9:1 upgrade from 8.5:1

[Lomax76]

Back to the ratio increase, it must not be forgotten that the higher the ratio the higher the octane ratio needed, if you plan to run on 95 better to stay with 8,5:1.
About the carburettor why not to stick to the SOLEX CSIC 26/35 I use the 26-18 and run @ 55MPG, I easily drive @60m/h on the gas flow, not flat out.

[Ken Hanna]

Yes, to both comments.
This article is well worth a read, especially the part about needing to retard the ignition timing from the ideal setting if using a higher compression ratio.
http://www.daytona-sensors.com/tech_tuning.html

Note that octane ratings in the USA are about 5 to 6 points lower than those used in the UK.
http://www.pistonheads.com/Gassing/topi ... UK+%26+USA
( Posts by 'WES77Y' & 'sunoco69' )

Citroen recommended using 98 octane in those A series engines with 9.0:1 pistons, with 95 octane acceptable for 8.5:1 engines, allowing them to use the same ignition timing for both types.

Also, it must be over 10 years since I've had to do anything with the Solex carburettors on our three 'daily-driver' Dyanes, apart from a minor tweak of the idle mixture screws at MOT time(s).
That's the beauty of fixed jet carburettors with a good in-line filter fitted; no needle to wear out or jet to centralise and no oil reservoir to top up...

Back to the ratio increase, it must not be forgotten that the higher the ratio the higher the octane ratio needed, if you plan to run on 95 better to stay with 8,5:1.
About the carburettor why not to stick to the SOLEX CSIC 26/35 I use the 26-18 and run @ 55MPG, I easily drive @60m/h on the gas flow, not flat out.

[QFAD]

Ref bonnet clearance between the top of the Solex and the bonnet - QFAD has less than 20mm. Even a pancake filter prevents the bonnet closing - I have managed to secure the bonnet, but it still sits on top of the filter housing. The pancake filter can not be not very efficient (airflow) and I know some folks run without an air filter - but I did not want my engine to ingest all the dust and debris on the Wiltshire roads...

This has been my main impetus to fit an alternative carb - if I could retain the std Citroen inlet assembly, especially the rubber elbow, I would be content.

So a search for an alternative began and many folks on this forum have been very helpful. I originally had a HS2 (1.25") carb on my 602. The tuning was going well with very good driving experiences. However now that I have a 710cc engine I have selected the Hif38 (1.5") carb as more appropriate.

It is also an interesting quest in its own right - learning new stuff is always good!

Steve

[Ken Hanna]

Steve,
I guess that's why, with one make of aftermarket chassis, the front crossmember which supports the engine is set about 10mm lower for 'Lomax specific' versions...

Ref bonnet clearance between the top of the Solex and the bonnet - QFAD has less than 20mm.
Steve

[Lomax76]

On my 223 fit with a pancake it is ok from air intake and clearence point of view but I am not confident with the efficiency of metal mesh for air filltering. ... I don't think foam will do the job specially with the breather fitted in!

Ref bonnet clearance between the top of the Solex and the bonnet - QFAD has less than 20mm. Even a pancake filter prevents the bonnet closing

Agreed it is a way to explore other routes, however it is also known that:
"Experience is like toothpicks: noone wants to use them after youhave.”
Roland Dorgeles.

It is also an interesting quest in its own right - learning new stuff is always good!

[Armando]

As promised, here are three jpgs showing the state of the nearside barrel:

(a) Middle jpg: is this degree of scoring normal/acceptable?
(b) Top jpg: the top of the barrel, at the TDC position, shows a 'rusty' ridge
(c) Bottom jpg: the bottom of the barrel is nice and flat - no lip

It looks like, during the long period of inactivity, gravity has acted on the piston such that it remained in contact with the bottom of the bore lining; there may have been a gap between the top of the bore lining and piston, where the liner has 'corroded'.

Thoughts?

(get a new set of pistons/barrels )

[QFAD]

10mm!

Ken I reckon I need at least of 30mm addiational clearance to fit a proper radiused elbow as per the original design - you know it is just going to supply loads free flowing air!

In my efforts to seek a solution I checked out the possibility of fitting a Le Patron bonnet (this has a flat profile as opposed to the Lomax profile tapering down to the grill) onto a Lomax - unfortunately it does not fit without major reworks. I considered a twin carb set-up, but the single carb solution instinctively feels right (econamy and simplicity); so the SU option is my choice.

Thats not to say I will not be intouch to discuss a new chassis at some point - it is on my list, but probably in a couple of years.

As to your pics Armando - is that pitting on the upper surface of the last photo? If yes it does not bod ewell...

[Armando]

10mm!

Ken I reckon I need at least of 30mm addiational clearance to fit a proper radiused elbow as per the original design - you know it is just going to supply loads free flowing air!

In my efforts to seek a solution I checked out the possibility of fitting a Le Patron bonnet (this has a flat profile as opposed to the Lomax profile tapering down to the grill) onto a Lomax - unfortunately it does not fit without major reworks. I considered a twin carb set-up, but the single carb solution instinctively feels right (econamy and simplicity); so the SU option is my choice.

Thats not to say I will not be intouch to discuss a new chassis at some point - it is on my list, but probably in a couple of years.

As to your pics Armando - is that pitting on the upper surface of the last photo? If yes it does not bod ewell...

No - on the last jpg what appears to be pitting is actually dust/dirt - but please see the top photo.

[Ken Hanna]

Steve,
a special owner (and serial builder) who lives near me ( Dennis Cawston) persuaded me to sell him an intake rubber which I 'think' came off a GS.
That was much shallower than the 2CV elbow, with an oval fitting at one end, perfect for a Solex 26/35.

67 and counting, btw.
In order to have some free time in my dotage and to spend time with our grandson George, I've already started offering chassis kits to those folk who have sufficient confidence in their welding ability to stitch a chassis together.
Virtually every part is laser cut now, so it's fairly straightforward...

Ken

10mm!
Ken I reckon I need at least of 30mm addiational clearance to fit a proper radiused elbow as per the original design - you know it is just going to supply loads free flowing air!

Thats not to say I will not be in touch to discuss a new chassis at some point - it is on my list, but probably in a couple of years.

[Ken Hanna]

Armando,
if I was you, I'd get hold of a cylinder hone and give the barrels a bit of a tickle, then a decoke, valve grind, new stem seals and reassemble with new rings.
The hone, used at slow speed in a battery drill and worked up and down each barrel, will remove that rust which has formed whilst the engine has been standing and give the correct 'cross hatched' finish required.

Note that if you do decide to shorten the barrels to increase the CR slightly, take no more than 0.3mm off the top spigot.
Removing material from the seating at the bottom of the barrel will force the top rings to cross any slight wear ridge, then even the stepped 'ridge dodger' rings which are supplied with some sets won't save things...

Ken
p.s. Just rediscovered this, from Roy at ECAS some years back.
http://www.ecas.co.uk/2cv_tuning.htm#A10

As promised, here are three jpgs showing the state of the nearside barrel:

(a) Middle jpg: is this degree of scoring normal/acceptable?
(b) Top jpg: the top of the barrel, at the TDC position, shows a 'rusty' ridge
(c) Bottom jpg: the bottom of the barrel is nice and flat - no lip

It looks like, during the long period of inactivity, gravity has acted on the piston such that it remained in contact with the bottom of the bore lining; there may have been a gap between the top of the bore lining and piston, where the liner has 'corroded'.

Thoughts?

(get a new set of pistons/barrels )