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.
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.