Cylinder head - Torque-down and head gasket problems
This is to help those floundering in an unknown sea of techno-babble and 'magical' cures…
Part No Applications: C-AHT288, CAM150, CAM151, TAM1617, CAM4545, 51K1193, TAM1521,
GEG300, C-AHT188, C-STR1057,
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; we all know there are always exceptions to the rules. This is to help those floundering in an unknown sea of techno-babble and 'magical' cures…
Camshaft Design
Elgin Cams is a company that is a direct descendent of such famous California specialists as Isky, Delong, Winfield, etc. etc. Elgin has taken the art of cams into the science of the '90's. Computer designed and handcrafted workmanship guarantee a first class camshaft. Custom designed cams are a specialty.
Part No Applications: CAM001, CAM002, CAM003, CAM004, CAM005, CAM006, CAM007
Elgin has made cams or sold his design to General Motors, Ford Motor Co., Nissan Corp., Zakespped International, Porsche Motor Sports, Winston Cup "Engine Builders. Elgin has the largest percentage of cams used at the SCCA Runoffs from GT-1 to Formula-V. He also has provided original or new technology for antique and vintage racers.
Much information has been recorded about the four stroke internal combustion engine and yet only a small percentage of people really understand how it works and fewer people know how to modify an engine to suit their needs.
CTR-STR1057 GROUP A TURBO HEADGASKET FOR RACING, BLOCK NEEDS MODIFICATION
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.
C-STR1057 Group A Turbo head gasket
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 tyres in each upward gear change. Even more impressive when you consider this was still on it's single 1.75" HIF SU carb!
All that was basically done was to take a standard production head gasket (the then all over silver TAM1521 - a great gasket it it's own right) and add a reinforced fire ring by over-lapping the existing one with an extra fold of metal.As a consequence the block needs to be machined to accept this gasket - rendering it useless for any other gasket fitment and any further over-bores (even to 73.5mm) unless a top-hat type liner was used.
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?
Considering the ‘get more in to get more out’ theme, the main restriction - all else being equal - is the valves and their behavior. How big they are, how efficient they are and how long they’re open for determines how much gets in with each gulp each bore/piston makes. Modified cylinder heads are popularly next, although it has to be said that although a well modified cylinder head will improve performance, the gain against cost is nowhere near that given by the ‘stage one’ kit application. A good stage one kit’s improvement verses cost is around £12.50 per 1 hp, a decent modified head typically £30 per 1hp - dependent on application. Hmm.
MSE6 - POST 1992 Unleaded Stag
Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation. Three-angle valve seats in head. Super-quality MG Metro valves modified to increase airflow.
MSE6 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head
Part No Applications: MSE6, TAM1059, TAM1061, TAM2069, 12G1963, 12G1015, ADU4905
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
Valve Springs: Nominal 140lb. Max actual valve lift 0.400" P/No. 12G1015
Stem Seals : Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905
Chamber Volume: Nominal 20cc
Combustion chamber volume used to give slight static compression ratio increase over
MSE6 - POST 1992 Unleaded Stag
Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation. Three-angle valve seats in head. Super-quality MG Metro valves modified to increase airflow.
MSE6 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head
Part No Applications: MSE6, TAM1059, TAM1061, TAM2069, 12G1963, 12G1015, ADU4905
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
Valve Springs: Nominal 140lb. Max actual valve lift 0.400" P/No. 12G1015
Stem Seals : Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905
Chamber Volume: Nominal 20cc
Combustion chamber volume used to give slight static compression ratio increase over
MSE4 - Post 1992
Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation.
MSE4 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head
Part No Applications: MSE4, C-AEG544, C-AEG106, TAM2069, C-AJJ4037, C-AEA526, ADU4905
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: Nominal 180lb. Max actually valve lift 0.500" P/No. C-AJJ4037
Stem Seals: Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905
Chamber Volume: Nominal 20cc
Three-angle valve seats in head. Cooper S size valves with current maximum flow profiles and Tuftrided for durability/longevity when used with unleaded fuel (hence 'black' finish).
