Fitting Misab Spacers

[William2]

When fitting Misab single rubber O ring spacers between carbs and manifold should they be fitted dry? Also, when tightening the rubber mounts should what should be the correct spacing between the 2 metal cup, washers? One person I spoke to reckoned about 20 thou.

[Briggs1]

fitted dry.

Are you using thakery washers on the top or the rubber with caps on top and bottom?

I believe .020 is too tight. I'm not sure about actual measurement but expect you to end up closer to .040" or more.

I mount and secure top and bottom so carb and manifold spacing is parallel from top to bottom and the Misab o-ring is compressed enough to prevent leakage

[Briggs1]

ooops - thackery washers on the bottom, not top?

[Grizzly]

Just a quick related question, Should the o rings be rubber as opposed to Viton etc? I ask because i have struggled getting a set of Viton o-rings to seal and i was told the rubber o ring is supposed to swell.

It kind of makes sense but i don't see why the Viton O-rings are such a pita because surly if the mating surfaces are both flat and the o-ring is not nicked it should seal??

[zog]

My 2 cents.....

I grease up the o-rings with a little Vaseline petroleum jelly before installing them. They don't come loose when you install the carbs.

My wife looked at me cross-eyed when she found the tube sitting on the garage shelf a few years ago.......

[GaryGTV]

When fitting Misab single rubber O ring spacers between carbs and manifold should they be fitted dry? Also, when tightening the rubber mounts should what should be the correct spacing between the 2 metal cup, washers? One person I spoke to reckoned about 20 thou.

Here's a new answer for an old question -- and it's from an Alfa guy!!! With my Weber 45s, I use machined aluminum carb mounts, with Misab o-rings, and the metal cup-rubber isolator mounts held on with Nylocs. The wizards at Alfaholics say to use a 2mm gap between the metal cups. That has worked fine for me.

[prezoom]

I was using regular rubber O rings on an intake manifold back in the early 70's. The manifold had been cut with grooves to help retain the rings. However, the racing gasoline I was using at the time was causing extreme swelling, which over a very short period of time would cause the O ring to expand beyond the groove. Air leaks galore. Switched to Viton and the problem went away. On the next car, I used a rubber isolator from Datsun Competition. Unfortunately, these are NLA, though I have a couple of NOS spare sets that I use on the Elan and installed on the Plus2. These are bullet proof. No thackery or rubber washers. Bolt up the carbs and forget about them. If you can find a set, grab them, They are worth the trouble to use them. They do move the carbs further away from the manifold, which requires some fussing with the air box cover to prevent it from hitting the inner fender well on my S2. The Plus2 required serious modification to get the air box to clear. Though much of this was caused by the Dunnell intake manifold which brings the carbs straight out from the cylinder head, and not at an angle like the TC head.