| Description | Date | Identifier | |
| Page 2 of a letter discussing push rod return springs and tappet adjustments. | 2nd Sep 1934 | Box 88 \ 4 scan0095 | |
| Blueprint for a hydraulic unit valve rocker for a 3½ Litre Bentley. | 2nd Sep 1934 | Box 88 \ 4 scan0096 | |
| Suggested modification to a 3½ litre Bentley valve gear mechanism. | 1st Aug 1934 | Box 88 \ 4 scan0097 | |
| Letter to Major Halford thanking him for prints and suggestions regarding the Bentley valve gear. | 2nd Aug 1934 | Box 88 \ 4 scan0098 | |
| Scheme for providing a return spring for Bentley Push Rods. | 3rd Aug 1934 | Box 88 \ 4 scan0099 | |
| Letter from Frank B. Halford discussing the design of a hydraulic rocker for a 3.5-litre Bentley engine. | 9th Aug 1934 | Box 88 \ 4 scan0100 | |
| Letter from Frank B. Halford discussing an alternative hydraulic rocker design for the 3 1/2 litre Bentley engine. | 14th Aug 1934 | Box 88 \ 4 scan0101 | |
| Letter to Major F.B. Halford concerning valve acceleration data. | 20th Aug 1934 | Box 88 \ 4 scan0102 | |
| Letter to Major F. B. Halford regarding a modification to the rocker shaft design. | 29th Aug 1934 | Box 88 \ 4 scan0103 | |
| Letter to Major F.B. Halford enclosing a print for a modified rocker cover with hydraulic rockers. | 30th Aug 1934 | Box 88 \ 4 scan0104 | |
| Request to reduce the coil clearance on the outer spring for Bentley Double Valve Springs by making a new set of packing washers and outer springs. | 6th Sep 1934 | Box 88 \ 4 scan0105 | |
| Drawing of Bentley double valve springs. | 6th Sep 1934 | Box 88 \ 4 scan0106 | |
| Comparing Halford and Cadillac silent tappet schemes, favouring the Cadillac design for the 20/25 and Bentley engines. | 6th Sep 1934 | Box 88 \ 4 scan0107 | |
| List of proposed modifications and considerations for engine components, including valves, camshafts, and tappets. | 6th Sep 1934 | Box 88 \ 4 scan0108 | |
| Recommendations for redesigning the 20/25 and Bentley relief valve and increasing the oil pump size. | 6th Sep 1934 | Box 88 \ 4 scan0109 | |
| Letter from designer Frank B. Halford discussing proposed modifications to the hydraulic valve gear for the 3 1/2 litre Bentley. | 6th Sep 1934 | Box 88 \ 4 scan0110 | |
| Letter discussing rocker clearance, plunger tolerances, and experiments with self-adjusting valve gear. | 6th Sep 1934 | Box 88 \ 4 scan0111 | |
| Comparative analysis of original, modified, and proposed hydraulic rockers for a 3½ Litre Bentley engine. | 7th Sep 1934 | Box 88 \ 4 scan0112 | |
| Letter to Major F. Halford regarding proposed modifications to the Bentley Valve Gear. | 8th Sep 1934 | Box 88 \ 4 scan0113 | |
| Major Halford's suggestions for reducing the weight of the rocker and hydraulic unit for Halford Tappets on a Bentley. | 8th Sep 1934 | Box 88 \ 4 scan0114 | |
| On Halford's suggestions for lightening valve gear, comparing Halford and Cadillac type tappets. | 8th Sep 1934 | Box 88 \ 4 scan0115 | |
| Request for comparative tests on large inlet valves for aluminium and cast-iron heads. | 25th Sep 1934 | Box 88 \ 4 scan0116 | |
| Request for a set of Stellited exhaust valves for a Bentley car, model 5-B-IV. | 3rd Oct 1934 | Box 88 \ 4 scan0117 | |
| Request to machine inlet valve inserts for a Bentley high compression aluminium cylinder head for testing. | 10th Oct 1934 | Box 88 \ 4 scan0118 | |
