I currently have a 93 K-3500 1 ton dump I use for tree work. The original 6.2 was a J motor that had seized. The used replacement is a C motor. I had no idea there was a difference. The problem is there is no power. If I take the J manifold and the 4979 Injection Pump and install them for a cost of around $1,000, will that give me more significant power or should I just turn up the current 4425 pump and advance the timing for around $150? The truck has new fuel and air filters and a bigger exhaust but it does have the restrictrive air intake. If the power isn't significant I will sell the truck and buy a new duramax. What's your advice?

It will give you more power to upgrade the intake and ip.

how much power you expect out of a 379 cubic inch motor will make the difference as to whether you are happy with the results or not. If you are looking for a very large power boost you might as well either pull out the pocket book and do it up right with a turbo or just get a different motor. What you are talking about is tweaking the motor you have for better air and fuel flow making (relativly) minor power increase , not major modifications for a drastic power increase.

If it were me I'd just unhook the EGR, advance the timing,and turn up the pump. but then I haven't driven your truck with a full load up a hill either.

Welcome to the forum!

Yes, it will give you a power boost. A power increase of 25-30 hp would not be out of the question if you not only install the J-code intake and injection but turn up the J-code pump as well. Considering that you only have 140 hp to start with, that isn't bad.

The C-code engine is most definitely underpowered for your application.

A turbo would also be a good investment, but keep the boost fairly low (10 psi). Should be able to push past 200 hp and 400 ft lbs (which is close to double the hp/torque ratings of a stock 6.2).

Hope this helps!

Welcome to the forum!

Yes, it will give you a power boost. A power increase of 25-30 hp would not be out of the question if you not only install the J-code intake and injection but turn up the J-code pump as well. Considering that you only have 140 hp to start with, that isn't bad.

The C-code engine is most definitely underpowered for your application.



So how do you tell the difference ? The VIN of my short bus indicates that it is a supposed to be a "J" code, I think. However, the engine was replaced with one out of an 88 suburban. Is there writing or any other identufying characteristics on the heads or block or pump that indicates J or C ? The one in mine has those black "GM Goodwrench" covers...

If it turns out to be a "C", are those mods to a "J" worth the cost ?

TIA...

Pull the air cleaner off and see what's under it. If the intake is wide open it's a J-code, if there is an EGR valve in the middle it's a C-code. At least that's what it means in effect. If it is a converted C-code it will have an open intake, but may still have the C-code EPR valves and injection pump.

It doesn't cost that much to switch to a J-code. The main cost is the intake manifold and gaskets. You can turn the C-code injection pump up to add fuel to match, so there is no need for a different pump.

I keep meaning to switch mine over, but I still haven't gotten around to it.