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DIY Classic Mini Cylinder Head Articles

C-AEA526 DUAL VALVE SPRING FITTING INSTRUCTIONS (Technical Information)
This valve spring set has been developed to fit standard sized top caps, and cope with high rpm and high valve lifts without crushing of up to 0.570” without modifications, when fitted to a cylinder head that has standard or near standard valve spring heights. However, where possible, it is always advantageous to correct and match the valve spring heights (measured from the spring seat in the head to the underside of the spring retainer cap), as these will vary particularly where new valve seats are cut. The standard heights for pre-A+ heads are approximately 1.32” to 1.37” for small-bore types, 1.40” to 1.42” for large-bore types, and A+ heads 1.35” to 1.38” for small-bore types and 1.35”-1.37” for large-bore types. However, ...
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C-AEA527 DUAL VALVE SPRINGS FITTING INSTRUCTIONS (Calver's Corner)
See bottom for useful part numbers.   This valve spring set has been developed to fit standard sized top caps, and cope with racing rpm and high valve lifts without crushing of up to 0.570” without modifications, when fitted to a cylinder head that has standard or near standard valve spring heights. However, where possible, it is always advantageous to correct and match...
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C-STR1057 Group A Turbo head gasket (Calver's Corner)
  This gasket was originally developed by Howley Racing way back in the mid eighties for what was then part of the factory Rover Group racing effort - the Group A Metro Turbo. The engines developed by Howley Racing were giving 220+bhp and 185lb ft running 16.4psi boost - quite a chunk of power in a car little bigger than a Mini! Despite 10" wide sticky slicks, the engine chirped the tyr...
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Competition Cylinder Heads (Technical Information)
A selected range of modified cylinder heads are available to suit a wide variety of applications. All port and chamber modifications are carried out by experts to current state of the art specifications. Therefore, actual specifications may alter slightly as gas flow and port velocity efficiency improvements are developed. Where large bore heads are used on small bore engines (i....
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Competition head stud and nut kit (Technical Information)
This kit has been produced by Mini Spares to reduce head gasket problems on performance orientated engines, especially those utilising large over bore sizes.Standard type head studs and nuts are mass produced which unfortunately compromises the specification of the end product. Worst affected are the threaded portions which create problems during torque-down; thread deformation, stud ...
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Cylinder head - Combustion chamber shape (Calver's Corner)
Since the reasonably recent publishing of a certain Mini tuning, performance and maintenance guide that has strangely coincided with a batch of new readers/devotees of a certain prolifically quoted 'bible' on A-series engine modifications - the subject of all things cylinder head have bounced into the fore once more. Something I was heavily canvassed over at this years (2003) Mini in The Park even...
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Cylinder head - Identification by casting number (Calver's Corner)
  Number Inlet dia. Exhaust dia. Nominal cc Standard fitment 2A628 1.0625"/26.99 1.00"/25.4 24.5 850, 998 Mini & 948 Sprite 2A629 1.0625"/26.99 1.00"/25.4 24.5 948, A35 & Morris Minor 12A1456 1.0625"/26.99 1.00"/25.4 24.5 850, 998 Mini & 948 Sprite 12G202 1.156"/29.36 1.00"/25.4 26.1 997 Cooper, Austin 1100 Mk CAM4180 1.0625"/26...
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Cylinder head - Min Tec head range (Calver's Corner)
  Cylinder head - Min Tec head range   I'm often asked about the range of cylinder heads I do for Mini Spares/Mini Mania, so here's the low-down…   Although the following range of heads accommodate specific fitments - like pre-1992 where by-pass hoses and heater take-offs on the clutch end of the head are used and post-1992 where neither of these exist, and on SPi (...
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CYLINDER HEAD - Suitability basics (Calver's Corner)
  See bottom for useful part numbers. Whatever else owners do to their Minis by way of interior/exterior modifications or none at all, a very large proportion desire and search for an increase in engine performance. Now this may not be super-sonic speed-inducing power, it could just as well be for maximum economy. In either case, it's the engines volumetric efficiency (VE) under scrutiny ...
