Engine/Transmission (1998.5 - 2002) HO vs SO engine

[dclassens]

Been around TDR a long time, looking to help a friend with a decision to buy a 02 HO. Give me ALL the good, the bad, and the ugly. What is the main difference between a HO and SO engine? What is the difference between a HO and a SO injection pump? Can a SO pump be put on a HO engine? The truck has a C VIN in the 8th spot any issues with that? Any info or TDR links to older threads would be a huge help. I spent a little time in search area but did find what I was after. Thanks



Dave

 

[Ram4Sam]

This is from the 2001 FSM, I would bet the '02 is the same.

 

[Houser]

I like my 02 HO. Gets over 20 mpg unloaded and 15-17 loaded with only minor mods. I drive the speed limit and use cruize as much as I can. The 6 speed is a little notchy And not as much fun in city traffic as an auto but 5th is about as low as I need on most hills with a load. over all I prefer it to my wifes SO.



Mike

Palmer, Ak

 

[VolsFan]

Not sure about the output, but I do know the 02 had 4 wheel disc and bigger 2 piston caliper brakes, started in 00. 5/01 I think. My uncle had an 02 auto and that thing was a dream to drive and stop, not to mention being a piece of cake replacing rotors as the hubs were not pressed in like my 99. He dogged that truck for a while(bone stock) before trading it in never experiencing any major mechanical failures.

 

[HBarlow]

There are significant differences between the '01/'02 HO and SO engines but I don't recall all of them from memory. Here are some random thoughts: the ECMs are interchangeable but are not identical. They produce different power output levels. The HO engine had a slightly lower compression ratio, cooling jets under the pistons, and different injectors. It was rated 245hp/505 tq to the SO's 230hp 450tq iirc. Years ago Joe Donnelly reported dyno results on an HO with Bosch RV275 injectors at about 275hp/550tq iirc. The one I had ran strong.

 

[BDaugherty]

the ho engine had higher compression and more timing. the injection pumps are not the same. the so responds better to a fuel box... probably because it had less to start with. for the'02, the ho still used the hx 35 turbo while the auto used the hy35. not sure which turbo the 5spd so used.

 

[Joseph Donnelly]

The HO pump had a more aggressive cam with smaller plungers, different program in its little computer module. RV injectors added 42 HP; 33 on SO 5 speed, and about 50 on automatic 24 valves. All engines had oil squirters to cool the pistons. You cannot simply interchange SO and HO injection pumps as the programming is different. One quick way rebuilders can "hop up" either type pump is to add the better part from the other pump--the cam or the plungers.

 

[HBarlow]

I remembered where I had seen the details. My memory of details was not very accurate.

Here is an old link to add to what Joe posted above:

http://dodgeram.org/tech/dsl/Facts/01ISBspecs.html

 

[Vaughn MacKenzie]

Good find Harvey. Another difference is the HOs had pressed in valve seats, SO did not.

The HO tends to get a bit better MPG. And they rattle more loudly, the loudest Cummins ever put in a Ram.