February 21st 2017 | 20 minute read

Running a blog about old cars can quite easily get to sounding like Bruce Springsteen’s ‘Glory days’ and that is not what this is all about. To make sure this all stays relevant I am going to take you on a real life adventure, a project just completed and something that will be a stepping stone to others as we travel the highways and byways of the 60’s and 70’s. The first is:

The Magic 1088.

The sixties were littered with uprated production based engines fitted to the burgeoning performance saloon car business of the period. From BMC we had the range of S engines destined for the Mini Coopers, Ford with the GT and Lotus Twin Cam mills and Renault with the 1100 and 1300 Gordini creations. These were but a few in the grand scheme of things and most front line manufacturers were in on the action….except General Motors Europe.

At the time and without direct support in some way from the General, there was little interest, so, in turn, very little was done. Apart from a few lone gunmen modifying the odd Vauxhall Viva and Kadett (locally SA) with some level of success, nothing came of it.  We can safely say that for the two OHV versions of the GM little block used in the Viva and Kadett respectively, there has been only one attempt to build a performance engine using the design to arrive at a Cooper S type performance version of the original. The Brabham Viva GTO of 1965 was that one attempt and done very well. Here was a 1200cc iteration of the little car able to match a Lotus Cortina in all aspects of performance and in the process blew the doors off the 1275 mini effort. Vauxhall put the kybosh on that quickly and as for the little Opel nothing happened at all. Not sure how to put this without sounding miffed….

When one considers that this was the heyday of performance saloons and given the real potential of these machines, not doing what should have come naturally is almost criminal. Vauxhall and Opel were asleep and, as I understand we cannot turn the clock back…., I have built a sixties relevant 1088cc German Opel engine that, quite frankly, makes one’s eyes water…

At the start of the project there was no requirement for specific horsepower but rather to put together a driveable package representative of the era that could have powered a performance version of an ‘A’ body Opel Kadett.  The base engine would be in the 1100cc range and all components to be strictly period correct, no fancy bits or modern cam profiles as well as the use of as many standard components as possible.

Early last year I built a prototype 1088cc engine using a modified cylinder head, a known mildly modified camshaft and an enlarged version of the stock single choke carburettor, using mods from the street engines I ran in the 70’s. The package was extremely successful with good mid-range torque and an estimated max power of 65bhp at around 5800rpm. (Stock is 40bhp) I had used available bits and whilst the engine suffered cold start piston slap it turned out to be an excellent start and gave good direction to the next step.

The big test on the proto engine was a radical move on squish clearance ie what was the minimum safe spec inclusive of loose piston clearances. Here is an attached pic of the piston combustion pattern on removal of the cylinder head., the squish area doing its job perfectly….clean crowns.

That was set for a max rpm of 7500 and no signs of piston to head contact.

The new engine is running tighter piston clearances, marginally above OE spec and squish increased slightly to allow safe max rpm of 8500. Pistons are original Mahle 75.34mm specced for the Vauxhall Viva engine but exactly the same design as the 75mm Opel equivalent. The pistons used were an incredible barn find about four years ago. Final engine capacity 1088cc

Crank is a stock Opel as are rods (nice steel bits) and all used in a bored stock 993cc engine block. So the bottom end, apart from valve pockets cut into the stock pistons, is made up of standard 1960’s spec components.

Knowing the free revving nature of these engines, the max usable rpm was set at 8500 simply to provide a safety factor to cater for probable missed gearshifts and the like…..Well that was the plan but the final outcome resulted in 8000r/min being a realistic top rpm limit under full power….amazing but true.

Cylinder head modification on the OHV have become pretty generic for me and I settled on the 34.5mm vs 30mm Inlet/Exhaust valve combination finalised on old road cars so many years ago.. This is the specification used on all Vauxhall Viva engines from the 1159 (70.7cid) Intro in 1967, whilst Opel ran 32/28. Porting on the inlet side is straightforward and ports are opened from the standard 993cc 28mm, to 34mm. Combustion chambers, learning from the 1272 race engine, have been kept compact to increase squish area. Exhaust ports, a strong flow feature of these heads, simply opened by about 30% and the radii cleaned and blended. No port reshaping required except for the valve throat area where multiple valve seat angles are employed as on the inlets. Pics of the final head:

