Heatran probably doesn't want Earthquake, especially with a modest nature. Run Earth Power instead. Also, in this gen, Heatran probably wants coverage > Protect and Taunt; run HP Ice or Dragon Pulse there. For the last slot, you can run any of the following: HP Ice, Dragon Pulse (whichever one you didn't use before), Nitro Charge, or Toxic.
This team is for Pearl version (4th Generation), so, no Nitro Charge. And, how can I "manipulate" (or choose) the attribute of the Hidden Power?
Gliscor's moveset looks okay, but if you're going to be using a Toxic Orb & Poison Heal set (which I highly recommend!) you can't run SR or Roost. If you do run that set, use Swords Dance and Protect.
I'm in 4th generation, so, no Poison Heal for me :(
Mamoswine wants Icicle Crash > Avalanche; it's more reliable and doesn't require you to be hit first since Mamoswine is surprisingly faster than some things that come in on it. Also, run Adamant. Jolly doesn't outspeed anything important.
Icicle Crash is for Black and White, isn't it?
Run Jolly for Garchomp, otherwise you lose its great speed stat. The set looks standard, though.
I s'pose Skarm looks good too. Standard, anyway.
How can I improve them? I want the best :)
DD Tyranitar is absolutely horrid in this metagame. Not only do a lot of things outspeed it at +1, priority moves demolish it and they're everywhere. It... just isn't good.
So, I need to sustitute Tyranitar? What about with Hippowdon instead?
Oh... Right. Just read the end now, haha. Your items can be mostly straightforward: Heatran wants Air Balloon, Gliscor wants Leftovers (or Toxic Orb if it's Poison Heal), Mamoswine wants Choice Band or Life Orb, Garchomp wants Life Orb or Yache Berry, and Skarmory wants lefties. The EVs can be straightforward too: Heatran wants max SpA and Spe, Scor wants max Def and HP, Mamo and Chomp want max Atk and Spe, and Skarm wants max Def and HP.
Okay, with all ur tips, this is my fixed team:
-Heatran.
Flamethrower.
Earth Power.
Dragon Pulse / Ice Hidden Power
******
Nature: Modest.
EVs: 252 SpATK, 252 SpDEF, 4 Speed.
Item: *****
I need help with the 4th slot and with the item.
-Gliscor.
Earthquake.
Swords Dance.
Protect.
Ice Fang.
Nature: Impish.
EVs: 252 DEF, 252 HP, 4 ATK.
Item: Leftovers.
-Mamoswine (thanks to PlatinumDude).
Ice Shard.
Stealth Rock.
Endeavor.
Earthquake.
Nature: Adamant.
EVs: 252 ATK, 252 Speed, 4 HP.
Item: Life Orb.
-Garchomp.
Earthquake.
Dragon Claw.
Fire Fang.
Swords Dance.
Nature: Jolly.
EVs: 252 ATK, 252 Speed, 4 HP.
Item: Yache Berry.
What about Dragon Dance instead of Swords Dance?
-Skarmory.
Spikes.
Roar.
Drill Peak.
Roost.
Nature: Impish.
EVs: 252 DEF, 252 HP, 4 SpDEF.
Item: Leftovers.
-Tyranitar.
Dragon Dance.
Earthquake.
Taunt.
Crunch.
Nature: Adamant.
EVs: 252 ATK, 100 HP, 100 DEF, 52 SpDEF.
Item: Choise Band.
Also, waiting for .Aero's answer, and thanks alot to all =)