I use WD40 to get old oil off. To get them really clean the dishwasher, works a treat! They do go a little dull grey but a light polish with autosol brings them up again. Vapour blasting is the best and will make them look brand new.
Yes, soda blasting is a good do-it-yourself technique as you just need a decent air compressor. You can knock up the gun yourself (loads of info on Youtube)
I'll echo the dishwasher advice, brings things up lovely.
An old trick for seized engines (and I mean totally seized to the point they won't come apart) was to put them in a bucket of diesel for a week.
The corroded steel parts would come up nicely if they were soaked in white vinegar (often sold as non-brewed condiment) bout they would need to be removed from the aluminium first.
I find a 50:50 mix of paraffin and ATF makes a very good penetrating oil for stuck parts.
Thanks Chris Tindal, PeterF, mauri, stinkwheel for your idea/suggestion
I have tried dish washing liquid and autosol it did some clean up. i am considering other brilliant ideas as well
i want to clean as much i do with my bare hands, I dont have any shed just tent in my back yard at the moment.