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CYLINDER HEAD - Torque-down and head gasket problems (Calver's Corner)
A regular visitor to the message board, and something I am asked frequently about in my other incarnations for other technical media. Generally when something has gone badly wrong! Many folks have just as many ways of dealing with the following subjects - all can and will claim their way has worked for them for the proverbial millennia - so a few words as a basic reference and guide as I see them;...
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CYLINDER HEAD - Unleaded Fuel Use (Calver's Corner)
The specter of 'unleaded fuel only' - instigated in UK on January 1st 1999 and seemingly from decades ago across the rest of the world - seems to be forcing more and more folk into frightened, panic orientated action. Mini, Midget and Sprite  owners are featuring heavily in this. The situation not at all being helped by all sorts of conflicting information from 'leaned' sources, such as lead ...
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CYLINDER HEAD - Valves; shapes, materials, and finishes. (Calver's Corner)
Mini Spares/Mini Mania race-spec valves, the reasons why.   Covering valve part numbers- Inlets C-AHT55   - 1.464"/37.2mm Exhausts C-AEG107 - 1.220"/31.0mm   C-AEG544 - 1.402"/35.6mm     C-AEG106 - 1.161"/29.5mm   C-AEG569 - 1.311"/33.3mm   C-AEG587 - 1.040"/26.4mm   C-AEG588 - 1.218"/30.9mm (small-bore...
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Cylinder head - What can easily be achieved (Calver's Corner)
  Cylinder head - What can easily be achieved   The engine build I recently covered in previous Mini Magazine issues developed into a bit of an ongoing 'project'. During a discourse with the editorial staff at Mini Mag, it was decided the build feature presented an ideal opportunity to demonstrate just exactly what such an engine build is capable of in days where it's generally believ...
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Cylinder Heads (Technical Information)
Everybody has their own opinion on this subject. The most experienced people will tell you that the best way to maintain your engine performance is to accept the fact that valve jobs need to be done 2 or 3 times more often than rings and bearings! And this data base was concluded when leaded gas was the norm! Now that unleaded is all you can get, valve jobs are needed even more often!The purpose o...
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Cylinder Heads - About Min Tec heads (Calver's Corner)
  Cylinder Heads - About Min Tec heads.   Terminology - VFM - Value For Money CR - Compression Ratio VE - Volumetric Efficiency   'Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Smoothed finish in ports - not mirror-finish polished to minimise drag. Four-angle valve seats in head. Cooper S size valve...
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Do I need to do a Valve Job? (Technical Information)
Do I need to do a Valve Job? Most engines will go at least 80,000 miles before "needing a valve job"!   But what are the signs? How do I determine if I really need it?  Do I do it myself or pay a local machine shop?.  The condition of the cylinder head valves and seats can have a big impact on the performance of the vehicle.  The valves take a lot of abuse even if you a...
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Head Work (Restoration)
Head Work November 28, 2012 The engine bay is empty, and the cylinder head is sitting on our bench The top head is not original to a 1275 Cooper S, but the bottom head is Once you start changing stuff, where does it stop? Our Mini came with a head, though it wasn’t bolted to the engine. Or anything, for that matter. In fact, it wasn’t even near the car...
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High lift rocker assembly, C-AHT436 (Technical Information)
SPECIFICATION: Material is drop forged EN16 with the valve pad face hardened to 52.5-55 on the Rockwell  C scale. RATIO: Rocker ratio is 1.5 as opposed to 1.25 of the standard rocker. TAPPET CLEARANCE SHOULD BE 3 THOU MORE THAN STANDARD. ON REALLY HIGH LIFT CAMSHAFTS AN EXTRA 2 THOU AGAIN MIGHT BE BENEFICIAL. Ensure that posts, spacers and rockers are evenly distributed...