MSE4 - Post 1992
Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation.
MSE4 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head
Part No Applications: MSE4, C-AEG544, C-AEG106, TAM2069, C-AJJ4037, C-AEA526, ADU4905
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: Nominal 180lb. Max actually valve lift 0.500" P/No. C-AJJ4037
Stem Seals: Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905
Chamber Volume: Nominal 20cc
Three-angle valve seats in head. Cooper S size valves with current maximum flow profiles and Tuftrided for durability/longevity when used with unleaded fuel (hence 'black' finish).
MSE3 -Pre 1992
Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation.
MSE3 - PRE 1992 unleaded Stage 2 (Road Rocket) large-bore head
Part No Applications: MSE3, C-AEG544, C-AEG106, TAM2069, C-AJJ4037, C-AEA526, ADU4905
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 Springs Nominal 180lb. Max actually valve lift 0.500" P/No. C-AEA526
Stem Seals Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905
Chamber Volume Nominal 20cc
Cylinder head - Combustion chamber shape
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 event whilst doing duty as Mini 'agony aunt' and 'doctor'… In particular the subject of the combustion chamber was foremost in discussion since the aforementioned 'guide' exhibited a number of wildly different chamber profiles with very little in the way of supportive technical information. Now, I have considered the pros and cons of doing this missive. On one hand, I am not out to increase sales of said guide since I'm not one of its supporters in any way. On the other I am certainly not attempting to belittle the efforts of the featured company as they have long been at the forefront of perf
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 (single point injection) heads where they don't usually have a threaded hole for the temperature sender - in reality it is easy to convert almost any of them to fit any other engine since holes are easily blocked off - or by-pass hoses not used, water pumps blanked off and drilled thermostats fitted (see articles on cooling/engine transplants). A list of which is what and what to do to each to convert is at the end of this article.
For more in-depth descriptions of the head specs, see article 'Cylinder head - About Min Tec Heads' - basically the valve sizes used have been decided on after extensive and in-depth flow test...
Cylinder head - Suitability basics
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.
See bottom for useful part numbers.
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 - it's ability to breath in as much correctly proportioned air/fuel mix as possible in any given situation. Although the induction/exhaust system plays an important part, there are effectively two major factors that dictate performance increases - the camshaft and cylinder head. The induction and exhaust elements (stage one kits, exhaust systems, etc.) and camshafts are covered in various other articles in my 'Corner'. So here we'll have a look at cylinder heads and dispel some of the myths and legends surrounding them.
Engine - 998 tuning, further options
Following on from the easily bolted on performance enhancing components out-lined in the stage one section, we need to consider where to go to get more power output.
Terminology: MSC/MM - Mini Spares Centre/Mini Mania BBU - Big Bore Unit (refers to all 1275cc-based units) SBU - Small Bore Unit (refers to all sub-1275cc units, here the 998) BHP - Brake Horse Power CR - Compression Ratio
To improve engine out-put, you need to increase the engine's 'breathing' ability. The stage one kit deals with all the easily bolted-on external parts, and represents the best increase for investment. From here on in the power increases will cost commensurately more money. Power production of any engine, once the 'breathing apparatus' (induction/exhaust system) has been dealt with to cause no restriction ...
Engine - Small-bore engine, 12G940 head fitting
There is no specific large-bore (1275cc-based) head casting number that will fit the 998 engine any easier than any other.
They all have the same problems - generally requiring exhaust valve relief cut-outs machined into the block and re-alignment of the front water gallery transfer ports. However, I would avoid using heads with valves bigger than 35.7mm on the intake since these are too big for most 998 engines unless they are absolutely full-race spec where top end power at high rpm is all that is required.
First of all it is worth checking that you actually need to make the relief cut-outs since some heads have a big enough head face to exhaust valve face clearance to allow fitment without the cut-outs when the standard cam and rocker gear is retained.
If possible, measure the actual valve lift you are getting with the current fitted set-up.
