I can't remember where I got the 40% more torque figure from. I thought it was the Cat's site but I've just checked: 2CV 39NM, Visa 48NM. That's a 23% increase, so I was quite a long way out!
I've had an aks400 and an Acad in the past: They seemed to hit an aerodynamic brick wall at about 50mph and 55mph respectively. The AK350 doesn't seem to be as badly affected, presumably because of the lower roof????
As I've managed with the Dyane box with the the M4 for the last couple of years, just having the Visa engine will be a huge improvement, so I might leave just the Dyane box in for a while and try to assess how it copes (or doesn't) with those ratios before deciding what to do long term.

You are a brave man doing all this then driving a van the best part of 2000 miles in 40oC!

Hi Daras,
a footnote on this topic...

As well as the difference in peak torque of the engines, I think that you also need to take their peak power into account.
From Jeroen's site, the strongest 602 engine has 32 bhp compared with a 652's 34.5/35 bhp, which is only 9% difference.

The next step is to use that information with this advice.
"Alternatively let's say we tune an engine and achieve 10% extra power - how much will top speed go up by?.
Speed is proportional to the cube root of power - i.e. to the cube root of 1.10 = 1.03.
So speed will only increase by about 3%."

From; http://www.pugheaven.co.uk/When%20a%20c ... tances.htm

ken

[quote="ken"]Hi Daras,
a footnote on this topic...

As well as the difference in peak torque of the engines, I think that you also need to take their peak power into account.
From Jeroen's site, the strongest 602 engine has 32 bhp compared with a 652's 34.5/35 bhp, which is only 9% difference.

The next step is to use that information with this advice.
"Alternatively let's say we tune an engine and achieve 10% extra power - how much will top speed go up by?.
Speed is proportional to the cube root of power - i.e. to the cube root of 1.10 = 1.03.
So speed will only increase by about 3%."

From; http://www.pugheaven.co.uk/When%20a%20c ... tances.htm

ken

Thanks Ken. I'm not really concerned about getting a higher top speed. I'm more concerned that the Visa engine apparently shouldn't be revved as high as an M28, (max 5750rpm if I remember correctly??) I don't want to be over-revving it at mototway speeds etc, (so I can see why the gap between 3rd and 4th on a standard Dyane gearbox would not be good on some hills).

I'm happy to go with the 2CV gears and Dyane diff. It was just that I wondered if anyone had tried the 8/29 diff with a Visa lump. I suppose that's unlikely as it was only used in AK from Oct67 to May68, Ami6 from Feb68-May68 and Dyane from Jan68-Oct68, so they are rather rare. If I didn't have one, I would have just done the 2CV gears & Dyane 8/31 diff combination, (which appears to be the best option anyway).

and to put the cat amongst the pidgeons you have an adapter plate that only lets you use Long spline input shaft (IIRC from aour short chat at reg day) so that kind of limits you to 2cv cog box with Dyane diff.

Or 2cv cogs with a 8/29 diff!
Actually, after I spoke to you, (and turned down you kind offer of a Dyane gearbox. Thank you), I spoke to Rick. He said that a short spline input shaft is fine as most of the Visa engined 4x4s use a 2cv4 gearbox. I've also got a different bracket now for the sensors that doesn't add 5mm between the engine and box.

im not down south till we go for the ferry in 2 weeks time

That's fine thanks Sean. I thought I needed a long-spline gearbox at the time, but I have actually got short-spline gearboxes (Dyane & AK), so I'm ok. Thanks enyway.

Hi Daras,
Visa engine, max (sustained?) rpm is 6,000 according to the owner's manual, so maybe check your source?

Also just realised that the 'mph per 1,000 rpm' table for a Visa gearbox is closest to that of a Dyane/Ami gearbox than any of the other (later) A series.

In mph for each gear.
Visa- - - - - - 3.32, 6.00, 9.17, 13.15.
Dyane/Ami. -- 3.08, 6.04, 9.22, 13.13

When we bought it 12 years ago, it had 155/80 tyres fitted, instead of the correct 13/80s and that 6% increase in the gearing was enough to make it feel sluggish to drive.
Shortly after my son passed his test and started using it, he got the speeding fine which proved it was capable of 'almost' 80 mph on the flat...

Since Tom's now earning and wants to buy a car which he likes driving ( ) the Visa is probably going to be scrapped soon and if it is, I'll be keeping the engine to replace the 250,000 mile 602 engine in my shed Dyane, which is why I'm so interested in your current project.

ken

Nooooo!