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MSE3 - PRE 1992 unleaded Stage 2 (Road Rocket) large-bore head (Calver's Corner)
Inlet Valves  35.6mm(1.401") dia. Tuftrided EN214N s/steel  P/No. C-AEG544 Exhaust Valves 29.5mm(1.161") dia. Tuftrided EN214N s/steel P/No. C-AEG106 Exhaust seats Latest type Beryllium-based for lead-free fuel P/No. TAM2069 Valve Guides Magnesium bronze P/No. C-AJJ4037 Valve ...
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MSE4 - Post 1992 unleaded stage 2 (Road Rocket) large-bore head (Technical Information)
Inlet Valves:  35.6mm(1.401") dia. Tuftrided EN214N s/steel  P/No. C-AEG544 Exhaust Valves: 29.5mm(1.161") dia. Tuftrided EN214N s/steel  P/No. C-AEG106 Exhaust seats: Latest type Beryllium-based for lead-free fuel P/No. TAM2069 Valve Guides: Magnesium bronze P/No. C-AEA526 Valve Springs: No...
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MSE6 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head (Calver's Corner)
Inlet Valves: 35.6mm(1.401") dia. Original equipment type    P/No. TAM1059 Exhaust Valves:  29.2mm(1.150") dia. Original equipment type   P/No. TAM1061 Exhaust seats: Latest type Beryllium-based for lead-free fuel    P/No. TAM2069 Valve Guides: AE Hepolite cast iron       P/No. 12G1963 ...
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Offset rocker bushes, C-AEG644 (Technical Information)
FITTING INSTRUCTIONS Using these bushes it is possible to achieve an increase in valve lift of upto 0.030". They must be pressed into the rocker with the thick section pointing forwards, ie. toward the rocker pad. It is advisable to use bearing-fit compound (Loctite) to ensure the bush does not rotate in use, taking up  wear in old rockers. Once fitted, they need to be reamed out to 9/16", ...
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Rocker Gear (Technical Information)
The new generation of short period, high lift cams have been developed to give the best results in large bore engines when used in conjunction with 1.5 ratio, hi-lift rockers. For the small bore range, the stock 1.3 ratio is optimum. In certain instances ratios of 1.7 to 1 are of benefit - but is really only applicable to fully developed race engines. 12G12211.3-1 ratio "Cast" rocker. Reprodu...
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Rocker gear - General compendium (Calver's Corner)
  Rocker gear - General compendium   Whether you’re building a solid road performer or fire-breathing monster, the main goal is to improve air/fuel flow into the engine. The more you can get in, the more power you can get out. Cheapest chunk of power improvement comes from sorting the asthmatic manifolding and exhaust by applying a stage one kit. Then what?   Conside...
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Stage 2, Budget big bore head (Technical Information)
STAGE TWO SPEC. BUDGET LARGE BORE CYLINDER HEAD AEG592 Inlet valve : 35.6mm (1.401") diameter, standard ‘S’ spec. material CAM4601 Exhaust valve : 29.3mm (1.156”) diameter, latest lead free spec. material 12G1963 Guides : OE specification cast iron, bullet nosed C-AEA526 Valve springs : Nominal 180lb progressive ra...
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Valve Guides - Materials and Usage (Calver's Corner)
See bottom for useful part numbers.   Material choices for guides are down to two distinct types - cast iron and bronze. Yes, cast iron. NOT steel as described in many adverts and by vendors. Never have been, never will be. These are as fitted to the various A-series cylinder heads as standard in all applications. Cast iron is used because it is a very dissimilar metal from a...
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Valve Stem Keepers (Technical Information)
Call them cotters, collets or keepers, these little items are often overlooked during a head rebuild.  If yours are worn and need to be replaced, make sure you order the right ones.  Minis used three different versions over the years. In general, the earliest cars used valves with a single, wide groove in the valve stem.  Often called the "normal" valves, the later, pre-A+ valves u...
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Valve Stem seals (Technical Information)
Valve stem seals are a critical part of rebuilding a cylinder head. The o-ring style seals are used on the early small bore heads. Later heads that have the moderm valve guides with groves in them can take the umbrella style valve stem seals. They can be used on both intake and exhuast valves....
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