Hi everyone !
I had to remove my 230hp turbo engine from my car (thanks to new french tech control
) and I'm working on a "near genuine but spicy" 2.2 engine
. Sooo, I'm looking for a good camshaft.
Everyone is talking in great worlds about Holbay 58C one, but it seems that no one can sell it now ...
I have most of sport camshaft specs ( S, Politecnic, Sodemo Gr4, .....) but not this one's !
Is someone can tell me the specs of this camshaft ? I think it would be the best choice for my car ...
Hello philiping, The first thing you need to realise is that the Matra marketing department lied about the horsepower of the original engines. The engines were tested by the factory for the original specifications and these figures were in kilowatts as is normal in France. A standard 2.2 produced 84.32 kw, the 'Prep 142 ' was rated at 101.4 kw and the genuine 'S' was rated at 100 kw. (Check the certificates of Conformity) However the marketing people then used a 1.4:1 conversion factor for horsepower to kw which is wrong and this gave misleadingly high horsepower figures. Also they did not state whether this horsepower was PS or bhp, but since they generally talk of horsepower DIN, that is PS... NOT bhp.
If you convert the original kilowatt figures recorded to bhp correctly, then the standard 2.2 produces 113 bhp, the 'Prep 142' uprate gives 136 bhp and the genuine 'S' produces only 134 bhp. All this has been on my website for some years.
The Holbay reprofile gives a lovely camshaft which easily produces as much performance as a genuine 'S' and on the road is better. I know, as I have driven both for many years. Furthermore the Holbay reprofled cam can be used with either a 'twin-choke' down-draught carb. or two twin side-draught carbs. and the only real difference is the fuel consumption. On a down-draught carb. it will easily top 31 mpg on the open road, and not generally drop below 25 mpg even around London! (that is where I live so I have proof if anyone needs it) With two twin side-draught carbs. the consumption will always be slightly less on the open road, but around town it can drop below 20mpg!
I once roller tested my Murena with Holbay 58C cam still using the down-draught Solex, and it gave 140 bhp, so you can see it slightly out performs even the 'Prep 142'. Unfortunately Holbay no longer exist, which is why you cannot get a Holbay reprofile from them, but that is not to say you could not get a similar reprofile from someone like Piper or Kent cams. It is simply a 'fast road' camshaft reprofile.
I did not like the 'S' profile as it has more lift but less duration which means the ramp angles are steeper, and since the lower lift but longer duration Holbay profile produces more power I decided a better cam would have more lift as well as longer duration. Working with Piper we came up with a high lift long duration profile fast road cam which produces a superb engine as I know from having driven the first one I built.
I should also point out here that the Politecnic 'maxi-route' profile which originally appeared to be a Gr.4 cam in their leaflet (of which I have a copy somewhere) is unlikely to be as good as it has a similar duration but less lift. (7.75mm lift compared to 8.30mm lift for our Piper and 296 inlet/300 exhaust degree duration compared with 298+ degree for both inlet and exhaust duration on the Piper, which they measure from 10 thou open to 10 thou before closed)
Again, I have driven a Murena with the 'maxi-route' cam which is stamped 150cv suggesting it is actually rated 150 horsepower but with optimum set up can give around 155 bhp, and the Piper is better. This is with both using the standard valves. To get a true 184 bhp Piper say the engine would need to have a lot more lift (maybe 9mm cam and over 12mm valve) and bigger valves or 4 valves per cylinder, higher compression, combined with optimum fuel feed from big carbs. or fuel injection and unrestricted intake, and even those special ROC engines only gave 200 bhp with a £2,000 special cast twin cam cylinder head and race build and preparation!
Finally, if you have a standard 2.2 engine, then you should get the flywheel lightened as it is too heavy for the Murena because it has the standard Tagora 2.2 flywheel! The lightened flywheel improves pickup noticeably.
Roy
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