Supersprint 1700 twin Weber mounting

[Anker]

Cross post from Lutus7.club:

 

I was getting ready to balance the carburetors, removed the air filters and warmed the engine up to operating temperature. Barely touched the carbs and noticed that this immediately caused the engine revs to go up and down.

I think I made a mistake believing that this had to be caused by an air leak and took a look at the manifold nuts. As soon as I put a bit of pressure on the carbs I could see that they moved against the manifold and though they were too loose. Tightened the top four a little bit (the engine was hot so I didn't want to put my hands underneath the manifold) and thought I heard and saw some improvement. Ran the car up to a service station to have it inspected (the Massachusetts equivalent of the MOT) and thought it ran a bit better.

Only after this did I decide that I better check here and the various books and e-books I have and then realized that there is a thick, flexible gasket that provides vibration isolation. See the picture below.

I did a search on this site and found a thread from 2001 on the same topic and saw two different instruction posts. One specified, as far as I remember, 8 ft lbs, the other said something like 1 1/2 turn of the bolt after everything just touches. Of course I can't find this post any more.

I checked the assembly guide and the Weale book and didn't find anything there.

I should know better

Any help and/or pointers will be appreciated.

Thanks/Anker

[The Stig]

The easiest way to gauge how tight is by the gap between the cup washers on either side of the rubber. The gap in your picture looks about right which must be the same on all the studs to ensure it’s straight. If the rubber is older, I’d suggest replacing them all along with the larger gaskets between the carb and manifold which look unusually thick on your picture for a Crossflow.

 

Air leaks will certainly cause popping, although that’s also part of the Crossflow experience!

 

These for the carb to manifold https://www.burtonpower.com/sandwich-plates-misab-40-45dcoe-x-2-set-of-4-webmisab.html

http://www.usa7s.net/vb/blob:http://www.usa7s.net/d9e7b36a-96be-4a89-8cee-4c88dfbb2641

 

 

these for the nut washers https://www.burtonpower.com/carb-mounting-kit-dcoe-carbs-x-2-webcmk.html

 

http://www.usa7s.net/vb/blob:http://www.usa7s.net/fd83baa5-f2e1-44ba-bee3-06c9425b4dd9

 

You should be able to purchase from Redline or Pegasus in the US.

[Anker]

Thanks Stig,

 

I thought the identity of the Stig was a closely held secret!

 

I have ordered a complete replacement set of mounting hardware with Misab gaskets.

 

Anker

[escondidoron]

For years I have used small pieces of -6 fuel line, each cut to about 1/4" length, covered by a flat washer and then a lock nut to tighten. Effective, cheap and readily replaceable every few years.

[MoBoost]

I like these better. Don’t have to deal with aging rubber.