| Letter from Frank B. Halford to W. A. Robotham enquiring about the progress of tests on hydraulic valve rockers. | 10th Oct 1934 | Box 88 \ 4 scan0119 | |
| Letter to Major F. Halford explaining a delay in testing proposed hydraulic valve rocker modifications. | 11th Oct 1934 | Box 88 \ 4 scan0120 | |
| Instructions for setting silent tappets on an engine. | 11th Oct 1934 | Box 88 \ 4 scan0121 | |
| Instructions on removing rocker shafts to prevent damage to cast-iron eccentrics during rebuilding. | 26th Nov 1934 | Box 88 \ 4 scan0122 | |
| Proposal to reduce Bentley exhaust valve tappet clearance from .006 to .004 for use in England. | 26th Nov 1934 | Box 88 \ 4 scan0123 | |
| The fitting of silent tappets to a Bentley, referencing the Spectre cam form. | 5th Dec 1934 | Box 88 \ 4 scan0124 | |
| List of design features for incorporating Cadillac tappets into a Bentley engine. | 1st Dec 1934 | Box 88 \ 4 scan0125 | |
| Proposal for a Bentley camshaft timing for use with silent tappets. | 4th Dec 1934 | Box 88 \ 4 scan0126 | |
| Modification to the Bentley Large Inlet Valve to reduce manufacturing costs. | 12th Dec 1934 | Box 88 \ 4 scan0127 | |
| Confirming the sending of documents and blueprints for creating adaptation drawings for silent tappets on Bentley and 20/25 models. | 17th Dec 1934 | Box 88 \ 4 scan0128 | |
| Instruction to use magnesium rocker covers for the silent tappet head on the Bentley. | 5th Feb 1935 | Box 88 \ 4 scan0129 | |
| The results of moment of inertia tests on two valve rockers. | 26th Feb 1935 | Box 88 \ 4 scan0130 | |
| Moment of Inertia (M.I.) test results and calculations for a valve rocker assembly. | 18th Feb 1935 | Box 88 \ 4 scan0131 | |
| Moment of Inertia tests performed on a valve rocker assembly. | 18th Feb 1935 | Box 88 \ 4 scan0132 | |
| Design of Bentley Hydraulic Tappets for a 25-HP engine. | 15th Mar 1935 | Box 88 \ 4 scan0133 | |
| The Bentley Silent Tappets, requesting a magnesium rocker cover be made. | 22th Mar 1935 | Box 88 \ 4 scan0134 | |
| Short internal memo regarding tappet clearance on Bentley vehicles. | 28th Mar 1935 | Box 88 \ 4 scan0135 | |
| Progress on valve gear silencing for the Bentley engine and requesting further modifications. | 26th Apr 1935 | Box 88 \ 4 scan0136 | |
| Bearing alloys, a Ford V.8 rear axle, Bentley tappet noise, and Adamant Co. steering. | 10th May 1935 | Box 88 \ 4 scan0137 | |
| Advantages of a double rocker cover and requesting a permanent oil-tight flange be fitted to the next large bore unit head. | 10th May 1935 | Box 88 \ 4 scan0138 | |
| Testing of Stellited Valves on specific Bentley chassis cars. | 3rd Sep 1935 | Box 88 \ 4 scan0139 | |
| Performance and testing of stellited valves, particularly with high-lead fuel. | 6th Sep 1935 | Box 88 \ 4 scan0140 | |
| Suitability of fitting Stellited exhaust valves to Bentley cars for use in the UK versus for French Trials. | 7th Sep 1935 | Box 88 \ 4 scan0141 | |
| Shipment and fitting of Stellited Valves. | 10th Sep 1935 | Box 88 \ 4 scan0142 | |
| Requesting details for a test to increase the valve lift on a 3.500 Bore Bentley engine. | 5th Oct 1935 | Box 88 \ 4 scan0143 | |
| Recommendation to remove a drilled hole from a Bentley exhaust valve. | 8th Oct 1935 | Box 88 \ 4 scan0144 | |
