Thick carb base gasket

[BDD]

OGTS says that the thick felt gasket is a must at the base of the carburetor (Weber 32/32) to prevent vacuum leaks and warping of the carb. base. They also say that sealant should be used with the gasket but do not recommend RTV silicone because it's difficult to remove later.

1) How can this gasket seal well without sealant since it has 4 plastic inserts at the bolts hole locations that would tend to prevent it from being compressed?

2) What sealant should be used? I see that some people are absolutely against using sealant at all with gaskets partly because it can come loose and get into the carb. or engine, etc.

[wrench459]

Check the carb base first make sure its flat.
Over the years they tend to get bent.. even the most highly recommended weber carb.. cough spitting up flem.....
A bastard file will do the trick just move it from one edge to another.
IMOA no sealant anywhere close to gasoline. It will plug up a carb in a heartbeat.

[BDD]

Does anybody else have opinions on this issue? How did you install the thick base gasket to prevent vacuum leaks?

[hrcollinsjr]

Can't find much to fault on Wrench459's suggestions. Check the surface of the manifold for "flatness", a file will work fine. Make sure you have the proper length studs for the Weber and gaskets. I really don't think you'll have any trouble as long as you've checked the surface for trueness and use new gaskets. If you plan to use the OEM heat shield it gets a bit trickier.

Harold

[Lindsay]

carb vacuum leak - Opel Community Forums

Interesting discussion on vacuum leaks and gaskets ...

[bigjim5551212]

Originally Posted by BDD OGTS says that the thick felt gasket is a must at the base of the carburetor (Weber 32/32) to prevent vacuum leaks and warping of the carb. base. They also say that sealant should be used with the gasket but do not recommend RTV silicone because it's difficult to remove later. 1) How can this gasket seal well without sealant since it has 4 plastic inserts at the bolts hole locations that would tend to prevent it from being compressed? 2) What sealant should be used? I see that some people are absolutely against using sealant at all with gaskets partly because it can come loose and get into the carb. or engine, etc.

The thick base gasket needs to be replaced once in a while. We have those available. We also have a really good sealer. Its Hylomar. The version we have is made by Wurth. Hylomar is a polyurethane based sealer that does not get affected by gas or oil.

[wrench459]

I love Hylomar its a great sealant but only in close tolerances.

[BDD]

Without extra washers and the thick gasket, I find that the nuts bottom out on the carb base without really tightening it down properly. It just seems thta way because they are bottomed out.

I ended up installing the thick gasket with no sealant. I added a stainless steel washer, stainless lock washer and stainless steel nuts to each threaded stud and gradually tightened down the carb in a pattern. This really made a big improvement. Before I had to leave the choke engaged and keep the clutch in and keep my foot on the gas for a while to keep the engine running till it warmed up. When accelerating, the engine would backfire.

Now, I can close the choke quickly and it will idle well with a slight load on the engine. I checked the valve cover bolts and they seemed a bit loose so I tightened them up too. The car starts immediately now with a turn of the key and idles well. With the main vacuum leak ended I am able to adjust the idle and idle mixture screws to tune the carburetor.

While the carb was off I also noticed that a filter screen was missing where the gas enters the float bowl. I have another Weber so I used the one I found there.

I would recommend to anyone who has not installed the thick carb. gasket to do it. This can really make a big difference. So far I have not needed to use sealant.

Also, check that your throttle linkage actually opens the secondary on your Weber. Mine might just need a small adjustment at the threaded rod where the gas pedal linkage exits the firewall.

[hrcollinsjr]

Originally Posted by BDD 1) How can this gasket seal well without sealant since it has 4 plastic inserts at the bolts hole locations that would tend to prevent it from being compressed?

The gasket is slightly thicker than the plastic inserts so the gasket does compress and seals the base to the manifold. Every gasket that I've removed has the impression of the carb base on one side and the manifold on the other.

Harold