Firstly compression ratio linked to camshaft selection. I had run every level of CR on the OHV engine from 9:1 to 12:1 in differing road and track applications. The learning curve was bumpy but I soon found the very strong link this engine has to camshaft application and dynamic CR. In addition to that, the test on squish clearance was to utilise this result in a combination that would do the following:

1. Provide maximum detonation/knock resistance
2. To allow the use of camshaft timing in the order of 255°/260° From experience this level of cam duration on this type of engine can, if properly timed, give the balance of low speed driveability, mid-range response and top end power required for a good performance road car application.
3. Optimise the dynamic compression ratio to ensure that cylinder pressures are maximised within the knock envelope in the driving range. Set the static compression ratio to support this requirement.

Now the above is a bit of a mouthful in itself but….we need to add one further variable to the mix and that is the choice of carburetion…..note….not EFI. The decision was simple, why consider anything other than the 36DCD Weber. I am not a SU or constant depression type carburetion fan, I just prefer fixed venturi carburetion and to be period correct. That is what we used back in the day, so don’t get complicated. Perhaps I should just say that if it were not necessary to be period correct my choice would be a set of split Dellorto side draughts incorporating a power valve. As it turned out, the next step in the build of this extraordinary engine came about simply because I had no availability for a properly engineered inlet manifold for either. I had to make one… and the DCD was it.

The final outcome was to be astonishing and even if I say so myself, one of the finest bits of compensatory engineering I have ever been involved in. The best ideas attack you in the most unlikely places and after scrounging a throw away Peugeot 36DCD manifold adapter from Maurice Rosenberg to use as the base plate for the project, was driving back from work one day and passed a Kadett D (first FWD Kadett)….there was that lightbulb moment.

Those first FWD Kadetts used the same pushrod engine in 1200cc form in the base models and I had two of those inlet manifolds in my ‘junk’ box in the garage.  To cut a long story short this is what happened. The tunnel ram was born.

Why was I so enthusiastic? Well for those that have done this type of stuff before you will understand that some ideas come and go and one or two just stick and scream “Do it…a gut feel that come hell or high water, this will work”…. It Did.

I still don’t know exactly why but a manifold having an offset primary running into a secondary blasting straight down into meat of the channel……it well just felt sufficiently different to either ‘bomb’ heavily or lead me on an adventure rarely encountered. There was no maths in this other than calculating the volume increase required in the runners to get to 95bhp (a 1272 version of the engine is on the cards), up from the stock 1200’s 60. I cut the two 1200 manifold in ‘half’ lengthwise and offset each so as to arrive at an assembly of the two wider halves that would entertain about 50% more flow. That done I added the 36DCD adaptor, Bolted & Glued it all together. More of this later.

Having come from an engineering environment in which a large part of the learning curve came from the GM engine plant at Aloes in PE, I could never understand the anachronisms that existed in engine manufacture at the time. We could build an engine requiring tolerancing in the piston to bore area of less than a thousands of an inch but in other performance enhancing areas, things were as rough as bears backside…but just as controllable as the piston fit requirement. The issue of blueprinting an engine was a reality, the variation in engine performance between engines was real and much of the improvements seen on modern engines are in exactly those areas today

So in the build of this engine I use that thinking to spec a package that could have been built exactly like this one in the old days. What am I talking about? Firstly, tolerancing in areas critical to stable ignition/cam timing. Crankshaft end float tight, camshaft end float tight, Distributor drive gear clearance minimised. These all end up resulting in absolutely mimimum spark scatter. Linked to similar controlled clearances like  piston to head clearance on each cylinder, it simply results in an engine that responds to tuning and if packaged correctly gives consistent results.

The next move was to tighten up on cam timing. I threw away the ratchet plate tensioner used on the more modern versions of the engine and replaced it with the original hydraulic unit. One mod. The unit converted to a manual adjustment to prevent hydraulic flop. In addition the slack side of the chain has no runner. So the wear block built into the cover was moved to provide tension on the slack side. That camshaft was going nowhere.

