The Blydenstein Project | Part Three

Finding The Power

Before we get into finding the power, we will cover the remaining issues affecting combustion control and engine knock/detonation. Part Two has resulted in some interesting comment from readers who ask the question as to why I have focused so much on this aspect of engine function. The answer is because increasing compression ratio brings benefits in engine response and power throughout engine speed ranges. We simply need to run the highest compression possible on any given engine within the constraints of available fuel. To do that, these are the factors to consider and in doing so unlock the sort of engine response that most would think unlikely.

Something that has also come up is the fact that the words knock, detonation, pinking and preignition mean different things to different folk…so next week we’ll cover these in detail and explain.

Something to note on the 1273 before we go any further.

Please remember that I am taking the opportunity in doing this work to pass on information to those interested but not necessarily experienced in some of the logic used in tuning a classic. The fact that we are doing this on a little-known engine type is fun because we are exploring new territory as we go along.  Most of the tech reasoning is well known to veteran engine men… but few have any knowledge of the Opel/Vauxhall Little Block OHV…and sadly the reputation of this package is not where it should be…maybe we can change that.

Being an ongoing development exercise where aesthetics take a back seat to the tech work, many of the following visuals show work in progress.  For example, the pic of the below engine in the inlet air section using the production aircleaner housing, makes this 110Bhp engine look almost stock in appearance. That is a powerful message to those who may be tempted to equate appearance directly to Bhp…

BACK TO THE KNOCK ISSUES.

Air inlet temperature

This is a combination of managing a cold air intake system and maintaining moderate inlet manifold temperatures. Ideally, we want to get the mixture reaching the combustion chambers to be as ‘chilled’ as possible.  BUT…. this is not a race car application. Being a road car running a conventional carburettor, a certain amount of heating is a good idea to ensure adequate fuel vaporisation, which just promotes good engine driveability, part throttle response and stable fuel consumption. So…

Cooling the Charge

• Channel ambient air directly to the carburettor… to be as cool as possible
• Use the Carb/manifold interface to regulate inlet charge temperature as required after that.

This is how it was done on the 1273.

COOL AIR PIPE TO THE AIR CLEANER

It is best to have an inlet system that directs cool air directly to the carb and that essentially means a ‘closed’ system rather than an expensive high-quality air cleaner element mounted randomly near front of the engine compartment. Whilst the cool air duct from the front cowl to the aircleaner in this pic looks like it provides a ram effect…that is exactly what must be avoided. Trying to use the incoming air as a mini turbocharger results in standing waves in the inlet tract which WILL cause unwanted mixture variations. The relief aperture shown bleeds off any of that, whilst maintaining adequate cool air to the carb…the engine will take what it wants.

THIS APERTURE KILLS ANY POSSIBILITY OF STANDING WAVES DISRUPTING AIR FLOW. THE DUCT TAPE (SPECIAL TOOL #1!) DOES THE JOB OF FINDING THE BEST APERTURE SIZE!

The other area where standing waves can bedevil the process with a system directed to the carb, is within the A/Cleaner body. One must remember that inlet valves are opening and closing at a massive rate and being the gatekeepers to inlet air flow, every time a valve shuts it sends a pressure wave back into the manifold. When these pulses are constrained throughout the tract, things can get a bit angry…and difficult to measure. Again it is just sensible to have bleed apertures in the housing to kill any nasties, this will not restrict the availability of cold air to the carb….The engine again will take what it wants and, as we will mention later, keeping air velocity high helps damping those pulses anyway.

A/C HOUSING APERTURES DAMPING ANY PULSING

Lastly on the flow front, this piece of duct tape on the A/C element opposite the inlet tube directs incoming air around the aircleaner housing.  Testing showed a minor improvement in Bhp but a significant improvement in part throttle drivability especially during the warm-up phase.

DIRECTING AIR AROUND THE ELEMENT.

