Hey guys just got myself a 1982 C20 6.2. I love ti one of the best trucks ive ever driven runs great. Just had a few questions. I changes the oil and typical of a diesel as soon as i put oil in it instantley gets dirty looking again. I have a ford powerstroke as well and i can go 3000 miles and the oil still looks like honey. How can i make my old chevy get that clean. Also i was instaling a new air filter and noticed a substantial amount of oil build up or just grease from over the years down on the inside of the intake manifold. Should i pull the manifold and have it hot tanked for it to run a little better, or not worry about it. However the truck runs great now i just didnt like the way the inside of that old intake looked. Thanks for all your time guys.

if the cdr valve(tuna can thing) is plugged up it can run excessive oil into the intake. the egr system also makes a mess of things. and you can't hot tank it, its aluminium.
your oil will never stay really clean in these from my expierence

on my intake i pulled it off to check ip timing(someone didnt tell me there was no marks down there:mad:) so when i had it out i took some carb cleaner after it and it ate about 2 cans then i took it to my powerwasher and just went rambo on it. spent about 2 hours powering gunk outa theregot 95% of it id say. theres still black spots on the lawn over there :rolleyes: . wouldnt say it helped the preformance but it just felt like it was better that way. when i had my oil pan adventure( learn from my mistakes :p: ) i had my engine oil in and outa the truck 4 times in total, and when i first changed the oil i dumped it in (and i had had the pan out so the pan was wiped all nice and clean inside) and i run the engine for less than 30 seconds and had a leak in my rear main so i shut it off and drained the oil and it was BLACK. im talkin black like a old 4020 john deere oil. dunno why its like that but it is.

Hey guys thanks for all the replies i just looked at the CDR valve and it is definatley original. Do you all think it prob would not hurt to change it since it is 27 yearas old???

good luck finding one. GM discontinued them so youll either have to find one off a junker or jimmy rig in a 6.5 CDR valve

One thing you can do is make sure you get all the oil out when you change the oil. Disconnect the lower oil cooler line on your truck and drain about another half quart out of the oil cooler and lines.
It will still turn black real quick.

good luck finding one. GM discontinued them so youll either have to find one off a junker or jimmy rig in a 6.5 CDR valve

gm discontinued them like they discontinue everything else. they are available at moost part place listed under the pcv valve

just cleaned my intake today...OMG. I cannot believe how thick the buildup was. I think it was 1/4" in most areas. I used ovencleaner and scraped the heck out of it. What a freakin' mess.

just cleaned my intake today...OMG. I cannot believe how thick the buildup was. I think it was 1/4" in most areas. I used ovencleaner and scraped the heck out of it. What a freakin' mess.



hey man let me know how the truck runs when your done mine looks the same way from the top looking in. i wanna know if its worth takin off.

hey man let me know how the truck runs when your done mine looks the same way from the top looking in. i wanna know if its worth takin off.
I don't think it is running any different now that I got it cleaned out. That 1/4" of buildup was more like a 1/2" in some areas....unbelievable.

I think I'd do it when you have another reason to remove the intake (IP issues or something like that). Or unless that buildup is making you lose sleep at night. Personally, I feel better that it's gone, but I can't say that it made any difference in the truck's drivability.

I am porting my heads and 3/4 of the air flow gains will come from scraping all the gunk out of the intake ports, cleaning off the valves, and chipping the carbon away from around the valve seats.
I must have been getting nearly now air flow below .100 inches of intake valve lift with all the carbon build up in the intake port, on the valve and around the valve seat.