After drolling around the interwebs for at least 100 hours most threads and website comments (wowhead) are retarded and offer very little advice in here im going to answer most/all of the common questions and such about cata level tinkers as a lvl 70-74 twink.
There are 8 tinkers from cata that are obtainable at 70 of the 8 tinkers 3 are worthless as we cannot use them the 3 (bad) are Grounded Plasma Shield, Invisibility Field, and Cardboard Assassin. These tinkers are useless as they require 500 engineering to use but not to obtain so if you get one of these 3 many sadfaces to you.
There are 5 tinkers that are useable to 70s some are better than others
Quickflip Deflection Plates: on use = 1500 armor lasts 12 sec. on a 1 min cooldown.
Z50 Mana Gulper: on use consumes a Mythical Mana Potion for increased effect. despite the potions needing lvl 80 to use this tinker ignores that and thus gives a huge mana boost (this shares cd with potions) does not work in arena
Spinal Healing Injector: The healing potion version of the Z50 it heals for at worst 15k generally im getting 17-18k on use not useable in arena... LOH for all classes in bgs what
Synapse Springs: on use = 480 int for 10 sec. on a 1 min cooldown. Have no fear blizz has you non int. using classes covered, next patch these will now grant 480 to you classes major stat (agi. for hunters str. for warriors etc.)
Tazik Shocker: on use shoots a ball of lol nature damage for 5040 (number may vary) on a 2 min. CD this works in arenas and is generally viewed as the most desirable of the tinkers for pvp.
Common questions
1. I am on a burning crusade account can I get them?
A. Nope a cata account is needed as the tinker need you to make cata schematics (this may have been changed but it seems to be the current case still)
2. When can I start getting these tinkers?
A. 441-450 is when you can expect to get your first one ( I have yet to get one before that and none of the twinks I know with them got the tinkers before that lvl of engi)
3. What level of engineering is required to use these tinkers?
A. 450 for the 5 glove enchants 500 for belt enchants.
4. Can I only learn tinkers from orange difficulty schemata?
A. Nope you can get them from all colors including grey, I reccomend obsidium bolts.
5a. I got a tinker I didn't want can I get any more?
A. Kinda, at 450 engi you only get 1 tinker and no more, you can go gnome and you will be able to get 2 more giving you 3/8 tinkers.
5b. I don't want to go gnome but I dont want this tinker what do I do?
A. relevel engi all the way back to 441-450 and you get a new 1/8 tinker... sry it sucks
6. Can I enchant a pair of gloves with a tinker then relearn engineering to get a new one do my gloves keep the old enchant?
A. Yep still requires 450 tho but the enchant will stick
7. It didnt say I learned a tinker (think alchemy), what are the odds I learn one?
A. Check your tinker tab the tinkers will just happen and be in your tab no alert or anything. Tinker procs are pretty common so you can expect to get them in well under 10 crafts in most cases.
This info is valid in the current patch of DOP and is subject to change in future patches