The Bazooka | 15 Minute Read

The Bazooka

The 70’s were a simpler times for enthusiasts. Chips were edible, maps were used to find directions and flashing a bit rude. Tuning an engine was a visceral experience…one smelled petrol, listened to the engine, read the sparkplugs and felt the pulse. In This article we go back to those times and do it with feeling.

1. Bazooka and 40DCOE

BUT……Before we get into the meat of our first article this year, some info on what we will be doing for 2018. Firstly we will be looking at more of the historical good stuff, F1, Aussie Supercars, and because it is the right thing to do, touching on electric cars with a bit of local EV history. I will cover these more consistently and will do detailed articles on both the upcoming F1 and Supercar seasons before they get going. February 2017 marked the start of this blog and I must say I have enjoyed doing it all and hope the stories continue to maintain interest.  

A Tale Of The Bazooka

2. Bazooka 40 DCOE - small pic

The first article this year has kind of ‘crept under the door’, simply because what started as a quiet little project almost as a sideline at the end of last year thinking it would not have a significant result, turned out to be quite surprising.  I have always been a ‘tinkerer’ and when Frans, a colleague of mine and fellow  petrolhead,  arrived at work with a 70’s Reversion carb adaptor….. some tinkering was required…. and figured it would be a good idea to give the device a try on the trusty Opel(See Magic 1088). I thought to publish this article because it has another important message to the more mature “tinkerers” out there…..keep those hands active folks. For me, the most satisfying years of my toil on this planet have come from getting involved with real stuff again after a very busy but brain numbing career in Corporate….. and most importantly found that the learning curve in things meaningful just picks up from where you left off…..This is for you.

For those who have not read the Story on the Magic 1088…please do….because this little engine continues to surprise. Even my good friend Maurice Rosenberg is left speechless by the shenanigans of this piece of iron and the result of this exercise will get him scratching his head a little more.

We will get to the reversion adaptor in a sec but first….the car we are using as a test bed…

4. Oliver
Kadett 1

The ‘A’ Body Opel Kadett ’63-’65

As you will have worked out by now, the ‘A’ body (Oliver) Opel Kadett is a machine of ongoing great interest to me….and this for a few reasons. Firstly, in pure engineering terms the car is a closet masterclass. When one considers GM’s overly conservative nature in the 60’s and the ancient levels of mechanical architecture available from most manufacturers at the time, the effort could have been a really cheap and cheerful shot at moving into the market……surprisingly, the General did not do that. The rear axle, driveline and engine were all something of a departure from the norm and at launch immediately shaded the major contenders in dynamic performance. The most famous of these cars is of course Richard Hammond’s Oliver and whilst the show traversing Africa was a bit of a spoof….The car did a great job of showing an inherent toughness. The second reason is that the engine is brilliant and so responsive to tuning that the work left undone in the early days now deserves its day in the sun…. an ideal package on which to test the device…..So, on-to that adaptor which I have nicknamed….. the Bazooka.

5. Bazooka

 BAZOOKA – The Reversion Carburettor Adaptor….A Hero in beating the restrictive 70’s saloon car racing rules…..this contraption explodes some closely guarded views on how inlet systems are supposed to work.  

Some time ago I decided to do a teardown of the Magic 1088. The engine has been running in the blue car now for 16 months and has completed 16000 km in that time….most of that being driven really hard and the Tacho visiting the nether regions regularly. I absolutely do not live by the theory that classic cars should be molly-coddled. I agree…no abuse…..but if it is supposed to be a performance car…give it the full beans.

Apart from the trip to the George car show from Pretoria in Feb 2017 where the machine spent all of it’s time at 130 -140km/h plus, with the tach running between 5000 and 6000rpm, I used the car extensively to work and back (130km round trip) and all opportunities over week ends. The engine simply repeated the history of the 60’s and 70’s, where our screaming modded Kadetts of the era ran faultlessly…..apart from the odd generator exploding from too much rpm. In those times the roads were clear…sometimes completely devoid of traffic and no speed limits….A trip to Cape Town from PE would be done with surprising safety, despite running flat out and the 750 odd Km done in 6 ½  hrs on the old road, passes and fuel stops included. The hilly bits attacked in 3rd gear at up to 8 grand and the little engine would simply come back for more.

6. Angry Oliver

ANGRY OLIVER RESTING BEFORE ‘THE TINKERING’.

