Distributor Cap Help!

[Spikehaus]

Today, I decided to remove the spark plug leads from the distributor cap and give the cap a clean due to the years of debris from the donor vehicle on the top (Pretty much the only untouched part of the original car. (Leads replaced not so long ago)

I also removed and replaced the oil pressure sensor.

Upon re-assembling the cap and leads, the engine will not fire. I did not touch the rotor arm or dizzy housing other than give it a quick wipe over. I have checked, checked and checked again the firing order from the Haynes book locating position 1 on the cap against the raised round moulding mark and book diagram.

I have tried this with an without the cap tower.

There are no cracks or carbon tracks in the cap

Photos on the build diary

Each time it makes a loud bang and blows a hole in the induction pipe, (it did this a few time when it was working if you did not press the accelerator down during cranking)

Do I need to manually turn the engine to TDC or make sure the rotor aligns with spark plug 1 before refitting the cap?

The cap only seems to sit in one position due the moulded lug below.

What was meant to be a simple maintenance job has gone wrong?