at the centre of the frame cross-member.
Valves
Valves should be adjusted to give a .015in. operating clearance on 1936-1942 engines. Before setting them, loosen the radiator cap to prevent overheating and run the engine at a fast rate (at least 700 r.p.m.) for half an hour to stabilise the engine temperature throughout. On models prior to 1936 the clearances are .008in. (hot), both inlet and exhaust.
To remove the valves and springs on all models, take off the rocker cover and cylinder head, then compress the springs and take out the locking keys. Before removing any valve-guides, measure down from the head face to the top of the guides, and make sure that the replacement guides are fitted to the same positions.
Valve timing calls for slightly different procedures on various models. On 1934-35 cars, with the valves closed, set No. 2 exhaust valve to .008in. clearance, then set a dial indicator on the spring cap so that it registers 0 and crank the engine until the No. 1 and. No. 8 T.D.C. mark on the flywheel, is visible through the inspection hole. At this point the valve should be open .163in.
On 1936-42 models the same procedure applies, except that the clearance should be set at .015in. and-the indicator readings should be: 1936, .150in.; 1937-42, .145in.
Engine Timing
To remove the timing cover for checking the marks on chain and sprockets, disconnect the headlight wires and any sheet metal which might prevent the radiator being removed. Take off the vibration damper and then the timing cover can be unfastened.
Caution: when replacing the cover on 1934-35 engines, see that it lies flat against the crankcase within .010in.—otherwise misalignment of the generator and water-pump shafts, as well as the timing gears, may occur.
On the 1938 models the cover contains an oil seal which fits around the hub of the vibration damper. To prevent oil leaks on earlier Series 40 cars, this later-type cover and seal assembly may be used.
On 1942 models a spring loaded synthetic rubber seal is assembled into the crankshaft opening to prevent as oil leak around the vibration damper hub. To install the seal, press it into its recess with the lip of the seal to wards the rear of the cover. It essential to centre the seal properly before tightening up the cover plate
Normal slack of the timing chain is ?in. to ?in. finger movement of chain when pulled away from the centre-line of the sprockets. If the slack increases to 1in., the chain must be replaced. Remove camshaft sprocket and chain, and place new chain over both sprockets in such a manner that there are 10 links (11 teeth) between the marks of the sprockets when the camshaft sprocket is bolted in position.
Camshaft Removal
To remove the camshaft, the radiator must he taken off, followed the distributor, oil filter, rocker arm, spark plugs, and pushrod covers, Disconnect rocker shaft arms, support bolts and oil fittings, then lift off the rocker arm assembly and take out the pushrods and valve-lifters. Remove the vibration damper, timing cover, chain camshaft sprocket, and thrust plate, then pull the camshaft clear of the engine.
A puller will be needed to replace the shaft bearings if take these out; but don't touch them unless it's really necessary, as new bearings must be line-reamed or bored, and it is necssary to see that the oil holes register in bearings and block.
Pistons, Rings, Conrods
Piston assemblies must be lifted out from above. Regular production rods are as a rule .marked with their respective cylinder numbers, but replacement rods are left unmarked and it is necessary to stamp or punch the required number on theme as you pull them out, or when installing new ones
To reassemble a piston and rod on all models up to 1940, fit the slot in the piston on the opposite side of the oil-spray hole in conrod and see that the spray hole is on the camshaft side of the engine when coupling up to the crankshaft... On 1941-42models the spray hole should be towards the hollowed side of the piston head, which in turn should face the spark-plug hole.
'When checking or replacing a piston, the work should he carried out at room temperature (about 70 deg F.), as a variation of 10 deg, can alter piston diameter .by about half. a thou. Always remove any ridge at the, top of the bore before replacing piston rings, failure to do this may result in a broken ring and scored cylinder or damaged ring lands on the piston
Recommended maximum "out-of round” or taper is .0005in. Pistons are available in .005, .010, and .020in. oversizes and should be checked for fit with a feeler strip ?in wide, inserted at the side opposite the slot and at right angles to the piston pin.
The pistons should pass down the bore on a feeler gauge of .0015in thickness and lock on a .00225in. gauge (ie, 1? thou "go" and 2? thou "no go.") , unless pushed by hand When checked with the "go” gauge the piston should move of its own weight. Always .check the piston and rod on the alignment jig before fitting to the engine.
When using piston 5 to 10 thou, oversize, fir 10 thou oversize rings, for oversizes above this 20 thou oversize rings must be used. End gap of the ring should be at least .010 when tried in the lower section of the cylinder bore. If the cylinders are not being rebored, any ridge .t the top should be removed before taking out the pistons, otherwise there is a distinct possibility of breaking the second ring land.
If the tool used for removing the ridge has no provision for controlling the depth of cut, the piston can be brought up so that the tool can rest on top in such a way that the reamer will not cut into the ring travel area. One way to be sure is to leave a small trace of ridge and finally remove this with a hone.
Gudgeon pins are fitted with clearance of .0003 to .0004in. at about 70 deg. F. This is equivalent to an easy finger-push, To prevent the gudgeon pin becoming distorted and binding in the piston pin bosses, do not tighten the clamp bolt with undue force, if you have a torque wrench, set it to a tension of 25 – 30ft./lb. Bushings are used on 1934-35 models and any 1942 models with cast-iron pistons.
Con rod beatings are of the integrally spun type; shims are provided to take up wear between the white metal and the shaft, and it's important to take an equal number of shims from each side. If the rods are too tight, the metal can be scraped to give correct clearance.
Before fitting the rod to the crankshaft, be sure that the sides of the rod and cap line up, to prevent scoring the thrust faces of the crankshaft cheeks. See also that the oil-spray hole face camshaft side of engine.
