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During the 1930's there were two similar Bonora type caps produced with the main difference being in the profile of the quick release lever itself, some having more of a tapered swirl shape which we note are being offered elsewhere. Ours are the original CMI (Central Motor Institute Ltd) design as produced for the MG factory in the 1930's and as shown above.

The initial sample run were completed with a non-original boss attached to the underside of the anchor arm. We suggested a modification to incorporate a concealed adjuster screw on the underside instead. There was also a problem in achieving a good chrome finish on the brass alloy casting. This issue has now been addressed by using an alternative chroming technique.

These are British made and the craftsmanship and finish is exemplary as our customers have commented:

"Just received the Bonora rad cap and once again it is absolutely fantastic. Well worth the wait and it is perfect in every detail, it just dont get any better than this with the superb plating it has transformed the look of my PA. I just can't fault it ..."

"Arrived this morning – and worth the wait: a beautiful item."

"I would like to express particular delight in the superb quality and workmanship in the Bonara radiator cap which shows perfectly again your consistent devotion to excellence without compromise."

These filler caps are investment castings where the quality finish will be noticably different from sand castings.

Price £124 (no VAT) - Radiator filler cap


With reference to the Bonora fuel filler cap, we were hoping to receive these in an unfinished state in order to incorporate our own important modification. As we were prevented from doing this for our customers, we have decided not to offer this part as it is.

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