Before doing the engine strip I decided to do a tad more work. The Bazooka had arrived unexpectedly and I figured it would be fun to see how this piece of history functioned before pulling the motor. Time was tight and the Xmas hols looming. The device was fitted purely as a ‘look and see’ exercise and was not expecting too much at all due to the fact that there were mismatches in carb to adaptor bore sizes (40 DCOE vs 45mm adaptor runners) as well as adaptor to inlet manifold bore diameter differences. Also the inlet manifold itself something of a departure from the norm. The results were surprising…..but before we get there, a little background.

I will be doing a detailed history of the device, its application and function in the racing world of the 70’s in future posts but for now just some info on why the Bazooka became a necessary tool in local saloon car racing.  This is a perfect example of how, more often than not, race engineers confound restrictive rules…… and this is a response to one of the more idiotic saloon car race regulations of our time. To understand that statement, we need to look at something  I have mentioned often before in these posts, the pre ’71 saloon car race regs….Essentially, during the latter portion of the 60’s the group 5 regulations, along with the appendix J, allowed modifications which were rapidly moving towards what amounted to a ‘free for all’. The rules, mixed with the fairy-tale homologation specs delivered by those manufacturers serious about racing, eventually saw us running turbo/supercharged versions of your average family car along with freedoms such as fabricated engine blocks…..the cars were hardly representative of what the original idea of saloon car racing was about. The Supercharged Scheckter Gordini, as well as Y151 the Meissner Escort in both 2 litre TC form fitted with that welded-up engine block and in 1400cc turbocharged form with a Boost tank in the boot, were products of brilliant engineering brains and fascinating achievements for those involved but….. really???……something had to be done to get things back on track……pun intended.  Enter the group two regs of 1971.

On the face of it, the new regs were a step in the right direction but one fundamental flaw showed this to be more of a cut and paste option than a well thought out solution to optimising saloon car racing……

……the rules required that the standard production inlet manifold and the same number of carburettor choke tubes as used on the production car should be used in the race application.…!??

For those that think that I am writing this just scratching up something to help fill the page, think again. I was incensed at the time…not only because it countered any common sense in race engine fundamentals by limiting cylinder filling but it excluded a range of cars which could have made saloon car racing far more representative of the car market than the rather stereotyped variation of product we had watched for most of the 60’s.

The most cost effective single ‘mod’ in BHP per Dollar terms of the 60’s….free carburetion….was chucked in the bin. When one considers that probably the most important issues in saloon car racing are the need to facilitate increased engine power and at the same time attempt to keep the playing field competitive …..the new rules did neither…spectacularly.

In the small classes it further entrenched the Mini/Renault hold on activities and apart from the appearance of the lone Santana1200 GX Datsun tuned by maestro Hennie, all having multiple carb set-ups in stock form….Fords were in a bit of trouble… but not for long.

At this point just consider the established small Ford race contingent. Having been allowed to run free manifolding and sidedraught  carburetion on both versions of the Kent engines in everything from Anglias, Cortinas and eventually Escorts since 1963, the gang were now restricted to what amounted to a manifold designed for a downdraught DCD Weber. Fortunately for the Kent men, the GT versions of the engine utilising that twin choke Weber carburettor had one piece of good fortune running their way ….. the manifold had fairly generous runner size. This could accommodate better air flow volumes….. so the application of a larger carburettor could bring significant benefits. The obvious choice was to move to the DCOE Sidedraught carb to give the increased flow and do so on some sort of adaptor. Conventional adaptors soon arrived, allowing larger choke tube sizes and better flow by using any of the big Weber DCOE sidedraughts…. power was up…. but not spectacularly.

7.Conventional DCD Adaptor

CONVENTIONAL DCOE to DCD/DCN ADAPTOR SHOWING FLOW            

Similarly the V6 Ford group, just beginning to flex their muscles on Capris with the triple twin choke downdraught applications under the group 5 regs, were dealt a blow with the new rules and forced to use the stock manifold. The adaptor and Sidedraught Weber/Dellorto application improved the situation here as well. Again the basic design of the stock V6 inlet manifold could flow more air, particularly with some judicious porting. Both applications worked better than the downdraught originals and very soon other racers were using the device.  Bob Thomas on the Firenza 2.5 running the big four cylinder Chevy mill being one…..But….power was still a problem….enter the Bazooka.

THE REVERSION ADAPTOR “BAZOOKA” SHOWING FLOW DIRECTION IN RED AND REVERSON PULSE DIRECTION IN YELLOW.