Design of the inlet manifold on the 1273 will be covered  in the Power section of this piece, however, as regards temperature, I found that running the manifold at the naturally transmitted temperature from the cylinder head without heat shielding from the exhaust manifold, gave a good balance of air temp at moderate values for normal operation. The below pic shows the heat risers from the exhaust ports blocked off. This was important on the 1088 using the tunnel ram manifold as no inlet spacer block was used.

HEAT RISERS BLOCKED

Fuel System

Delivering fuel to the engine at the correct pressure and temperature is another one of those issues that requires attention. First-off, on any OHV producing really good power, the 4mm ID fuel tubing to the engine should be repurposed as a fuel return line and a new delivery pipe of at least 6mm ID installed. This change must include a modification to the stock fuel tank connection (as shown in pic) where a 6mm pipe/tube combination is fine for even the most demanding road work. ( I use an 8mm ID exit tube and Dual Filter arrangement in testing) the exit from the tank must go directly into a fuel filter below the tank and  then into a high capacity “push” type electric pump. It is sensible to keep the pump and filter immediately below the tank.
Modern fuel systems tend to make use of pressure regulators to control fuel pressure, nothing wrong with that, but I prefer to use a fuel return line fitted with a restrictor, its cheaper, in my opinion more consistent and provides the advantage of cooling the fuel and preventing vapour lock in our hot climates.

Let me stress that any OHV running a fuel return line in which a restrictor is used in the return line to manage fuel pump pressure, should have a larger ID delivery fuel line. Try not to use the mechanical fuel pump, it is an unnecessary heat sink and does not have sufficient delivery to handle high power in addition to a return line.

In the engine compartment, as close to the carb as possible, install a T piece fitted with a restrictor that will return fuel to the tank and maintain fuel pump pressure. On this Weber carburettor installation, the 1.5mm restrictor maintains 3.5 lbs minimum fuel pressure at full throttle max power.

Many ask why so much focus on a simple fuel delivery system….because it provides the basis for absolutely stable fuel delivery and temperature…. which in turn keeps mixtures stable….which in turn allows us to set fuel mixture for optimum power and driveability…. and so to manage the knock monster. And we will cover the fuel mixture side when in ‘finding the power’.

1.5MM FUEL RETURN LINE RESTRICTOR LIMITS FUEL PUMP
PRESSURE TO 3.5-4.0 LBS AT FULL POWER.

FINDING THE POWER in the OHV Little Block

Like any successful engine in the tuning game it is only about finding the key response points and identifying any potential weak spots. For the OHV, finding how it responded was easy…the engine reacts to any sensible modification…. but it was a little more difficult to establish which mod gave the best return and in which sequence it should be done. Over the years I have learned which is which and some of it is surprising.

As for the weak spots…there are not too many.

I could write volumes on what has been tested over the years but as a departure point, lets take look at the inlet manifolds and carburetion systems for a start….because many have questioned my use of a single downdraught Weber 36DCD (and a pretty old one at that) for the 1273 road engine..  Given the options available, here for example are some of the inlet manifold and carburettor installations tested/run over the years. Horsepower figures quoted are real and, if anything, conservative.

1.ORIGINAL RACE CAR 1970’s – 46IDA WEBER – MODIFIED VM BLYDENSTEIN MANIFOLD – 112BHP/1160CC

THIS WAS A VERY COMPETITIVE PACKAGE LIMITED ONLY BY AVAILABLE RESOURCES AT THE TIME BUT EASILY ABLE TO MATCH THE MINI 1275/1293 RUNNERS AT 1160cc.

2. RACE CAR REPLICA BUILD  (GERMANY) Local (SA) MACHINED BILLET MANIFOLD –  SPLIT 45 IDF  110BHP /1150CC

THE ADAC INITIALLY AGREED TO ALLOW US TO USE A TWIN CARBURETTOR ARRANGEMENT FOR THE BUILD IN LINE WITH THE ORIGINAL CAR….HENCE THE BILLET INLET MANIFOLD MADE BY ROST ENGINEERING IN PRETORIA. THIS PACKAGE HAD THE POTENTIAL FOR 120Bhp BUT THE CAR WITHDRAWN FROM THE OLDTIMERS SERIES BASED ON PROTESTS FROM OTHER COMPETITORS….TOO FAST I GUESS…..??

