Doing the final prep on the car while I await DVLA I want to clean up the ali engine casing. Any ideas, how about oven cleaner do you think that would bring back the sparkle. Any ideas?

Oven cleaner will eat the aluminium! Most oven cleaners are based on caustic soda, which reacts nicely with aluminium.

Why not use commercial engine cleaner? Cheap enough in a motor factors.

really depends what you mean as clean up

if its dirty and grubby some form of cleaner, if its dull and scratched the good old wet and dry and elbow grease!

use a good engine degreasent,,, then try this with a bit of elbow grease,
http://cgi.ebay.co.uk/GLIPTONE-ALUMINIUM-CLEANER-ALU-MAGIC-250ML_W0QQitemZ280369020804QQcmdZViewItemQQpt
i use it on my aluminium side panel's come's up a treat

at my old job i had to clean alloy Gardner diesel pumps first steam clean and while the case was still hot brush on auto smart alloy wheel cleaner neat it fizzer's like hell and wash it all off after a few mins then clean with diesel again to stop it furring up job done

Cillit Bang cleans ali nicely.

Its acidic so will eat into it if left too long. But if you just spray it on, work in with a brush then wash off it works very well.

I have doen a few sets of carbs like this now.

Cheers,
David

Brake cleaner

Degrease with cellulose thinners then to remove oxidation use phosphoric acid (aka Naval Jelly or Cilit Bang) or Boric Acid ( as in boiled up Rhubarb Leaves) and wash with water.