Seeking a "C" and "J" Education

[ThePIGSmith]

This what I understand:

6.2 "C" engine - Light-Duty w/EGR.
Installed in vehicles rated as 1/2 ton.
6.2 "J" engine - Heavy-Duty non-EGR.
Installed in vehicles rated as 3/4 ton.

The "J" motor has more HP than the "C" motor
A "C" Motor can be upgraded to "J" specs with a intake swap and other bolt on items from a "J" motor

Now, what are the real world differences between the two?

I been studying the 6.2L Build Up in Diesel Power Magazine and have come away that the "C" motor is junk.

If I have a "C" motor, do I throw it away?
What are all the steps/details to upgrade to a "J"
What are nice upgrades, but not necessary (like V Belts verses a Serpentine belt) and what are the must dos (like the "J" intake)

[DmaxMaverick]

Essentially, the only difference is the intake, pre-cups, and fuel rate. A C engine can be converted to a J by swapping the intake and turning up the fuel a little. The pre-cups offer some gain in power (and MPG loss), but rarely will offer an appreciable gain. Depends on how picky you are. C engines were available in 1/2 ton trucks/SUV's, and some LD 3/4 ton trucks and Suburbans, depending on year model and the state they were delivered.

Upgrading the intake isn't necessary. The EGR valve can be removed and the ports plugged. There are gains to be had with different intakes (there are more than just C and J), but gains are marginal. Upgrading to serpentine is more than just belt and pulleys. Water pump, and fan are different. Pump and fan rotate reverse of the engine. While costly, a conversion kit available from some suppliers is the best way to go, and will include all necessary components for the change.

[mark g]

pump is gear driven on "J" versus chain driven on "C". all military trucks, blazers and trucks had "J" motors. 8 th digit of the vin will identify the engine you have or what it was born with. 6.2 made through 1993 with the first year being 1982.

i actually new a guy who ordered an 1981 chevrolet 1/2 ton truck with the diesel option knowing it would come with the famous 5.7 olds engine.

the dealership made him pay for the truck before they would order it. i wonder how many 81( new body) trucks came with 5.7 diesels. not many i bet. i hate to admit it but i owned many 78-80 5.7 diesels. cars and trucks. my favorite was an 85 olds cutlass, 5.7 d. gear reduction starter, got consistant 32mpg.:D

[High Risk]

i hate to admit it but i owned many 78-80 5.7 diesels. cars and trucks. my favorite was an 85 olds cutlass, 5.7 d. gear reduction starter, got consistant 32mpg.:D


My uncle has an 80 Cutlass with the same motor I've been trying to get a hold of. I know theyr'e slow and doggie but how doggie are they?

[DmaxMaverick]

pump is gear driven on "J" versus chain driven on "C"......

To which pump are you referring?

The valve train and IP drive are exactly the same, C or J. The cam is chain driven from the crank, and the pump is gear driven from the cam. If you find anything else, it's an aftermarket modification.

[mark g]

To which pump are you referring?

The valve train and IP drive are exactly the same, C or J. The cam is chain driven from the crank, and the pump is gear driven from the cam. If you find anything else, it's an aftermarket modification.

sorry, brain fart;)

high risk
i think the later models were better, overdrive transmission in 82, along with gear reduction starter. i had rocker arm stand wear on some. lots of starter failure and some head gasket problems.