Note that the 1942 models use a new-type rod with cast-iron. pistons. These can be fitted singly or in sets, but must not be used with rods designed for aluminium pistons.
Oil System
On models which use a stabiliser bar, notably 1936-38, this must be disconnected before the sump can be lowered. On 1941-42 models, the engine side -pans can be removed and. the pitman arm disconnected from the tie-rod. The engine should be turned over to bring numbers 1 and 2 pistons as near to the centre of their cylinders as possible, so that crankshaft throws will not interfere with the sump as it is lowered.
When reinstalling the sump, obtain a couple of suitable screws and remove the heads, then cut slots in them so that they can be used as guide-pins and subsequently unscrewed and replaced with the normal sump-holding screws. The guides will keep the gasket in place, and bring the sump into proper alignment with the crankcase screw-holes.
Before replacing the sump, thoroughly clean the oil float, screen and tube. If the screen has been crushed, it is advisable to replace rather than repair it.
Should the oil pressure drop, make sure it isn't merely due to a faulty gauge before you start dismantling. Normal oil pressure is 451b. p.s.i. and clearance between pump shaft and bearing and idler gear bearing should be 1 to 2? thou. and air filters, the crankcase outlet is provided with this Driving-gear backlash should be 3 to 5 thou, and an allowance of 3 to 6 thou is quoted for drive and idler gear backlash; and pressure relief valve clearance. End clearance of the drive and idler gear should be thou to a maximum of 4 thou. Clearance between the gears and cover may be checked by placing a straight-edge across the pump housing and using feelers. It is possible to grind the housing down with a surface plate and emery cloth, if care is taken.
The oil-pressure regulator is non-adjustable and located in the base of the pump. The engine ventilating system uses the crankshaft as a blower to eject fuel and water vapors from the crankcase through the ventilator outlet pipe. On the left side of the block, an oil-wetted copper gauze acts as a dust trap.
On some models the oil filler cap also contains copper gauze, while on models equipped with heavy-duty oil and air filters the crankcase outlet is provided with this copper element. To clean the elements, they should be removed and thoroughly washed in petrol, then dried out and dipped in fresh engine oil.
Other Engine Points
When fitting a new head gasket on 1941-42 engines, note that the imported-type gaskets are already lacquered and shouldn't be treated with any other substance.
Caution: before replacing the cylinder head, be sure that all carbon or other foreign matter is removed from the blind tapped cylinder-head bolt-holes, otherwise "the bolts won't tighten properly.
The radiator core on models up to 1936 comes off together with the shell and grille, while on later models it can be withdrawn as a separate unit, after removing the water pump.
To adjust the fan belt, set it so that is can be deflected about ?in. at the centre with a- light pressure of finger and thumb. Overtightening will accelerate bearing wear, while a loose belt won't drive the generator.
If you want to test the thermostat, place it in hot water with a thermometer; it should start to leave its seat at 148/155 deg. and be fully open at 175 deg.
To remove the flywheel, take off the sump and the rear main bearing cap to gain access to the flywheel retaining bolts. Of course, the gearbox and clutch must be taken off.
To re-ring the flywheel, drill a 5-16in. hole in the ring gear, then split the gear with a cold chisel—never attempt to knock it off. To refit a new gear, heat it to approximately 600 deg., but no more. An ordinary oven thermometer can be used to check the temperature; this isn't available, polish the gear in several spots with sandpaper; when these spots begin to turn blue, the gear is hot enough.
Working on Clutch
Before adjusting clutch pedal lash, see that the pedal clears the underside of the floorboard by 3-8 to 5-8in. A stop-screw at the lower end of the pedal controls this clearance. Free play of the clutch is adjusted by turning the screw or clevis which controls the length of the rod. On 1938-42 models, do not mistake the tension of the return spring as an indication of lack of free play.
To remove the clutch, remove the rear end, shaft and gearbox and drop the flywheel underpan, then disconnect the clutch linkage at the outer end of the release yoke. Remove the spring washer in the flywheel housing which retains the clutch release bearing support, and take the latter out. The release bearing and yoke is removed from the fulcrum by pulling on the yoke.
Before removing the pressure-plate assembly, centre-pop the cover plate and flywheel, or mark them with paint, so that they can be reinstalled. in their original positions. Always unscrew the bolts evenly a little at a time to avoid distortion.
After unscrewing the holding screws, the clutch can be taken out from below. When reinstalling, centre the clutch plate properly, seeing that the pilot bearing is not over-lubricated, as slip might occur if any grease drops on to the facings.
Brake Adjustments
The 1934-35 models used the Bendix mechanical brakes, but in 1936 Buick changed to a hydraulic system. Brake adjustments on the mechanical type are more critical and require constant attention to maintain an even balance. To adjust the mechanical type, jack up all four wheels, release the brakes, arid make sure the cross-shaft is free from binding and is tight against its stop. Lubricate and check all moving parts, linkages, etc., and see that the rods and cables will allow the levers to return to their proper position when the brakes are released.
Check all road spring clips or U bolts for tightness, and inspect the wheel bearings, making any adjustments that may prove necessary. When a control lever and a camshaft lever are used on the front brakes, the control lever should be set so that the centre of the ball on it is to 5/16in. back of the centre-line of the kingpin with the brake pedal and lever in the "fully off" position. This position Is obtained by turning the adjusting nut on the brake rod or cable. There should not be more than 1/64in. clearance between the two levers.
Never attempt to adjust for lining wear (shoe clearance) on the cables. Each shoe must be adjusted separately to give a .010in. clearance between lining and drum. The clearance should not vary by more than .003in. at any point on the shoe; if wear, is so uneven that the variation exceeds this amount, reline the shoe. • • •
Posted 03/2007 |
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