3. NEW RACE ENGINE LOCAL (SA) FABRICATED MANIFOLD SPLIT 45 DELLORTOS – 127 BHP/1273CC

THIS WAS A FIRST-OFF ENGINE BUILD AND JUST A SNIFF AT THAT 140BHP POTENTIAL

4. 1^ST PROTOTYPE TUNNEL RAM MANIFOLD  RUN  WITHOUT MANIFOLD SPACER – 36DCD WEBER 1088CC/83BHP. MAGIC  1088 ROAD SPEC.

THIS MADE A 100Mph ROAD CAR.

5. REVERSION ADAPTOR ON TUNNEL RAM MANIFOLD, WITHOUT SPACER, 40 DCOE WEBER 88 BHP/1088CC ROAD SPEC ENGINE

6. SINGLE CHOKE OPEL CARBURETTOR – MODIFIED STOCK ‘S’ MANIFOLD – 1088cc/72BHP

THIS PIC IS SHOWN TO ILLUSTRATE THAT OHV’S RESPOND
WELL TO CYLINDER HEAD MODS ON STOCK CAMS
PRODUCING 13Bhp MORE THAN A TWIN CARBURETTOR SR 1078

7. MODIFIED 3^RD GENERATION TUNNEL RAM MANIFOLD WITH MANIFOLD SPACER – 1273CC/110BHP ROAD SPEC.

THE SUBJECT OF THIS WRITE UP

8. TUNNEL RAM + SPACER + REVERSION MANIFOLD AND 40 DCOE 1273CC…STILL TO BE TESTED EST 115BHP ROAD SPEC.

LOOKING FORWARD TO FINISHING THIS ONE…IT DOES NOT LOOK LIKE IT SHOULD WORK…BUT IT DOES.

9. Conventional DCOE Sidedraught Aftermarket   Manifold   1196cc  80-90 Bhp

So….after all that we learn a few things,  first of all, what looks the best does not necessarily result in best power. Next is the fact that in none of this work have we achieved the ultimate performance. When we eventually finish the exercise, the best road engine power will come out somewhere around 118 bhp with good mid-range response ….. and as a race engine, 140 Bhp and more, although at that power level we may be needing some special internal bits.

Back to this 1273…

THE 993CC CYLINDER HEAD.

It may come as a surprise to 1078 and 1296 fans, but the original 993cc (1962-’66) cylinder head flows hugely more inlet air than those later engines. The change to inlet ports was made by both Opel and Vauxhall on their “B” body cars. The story is that engineers were looking for improved mid-range engine torque and response to help in the job of lugging those heavier bodies around and constricted the inlet ports midway down the port runner. On the dyno and at part throttle one can see the improvement but despite retro -fitting these ‘heads to older engines back in the day, could never feel the difference. The restriction never reduced flow at high engine speeds to the point that power was affected on stock engines but unfortunately limited flow in a tuned application. I have always used the 993 castings and a pic of the massive difference in a stock 1196 port (similar in the Vauxhall port) vs a fully worked 993 port illustrates the point pretty clearly.

THESE TWO SHOTS ILLUSTRATE THE BASIC VARIANCE. THE ANGLE OF THE SHOTS IS SLIGHTLY DIFFERENT BUT THE SCALE IS EXACTLY THE SAME.

The use of the 993cc Cylinder head on a Bored 1196 at 81.5mm making up the 1273, does come with some complications. 993 water jackets move uncomfortably close to the combustion fire ring as shown in this pic. However those that are experienced OHV tuners will also note that due to there being no dowel locations for the cylinder head, the correct positioning of the head directly opposite the cylinder bores is something that needs to be done anyway.