NOW….the choice of camshaft. What does one do when you have a fifty year old piece of Iron and the only cam grinders you know are purely commercially inspired with no real interest other than the commercial proposition?. You find someone that is driven by wanting to do a steller job. I found that person in Nelis in Cape town. What a breath of fresh air. One telephone call and a few E mails and we have nailed the possibles down to a few and, amazingly again, the profiles are out of a little black book from the sixties.

One thing quite surprising about this OHV Opel engine is the ability to live with ‘bigger’ cam profiles than one would expect for such a small capacity. I had stumbled on the use of Cosworth based profiles in the late 60’s and never moved back. The race profile ended at an A6 and the road profiles other A’s, I seem to remember an A3 for the road 1000 back in the day. Nelis’s suggestion is surprising, “what about an original Meissner” This was a local profile used very successfully on quick 1498 and 1640 versions of the Cortina GT engine back in the day and at a duration around 268° was a little wilder than I had planned. In the 1088cc OHV it may be a handful. Valve lift was OK at 9.6mm. ….That gut feel was still running wild and somehow I had the thought that if I got the dynamic CR right we would be OK on both low speed and mid-range response. We selected an appropriate Lobe split and held our breath.

Valve springs. With the target safe rpm set at 8500, readily available aftermarket springs are just scarce and if available, out of the budget. So the set up was to use the 1200 conical outer from the stock Opel and the Terrys based inners from the race engine. Each spring was individually tested and put together in matching pairs to arrive at he required seat and valve open loads.

The Engine block and cylinder head prep. Old parts need TLC and the first task was to de-scale the block/head water channels and get back to virgin material. When looking for max detonation resistance the need to channel heat away from the working face is critical. This done, the block had been bored to the new piston clearance spec. The piston/ring package was original and not being happy with previous hone jobs from this engineering operation decided on a flex-hone alternative which I know is done brilliantly by Maurice Rosenberg. This was the best decision possible, as once I did get to starting the engine, the rings sealed in minutes….no blow-by and stellar cranking pressure.

Choice of exhaust manifold? This was a bit of a head scratcher but in the end sense prevailed and I went with a known performer rather than a fancy tubular arrangement. The cast stock dual outlet unit off the 1200 FWD engine is known to give good flow performance and a small mod to fit the centre port to the modified cylinder head was needed.

Oils. Old engines need Zinc and modern oils are zinc free so camshaft lobe wear is guaranteed if one does not have a working alternative.   Fortunately a local oil manufacturer makes a synthetic mix which so far has done the job. Just to be sure, I used an additional shot of the Zinc additive during start up and the hardening phase of the newly ground camshaft.

Dynamic compression ratio. Despite working at an altitude of 1500M I have calculated DYn CR using sea-level values This because I want to optimise a production engine at sea level not at altitude. I had, on the proto engine run a dynamic CR of 8.9:1 and found this to be satisfactory at altitude but figured it would be borderline at sea level. The new cam gave an IV closing point of 6° later with a static CR of 10.5, slightly down on the 10.8 of the proto giving a dynamic of 8.6. This was the right move as a recent trip to the coast needed only a reduced vacuum advance curve to prevent light part throttle knock at around 3000rpm, full throttle was clean from idle.

In a nutshell with 95 RON being best octane available at both coast and sea level am sticking with the current set up knowing that the package would be happy with a Static CR of over 11:1 if optimised to 5000ft… Now that is quite something when one considers that we are working with a design out of 1961…56 years ago.

Back to the manifold. On start-up I utilised the modified stock carburettor (enlarged choke tube) and modified stock inlet manifold off the proto. The new 1088 was one of those engines that was ‘right’ straight off the bat. I don’t think I did more than 80km before giving it the full beans and found a sizeable improvement against the clock compared to the proto. Everything was better and when one considers the 28mm choke tube running on a dinky 1088cc engine and 268°cam, low speed response and the lack of low speed ‘up throttle bump’ were staggering. The engine would pull strongly from 1000 to around 6800rpm in third (good test gear) and naturally easily to 7500 in the lower gears. So good, I challenge any of the engines of this era to perform this way with similar mods….I could not wait to get that DCD going.

The above pic is a shot of the basic manifold prior to final shaping and prep. Note that the primary barrel is on the outer portion and secondary immediately above the inlet runners. This posed an interesting debate as to tuning possibiliies.

