[urq] Rebuild engine seizes after 15sec's . ( non audi )

[Patrick Carlier]

So guy's , i'm a bit at wits end here . 

Car is a 1987 nissan coupe , 8 valve carb , 1600cc . ( E16s engine ) 
Bought it as a fisrt car for my 17 year old son who's very enthousiastic about it :) .  

It came with a known broken engine , head froze to pieces . 
Found me a 1500 Turbo ( E15ET)  engine with severe big end damage 
The blocks  are identical as are the heads , only the 1500 crank throw is smaller , and the compression is lower . 

With a bit of this and a bit of that I put together a complete engine 
Had the 1500  honed , and the head shaved . 
Used the 1600 pistons and conrods with new pistons rings . 
The 1600 crankshaft was also used with its main bearings shells  in the 1500 caps . 
Bit of a puzzle , i know :) . 
And i've put in new conrod beraings . 
Meaning all moving parts are either new or matched as they were . 

Assembled it all , put it in the car , and fired it up . 
It won't  really idle , most likely a carburettor problem , so I have to rev it a bit , and use the accelerator pump 
to keep it going .I can keep it running at abt 1500 rpm 

It runs for about 15 seconds and then it stalls . 
Dead stop all of a sudden . 
Tried to start again , and the starter engages but fails to  crank the engine . 
Using a wrench at the crankshaft pulley , with the plugs removed , and it barely turns . 
Looking inside shows no sign of hydrolock 
Wait 10 minutes , and all's back to normal . 
Engine fires right up , and seizes again after thesame 15 to 20 sec's  time period . 
Plugs are oily when pulled , fresh oil , not burned or carbonized . . 
With a cold engine and the plugs removed I can turn the crank with my bare hands by grabbing the crankshaft pulley . 
Also tried two grades of oil , 10w40 and 20w50 , no avail . 

Now I've done my share of engine rebuilds and I've never seen this before . 
And quite frankly , I don't quite know where to go from here . 
Sure , I need to pull it apart , buit then what ? 

Any thouhts , comments btdt's ..... 


Pat 
VERY unhappy for now . 
 .