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Hi all

I am in the proses of doing a overhaul on my weber 40 carbs and have seen that the rubber carburetor mounts have perished badly i saw a clip on youtube of an Alfa with aluminum mounts. Machining these would not be a problem for me to get done is it a recommended mod would it improve performance in any way ect. Any feed back on this would be much appreciated
 

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There are indeed solid aluminium mounts which have grooves for rubber "O" sealing rings. They are readily available from lots of places....I got mine from ClassicAlfa. I would suggest that buying them would be the inexpensive option.
 

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1965 Giulia Sprint GT
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I have no personal experience with aluminum mounts and am open to any opinions. One noted Alfa engine and SPICA located specialist located in the Pacific Northwest did however tell me that by using aluminum mounts all of the engine's vibrations get transferred to the carbs with the result that the carbs go out of tune more quickly and are prone to getting cracked and damaged. Again I have no personal experience, but I just thought I'd share.
 

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The secret is the rubber "O" rings which coupled with the special Cosworth washers allow a certain amount of movement. I have them on three cars with no problems.
 

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1965 Giulia Sprint GT
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Stuart. Thank you. Perhaps I'll give them a try, especially since they'll be less prone to vacuum leaks than the rubber ones.
 

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Original rubber mounts were great, the recent reproductions are a headache ... they need planing and loctite gasket eliminator (515) or similar to seal reliably and need to be torqued carefully as they can distort to boot.

The aluminum set-ups avoid that. As Stuart points out, the O-rings or MISAB plates are there to reduce vibration. How good they are in doing that compared to the original rubber mounts - I don't know. Nevertheless MISAB plates are the standard for setting up aftermarket Webers.

Now the local Weber distributor recommended that I take floats (old style) as spares on a long distance event, as the solder joints apparently start leaking relatively frequently due to vibrations - however, I have never had that happen on an Alfa with many miles on both track and road - however, all these cars had original rubber mounts.

Having said all that, on my cars I have stayed with rubber mounts just in case there is less vibrations with original mounts. Never had a problem with leaks on the originals but did have leaks with reproductions when used w/o loctite.
 

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Leaks in the rubber reproductions mounts

Original rubber mounts were great, the recent reproductions are a headache ... they need planing and loctite gasket eliminator (515) or similar to seal reliably and need to be torqued carefully as they can distort to boot.

The aluminum set-ups avoid that. As Stuart points out, the O-rings or MISAB plates are there to reduce vibration. How good they are in doing that compared to the original rubber mounts - I don't know. Nevertheless MISAB plates are the standard for setting up aftermarket Webers.

Now the local Weber distributor recommended that I take floats (old style) as spares on a long distance event, as the solder joints apparently start leaking relatively frequently due to vibrations - however, I have never had that happen on an Alfa with many miles on both track and road - however, all these cars had original rubber mounts.

Having said all that, on my cars I have stayed with rubber mounts just in case there is less vibrations with original mounts. Never had a problem with leaks on the originals but did have leaks with reproductions when used w/o loctite.
How you see and/or understand that there is a leak coming from the rubber mounts?.
 

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You usually hear it - an air pumping like sound and car doesn't quite run right. Also it tends to interfere with carb adjustment, mixture is off on the affected cylinder(s). Using plastic tubing as a stethoscope can be helpful. You can also chase it down by spraying ether (starter fluid) on the likely areas of leakage. Sometimes taking the intake manifold off, pressurizing it and having water with dishwashing soap on the likely affected areas and looking for bubbles can assist in locating the leak. Though if one mount leaks, in the end it probably pays off to reseal all of them.

How you see and/or understand that there is a leak coming from the rubber mounts?.
 

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How you see and/or understand that there is a leak coming from the rubber mounts?.
Squeaking/chirping in time with the idle.
Depending on where the air is getting in, moving the carbies up and down on the mounts will make it more or less audible.

Movement on the mounts is sometimes worsened when the T-shaped mounting bracket is missing from the inner side of the airbox, thus allowing the carbies and airbox to swing in the breeze.

I replaced my mounts with new rubber ones some time ago. Made sure that they were 'gasket sealed' and torqued correctly.
No problems since.

