Misab plates

[jono]

I fitted some of these 4 years ago in place of the original alloy spacers with O rings.

I was surpised to find that they are quite badly cracked and degraded after only 11k miles. I was going to go back to the O rings and spacers but I could readily obtain Misab plates and they were cheap so what the hell!

Question - do I still need flexible mouting of the nuts with these or can I bolt them straight on, the assumption being that the Misab plate design provides all of the required 'flex' / anti foaming effect (which I've also heard tell is a myth)?

It was interesting tighetning them up (re using the rubber diablo mounts) to hear the engine note change when they were tightened further which made me think that thye need to be quite tight in order to form a proper seal.

Any observations welcomed

Jon

[MarkDa]

I have no experience but read that rubber cup nuts needed as well.
Viz - at random
http://www.rallynuts.com/motorsport-web ... plate.html

Presumably these nuts provide the compliance that would other wise be provided by Thackeray washers?

As you say they're a much cheaper solution but I expect some are better quality than others.
Perhaps choose a supplier with a good reputation?

[Chrispy]

I'm about to remove my Misab plates and put on some new ally spacers with o-rings. I wanted it to look more correct and I feel (with no actual proof ) that the spacers would provide some better isolation.

[rgh0]

I have used "Misab" style plates for many years and never needed to replace them so not sure why yours would have cracked, it may depend on the actual manufacturer. I still use the Thackeray washers on the bottom as they are more resistant to fuel contamination they are exposed to and rubber equivalents on top as Thackeray washer on top tend to crack (a Dave Bean recommended method That works for me )

The alloy plates with O rings have their own problems as they are very thin between the two O rings and tend to crack giving air leakage problems. I have lots of examples of these.

The Lotus 912 SE engine which was their last carb engine used a special venturi style anti back flow alloy plate to help performance. These applied to a race twin cam certainly help one of the race tuning secrets that not many talk about

cheers
Rohan

[jono]

..I was surprised as well Rohan - they were stamped 'Misab Sweden', just like the new ones.

I wonder whether it's ethanol which has caused it?

[rgh0]

..I was surprised as well Rohan - they were stamped 'Misab Sweden', just like the new ones.

I wonder whether it's ethanol which has caused it?

The original Misab style plates i used were made by Borg Warner. I installed them about 30 years ag0 in my Elan on 40 webers and use them now in my Plus 2 still. More recently I have used the Misab Sweden stamped plates in my Esprit and Elan on 45's without any issues but in Australia no ethanol addition to 98 Octane I use for fuel usage on these cars

However I wonder how many fakes are out there potentially with the same stamping but made to lower standards ??

cheers
Rohan

[MarkDa]

You've certainly had your money's worth out of those plates Rohan.
Maybe this where we can whinge that modern bonded rubber products are not a patch on what they used to be ?
I'd have thought that modern 'rubber' would be better in anticipation of ethanol.
NBR seems to be impervious to practically everything.

As an aside after having problems getting copper washers to seal thr banjo bolt on one of my carburettors I used some M12 bonded rubber washers and they pull up beautifully without undue force.