ENGINE
1. The blocks are the same. They both have oil squirters that direct oil towards the underside of the piston, although they point at slightly different angles, they are still interchangeable. They have all of the same oil passages. Two passages are plugged with a bolt on the NA block (one on each outside face that feed the turbos on a TT). The TT has two oil passages plugged inside where the oil filter bracket mounts, the NA has two small check valves in this location. They are plugged in the TT so that the oil will go through the lines to the oil cooler, which returns back to the oil pan.
2. The crankshaft is the same.
3. Connecting rods ARE the same!! (Same Nissan part #)
4. Piston rings, and Crankshaft (main) bearings are the same. The rod bearings are the same size but the TT ones are a different alloy.
5. Of course the pistons are different because of lower compression ratio in the TT.65. Oil pumps are different. They mount the same but I assume the TT one is higher capacity.
6. Oil filter bracket on a TT is different it has an outlet that accommodates the hose going to the oil cooler.
7. Cams, Lifters, and valve springs ARE the same (90-93)(same Nissan Part #) The Auto TT has different intake cams (lower lift) but the intake cams on the 5 speed TT, NA, and auto NA are the same. All the exhaust cams are the same. The 94-95 cams were different than the 90-93 but just like the earlier ones they are all the same except for the intake cams on the auto TT. The 96 cams were all the same.
8. The valves are all the same size. But the exhaust valves on a TT are made from a stronger alloy.
9. Nissan claims the bare heads are different but I no longer believe it. I used to think the thickness was different but after some measurements I believe they are the same and have been using them interchangeably (just making sure the exhaust valves are the stronger TT ones)
10. The oil pan is different because the TT one has 2 tubes protruding on the sides where the oil return hoses for the turbos mount and another one for the hose returning from the oil cooler.
11.The turbo engine obviously has a few different accessories and systems to accommodate the turbos. The exhaust manifolds on the TT are much shorter than the NA ones, which go all the way down and tie into the exhaust section including the catalytic converters. The turbos are oil lubricated and water cooled. So there are oil and water feed and return lines.
12. The throttle bodies are the same size but the passenger side one is different on a TT simply because one of the water lines attached to the bottom of it has a junction in it to feed water to one turbo.
The upper and lower intake manifolds are the same TT and NA although the 94 up ones are different from the earlier ones.
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