Chris
 

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use alu mounts allways on the racers, never experienced any problems with going out of tune or whatever.
(and just that is more important on a racer...). I would advice on the longer ones for more torque.
 

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The secret is the rubber "O" rings which coupled with the special Cosworth washers allow a certain amount of movement. I have them on three cars with no problems.
Yes, on mine too with no problems. Do not overtighten them onto the head - if you squash the rubber O ring too much it loses its ability to soak up vibrations.
 

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Discussion Starter #12
Thanx for all the info guys i thing im really gona try make a plan for ali mounts. Ill see if i can get them in South Africa if not i'll look at getting them made.
What torque must i tighten them to.

Thanx
 

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I have reservations about the ability for O rings to absorb vibrations as folks here are suggesting . O rings are a seal. In hydraulics at least, the connection is metal to metal and the O ring is situated in a groove or cavity between the two without being deformed as the joint is tightened. As the pressure of the oil builds up the O ring is pressed to bridge the minute gap between the metal surfaces and seals it.
I cant see how this principle allows it to absorb vibration as a carb mount.
Perhaps someone can enlighten me.
 

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As I understand it the "O" ring is not fully compressed and there is an allowable movement between the carb and the inlet manifold. The Cosworth washers tend to dampen any vibration also. In short they have worked perfectly well for me.
 

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Spence, where are you in SA? I'm in Stellenbosch. If you're in W Cape, maybe we can both order aluminium mounts and save on postage?
 

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As I understand it the "O" ring is not fully compressed and there is an allowable movement between the carb and the inlet manifold. The Cosworth washers tend to dampen any vibration also. In short they have worked perfectly well for me.
And for me for over 12 years.
 

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Kiwi 74 Alfa wrote

I have reservations about the ability for O rings to absorb vibrations as folks here are suggesting . O rings are a seal. In hydraulics at least, the connection is metal to metal and the O ring is situated in a groove or cavity between the two without being deformed as the joint is tightened. As the pressure of the oil builds up the O ring is pressed to bridge the minute gap between the metal surfaces and seals it.
I cant see how this principle allows it to absorb vibration as a carb mount.
Perhaps someone can enlighten me.
It's not the job of the o ring to provide the flexibility, they are there to make the seal. As another reply states, the Cosworth flexible mountings , or indeed thackeray washer in earlier times, provide the flexibility.
Hundreds of thousands of cars are out there fitted with exactly this set-up, indeed bolted straight to the cylinder head in most cases, typical example being a 1558cc Lotus Twincam.
I have been using thackeray washers on T/C engines, MGA/B engines, Ford Kent / Pinto and Cosworth engines for the past 35 years with no such problems. It should be noted that they should never be overtightened, as by doing this you eliminate the flexibility, indeed, I always leave at least 1mm clearance between the coils of the thackeray washer, or between the two "washers" of the Cosworth flexy mount configuration, whichever I'm using.
It is the standard way to mount DCOE's on the greatest percentage of engines, and is very reliable.
I am in fact just about to order some solid mounts for my Alfa Twincam.
Hope that helps
GTAR
 

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GTAR, absolutely right..... and if I remember the twin cam setting up gives precise clearances for the Thackeray washers to achieve the correct amout of flexibility. No problem to achieve with the engine out of the car but next to impossible with the engine installed.
However I have had cracking problems with Thackeray washers which is why I moved on to the Cosworth type....the only drawback being the need for longer studs.
 

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Thanks for the explanations.
The names Thackery and Cosworth washers were new to me. Google managed to find some pictures of Thackery washers and I realised I knew what they were, just didn't know them but that name. Google wasn't so helpful with Cosworth washers. It kept wanting to tell me about windsceen washers on Cosworth Escorts. Can somebody enlighten me?

I had a 2000 GTV back in the seventies and I used to delight in showing people how the carbs were rubber mounted. Why did Alfa go for rubber mounts when, as far as I can tell, no one else did? Why are you guys so keen on getting rid of them?

I recently did the motor up in my current GTV and put new rubber mounts on as part of that.
 
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