6.2L Diesel - swap to J-code intake or not?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

golf12

Junior Member
Joined
Nov 20, 2022
Posts
2
Reaction score
1
Location
Ontario
First Name
sb
Truck Year
1984
Truck Model
K5 GMC Jimmy
Engine Size
6.2L Diesel
Hi all.. First post here.. I have an 84' K5 Jimmy with a 6.2L Diesel that I've had for 8 years. The truck and engine are original and have 315,000 kms (195,000 miles). The engine starts easy - doesn't smoke - has almost no blow by and runs beautifully. This engine inspires as much confidence as my brand-new truck does in terms of starting and operating regardless of conditions. I would trust it to drive cross country without hesitation. I am harping on how well this truck runs because its reliability is the crux of why I am posting. I bought a J-Code intake for it not long after I bought the truck. The first thing I was gonna do is ditch the c-code and all if the emissions garbage. Not for power of course, because unless you turbo a 6.2 I don't think there's really anything you can do to increase power and actually feel it. But the J-code has other benefits that should make the engine healthier. So my dilemma is this. Do I dig into an engine that runs as nicely as this one does to swap intakes?. Or should I just leave it the heck alone?. The "what if's" are why I am being so indecisive on this project. What if the J-code makes it run even better than it does now?. What if I do actually feel a bit more seat of the pants power?. What if swapping makes my engine last longer?. Since I've been on the fence so bloody long trying to decide whether or not to do it. I thought I might solicit some "what would you do?" opinion's. Is it worth the fuss to remove the intake and probably realize no benefits that I can actually notice or feel?. I suppose time spent turning wrenches is never a bad thing. Its a reason to be in the shop. But my biggest concern is regretting it and somehow making the engine run worse after swapping intakes. Has anyone here done this swap and regretted it or even just felt like it wasn't worth the effort?. Thanks for any input!
 

Originalthor

Full Access Member
Joined
Aug 22, 2021
Posts
1,085
Reaction score
3,662
Location
Saskatoon Saskatchewan
First Name
Scott
Truck Year
1989
Truck Model
Suburban
Engine Size
5.7
Having lots of 6.2 and 6.5 diesels in my day. I would do it. Its nice that you don't have to touch any injector lines. I've done the swap a few times it brought my egt down a 100 degrees on my 6.5. Was it a noticeable difference. Yes and no.
 

Originalthor

Full Access Member
Joined
Aug 22, 2021
Posts
1,085
Reaction score
3,662
Location
Saskatoon Saskatchewan
First Name
Scott
Truck Year
1989
Truck Model
Suburban
Engine Size
5.7
Also welcome to the forum. Let's see some pictures of your truck. We like pictures.
 

Strick

Full Access Member
Joined
Nov 25, 2020
Posts
1,354
Reaction score
3,315
Location
Dunn, NC
First Name
Harold
Truck Year
1979
Truck Model
C20 Crew
Engine Size
350
Welcome from NC central.

Strickland
 

Blue Ox

Turning Diesel Fuel Into Fun
Joined
Mar 27, 2018
Posts
5,218
Reaction score
12,014
Location
LI-NY
First Name
Derek
Truck Year
MCMLXXXV
Truck Model
K20HD
Engine Size
6.2L
Bad as it is to dump an engine's exhaust back into it, the performance difference comes from the injection pump calibration. If it wasn't that, you could just lock out the EGR valve out and experience the magic.
 

golf12

Junior Member
Joined
Nov 20, 2022
Posts
2
Reaction score
1
Location
Ontario
First Name
sb
Truck Year
1984
Truck Model
K5 GMC Jimmy
Engine Size
6.2L Diesel
Thanks everyone.. I think I'm inclined to just do it. Winter is the ideal time anyway since the truck doesn't see the road again till spring. I was just wondering if the general tone would be "don't mess with it" or "go for it". Seems like no one has any particular concerns and the risk of messing something up seems low so why not I suppose.. Apologies for bad form in not posting a pic so here's one..
 

Attachments

  • Truck pic.PNG
    Truck pic.PNG
    787.3 KB · Views: 73

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,439
Reaction score
5,581
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
Personally, I wouldn't mess with it if everything is working fine now. You are far more likely to mess something up than you are to improve anything.
 

Albrigap

Full Access Member
Joined
Jan 16, 2021
Posts
75
Reaction score
71
Location
South Dakota
First Name
Alan
Truck Year
1991
Truck Model
Suburban
Engine Size
350
I have overhauled a number of these Roosa Master DB diesel pumps. Timing is critical to keep them running smooth. Only a couple degrees off can make a big difference. To easily check timing, with the engine warmed up, mash the throttle to the floor and hold it a couple seconds. If the governor surges at the top, your timing needs to be reset. If it holds smooth, timing is OK. Take the return line fitting out about every 6 months. If you find what looks like coffee grounds in that fitting, your governor elastacast weight retainer ring is disintegrating. There is a solid weight retainer that does not use that ring and you will never have this issue again if used. Inside that fitting is a clear ball and spring. I always carried a spare fitting with that ball and spring removed. If the return line plugs with the coffee grounds looking stuff on a Roosa Master, it quits. The one without the check ball could be put in, to get home, and it will start right up. The case, if overhauled should have a sleeve installed in the advance piston to insure the advance works as it should if overhauled.
 

Forum statistics

Threads
44,163
Posts
950,684
Members
36,276
Latest member
2manysquares2care
Top