Both issues have been corrected by fitting offset aluminium plugs in two end bolt locations and rotating these to move the cylinder head 0.6 mm forward and 1,5mm laterally.

OFFSET DOWELS  – THE REMAINING BOLT APERTURES WERE OPENED 3MM (DIA) TO ACCOMMODATE THE HEAD MOVEMENT.

993CC CYLINDER HEAD MODIFICATIONS

I will be doing a detailed cylinder head tuning section on the OHV in future Posts including mods on the 1078/1296 heads, but the following is a summary of what works ….along with before and after pics.

Valve sizes

For all road applications on engines larger than the 993 and irrespective of cylinder head type, the 34.5X30mm valve size combination works well and pics of typically profiled valves shown. Dumping big valves into the head without shaping and porting the head properly is a waste of time and money. Better results will be achieved by maintaining valve sizes and doing the port and valve job on smaller valves. Strangely Vauxhall did the 34.5X30 thing on later 1159 and all 1256cc engines as early as 1969 and whilst it hardly improved power in production it certainly helped waking the engines up from a deep sleep when porting the head and reprofiling the valves. One warning on the Vauxhall side is that the stock valves have butt-welded stems for reasons only VM could think up…Don’t use them.

For the 993cc Engine the 33x28mm valve combination works best unless in a race application, where the 34.5 x 30 works…but with smart combustion chamber work and machining of the cylinder block top face to free valve shrouding on the top cylinder wall.

PORTS

For this piece I will stick to the 993cc ‘head, although apart from inlet port the later cyl heads can be worked the same way. Starting with the inlets and a fairly simple rule of thumb.  For inlet ports the stock 993 port dia is 27mm and there is plenty of material available to open these to 32mm. The next rule is to remove material evenly right down the port…do not attempt change the shape of the port, the thing flows excellent air just like that. Leave the bifurcation between the two inlet valves the same height but remove material on the flanks while opening the valve throats and simply blend the radii. There is a casting/machining offset which runs front to rear which will be picked up as soon as you start work….. look for this in the exh valve throats. (Pics). This requires that in the porting /reshaping of all aspects of the cylinder head this check is done first…. Use the valve guide positions as the datum for all work for a road spec head*

THE CASTING/MACHINING OFFSET IS ILLUSTRATED IN THESE PICS AND IS CONSISTENT THROUGHOUT
THE HEAD. INDIVIDUAL HEADS DO VARY BUT THE POINT IS THAT MATERIAL REMOVAL SHOULD TAKE
THIS INTO ACCOUNT

*For full race cylinder heads on any of the castings, the trick is to carefully assess this casting offset and correct all machining to the central point in the casting before starting work…That means when fitting valve guides,  do so offsetting the valve guide positions to that central casting position and cutting the new valve throats first.… and doing all work from that point. We will cover another mod on race engines where we go to valve sizes of up to 37mm X 31mm on the 81.5mm bore, a development we will be using as the basis for the high power race engine.. Don’t forget these engines will produce up to 110Bhp/Litre if some logical thinking is applied.
I may run into a little bit of flak from BMC A series fans at this point but I use the old ‘A’ as the datum to illustrate exactly how stunning the OHV engine really is. The ‘A’ went through innumerable upgrades through its gestation from the very average 997 through to the very good ‘S’ range. The point being that huge energy went into getting the engines to that point. Casting changes, Block reinforcements, specialist steel cranks, rods, bore centre changes etc etc, ad infinitim. Since then, literally thousands of aftermarket bits have been generated with the list of trick stuff that could fill a library…..But here… I am talking about practically matching the best those machines can do using the original castings, crankshafts and valve train parts from the baseline engines used in absolutely stock form from the 1962-66  originals …if that is not spectacular I do not know what is….

