And how is it different to, say, the late 1980s engine I have at the moment? I have one which I've pulled out of the shed to strip and rebuild and put in my road car, and without wanting to be a geek I wondered why it was designated differently.

AK2s were fitted to Belgian built 2cvs, but the reason I know not. So your Forest single-demiser 2cv would have an AK2 but a later Frenchie would not.

Maybe just a factory indicator, as I think it was no different technically?

Martijn reckons they're quite rare. I think they have greater power output as they were designed for single choke carbs. It was a development of the AK engine which was the initial M28 style (but external oil filter-less) 602 fitted to early vans and Ami 6s. I shall consult my trusty list when I get home.

I'll be interesting to see what engine the yellow beast has when I fetch it at the weekend. Single choke carb engine, but an early French-build (twin demisters etc)

AK2 is same as AM2A, same as A06 635, just different carb. manifolds, air ducting, flywheel etc. as appropriate.

Some say early AK2 has the best crank - really just from those early ('70s) days when 2cv6 really was a 'proper' car at the head of its game.

Hi

Actually the AK2 is 28.5 hp compared to 29hp of your standard 1980's 2CV M28/1. As Roy says its down to carburation and manifold design. They were usually fitted to 2CV's to September 1978 and early Acadianes too.

It's not a Belgian thing either as these were fitted to French and Belgian built vehicles.

Some late 1960's AM2M units had bigger bore inlet manifolds and bigger jets so Citroen were experimenting all the time to get the best out of the flat twin.

Actually Sam the AK2 is the detuned version of the AM2 M version used in the Ami 6. The compression was lowered to give it more torque in the AK350. Both of these units came out in May 1968.

Matt,
a lower compression ratio does not give more torque than an otherwise identical engine with a higher CR , however it does make for a 'softer' engine, more suitable for load lugging hence their use in vans by Citroen.

As an example, compare the M28/1 ( 8.5:1) engine with the M28 ( 9.0:1).
Peak power for the former is 32.8 HP SAE against 35 for the latter, both @ 5,750 rpm.
Similarly, peak torque is 4.1 m. kg. @ 3,500 to 4,500 rpm vs 4.7 m.kg. @ 4,750 rpm.

ken

Hi Ken

Really? I always thought that. It show that every day's a school day. So why are the gearboxes fitted to the 9:1 engines have lower 1st , 2nd and 3rd ratios? Is that to help the harder engine rev higher where its higher compression is more use?

Thanks guys, so basically once my twin choke manifold and disc brake flywheel are on it it'll be the same as any other 2cv engine. Grand!