Stromberg Carburetor Dash Pots

[jfjharry]

My carburetors are loosing the oil in the dash pots in a matter of weeks without using the car. 3 being completely empty and 1 with a small amount left. Is it a matter of just replacing the diaphrams which I assume can be done with the carburetors still on the car and where would the best place to buy them from?
On starting sometimes the connection breather tube between the carburetors which exhausts to the motor cover near the oil filler has become disconnected due to a backfire. I am assuming this to be due to oil build up. Any help from anyone with knowledge in this area would be helpful.

[Heuer]

Harry

Start by reading up the various Stromberg instruction manuals in the Forum Knowledge Base: http://etypeuk.com/forum/viewtopic.php?t=1664 which could give you a clue as to the problem and whether a complete or partial rebuild is required. Various vendors supply parts, no doubt someone here can point you in a good direction.

[vee12eman]

Hi Harry,

I had exactly the same problem of dashpot oil leakage until recently on my Series 3. I had rebuilt the carbs with a kit from Andrew Turner, but for some reason I had not changed the brass adjuster screws in the bottom of the dashpots. These little devils came with the repair kit but I could not at the time see where they were used, so did not replace them. You have to remove the dashpots and the pistons, release the screws retaining the needles (located at the bottom of the piston, on the side) and remove the needles. I won't go any further, since the guides on the Knowledge base describe the job well. Look at page 25 on this link:

http://dl.dropbox.com/u/8496016/Buckeye ... mberg2.pdf

which is one of the links on the page Heuer (David) pointed you at. At the bottom of the page is a photo, showing the adjuster screws, needle and all the retaining pieces - a good description on removal/refit is included. The new adjuster screws come complete with new O ring seals and this should cure the leaky dashpot oil. My carbs drained in about two weeks, now they stay full.

The carb adjustment will be thrown out by the removal of the needles, so then it is time to set them correctly and hopefully this will cure your other problems. Backfires tend to be caused by weak mixture or timing problems, so check your timing and also check all the other electrics in the ignition. If you are a member of the club, there is a good article on the Opus Ignition in the June issue of the magazine, this may help you to set up the gap in the distributor, which may have an effect. I doubt the problem is due to oil build up - there should be some vapour in this tube, it is connected to the breather system but on start up, I doubt this vapour would be present or, if it were, warm enough to ignite and backfire. My guess is that fuel vapour is building up in the carbs due to a poor state of tune or some problem with ignition, when it finally starts, the vapour is igniting in the manifold and blowing the breather of as a form of pressure relief valve.

Changing the adjuster screws in the carbs can certainly be acheived with the carbs still on the car, but you may need to go further and rebuild the carburettors completely, this definitely requires removal.

For parts, try Andrew Turner or Burlen Fuel Systems, they both sell complete rebuild kits and may sell the adjuster screws or O rings separately. You will also need a Stromberg carb adjusting tool (a long allen key and collar, which prevents the piston turning on adjustment) like this:

http://www.rimmerbros.co.uk/Item--i-RX1222

For adjustment of the carbs you also need a carb balancing tool to balance airflow. Some use a hose and listen to the carbs through it, but I doubt many can balance four carburettors accurately that way. There are several types, my favourite is the Uni-Syn type - like this:

https://shop.rocketindustries.com.au/products/ED4025

Other types are available.

Hope this helps,

Regards,

Simon

[Heuer]

The German made Syncrometer is the best I have come across and I have owned most other types:

[jfjharry]

Thanks for the information guys, the web sites given were most helpful. I will now have a go at replacing the 'o' rings first off as our local rubber store has the nitrile ones.