Exhaust ports

When first viewing the port arrangement on the OHV back in the day, the really good inlet set-up was damped by  the exhaust design which, given conventional wisdom, was questioned because the valve angle is directed away from the port exit….and here is the next lesson. … the chasm that often exits between theory and practise. The one piece of information that has come out of the Blydenstein experience on these engines is just that…the exhaust ports flow air very well. As with the 993 inlet ports, exhausts on all OHV’s need only to be cleaned, with minor shape changes shown in the pic below: For a road engine final port size at the Gasket face to be  25X31… opened evenly all the way back to the  Port as shown. What will be found is the two centre ports are marginally narrower than the outer ports and this can be corrected in opening these to exactly the same dimensions. My race engine ports are 27 X 33. There is some trick stuff to be applied in the valve throat area but I will cover this in future writings.

BIG VALVE POSITIONED PRIOR TO MATERIAL REMOVAL

Centre Exhaust Ports

From work done over the years, the point at which one fits a tubular (Header) manifold setup to an OHV (Opel or Vauxhall) is long after the 80-85 bhp threshold… and given the $ spend, don’t do it unless you do the mod to the centre port bifurcation. The stock Dual outlet castings are good and if ported and matched to decent sized secondary pipes (40mm) will be good right up to 90 Bhp, given the rest of the groceries on the engine are up to it. Yes a tubular arrangement will help but in $ per Bhp terms and underbonnet (Hood) temperatures…rather spend the money on other good stuff.

If however you do go the Header route, carry out the mod to the centre exhaust port and get to a decent four port arrangement. See pic. The first step is to move the bolt attaching holes outboard by half a bolt diameter. With some care this can be done in a home drill press. Don’t try to fit a decent set of headers without doing this mod because the centre pipes become cramped and proper matching of the ports and pipes is not possible. The rough bifurcation separator extension can be put in place before head work begins and finished with head porting to end up as shown.

Combustion Chambers

The Stock Bathtub/Wedge chambers are modified and ended up being very similar to modern Alloy Head Small Block Chevy chambers. Here is typical shot of how it turned out on the 1088….

PICS TAKEN FROM BOTTOM OF BORE 350 CHEVY EDELBROCK ALLOY HEAD CHAMBER/BORE VS
1088 OHV CHAMBER/BORE.

For the 1273 I was forced to open the 1088 chambers more than I would ideally have liked in order to increase volumes to make that 11.6:1 …but maintained the same squish area. The following pic of chambers before final polish and volume check.

Moving to the 81,5mm bore allows the chamber to be within the Bore confines, unshrouding the valves. In addition oil feed was improved to the rockers.  Head coolant flow to the spark plug core area improved by increasing the depth of the slot area immediately opposite the gasket coolant port.

THE MODS SHOWN NEED TO BE CARRIED OUT WHERE MORE THAN 1.5MM HAS BEEN REMOVED FROM THE CYLINDER HEAD FACE.

SPARK PLUGS

I have been an NGK convert for years and in all OHV road applications going back to the 60’s used the NGK B7H ‘plug
without incident throughout the time and continued this on the 1273. The colder B8H ‘plug was used for Dyno work and the Krugersdorp hillclimb. It is important to ensure that the cooling slot casting around the spark plug location is opened to ensure adequate coolant flow around the ‘plug when more than 1.5mm is removed from the head gasket face.

SECTIONED CYLINDER HEAD

The following sectioned pics of the cylinder head are shown to illustrate the casting change on the later series of cylinder heads. In the Opel case the casting was modified by simply increasing wall thickness which allows material removal. The Vauxhall engines are not the same and whilst material can be removed wall thickness is not as generous.

INLET MANIFOLD

THE PROTOYPE MANIFOLDS SHOWN…ORIGINALLY, USING ADHESIVES AND FEW PLATES AND SCREWS TO JOIN THE THREE PARTS TOGETHER PROVED IDEAL IN MAKING INTERNAL CHANGES WITHOUT HAVING TO MAKE NEW PARTS EACH TIME.

