...and once you have sorted out the compression problem, don't bother with the HIF44, fit a proper SU, an HS6. Piston and jet and that's it, none of the bastardisation of the lovely simplicity of the original SU that you get with an HIF - and you get that lovely mixture adjusting nut on the jet. I'm on the lookout for a pair of SUs to replace the Strombergs on my 164 and it's definitely the HS6es that I'm looking for, not HIFs.