83' C30 6.2L diesel

[agertz1]

I'm a newbie to diesels, so other than piston speed, without air flow control on intake side, how to build port velocity ? Seems like it should matter ?
Thanks, Art.

[HDBD]

A turbo will do that. The NA 6.2 is an anchor. Lots of them have been pulled and replaced with gas motors

[Racer71]

Unshrouding the valve reliefs in the head help especially on the 4v diesels. I haven’t worked on one of those 6.2 in so long. Don’t remember the head layout but a bit of common sense should go along way with helping things get better. I don’t know that those engines are capable of making much power.

[ProPower engines]

I'm a newbie to diesels, so other than piston speed, without air flow control on intake side, how to build port velocity ? Seems like it should matter ?
Thanks, Art.

The 1st question is what type of build are you doing?? Stock ?/ HP??
How much boost do you plan to run??
The same things apply to NA engines as boosted just with a boosted application the air is forced through the ports so any improvement helps fill the holes faster.

The valve job and guide work is the place where you will see the most improvement just like a gas engine.
Too much guide clearance will allow the valve to not seal quickly thus letting cyl. pressure escape reducing power.
Since both valve and seat angles are 45 degrees it will make it easier to do a good valve seat.

[agertz1]

Just a work truck/ tow vehicle. Odometer shows 67k mi. more likely 167K. Little, blue smoke on cold starts. Guides or oil drain back ? Rear main checked at .002" clearance,( new oil pump, rear main seal and pan gasket while up-dating to 4L80E trans). 4:10's out back, engine likes the 25% OD.
Compression test B4 decision to add 6.5L design , turbo conversion ?
Thanks.

[PackardV8]

The NA 6.2 is an anchor. Lots of them have been pulled and replaced with gas motors.

For true. If someone gave me a 167,000 mile '83 6.2, I'd still think long and hard before investing in a performance rebuild.

Little, blue smoke on cold starts.

IIRC, they did that when new.

[Monzsta]

Yank that 6.2 before it breaks the crank and drop a 12v Cummins in it. Any Chevy diesel is a problem waiting to happen.

I swapped a 6.5in a '90s 3500HD rollback that broke the crank for a 12v cummins. With the NV4500 I swapped the input shaft and bellhousing and with a mount kit it dropped right in with the chevy motor mounts. Had to slide the crossmember back a few inches and redrill the frame and shorten the driveshaft, but not a big deal. Made amount for the 6.5 alternator as that's where that truck reads the tach from, and had lines made to adapt the Dodge A/C compressor to the chevy lines.

[agertz1]

Good advice. If short block is good, how much perf. N.A. gain by workin the heads ? It currently pulls 7+k lbs. in O.D., on level. NV4500 is a manual ?

[dannobee]

There's no guarantee that the short block is good. We'd see them in for oil consumption only to find the upper parts of the cylinders worn out.
But even turbocharged they were still gutless. Without a turbo they were slower than a pregnant nun going to confession.
Brings back memories. All bad.

[rebelrouser]

I worked at a Chevy dealer when the first old's based diesels came out. GM told us that they were switching to diesel from gas to get around emissions regulations. Every model that year had a diesel option. Most were junk and to my memory none had turbo's The only one I really liked was the Chevette diesel, it was made by Isuzu, kind of underpowered, but it got an honest 60mpg. The whole deal turned me against diesel engines. Until I bought a 1998 24 valve Cummins dodge. The Dodge B series Cummins is designed as a medium duty truck engine, and is designed to last at least 500,000 miles, It has to be one of the greatest light duty truck combinations ever built, great fuel economy and the engine will outlast the body three times over. I spend a little money on mine each year to keep it up, and it is weird but numerous times I have notes attached to my windshield from people wanting to buy the old truck.
I helped a buddy who tried to make a 6.2 into a tow rig for his race car. He spent a lot of money and bought every aftermarket hot rod part to pump up the power. He followed me to a race about 5 hours from our town, and after that he bought a Dodge Cummins, He could not keep up and I got twice the fuel mileage. Not wanting to piss on your parade but a 6.2 may push the truck around OK, but never try and hook anything heavy to it, it has no guts, and their is nothing you can do to give it guts. Just my experience for what it is worth.

[rustbucket79]

All the 6.2 and 6.5 crack between the seats and eventually leak coolant, there is a repair kit for that, it puts bronze liners in after boring the coolant passage out with a reamer.

I’ve seen more than a few broken 6.2 cranks, not sure if it’s better or worse than the 6.5’s cracking main saddles.

Perhaps regular maintenance and nothing more will keep it alive, and once it dies replace it with something else. I wouldn’t beat on it too much.

[Leftcoaster]

The 6.2 and 6.5 engines are indirect diesel injection, with two combustion events for each power stroke

Rebuilding a fundementaly flawed design is risky, and modifying it for greater torque further decreases its lifespan

For reference to "tuning" an indirect injection 2.4 litre 4 cyl Toyota diesel search out "Turbo diesel flow gain" on this site