Development of the inlet manifold started on the 1088 and I promised to give an idea of why we have stayed with the single twin choke progressive carburettor. Two reasons. The first was to continue to explore theory where the plenum portion of the manifold is offset to one side away from the main runner. I have never been comfortable  with the idea of dumping the charge into what amounts to an open chamber immediately below the carb on a Twin Choke application. The change in charge velocity is significant and the task really was to find a manifold design that would maintain light throttle velocity without impacting full throttle flow and power.

As explained in the Part Two, one of the keys to maintaining low speed response in a classic engine running a long duration cam is maximise compression ratio. Most of our driving is at part throttle anyway and delaying the inlet valve closing point and longer overlap periods increase pumping losses under low/medium speeds. To recover much of that, we can do a few things…First is raising compression to the max using the Dynamic Compression ratio calculations and reducing those pumping losses at part throttle…. that is helped considerably by keeping inlet charge velocity as high as we can…hence the tunnel ram manifold. For the 1273…. I made a number of internal changes from running the 1088…. and separated the manifold again to make some more changes…mainly to runner volume and internal radii. I decided also to include the manifold spacer block to improve cylinder to cylinder distribution. Lengthening the inlet tract was likely to help anyway…..

We are extremely fortunate to still have some old school specialists in the business who just radiate competence …so the manifold in three bits was given to Piet Westraadt who welded it all together amongst characteristic good humour.

MANIFOLD WELDED & HEAD READY FOR ASSEMBLY

Let me change the thinking here for a second as well…there is another positive… and it is the siamesed inlet port arrangement on the OHV. So much blurb is written about the disadvantages of siamesed inlet porting that one only has to look at the ‘A’ series Mini and understand that low speed engine response is most definitely not an issue. Yes we all know that a 1275 has a stroke equivalent to a 327 Chevy…however, Part of that good bottom end punch is the function of paired inlet port arrangement simply because better inlet charge momentum is maintained at low speeds (More air going the through the same aperture). So far, the test results bear out the thinking 100%. This 1273 is not only responsive at low rpm at light throttle but does not “dip” the torque curve when cracking things open to WOT (Wide Open Throttle) at low engine speeds….in fact it feels like it can pull tree stumps out of the ground.

THIS PIC GIVES A GOOD IDEA OF THE PORT ARRANGEMENTS. THE INLET PORTS MUST BE ABOUT THE MOST EFFECTIVE SIAMESED SET UPS ON ANY PRODUCTION ENGINE EVER.

A departure from conventional thinking in this manifold design always fires up the possibility of testing random ideas “just for the hell of it” whilst involved in the activity, and this is the second reason for that 36DCD. Maurice and I started with the conventional thought process in tuning both the 1088 and more recently the 1273. 1300cc engines and a 36 DCD need choke tube sizes of around 22 to 24mm…for primary and secondary…we know that don’t we??  We arrived at 23 x26with power increasing till we got there….driven by the logic that “this thing is flowing air and the engine wants it”. Then the thought arrived involving gas velocity variation, driven by the need to see what happens when we switch the primary and secondary choke tubes ….3 Bhp instantly. After some further work we arrived at 109.7 Bhp at 6800Rpm helped by reducing the secondary choke to 22mm.  Nothing….and I mean Nothing folks gives the pure sense of satisfaction when one achieves better than you had hoped….and a laugh when you don’t yet fully understand why……?? More on this in future tales.

The practical result….(measured in Bhp/litre for direct comparison purposes) and the 1273 hit the Max Bhp/Litre of the OE  1078 Twin Carb SR engine of 49 Bhp/litre @ 5200Rpm …. At 4200 Rpm….plenty of good cylinder filling there.

More to the point …matched the 59Bhp max of the SR at a low 3800Rpm.  Put into seat of the pants thump, this 1273 will nail even a mildly tuned 1900 CIH.  For those running a 1078 TCarb engined Opel GT …look no further, this sort of power would give you a 120Mph  barnstormer and besides…what is better than listening to that OHV hitting 8000Rpm through the gears.