| Superior materials for stellited exhaust valves and requesting the manufacture of three sets of Bentley exhaust valves. | 28th Oct 1935 | Box 88 \ 4 scan0145 | |
| Steel types for exhaust valves and requesting the manufacture of 3 sets of Bentley valves. | 29th Oct 1935 | Box 88 \ 4 scan0146 | |
| Spring top washer failure on a 3.500' Bore Bentley engine valve gear following an endurance run. | 14th Nov 1935 | Box 88 \ 4 scan0147 | |
| Blueprint detailing a fracture location and a suggested modification for a component. | 14th Nov 1955 | Box 88 \ 4 scan0148 | |
| Broken top spring washer on Large Bore Bentley and 25-29 HP engines and proposing a strengthened design. | 14th Nov 1935 | Box 88 \ 4 scan0149 | |
| New drawing for a strengthened top valve spring washer for the Large Bore Bentley Chassis. | 26th Nov 1935 | Box 88 \ 4 scan0150 | |
| Request to produce a set of six sodium-cooled Bentley exhaust valves to test their effect on engine pinking. | 7th Dec 1935 | Box 88 \ 4 scan0151 | |
| Inquiry regarding recommended tappet adjustment for Bentley cars being used abroad. | 9th Dec 1935 | Box 88 \ 4 scan0152 | |
| Exhaust and inlet valve clearances for a Bentley under various driving conditions. | 13th Dec 1935 | Box 88 \ 4 scan0153 | |
| Replacement and testing of Bentley Tappet Door Washers due to oil leaks caused by shrinking. | 24th Dec 1935 | Box 88 \ 4 scan0154 | |
| Letter concerning suitable valve material for a Bentley car, specifically about Stelliting valves. | 6th Jan 1936 | Box 88 \ 4 scan0155 | |
| Requesting the urgent manufacture of 24 valve springs for a trial surge comparison on a Bentley. | 22th Jan 1936 | Box 88 \ 4 scan0156 | |
| Sticking exhaust valves on Large Bore Bentley engines, proposing a modification to the valve guide dimensions. | 13th Mar 1936 | Box 88 \ 4 scan0157 | |
| The weight reduction on the big bore Bentley chassis compared to the small bore version. | 24th Mar 1936 | Box 88 \ 4 scan0158 | |
| The adoption of a .094' hole on the push rod side of the rocker for the Bentley & 20/25 valve gear. | 9th Apr 1936 | Box 88 \ 4 scan0159 | |
| Alteration to the valve gear for Bentley and 25/30 HP models. | 15th Apr 1936 | Box 88 \ 4 scan0160 | |
| Modification of the valve gear for Bentley and 25/30 HP models. | 20th Apr 1936 | Box 88 \ 4 scan0161 | |
| Outlining a series of proposed valve tests and questions. | 29th Apr 1936 | Box 88 \ 4 scan0162 | |
| Request to produce a set of Bentley exhaust valves to EB.2820 for use on engine B-56-BN. | 30th Apr 1936 | Box 88 \ 4 scan0163 | |
| Request to manufacture 24 valve springs to specification Rm.124 for use on test beds. | 5th May 1936 | Box 88 \ 4 scan0164 | |
| Design and trial of an exhaust valve for a Bentley unit. | 22th May 1936 | Box 88 \ 4 scan0165 | |
| Status and position of valves and cylinder heads for Bentley and Phantom III chassis units. | 5th Jun 1936 | Box 88 \ 4 scan0166 | |
| Requirements for new standard cylinder heads and valves for the No.12 unit. | 5th Jun 1936 | Box 88 \ 4 scan0167 | |
| Use of stellited silchrome valves for a 15,000-mile test on a small bore engine. | 16th Jun 1936 | Box 88 \ 4 scan0168 | |
| Bentley valve failures during Le Mans race preparation and proposed solutions. | 18th Jun 1936 | Box 88 \ 4 scan0169 | |
| Manufacturing delay of 1.6' diameter inlet valves pending further endurance testing. | 18th Jun 1936 | Box 88 \ 4 scan0170 | |
