How to change the ORings in the Dashpot of a TR6 Stromberg Carburator

My dashpots have leaked oil quickly ever since I bought the car.  They richen the mixture on acceleration, making it go faster.  Faster is better….    I just now am getting around to fixing it.  I kept forgetting to order the ORings when ordering other parts, and didn’t want to pay more for the shipping than the ORIngs cost.  Finally, I saw on a forum that John Twist at University Motors mentioned that they were size #10.    So I went to Napa, and was able to purchase 10 for $5.60. (Minimum order since they had to have them brought in from their warehouse. )  This project took me about 2 lazy hours from start (finding all my tools, answering the phone, watching the John Twist video, watching a movie at the same time, etc.)

I am not going to repeat anything in John’s video, just post the link here

John Twist’s Video on Replacing Dashpot ORing in Stromberg

I do want to add some things that weren’t clear from the video, and maybe save multiple trips to the store getting tools/supplies.

  1.  Napa Part Number is 727-2010, #10 = 1/4×3/8×1/16  – these are Nitrile, rated for oil.  Others have recommended viton.


2.  Loosen the Air Filter housing and the Carb Top will clear – you don’t have to take the air filters completely off.  Loosen, put them away a little, and the top of the carb will clear and remove easily.  Otherwise the air filter housing is in the way when you try to remove it.

3.  Brass Brush – John shows using a brass brush to remove scratches from the inside of the tube the ORing rides in.   I found a brush for a 9mm handgun cleaning kit, fits perfectly.  I did not use a drill motor, but rather pushed it in/pulled it out until the scoring appeared gone.  It took 100 passes on the worst carb.  You can get a very basic kit for $10.00 at Basspro or Walmart.  Use WD40, no need to buy the gun cleaning solvent.

4.  Retaining Lock washer – which orientation?   The tangs are bent slightly.  The washer should go in with the tangs bent up as you put the washer in the tube. Probably won’t go in the other way around anyway.


5. Filling the Dashpot – My oil squirt can has 90wt in it.  I had just finished changing the lawnmower oil and that had a spout on it.  Very neat and clean. Fit to a bottle of 20/50 weight Valvoline Racing Oil which I use in the engine.  John recommends 90wt, folks on the forums recommend all kinds of things like ATF or regular engine oil.  I will try the 20/50, if it still leaks because of scoring or whatever I didn’t quite remove I will try the 90wt.  20wt is recommended, and you can buy that as 3-in-1 oil at the big box stores.  However it also is more prone to leak as it is thinner, the 90wt least likely to leak.   I decided to try the 20/50 as a compromise, assuming I fixed all leaking. If it doesn’t leak, maybe I’ll try 20 wt in the future sometime.


All done –  Unfortunately it is raining right now, so I can’t try it out…

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s