But we are getting ahead of ourselves……how did we get here….Camshaft choice next.

CAMSHAFT

At this point I don’t want this to sound like a lecture….but I have learned the hard way about camshafts and that is there is no magic bullet, anywhere. Through the years the comment “XXXcam does the job or YYYcam  is no good” are throwaway lines that have absolutely no value at all. What does have value is when a particular engine type is confined to certain race rules, with many folk chasing a similar target….a pattern will develop… and then comments like that tend to carry some weight. BUT in an environment where there is an open book and the variables are not backed up by gazillions of examples of what does or doesn’t work, choosing a cam set up that works is best left to experience, logic and common sense…quite exciting really. I mentioned at the start of this story that one does need to get to know an engine type quite well because there is a pattern that tends to emerge, broadly speaking, around the basic characteristics the engine has.  SO…this might sound counter to my opening comment here but….the OHV responds to Ford Kent profiles…if it works in a Ford Kent there is a good chance the OHV will respond. I learned that when Basil van Rooyen sent me my first TR68  way back in 1969 and then the TR71, the latter from memory being basically a Cosworth A6 and that has never changed (and resulted in the 127Bhp 1273)…again so why try to reinvent the wheel.

What has this got to do with the road spec 1273..well, remember my opening objective was to make this 60’s relevant and so far everything that has been done is just that. There are many knowledgeable, professional camshaft providers in the country I could choose from any of those, however, I wanted to do so with someone who would be a partner in the exercise rather than a purveyor of hardware. When starting out with the 1088 I was fortunate to have had Maurice put me in contact with Nelis Faure before his untimely passing. We bounced ideas around on what profile to use for a hot road application and he called one day to suggest the M7 Meissner profile from the 60’s but did warn me that for what was basically a 1000cc engine at altitude, it could be a bit on the hairy side. Used mainly on tuned 1498cc Fords back in the day I relished the idea because….and here we bring in that engine characteristic issue.. the OHV has always been able to handle “bigger” cams than popular belief would have us believe for a small engine .

From this data, the fact that it was 60’s relevant and that I had someone interested in the work, made the decision easy…whatever the outcome, it would have good historical roots and we would learn from the exercise. I then built the engine around the camshaft as best I could, rather than hoping that the camshaft would miraculously “do the job”. The story of the 1088 is covered in the “Magic 1088”…the combination worked brilliantly.

For the 1273 I followed the same discussion with Nelis and I am sad to say that during this period he was taken ill, a period from which he did not recover. Whilst I never met the man, my interactions with him over the phone and by mail were the type of communications that I will remember forever… knowledgeable, experienced and forthright…can’t get better than that. RIP my Good Man.

The outcome of those discussions was the Meissner M8…a logical extension of the thinking and set at 107 centres figured in the enlarged engine, would do the job. This was a camshaft produced by Meissner for Sidedraught applications on both the original Kent 1498 and the later 1598 X flow Kents.  At 276° Duration, up from 268° on the M7 it was, theoretically at least, the next step in waking up an OHV….Along with the other hardware changes, I expected a big improvement on the 1088 in terms of Bhp/Litre. His Son Riaan produced the camshaft and did an excellent job …..that 110 Bhp does not come from the wrong valve timing.

Valve Springs

This is another of those issues where I find it difficult to understand what all the fuss is about. This engine runs a dual valve spring arrangement where the outer springs remain as the original Opel tapered spring which is a brilliant design, helped by a Kent Cams Ford Kent inner spring where the pressures are set at 55Lbs seat pressure and 160 Lbs valve open at 10mm. This set up is safe to 9000Rpm due to the lightweight basically stock (except for the valves) valve train, helped of course by those Opel valve spring retainers and hollow pushrods .

THIS PIC TAKEN OF THE STOCK OPEL TAPERED SPRINGS – IN THIS CASE USED IN SINGLE FORM
TO DO THE CAM RUN-IN FOR THE FIRST 500KM. NOTE STOCK VALVE SPRING RETAINERS.

