Which engine is better? What are the design weakness and strength comparisons? How can any of the design weaknesses be cured when adding horsepower?

 

Well the list is kinda long, but for starters:
fuel delivery is different. 305 lift pump is at the enigne, 325 is in the tank (except 04.5 models).
Turbos are different also 325 has electronic wastegates, 305 are manual.

I know others will continue the list...

 

305's get considerably better mileage than 325's.

 

325 has a 4 in turbo outlet ,electronic wastegate ,4 in exhaust and a whole slew of upgraded parts .

 

325 ECM is faster and has more memory and more protective measures for truck. 325 torque management is harder to get rid of (scary larry). 325 Injectors are bettter design stock. 325 has three injection events, 305 two injection events, (third to heat the exhaust cat). 305 ....no cat. 325 rods are plastic .....just checkin to see if you were paying attention. Some 325 motors in 05 had plastic end tanks on the intercooler. All 305 were metal. Al 305 had od lock out on the auto. 325 up to 06 had tow haul with no od lock out. Plus what everyone else said. ks

 

only one disagreement. only the 05 trucks had no OD lockout. the 04.5's have OD lockout

 

My opinion from having both.
305 gets way better mileage, and has better throttle response. 305 pulls better at lower rpms.
325 is alot quieter. And the new tow/haul set up on the 06 is better.
This is just from comparing the two trucks I had/have. But the 305 I had would run circles around this 06. Both with the same gears, and both with Edge EZ boxes.
It is not that I dislike this 06, but I miss the way that 04 ran. And the mileage that the 04 got.

 

just wondering. i have an '05 with 325 hp. can i look at the vin to tell if it was manufactured as an 4.5 model? i am wondering if the lift pump is in the tank.

thanks,
david
socal

 

How significant is the difference in mpg's? Do the differences remain the same after building to 500hp? Once again I'm also looking for inherent weaknesses and what measures can be taken to correct them to determine which would be the best engine in the long run. Thank you for your input.

 

Plastic....hmmm....saves weight

 

Dh just look at your fuel filter. The pump is mounted to the side of the canister on the firewall side. Mine is still factory with 26k on it. I wouldnt sweat the fuel pump.

 

600's have fancy Iconel (sp?) valves...but they fall out! LOL

They are both very stout...almost identical engines. I like not having the third injection event.

 

That is exactley the same results I had between my 305 engine compared to my 06 325 engine!!!!!!! (I had 6 speed and 3.73 in both trucks)

 

The 3rd gen engines are always quieter when new,

with miles and hard work they get louder

 

dont want too start a war here....but how much better can mileage get?? This 06 is pulling 19 mpgs HAND CALCULATED (O/H reads 19.9), with only 4125 miles on the clock.....i currently have 505 miles on this tank and still have 3/8ths of a tank!! My '02 24 valve couldnt do this!!