FastCougar

I was just wondering ... asked the question a while back and don't remember getting any answers. This is very important because it could mean rebuilding an engine could cut a lot of costs by using swappable 3.0 parts that are more readily available. For example, Ford's 3.0L Duratec V6 uses the same block as the 2.5L Duratec V6, only it's bored out with different cylinder sleeves. This means that the rods, crank, bearings, and almost everything else is swappable. With the exception of a few oil/water passages, the heads are swapable as well.

WILLSE

close but soooo far.... new intake manifold to start im sure many more changes..... not just a simple bore and go much much much more involved!!! sorry

FastCougar

These changes are standard if you think about it ... more volume means different intake is needed, thus almost all engines that share blocks but have different volumes have different intake systems. My above example of the Duratec V6's also have very different intake systems (Upper Intake Manifolds), but very similar TB and Lower Intake Manfold setups.

Still doesn't answer the question ... are the blocks the same? First clue would be looking at detailed specs ... do they share the same stroke? If so, that could be an indication.

PhatGuy

http://forums.maxima.org/showthread.php?threadid=91939

Keven97SE

The above post says it all, but in general:
- 3.5L motor has more bore AND stroke. The displacement increase is mainly due to increased stroke (81 vs 73mm)

- 3.5L motor has infinitely variable intake cam timing. The intake cams are correspondingly more aggressive than the 3.0L motors (that have no variable intake valve timing - 240deg vs 232deg). On the 3.5L, the exhaust cams are also slightly more aggressive (238deg vs 232)

- 3.5L motor has slightly larger intake valves. Exhaust valves are the same. I've seen no specs regarding port sizes but I'd imagine they are slightly larger as well.

- 3.5L motor has a different-style variable plenum volume intake manifold. This is likely more just a sizing change to satisfy the larger 3.5L's flow requirements. The 3.0L motor also has a variable intake manifold that operates on the same principle (variable plenum volume).

- 3.5L motor has an improved exhaust y-pipe (convergence section for the two downpipes). The 3.0L y-pipe was quite restrictive. The 3.5L pipe is designed more like the '95-'01 aftermarket y-pipes (smooth transition).

The 3.5L motor is definitely not just a bored out version of the 3.0L motor. The motor has been completely retuned. The external dimensions of the block and heads may be very similar (if not identical) to the 3.0L motor, though.