KI-Gas Pump Threads - Lagonda Club

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Posted in: Carburetion and Fuel
Mike Heins

6 December 2008 at 15:43 #47494

I have currently got the Ki-gas pump from my 1929 2 litre High Chassis stipped down to undertake the seal modifications outlined in a previous lagonda club magazine. This I understand and have no problems in doing it. Whilst removing the unit from the car I found the input and output fuel pipe brass securing nuts to be in a very poor state. At some time i would like to replace them but I am having difficulty in identifying exactly what thread they are.
I have tried all the thread guages i have and cannot match either of them.
Anyone know what thread forms were used.

Colin M34

6 December 2008 at 16:25 #47496

Hello,

I have had similar problems with the Ki-gas pump on my M45. The thread is 5/16 inch British Standard BRASS thread, which is 26 TPI. It has a 55 degree thread form. Cycle thread is also 26 TPI but has a 60 degree thread form. Cycle thread is used on Lucas headlamp bolts.

BSP (and Cycle) taps and dies are availble from the nice people at Tracy tools (http://www.tracytools.com/).

For those of you on the Continent, you may have spotted that with 25.4 mm to the inch, you could get away with 1.0 mm pitch metric threads.

My Ki-Gas now works beautifully…

Colin M34

Mike Heins

7 December 2008 at 10:24 #47497

Thanks Colin for the info.
Are both the input and output unions 5/16″ on the M45 ki-gas pump?
On the 2 litre the output to the manifold is 0.307 (approx 5/16″) but the input from the fuel supply is 0.349 which is an odd size ( 11/32″ is 0.34375 and 23/64″ is 0.359375)

The nearest pitch I could get for the 0.307 (5/16″) was the1mm as you stated

Any ideas on this?

Colin M34

7 December 2008 at 12:43 #47498

Hi Mike,

I should have mentioned that it is the threads in the Ki-Gas pump body that are 5/16 BSB. Yes the larger pipe is the input from the fuel supply.

To solve your problem, you might want to modify something like a BSP union body to make up a new adaptor and then use a standard BSP solder nipple and nut on the pipe. Again, talk to Tracy Tools for the right BSB tap, and Vintage supplies (http://www.vintagecarparts.co.uk/) for the pipe fittings.

A Myford lathe would be ideal for this job…..

By the way, I think the centralised lubrication fittings on LG45s are also BSB.

Colin
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