EXHAUST MANIFOLD

In putting together a spec for a protype race engine some years ago I had planned to build a replica race car in 1273 form….but as things panned out…life got in the way before the project moved much beyond the engine prototype stage (that 127Bhp 1273) However, during that time I had called on the services of the best pipe man in the business Etienne van der Linde to make the exhaust manifold. All I did was give him the car fitted with a dummy engine and a spec for the engine, he did the rest, so I cannot claim responsibility for pipe lengths. The final result given the space available in cramped RHD ‘A’ Kadett engine bay was a work of art. I did however learn that what he did was right on the money….and in discussion with Etienne on selecting large pipe diameters relative to the engine capacity…a man of few words… his response was a very laid back …“it’ll work.” And it did…not only on the race engine but in the role of the road 1273 as well.

ETIENNE VAN DER LINDE’S WORK OF ART

TUNING

This is Maurice Rosenberg territory and arriving at Autorosen with a car not ready to be tuned is not a clever thing to do. Maurice is a stickler for doing the basics and we managed to get all done on issues of fuel pressure as well as ball park timing and fuelling ready for work to commence. It is not surprising that when this is done it does not take long to get to the best the engine can give. We started with ignition timing set to the same values as the 1088…that amazing 19° BTDC static timing and 30° all-in at 3500Rpm…still on Sasol 95 RON keeping a keen ear for the knock monster coming to say ‘hello’. The first run clean and subsequent adjustments showed the engine to like that setting so that was locked…and we commenced the fuelling side and messing with the choke tubes.  Four runs in total and Maurice had nailed it …110 Bhp at 6800Rpm A/F ratios around 12.8 to 13… a fraction on the lean side but ideal to test for Knock.

One more test to do and this is a quick way to assess knock sensitivity.. but this I do on the road….because there is the perfect test track to do this in the east of Pretoria. The test method is something developed in my days on the GE Engine Dyno in GM engineering so many years ago. First…wear ear protectors to damp out most of the ‘noise’…you will quickly establish that knock frequencies penetrate the insulation pretty well ….if you know what you are listening for. Next step…..advanced the ignition timing 3 degrees from the Dyno optimum and raised the engine temp to 95C by switching off the fans for a while. The perfect test track is not far from my home and a piece of road that allows me to run the car up to 8000 in each gear and into top at around 6000 rpm running down hill.. and immediately into steep uphill section in which the engine at WOT (Wide Open Throttle) is hauled back progressively down to 4200rpm. Yes it is just that steep.

We are running through the max cylinder pressure area of the engine and…this is the key…due to higher charge velocity cylinder pressures will always be higher in the decelaration WOT mode than in the acceleration WOT mode. Learned this on the GE electric brake quite by chance where simply by turning the engine speed controller down on a high compression test engine at WOT, could induce knock not found at steady state. With the 1273 I found trace knock at around 4800 rpm and from an engineering perspective found this to be reassuring rather than a threat….because in a strange way it bookended all the work.  Returning the timing to the dyno figure and getting engine temp to 80c removed the knock monster….It did however tell me that  at sea level, margins would  not be as good and may require a mild timing retard in that mid-range and getting those A/F ratios to around 12.

Absolutely cannot wait to get this machine down to the coast…..

Our Original target was to match the 103 Bhp of the Gordini, equal or better mid range response and do so using 60’s tech. That has been achieved and the performance figures bear that out easily. Everything done on this engine could have been done in 1965 with considerable refinement added through proper development…A production version of this spec could have been developed easily. Given that this engine visited the Dyno only once…. with both Maurice and I having a list of “things to do” as long as your arm…we have but scratched the surface.

BTW the car is just magnificent to drive….

Next Week we will dissect the terms “pinking”, “Knock”, “Detonation” and all time nasty… “Pre Ignition”.