Who hoo! Glad you got it sorted out.....

G

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--Insert legal disclaimer here--

Eh... i am worried about this now.. what should the clearance of dim a and dim b be?

I did an eye comparison and it is roughly the same length? There is pressure buildup in the cap, as I have tried openning it when hot and air does fizz out...

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Lillee - 1969 Morris Mini K

I would guess a couple of mm.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I dun get it. Is the spring in the cap not supposed to hit the neck seal inside of the radiator therefor creating that hard press in feeling when you put the cap on?

When I put the new cap on it fits so that the rubber bit on the end of the cap hits the inside seal at the bottom of the neck, makes contact and compresses the spring in the cap when screwing it down tight.

Is this not right? if it is a few mm clear of the seal, then it is not sealing at all right? cuase the old cap was a few mm from the seal at the bottom of the neck and this was the problem...

I showed the dude at Padstow and he was more than certain I needed this cap as he asked me "what mini do you have" I said "I have a delux with a clubman 1100 engine with a clubman radiator" right away he said "you need the such and such part number cap for the longer neck radiators, I carry 2 types of radiator caps, one short one for early minis with short neck and one longer one for aussie clubman long neck radiators"

So when i went there, sure enough there are only 2 caps being sold, one looked exactly like mine, and was shorter than the other (the one i baught) which has a longer spring and rubber plunger bit.

There is a number on it, the new cap's number is 15/90.

Dimensions are:

Dim A : 26mm from top of neck to sealing surface at bottom of neck
Old Cap Dim B: uncompressed from cap to bottom of rubber bit is 22mm
New Cap Dim B: uncompressed from from cap to bottom of rubber bit is just a fraction over 26mm

I suspect this is the correct cap as when I compress the spring by hand it decompresses Dim B to less than 20mm in length

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Lillee - 1969 Morris Mini K

Just realised you meant to measure it compressed by hand, in this case if compressed by hand the Dim B for the new cap is like 20mm.

The fact that the uncompressed dim B for the old cap is 4 mm clear of the sealing surface is the culprit I think... right??

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Lillee - 1969 Morris Mini K

Right. If there's daylight there the cap cannot seal..

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Sweet!!! no more overheating just in time for summer

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Lillee - 1969 Morris Mini K

The desing there is that the spring seals the mouth maintaining pressure untill the heat is excessive and the pressure rises (thats where the 13lb\8lb etc rating mean - resistance to steam pressure) pushing the spring up, breaking the seal and relieving the coolant out of the side opening.