Testing and dyno runs. Weber DCD

A first shot stab at setting up the carb was based on historical settings with conventional primary secondary choke tube config ie smaller primary. First trials were difficult because the initial manifold sealing of the two halves was not 100%. Once that was sorted and the original Opel air cleaner  modded to fit the weber, stability returned and the engine showed its true potential.

To avoid advance curve mismatch, knowing the max timing point to be 30°, I chose to start with the race car distributor which has only 10° of mechanical advance, so static timing was 20° I figured that if I was careful, with progressive retards of the distributor off the 30 max I could quickly gauge the sensitivity to part throttle and full throttle knock below 3500 r/min and build that into the final distributor. This is where the engine threw its first curved ball. Despite the 20° static advance there was no knock….anywhere…at full or part throttle. I tried to find the knock point and gave the engine a dose of 24° static…still no knock.

At this point I decided not to be smart, trust the numbers and get back to the known 30° max and start some ‘seat of the pants’ testing. I have decided not to use expletives in any portion of my blog, but this is a situation deserving of some sort of verbage…The engine’s response at those ignition numbers was startling, so I left them as is and concentrated on carburetion. The first task was to evaluate the subjective difference between the stock carb/manifold  and the Weber/untried manifold.  The engine had lost snap below 2500rpm but remained extremely driveable and could keep up with modern traffic flow even using part throttle in the sub 3000rpm range. Whilst it had lost the bite of the stock set-up at low rpm, it still had excellent response and as a replacement to that introduced noticeable ‘kick’ from 2500.

The next step was to try the Full throttle @ low rpm test and measure the expected ‘up throttle bump’ which normally ensues from closing the throttle to around 20% after a brief stab at WOT from say 2000 rpm. NOTHING, a clean bill of health!  Despite the 23/24mm choke tube selection (slightly big for a dinky engine) the engine responded smoothly without a hint of bogging or torque loss of any kind.

Top end power was excellent with 7500rpm attainable easily in the three lower gears, in fact 1^st gear was so responsive that any delay would result in a 8000 showing up on the tacho in no time at all.

When one starts with the manifolding being distinctly ‘odd’, the need to experiment and deal with those powerful gut feel forces becomes overwhelming…So larger choke tubes installed immediately to provoke the little engine, 24/25 mm just improved top end response with no change in low speed behaviour. Then the grand switch …primary to secondary 25/24, all changes incorporating required jet adjustments. The engine felt better so went to a 26mm primary. My view of this sort of thing is to do the provoking to see what happens, the engine ‘felt’ even better. I could not get the engine to do anything stupid and so the next step was to go to the Dyno to verify and or find an alternative.

I did, and the final choke tube sizes ended at 26/23 with a 4 bhp power loss when fitted in the conventional 23/26 prim/sec forma. Mixtures were maintained at set values during the various tests. Not only was the engine producing good power at 82 flywheel horsepower @6250 Rmin (40 Stock) but take a look at the torque curve. The magic 1088 produces 85% of max torque from 2800 to over 6500rpm…..and feels like that on the road. The curve looks very much like a modern turbo engine.

Road performance. At the coast the car ran a 0-100  in 9.3  seconds (21.5 stock) and a WOT max speed run pulled 6800 rpm = 161.5 Km/h (120 stock). For a first stab at building a production spec performance engine, this package would be a handful for any of the established quickies of similar engine capacity.

TRIP TO GEORGE CAR SHOW.

After all this work there was the need to get to know the package a little better so a 3000Km round trip to the George Car Show in the Eastern Cape sorted that out. One word…Stunning. When one considers that the standard 993cc package with a tiny 40 bhp needs a gearbox to traverse the scenery, this does not.  Once in 4^th gear this machine needs a gearbox only to move from rest. Cruising at 120 km/h (5000R/min) was a doddle and with many full throttle blasts to territory far north of that averaged 7.1 L/100 for the whole trip. Many sections of the road, I would estimate fully 30%, the cruise was at 140.

For a 54 year old car to eat up the road in synch with modern cars is the measure of just how well this package works…..I now will not be period correct … I need a five speed gearbox, as the thing has far too much grunt in 4^th…..& too much rpm!!