H.O. vs. non H.O. whats the difference?

[CurtisM]

I would like to know what the difference is between the H. O. and non H. O. motors. Iknow that the H. O. makes more power and it only came behind the manoul or the 48 auto trans but what makes it have more power? Is it the injectors, turbo, electronic tune up, more fuel preasurre, what? I am whanting to know this because I am going to buy a third gen truck and wanted to know if I get a non H. O. or an H. O. if one will make more power than the other after the same mods are done to it.

 

[JRD]

Well Im not too sure on the differences between the HO and SO motors. What I do know, is SOME of the differences between the 305HP/555TQ engines and the newer 325/600,610 engines. Some of the changes were the piston bowls in the "600" series motors were different and also the angle of the injection was changed. As well as a additional injection event, which has nothing to do with power output, but emission regulation requirements. So maybe between the SO and HO motors is the same type deal, Piston bowl changes, and injection angles, maybe a few more factors as well. Somebody far more diesel intelligent will be able to answer this more thoroughly but I thought Id shed a little light on the subject from what I know.

 

[GECCO]

The compression ratios were also different, the non HO was about 16. 3 and the HO was 17... . I learned that here on TDR when I had a similar question!



Check out THIS THREAD for some more info...

 

[JCleary]

The HO has oil-cooled pistons, the SO does not.



The SO makes HUGE power. It seems the SO's respond better to mods than the HO's do.



I was looking at my mods vs. Tomeygun's mods, and we're at the same HP level. He's got a TST/EZ stack with a FASS and a SP66. I've got my #'s with a TST/BDDL stack with a FASS, SPS66, and a couple of other items.



So, similar mods, the same end result. But TG started with 55hp less.



I would not worry about the SO/HO difference, just find a truck with the 48RE. It was available towards the end of '03 on both models.



BTW- Welcome to TDR!

 

[DPKetchum]

Supposly the exhaust manifolds are differant and flywhhel is heavier on the H. O. as well as pistons etc.

 

[betterthanstock]

With the oil cooled pistons, the HO is able to run at higher sustained power levels without piston meltdown. Important for towing more than drag racing.

The other difference is the transmissions. The HO came with much heavier duty NV5600 and 48RE, the SO with NV4500 and 47RE, (though some late trucks may have the 48RE???).

 

[daytripper63]

The S. O. also has oil cooled pistons as well ALTHOUGH it is a different design

 

[jwilliams3]

The compression ratio's on 3rd Gen's are all the same.

The 17 vs 16. 3 numbers only apply to 2nd gen ISB's.



All 3rd Gens are typically 17. 3 to 1 ratio: SO's, HO's, And 600's, 610's etc.



They ALL have oil cooled pistons.

The SO's did not have the j-jets to shoot oil into the internal cooling chamber that is in the HO pistons.

The SO's retained the earlier upper bearing saddle based piston cooling nozzles.

On each engine the oil passage that is not used for cooling and lubrication is blocked off to retain oil pressure.

Its either one or the other: J-jet vs. Piston cooling nozzle



As far as early 03 and 04 engines the SO's had the same injectors, turbo's, blocks, ECM's, heads as the HO motors.



Your mostly looking at programming as being the major difference as I recall.

 

[CTieman]

Check out the Cummins web site for SO and HO differences. There is some good info in the FAQ section. My question is, what is the difference between the SO Cali edition and non-Cali? Can't find any info on the differences.

 

[betterthanstock]

My question is, what is the difference between the SO Cali edition and non-Cali? Can't find any info on the differences.

Cali : 235 HP + catalyst

Fed (SO): 250 Hp no cat

Fed (HO): 305 Hp no cat