| Adoption and testing of inserted exhaust valve seats. | 7th Aug 1936 | Box 88 \ 4 scan0171 | |
| Investigation into an unexpected increase in production chassis costs due to a modification of the tappet doors. | 12th Sep 1936 | Box 88 \ 4 scan0172 | |
| Misleading cost comparisons between sand casting and die casting for guiding design policy. | 4th Sep 1936 | Box 88 \ 4 scan0173 | |
| Difficulties in obtaining satisfactory valve springs, comparing American and English suppliers. | 4th Sep 1936 | Box 88 \ 4 scan0174 | |
| Effects of temperature on lead attack on Stellite valves. | 14th Sep 1936 | Box 88 \ 4 scan0175 | |
| Graph showing the effect of temperature on the rate of lead attack. | 11th Sep 1936 | Box 88 \ 4 scan0176 | |
| Effectiveness of salt-cooled exhaust valves in reducing temperature and lead attack. | 22th Sep 1936 | Box 88 \ 4 scan0177 | |
| Standardisation of parts for overhead adjustment of tappet push rods and deletion of removable tappet doors. | 19th Aug 1936 | Box 88 \ 4 scan0178 | |
| Estimated cost of £96 for extra jigs, tools and equipment for an item already in production. | 13th Jul 1936 | Box 88 \ 4 scan0179 | |
| The condition of engine valves after a 15,000-mile run, detailing clearances and materials. | 6th Oct 1936 | Box 88 \ 4 scan0180 | |
| Cost-effectiveness of a two-piece push rod scheme, comparing material costs between different engine models. | 15th Oct 1936 | Box 88 \ 4 scan0181 | |
| Proposal and testing of valve springs made from an aluminium alloy. | 4th Nov 1936 | Box 88 \ 4 scan0182 | |
| Complaints of bending push rods on the Bentley chassis, proposing material changes and temporary hardening solutions. | 17th Nov 1936 | Box 88 \ 4 scan0183 | |
| To halt production of stellited silchrome valves due to cracking and burning issues found during testing. | 11th Nov 1936 | Box 88 \ 4 scan0184 | |
| Weight analysis of a 3.B.4 chassis fitted with a Park Ward wide door saloon body, with comparison to a Bentley. | 13th Nov 1936 | Box 88 \ 4 scan0185 | |
| The procurement of aluminium alloy wire for experimental valve springs from High Duty Alloys Limited. | 13th Nov 1936 | Box 88 \ 4 scan0186 | |
| Production issues with S/SLV exhaust valves and a specification change for oil pump gears. | 13th Nov 1936 | Box 88 \ 4 scan0187 | |
| Failure of Stellited exhaust valves and proposals for further testing and material experiments. | 16th Nov 1936 | Box 88 \ 4 scan0188 | |
| Letter from the Experimental Department querying a claimed 20 lbs weight reduction on a 3.B.IV. body. | 23th Nov 1936 | Box 88 \ 4 scan0189 | |
| Investigation into the weight of the 3-B-IV body, comparing it to other Park Ward Saloon models. | 24th Nov 1936 | Box 88 \ 4 scan0190 | |
| Breakdown of vehicle component weights and discussing increases in body weight. | 24th Nov 1936 | Box 88 \ 4 scan0191 | |
| Diagrams showing relative weight increases of Bentley chassis and bodies from July 1933 to July 1936. | 20th Nov 1936 | Box 88 \ 4 scan0192 | |
| Standardisation document for a strengthened exhaust valve (KE965) for a Bentley. | 14th Dec 1936 | Box 88 \ 4 scan0193 | |
| Estimated cost for new tools for the 'L' Series chassis production. | 16th Dec 1936 | Box 88 \ 4 scan0194 | |
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