The inlet tract of a race car using a stock inlet manifold is a busy place. The opening and closing of inlet valves sending shock waves back and forth in that confined space akin to a rock drummer on crack…only a hundred times faster…….the Bazooka utilises these reversion pulses to ‘bounce’ off the back wall of the adaptor reducing internal flow restriction. I suppose the analogy of sending the negative energy to go play somewhere else is a good one. So much for us thinking that smooth direct tracts and porting are the only way to big power. Racers back in the day had test manifolds on the dyno fitted with rubber bath plugs fitted in the rear end of the device and moving these back and forth to ‘tune’ the  reversion pulses for best results before sealing off the adaptor.

9. Kadett Tunnel Ram Inlet Manifold

KADETT INLET….. THE TUNNEL RAM DCD MANIFOLD ONTO WHICH THE BAZOOKA WAS MOUNTED.

The fitment of the Bazooka on the Kadett was pretty straightforward from a hardware perspective with the carburettor now facing forward and the adaptor bolted to the downdraught manifold described in the 1088 write up. The pics make it look like the carburettor is mounted on stilts I know but…..is this sort of thing not just what we were all about back in the day??… cool is the current expression. I have had two 40 DCOE Webers knocking around in the workshop for some time and one of these was inspanned to do the Job. I would have preferred to use a 45 DCOE version to match the adaptor tract diameters but went ahead with what I had. The initial choice of choke tube diameters was made for me with two 32mm units in the carb. Having had much experience in carb work over the years covering development at a factory level as well as modified road and race cars, there are certain “rules” one gets to know and abide by. One of these is the choice of choke tube size and the little engine should, according to these rules be optimised at choke tube sizes of 22 and 23mm. This rule was broken pretty smartly when optimising and setting up the 36DCD downdraught on Maurice’s Dyno originally, with 20% larger area being the order of the day, along with the engine responding to transposed primary and secondary sizes. Large choke tubes can sometimes work on the Dyno but fall flat when trying to get decent driveability and part throttle response….. again the engine surprised, with not only excellent driveability but first class fuel consumption.

10. Reversion Adaptor Mounted

THE “BAZOOKA” PACKAGE FACING FORWARD MOUNTED ON THE TUNNEL RAM MANIFOLD.

 

11. Unique Carb Mounting

ABSOLUTELY UNIQUE CARB INSTALLATION…HIGH ABOVE THE ROCKER COVER!

FIRST TIME START UP

But when we got to the 2 x 32 mm tubes in the sidedraught which operate simultaneously, unlike the DCD which is progressive, I figured the machine would finally call it quits……no such thing. The choke tube size now represented an 87% increase in area over the norm and should have resulted in horrendous driveability. Yes the engine felt soggy using WOT below 2500 rpm but the part-throttle and high rpm stuff felt reasonable…surprising. From this point I worked on optimising the carb settings and with help from a few sources obtaining choke tubes down to 24 mm in various sizes and a good range of jets I learned a whole bunch of new stuff.

13. Choke Tubes

 TWO OF EACH CHOKE TUBE SIZE PROVIDED A GOOD BASE FROM WHICH TO WORK  

Firstly, setting-up idle, part throttle and pump jet sizes was eventually quite easy.    After initially trying to set this lot up on both barrels (both feeding a single plenum), I realised that blocking off these circuits on one barrel and getting pump, idle and off-idle to function on the other, allowed accurate setting-up and beautiful part throttle progression. The main circuits functioned on both and choke tube area ended at 30% up on the norm, using two different sizes and the larger tube again working best in the ’wrong’ position.  Considering the tiny engine and the mismatched tract diameters described earlier, I was expecting soggy throttle response at lower engine speeds but to my surprise it was all good. There was one characteristic not able to be resolved and that was an occasional ‘hole’ in a snap part throttle opening from idle, caused by the relatively low air speed in those runners. Two further aspects of the fitment requiring attention were the fact that no air cleaner could be fitted due to the upper rad hose being in the way and Maurice correctly pointing out that the installation angle of the carb was far too steep…both would need attention in the long run.

As far as the road test goes…..the 1088cc engine has been surprising in the form described in the Magic 1088 article, producing over 82 BHp despite being in a medium state of road tune and utilising the stock Opel cast dual outlet exhaust manifold. I was not kidding when stating that this was an attempt to produce what could have been a decent performance version of the car back in the day. Sea level performance resulted in acceleration to 60 mph in ten seconds and a max top wack of just short of 100mph.

