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Technical Tips For The 346 and Star

Advice and guidance for the maintenance of Armstrong Siddeley cars. If you have other technical advice for Armstrong Siddeley owners you would like to share here, please contact

Please note, technical tips are given by individual members and ASOC Ltd does not warranty the accuracy of them or endorse them in any way.

More tips can be found by using the links to the right.

Lubricating 346 hinges - Supplied by Keith Dewhurst

Did you know that the slotted domed head on the top of each of the door hinges on a 346 is actually the top of a screw head? If you unscrew and remove these screws you will find the hinge pins are hollow almost to the bottom and are in fact cross drilled to allow the cavity to be filled with oil and the oil to penetrate and lubricate the hinge? Be aware however, that after a high speed run with newly oiled hinges a bit of oil blow back aft of the newly oiled hinges on to the back doors is to be expected, so don’t do this the day before you take a bride to the church!

Boot leaks and boot lid rust in the 346 and Star - Supplied by Keith Dewhurst

The factory obviously intended that a little rain water would enter the rear well of the 346 boot as they provided it with two drain holes with rubber drain tubes (now usually lost). The trouble is a little water also gets into the inner structure of the boot lid and cannot escape. All of this I found troublesome, so I sought to find the source of the ingress, (me in closed boot with torch, friend with hose pipe outside). What I found was that water entered around the Sapphire script badge or badges, boot handle and number plate chrome trims. Most of this dripped off the inside of the lid in to the boot rear well around the open area adjacent to boot handle fixings, some however just went into the boot lid lower structure.

To stop this I fixed large washers with sealant under the script badge fixing nuts, fitted a new home made gasket beneath the boot handle and applied sealer all the way around the number plate chrome trim and the chrome trim above it. For Star owners I would also recommend that they use a sealant around each of the fixing studs for the chrome trims that attach to the edges of the boot lid. To be doubly sure I made a closing plate to fit in the area immediately beneath the handle and extending to the part of the boot where the boot light is fixed, to direct any slight ingress in to the lower inner structure of the lid.

However, what I also found was that there were no drain holes in the bottom lip of the boot lid. I drilled a few 5mm holes, 4 I think, across the bottom of the boot lid to let water escape. I also drilled two small holes in the inner skin (be careful not to puncture the outer skin) of the boot lid at the corner above the back wings where the boot lid turns to go over the car behind the back window. I have noticed a lot of 346’s and Stars develop bubbling here. In my case some dry red dust escaped when I drilled. I then used an aerosol of Waxoil and sprayed the entire contents of the can in to these two holes. I added more Waxoil though the aperture on the inner face where the boot light fits until I had Waxoil running out of the newly formed drain holes. Ever few years I re-inject all of this and to date I have had no boot leaks and no bubbling on the boot lid.

346 Mk II brakes - Supplied by Keith Dewhurst

The braking system fitted to the MKII 346 is superb; I have traversed the most demanding of Alpine passes with no fade and every confidence in their operation. However, it is often difficult to get ‘a good pedal’, that is, one which is firm and with not too much travel. Usually this is a problem with the bleeding of the system and in my experience the system always has to be pressure bled after any work on the hydraulics. Recently one thing I found on my high mileage car did surprised me by how it affected pedal travel. I was fitting some of those excellent reconditioned sleeved front wheel cylinders that the Stores now carries and what I discovered was noticeable wear on the sides of the large bolts that hold the cylinders in place and on to which the rear end of the brake shoe rests and pivots. Carefully repositioning these so the shoes bore on unworn portions noticeably reduce pedal travel.

How to deter rust in 346 ‘A’ posts - Supplied by Keith Dewhurst

The ‘A’ post on a 346 is a somewhat complex multilayered structure. The face you see when the door is open and onto which the door catch is attached is a small, rectangular box section. On a number of cars I have seen rust bubbling develop here. At the top of this section there is a largish and approximately rectangular rubber block that the door closes onto in the area of the wooden interior door trim. This bock is secured by a steel plate held by 2 screws. What you will find if you take this off is the open section of this part of the ‘A’ post structure. This is another good area to keep filled up with an antirust product such as Waxoil. Keep whatever mixture you use fairly thin however, as the solution will have to squeeze its way past the compressed area of the double skinning around the door catch to reach the lower sections. If often takes a few days of toping up to get the whole box section full. From time to time I top up these sections rather like checking the back axle oil!

346 automatics jumping out of reverse gear - Supplied by Keith Dewhurst

Some 346 automatics have a tendency to jump out of reverse gear, especially when the engine rocks taking up the load when moving off. On my 1956 346, after fitting an exchange gearbox, this became a problem.

Now whilst there are variations between different generations of automatic gearboxes as used in the 346, as far as I know the gear selector mechanism in the box is the same in all boxes, each gear selection position having a positive location. For reverse it is this locating mechanism in the box which holds the lever on the steering column in position, the quadrant merely having a sloping section to guide the lever to the reverse position, but no positive locking in the position – or so I thought. My assumption is that my exchange box was weaker at holding the selector mechanism in reverse when compared to my previous box and that this was why a problem had now occurred.
Anyway, as I also own a 1955 346 Automatic, I decided to have a look at this. To my surprise, as this is an earlier car, I found that the brass arc which fits beneath the Bakelite cover on the column selector mechanism and provides positive location for neutral, normal/fast and fixed second as on the 1956 model, had a piece of brass riveted to it to create a step and therefore positive location for the reverse position as well. Looking at it closely this looked to me to be an original fitting. Moreover there were subtle differences in the metal case of the selector quadrant, which prevented the brass arc on the 1955 model being fitted to the 1956 model and vice versa.

As far as I could tell the box in my 1955 car, which I think is the original box, had the same resistance in the mechanism when it came to moving in to and out of reverse, as the new box in the 1956 model, which was incidentally quite a late numbered box. Also the 1956 model had new engine mountings and less engine rock than the earlier car, so it did not seem to be this causing the problem. So what causes the problem on the 1956 model and why an earlier car has a modification not on the later car remains a mystery to me.

However, the solution was easy. I drilled and tapped a small hole into the brass arc just above the reverse position and fitted a setscrew and lock nut, adjusted to protrude just enough to lock the lever in reverse. Pushing the lever away from the driver, as you do for other gear-changes, allows the lever to slip out of reverse easily, but without this it is locked firmly in position. Hey presto problematical symptom solved. But can anyone shed any light on the variations in the quadrant design for automatics and the thinking behind it?

By the by, there should be a rubber sleeve fitted over the brass arc covering the normal and fast positions to prevent lever chatter at speed. If your selector lever makes a zizzing noise when you drive along then this is likely missing.