Nissan Repair: Loss of compression, nissan skyline, definite cause

Question
I have a  4 cylinder 2.litre 1990 nissan skyline ,the head has just recently been done ,the car has been standing for about six months ,I got it started and after about 100 meters it starts to loose power then I have to change to a lower gear and put my foot down on the accelerator to give it some power to drive,the exhaust manifold gets red hot and of course my heat gauge goes up ,what is causing these problems

Answer
Hi Sebastien -

If the exhaust manifold is getting red hot, then you have excessive back pressure in the exhaust system. Is it both exhaust manifolds? Back pressure is the definite cause for loss of power as well.

I would check the relative CAT converter or muffler/pipes. The car has been sitting for quite a while, perhaps the inside of the pipes (double wall), or muffler collapsed.

Hope this helps -
aloha
calvin