05 pete 625 cat info

Depends on the condition and millage of the truck pay close attion

 

Unfortunately, if its a 625 stay away unless you want to spend some $$$ on it to make it go good. Stock 625s are very poor power wise and heavy on fuel due to the lower compression compared to the 550s.

 

Shoot a PM to Mr Haney I'll bet he could help..

 

How do you figure the lower compression hurts the fuel mileage??? 6NZ Cat has 16:1 if I remember correctly. From what I understand the 625 Acert has 17:1 and the 475-550's (SN# BXS, MXS, NXS)have 18:1. I would like to lower the compression on my 625 NXS when it's time to overhaul...

 

Lower compression helps build horsepower because it allows you to run more boost and timing without poping head gaskets but all other thing being equal a lower compression motor will be less efficient. You cant really compare the compression of a 6NZ to an Acert, although the Acert has higher static compression it uses the IVAs to stuff around with the dynamic compression. The emmision junk is the reason Acerts are worse on fuel than the per Acert engines rather than the compression.

Once you start adding aftermarket stuff things can change a bit, you can drop compression but gain in fuel economy because you add timing, better exhaust flow, etc. Dropping the compression still losses efficiency but you more than make up for it with the mods that support the lower compression, if that makes sense...