i have a npi motor with 135k miles on it, and i'm about to do a ported pi head swap with some other goodies. will my shortblock hold together or should i invest in a new one?
if someone has a modded npi of similar miles your input would be very helpful
No need. I'm a good example. 120k miles. MMR Stg II ported heads, bronze guides, +1mm valves 10.3:1 compression with VT stage 1 cams and PI intake + bolt ons. Did a leak down test, piston rings held liquid/pb blaster indefinitely, compression test showed 5psi max difference between cylinders. All good to go. If i touched the bottom end it'd be left with all forged rods and pistons.
Never got that argument. Your replacing the top half of the engine with new stuff, how is that bad? More compression? If you run a compression test and it's good, and you run a good tune it should be running better than before.
The 4.6 is no joke. Sure it doesnt make much for power in N/A form unless heavily modded, but it sure is reliable! 125k on my odo.
I've also seen an 03 cobra with 200k, stock bottom end. A while back someone here posted a link to a user on another forum with an NPI stang that had a supercharger installed around 100k, had 300k+ on it at the time (200k supercharged, 9-11psi). Also stock bottom end.
Dont abuse it, and maintain it with a good tune and you wont go wrong. There are more than enough people out there with a 4.6 to attest to how reliable they are.