Engine transplants - Changing FDs and speedo drive ratios.
What they don’t tell you in the manual!
Terminology -
FD - Final Drive (diff ratio)
What they don’t tell you in the manual!
If you’ve decided the FD fitted isn’t what you want, changing the FD is possible without separating the engine from the gearbox. Removing the diff case will allow you access to the diff assembly to change the crown-wheel, and access to the gear-change linkage. Use a manual for crown-wheel replacement. While you’re in there it would be just as well to replace the thrust washers and diff-pin as these are the source of many a gearbox problem. Particularly for up-rated engines where fitment for the competition diff-pin is highly recommended. Once again, follow the manual here. Now the bit they don’t tell you how to do...
Rod-change types -
Removal of the speedo drive housing gives access to the pinion retaining nut (1.5”AF socket needed and a long bar). To be able to undo the pinion nut (torqued up to 150lb ft !!) you need to engage two gears - 2nd and 4th - t
Engine transplants - initial information and engine choices
Is this familiar? - You take the small one out; you put the big one in. In, out, in, out, shake your fist about, you do the hokey-cokey and you turn around, that’s what it’s all about...
Terminology - BBU - Big Bore Unit SBU - Small Bore Unit Bodge - English term for 'make do' engineering- assured to fail at an in opportune Moment. Dizzy - Distributor
NOTE; this information is largely for transplanting large-bore units into small-bore engined cars.
Is this familiar? - You take the small one out; you put the big one in. In, out, in, out, shake your fist about, you do the hokey-cokey and you turn around, that’s what it’s all about...kinda sums up the situation many folk find themselves in when attempting to endow their beloved Min with a more impressive turn of speed.
Exhaust - CAPTIONS for manifold article pictures.
Standard cast iron manifolds
Pic 1. Standard cast iron manifolds - Mini on left, Metro ‘LCB’ type right. One major benefit of cast iron is noise absorption. Tubular steel amplifies resonance caused by exhaust gas phenomena. Stainless steel being THE worst.
Pic 2. Cooper Freeflow. Careful, exquisite forming of primary pipes and neat welding ensures un-interrupted flow of exhaust gases. Medium length primaries promote performance where mild cams are used.
Pic 3. Ubiquitous LCB. The two outer ports are connected by short primaries joined to a larger secondary pipe, the centre port getting one pipe all to it’s self. These equally sized pipes continue down under the car, ending in a ‘Y’ piece to join them to the system.
Exhausts - RC40, Millennium and others tested
The recent rolling road re-test of the 1275 engine build I did saw an opportunity to do some exhaust systems testing.
I had noticed a few years back that the RC40 was being manufactured by a different process than the originals - giving rise to a change in the shape of the bends applied to the system. I had wondered if they would be causing a restriction at all - but hadn't had the opportunity to test it. The lack of expected power from the aforementioned engine lead me to investigate all possible angles from the tyre contact patch to the carb mouth. I found nothing that explained the 14 or so bhp I was 'missing'. After some application of the old grey cells I mentally narrowed cause down to one of two things - either the piston oil control rings were still causing excessive drag (75% of all internal friction of an engine is generated by the piston rings) or perhaps these new bends in the venerable RC40 were indeed causing a power loss.
Bill Sollis - Thruxton race report.
Our Brands Hatch successes were followed by a five week break and with holidays to take what better way to enjoy the first two wins of the season.
Thruxton loomed up and the sense of expectation is never greater than when contemplating the mega fast Hampshire circuit. Preparations went beyond the usual full spanner check. We have acquired a cylinder leakage....
C-AHT136 - TPi BUDGET UNLEADED STAGE 2
(ROAD ROCKET) LARGE-BORE HEAD.
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. Multi-angle valve seats in head. Super-quality MG Metro valves modified to increase airflow. Combustion chamber volume used to give slight static compression ratio increase over standard. Head mods employed greatly increase volumetric efficiency, boosting actual running (dynamic) compression ratio.
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