I should add that the 8.5:1 set I removed weren't in the best shape.

OK 9:1 it is then, I'll try the Dyane box out and see for myself which I think is better.
How about the carb' jetting, Can anyone tell me what I need? Is there a 105 main jet? I'm also wondering if it's worth the faff to rig up the forced air contraption?

IME, no. My first 2cv went onto a Dyane chassis after meeting a dry-stone wall at speed - so, of course, I wanted to use the turbo tube...

If you use the Dyane setup, the tube is very tight around the upper wing retaining nut, and the air filter tight against the inner wing. Fitting and removing the tube is a bugger, and needs to be removed to get at that nut. Forget changing that plug with the wing on - you can barely see it.

So, of course, it ended up being run with the tube off as much as on. No noticeable difference.

I agree with Adrian, I've driven dyanes and 2cvs, and Ami8s, I couldn't tell a difference. I'm sure if all engines were constantly kept in optimum condition and every parameter were kept strictly the same, then 9:1 would be a bit quicker. But you're unlikely to notice it. The same for the turbo tube.

For my carb jets one of the jets was taken out (main) and simply just drilled the hole bigger (0.7mm drill bit) (guessing?)

I don't think the forced air does much tbh I've got a massive cone type air filter straight on the carb and i think that just makes more induction noise than anything really

The table at the top of this page is quite a good summary, bearing in mind that a standard 8.5:1 A series engine should give around 150 psi at cranking speed, compared to 175 psi for a 9.0:1 engine.

< http://www.nightrider.com/biketech/hdhe ... ession.htm >

Harley engines must have more overlap of their valves, which is why the CR and cranking psi figures for the bikes and our engines are not directly comparable, but I'd agree that 'around' 9.0:1 is a good choice.

'Blown induction' has the advantage of providing cooler air to the engine, by drawing it from the front of the car instead of from under the bonnet, but the increase in power is much less significant than that available from an increase in CR.

However, because carburettors are sensitive to air velocity, not pressure, the slight increase in air pressure from blown induction will be enough to weaken the mixture, because the level of fuel in the emulsion tubes is depressed by that increased pressure.

So, unless the carb is rejetted to suit, blown induction may well be counter-productive.
Probably explains why Adrian noticed little or no difference...

ken.

Our S plated Dyane was by far the quickest A series I have ever driven - with a 9:1 engine and forced induction it could easily hold 80mph all day on the motorway - A good set of 8.5:1 pots are almost as good as 9:1 and often more easily available and I believe are better suited to low octane fuels. I rebuilt Scoobas 2CV with these and it made a massive difference over the old cylinders and I guess any new barrels and cans will be better than an old worn set of originals - pays your money, takes your choice etc...

And after 5 yrs playing race car the blown air is a pig to set up, get better results with normal set up on the race car- on overrun and quick pickup it causes real issues for the carb.

Nail the dyane box will make a differance first 3 gears lower so you think its going like a bat out of hell, longer top means you can go faster in top, till you get a head wind or a hill.

As said in the other thread a good 8.5:1 will perform almost as well as a 9:1
heavy flywheel is a joy to drive its almost unstallable the engine becomes an inertia unit, spin up the flywheel and drop the clutch and you are propelled forwards like you are on the end of an invisible bungee rope. the trend toward the lighter flywheel is due to racers using them for a faster pick up and throttle response, ok on the track but trundling round in the real world in a relaxed heavy flywheel car is a joy.

The carb came from the same Dyane as the engine and the induction setup... It was, literally, just a Dyane with a 2cv shell.

Indeed, I always advise people against them, mine goes like stink but you don't half miss it when you come to a long hill. That is unless you're already trundling and you want to overtake something fairly slow and you want to overtake, the lightened flywheel can come into its own then.