Author Topic: Carb - gaskets/sealing  (Read 2186 times)

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hoogerbooger

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Carb - gaskets/sealing
« on: 24 April, 2018, 15:44:38 »
Rupert ratio says use greased paper gasket against the head then 1/16" to 1/8" tufnol heat proof spacer, then O-ring .....then don't over tighten.

He also says too soft a spacer can be a cause of bending the flanges.

My Concentric has no 0-ring groove. It was mounted to a 3/8" rubber spacer  ( tufnol ?)with a paper gasket either side ( & no O-ring). I was just going to put it back as I found it greasing the paper gaskets both sides.

1) This sound Ok/likely to be sufficient to make a seal ?

2) Should I presume my 3/8" rubber spacer is best replaced with a narrower one or should I just be a bit more careful when tightening the nuts ?

3) Also Should the gasket on the bowl be greased or not ?

( I will fit as a reassembled whole carb....having checked all mating surfaces are flat.....& lightly tightening to avoid warping it.)


JulianS

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Re: Carb - gaskets/sealing
« Reply #1 on: 24 April, 2018, 16:53:07 »
Without the O ring surfaces need to be really good to give an airtight seal.

I would avoid a rubber spacer and use a tufnol or similar hard spacer.

Float bowl gasket does not need grease, they self seal to a certain extent - on removal you may see where the gasket has sealed on bowl or carb body.

hoogerbooger

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Re: Carb - gaskets/sealing
« Reply #2 on: 24 April, 2018, 18:25:59 »
Am having trouble searching out a tufnol spacer on-line

Amal list phenolic spacers. These the same/do same job ? :

http://amalcarb.co.uk/phenolic-spacer-26mm.html

My carb is a 27mm choke. Spacers found so far are either 26mm or 28mm. So what's best. Will one or other do as they are ......or should I get a 26mm and sand it out to 27mm ?

So then greased paper gaskets either side of the tufnol/phenolic insulator ?






« Last Edit: 24 April, 2018, 18:29:02 by hoogerbooger »

hoogerbooger

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Re: Carb - gaskets/sealing
« Reply #3 on: 24 April, 2018, 22:04:59 »
Just looked at Amal website on installation which includes:

1) Nuts and spring washers should be tightened until the spring washer is just flattened nuts should
2) always be used to mount Amal Mark 1 carburettors.

I have neither springs washers or nylock nuts. ( & with a 10mm rubber spacer and no -O-ring groove I'm getting the picture that previous over tightening is why I have no o-ring groove  -  it's been ground away re flattening the flanges !!!

(answer to my previous post appreciated )

(I guess I could try using a circular wood corer to put an o-ring groove in the heat insulator spacer - if I can find the right size )




AWJDThumper

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Re: Carb - gaskets/sealing
« Reply #4 on: 24 April, 2018, 23:10:29 »
It's best to get one of the correct size but a 1mm difference is not going to make any practical difference. The larger diameter would be the better size.

hoogerbooger

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Re: Carb - gaskets/sealing
« Reply #5 on: 17 May, 2018, 18:36:19 »
I have a new tufnol spacer. holding it against the flange with fingers, then holding it up against the cruel light of day, I can see a little bit of light peeking through in the mid portion.  May be up to 0.25 mm at most would be my estimate. So flanges are slightly bent towards the manifold.

So do I wet and dry sand on glass ? what grit is sensible ?

then as I have no O ring groove do I use a paper gasket instead ( so it'll be a paper gasket tufnol sandwich)

AWJDThumper

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Re: Carb - gaskets/sealing
« Reply #6 on: 17 May, 2018, 19:28:30 »
I normally use 400 grade emery and it doesn't normally take much to rub the flange flat but check with steel rule. Paper gaskets either side of the spacer will be sufficient to seal the interfaces.