Pressed for time to get the adaptor work done before the holidays I did not get to running the final package on the Dyno (I have a third gear test hill and use a stop watch to assess variations as best I could) and the ‘seat of the pants feel’ measuring response is a faculty still working in my old body. I then decided to complete a few quick acceleration runs to compare to the DCD set-up. The speedo in the following clip is calibrated (easy spring pre load adj) to be dead accurate at 75Mph (120 km/h) after which it goes a bit nuts and fibs by about 6 Mph at 90. I use the tacho to assess speed points and 7400Rmin in third is spot on 80Mph. Also no dropped clutch start or snap changes….

Just as a note, the bottom end of this engine is built from original Opel parts down to a set of original pistons, crank and rods. Cam is a 260 degree number, the Cyl head is an original 993cc casting, ported with bigger valves. The inlet manifold onto which the Bazooka is fitted is as noted in the 1088 story and the exhaust manifold a stock Opel dual outlet casting.

This is the result at 1500 meter altitude on a full throttle run.

FULL THROTTLE RUN  VIDEO

That was effectively zero to 80 Mph…. with 60Mph coming up in just over 10 seconds and 80 (7400Rpm in 3rd) in 18 seconds. These figures match the sea-level DCD downdraught times. Both runs done gently without being ruthless. The result translates into a conservative power increase of between 12 and 15%. So my estimated new max power figure( Sea level ) for the magic 1088 is 90Bhp +.

That folks is plenty of horsepower…… over 80 bhp/litre for a perfectly tractable piece of 60’s hardware…… that would have ruffled a few feathers in the Renault and Mini camps back in the day.  Some other notable stuff:

At a 10.5:1 compression the engine retains good knock margins and refuses to detonate or pink even when provoked…. here is snap video of mid-range response also at altitude.

PART THROTTLE RESPONSE  VIDEO

A friend of mine was muttering the other day as to why this was all being done so long after the horse, as it were had bolted, and looked a little confused …..the answer of course has two answers….firstly…’Because it is there’….. and secondly …..’because it is unfinished business’

In Summary what have we achieved? Well firstly the Bazooka works…… despite the odd design, mismatched runners, limited test time without the benefit of fine tuning on the Dyno and finally, the fact that this is not a race engine . Most notable is that from the work done so far, this device could easily be refined for road use and showed potential in the fuel economy stakes as well by achieving fuel consumption figures within 10% of the well- developed DCD application. This set-up fitted with reduced and or matched runner sizes to suite the 1088 along with cold air airbox and some Dyno optimisation would be a really good package for the street..

Where do we go from here…. Well the engine is coming out and will be rebuilt as a 1256….and we will run the car then with three carburettor apps. Firstly the DCD carryover from the 1088, then the Bazooka fitted with a 45 sidedraught and finally the 45 Dellorto split sidedraught package.  The target…..matching the equivalent Gordini…..a daunting task at the best of times……Let’s see how close we can get.

Lastly, I guess you would be asking what the outcome of the Bazooka was on the Fords? The answer to that is that it made them extremely competitive. I am doing the research for the write-up on that at the moment but from what I experienced back in the day and info found to date, power was up 10% to 15% over the Conventional DCD to DCOE adaptor. From memory the class leaders running 1300, 1600, and 3liter engines all used the adaptor,  with the 1973 Onyx production car championship going to Bob Thomas in the Firenza. Inside knowledge on that one is special because the 2.5 Chevy is a lazy beast unless one runs long runner inlet tracts and the Bazooka the only device known to wake the engine up a little whilst using the stock Weber DCD inlet manifold.

NEXT ARTICLE

I have intentionally delayed this one and finally we get to Part 4 of Fordomination. The story is a wonderful combination of corporate intent, engineering brilliance and serendipitous circumstance. This part of the story started in a shed in the UK in 1958…two engineers, a production engine and the will to create horsepower. It resulted in the comprehensive domination of most motorsport categories in the UK for nearly 10 years after that….. and then took over Formula One for another 15 years.

About the Author:

I have been in the motor industry all my life and despite spending 20 odd years with Datsun/Nissan, remain a GM man at heart.

2 Comments

  1. CraigJ January 31, 2018 at 6:07 pm - Reply

    Enthralling read, as per usual.

  2. Johann W Grobler February 5, 2018 at 9:51 pm - Reply

    I had a 1968 Opel Kadett that had a 36DCD fitted and that conversion I did was amazing!! The present 65/66 Opel Rekord has a 3.7 rear diff and the 36DCD7 Carb! I will speak to my son to take some pics showing the rear wheel spin!! I agree the engine 2500 is lazy but built like a Mule!!

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