I'm at the point in my build where I need to make a decision about which style CDR to run. My '99, of course, has the 'valve cover' style which I will refer to as a 6.5L CDR. I know some guys have gone to the 'fill tube' style, which I will refer to as a 6.2L CDR, in an effort to suck less oil through the turbo. I've also heard that, as of late, AMG has gone back to the 6.2 style. What do you guys think? Especially those who've swtiched and have first hand experience.
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Which CDR is prefered?
- Thread starter restoguy
- Start date
I'll have new rings and valve stem seals, as I'm going a ring/bearing job on the old girl. I've noticed a little oil film coming from the CDR before and if using the 6.2 style would stop it, I would make the switch. Its a little more effort to find the parts, but not much more work becasue the engine is just going back together now. But after it's in the truck with the injector lines on and what-not it becomes a lot harder. Maybe it's not worth the effort for a new engine....
ak diesel driver
6.5 driver
bobbi martin comes to mind
He had a "pro-vent" and took it off. He went back to stock. I sold him the oil filler tube.
Missy Good Wench
Wild Blonde from Cloud Mt
A little history here and some practical application.
Back in 1993 I bought a "then New" 93 GMC 2500 4x4 with the 6.5 TD This rig was spany new with LESS THAN 20 MIES on it.
By the time the truck had 5000 miles and one summers running I changed the air filter, and to my supprise the turbo inlet was sloppy wet with oil.
This was a nearly new truck and had far too much blowby.
The condition never changed over the course of a few years until I traded the truck in on a new crewcab dually 4x4.
Now fast forward to 2005/2006
We had a well used high mile 1994 Burb and the beast blew a head gasket. I yanked the engine and rebuilt it.
After the rebuild (just honed, rings, heads and bearings) That engine had nearly zero blowby and the turbo inlet was totally dry all the time.
The amount of crap in the turbo inlet is the result of the amount of blowby and not the placement of the CDR valve.
An engine thats showing a lot of blowby (smokey vapor at the oil fill or VC port) is going to have a sloppy turbo inlet.
This is oil vapor mixed with combustion gases (leaking past the rings) thats being sucked out of the crankcase.
The 6.5/6.2 is supposed to run with a slight crankcase depression (vacuum) as this keeps oil leaks to a minimum.
Wherever you decide to install the CDR, the amount of blowby is what determins the oily mess.
I have seen a couple crankcase vent contraptions that had a canister that trapped the oil pullover and drained it back to the pan via the turbo drain.
Sort of a bandaid for a deeper problem.
Missy
Back in 1993 I bought a "then New" 93 GMC 2500 4x4 with the 6.5 TD This rig was spany new with LESS THAN 20 MIES on it.
By the time the truck had 5000 miles and one summers running I changed the air filter, and to my supprise the turbo inlet was sloppy wet with oil.
This was a nearly new truck and had far too much blowby.
The condition never changed over the course of a few years until I traded the truck in on a new crewcab dually 4x4.
Now fast forward to 2005/2006
We had a well used high mile 1994 Burb and the beast blew a head gasket. I yanked the engine and rebuilt it.
After the rebuild (just honed, rings, heads and bearings) That engine had nearly zero blowby and the turbo inlet was totally dry all the time.
The amount of crap in the turbo inlet is the result of the amount of blowby and not the placement of the CDR valve.
An engine thats showing a lot of blowby (smokey vapor at the oil fill or VC port) is going to have a sloppy turbo inlet.
This is oil vapor mixed with combustion gases (leaking past the rings) thats being sucked out of the crankcase.
The 6.5/6.2 is supposed to run with a slight crankcase depression (vacuum) as this keeps oil leaks to a minimum.
Wherever you decide to install the CDR, the amount of blowby is what determins the oily mess.
I have seen a couple crankcase vent contraptions that had a canister that trapped the oil pullover and drained it back to the pan via the turbo drain.
Sort of a bandaid for a deeper problem.
Missy
bison
Well-Known Member
Pipe the FF en thing to the world and be done with it.
Its like Missy said,a oily intake is the result of blowby which is bound to happen on a re ring or as a new engine wears.
Prior to the "emision" BS every single engine was vented to the world.
Its like Missy said,a oily intake is the result of blowby which is bound to happen on a re ring or as a new engine wears.
Prior to the "emision" BS every single engine was vented to the world.
Missy Good Wench
Wild Blonde from Cloud Mt
The CDR needs to be used in order to maintain a slight negative pressure in the Crankcase.
Missy
Missy
Joey D
Member
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If you vent to the atmosphere like I do the CDR will cause pressure buildup in the crankcase because it has no vacume from the intake to pull it open, would you agree?
I know I have seen guys who tried to get rid of the CDR and just use breathers and vent to the sky but they lost oil out the breather. So I kept mine in place just got rid of the intake hose.
bobbiemartin
Author of The DB2 Conversion Guide
I had the oil fill vent on my engine for a while and then went back to the valve cover/CDR setup. I think it really doesn’t matter where you vent the engine from, perhaps the oil tube is the best location, but the valve cover seems to work just as well.
At first, I went with a only a Mann Pro Vent. I found it would slightly pressurize the crankcase and had several small oil leaks, more like seeps. Just for a test, I temporarily rigged up the CDR to the oil tube vent and the oil leaks stopped, along with a slight vacuum in the crankcase. So, I changed back to the vented valve cover (not exactly an easy job) on the right side and went back to using the CDR in the stock location. I haven't had any oil leaks since. I'm thinking of testing the Mann Pro Vent with the CDR, but haven't yet.
I would decide what type of vent/CDR/open to atmosphere system you are going to run and then select the vent location that works best with your system. If you go with the stock CDR, its much easier to plumb using the valve cover. Plus, you are using all stock parts. If you choose something else, then maybe the vent tube would work. I think all NA 6.2/6.5's use the oil tube vent, but cannot say for sure.
One more thing, the NA's have a shield over the timing chain. I'm guessing its some sort of splash shield for the oil tube vent, but cannot say for sure.
Here are some pictures of the vents in use:
Here is the oil tube vent, plumbed to the Mann Pro Vent.
And the current, stock CDR setup
I had not changed the vented oil fill back to stock when this picture was taken.
At first, I went with a only a Mann Pro Vent. I found it would slightly pressurize the crankcase and had several small oil leaks, more like seeps. Just for a test, I temporarily rigged up the CDR to the oil tube vent and the oil leaks stopped, along with a slight vacuum in the crankcase. So, I changed back to the vented valve cover (not exactly an easy job) on the right side and went back to using the CDR in the stock location. I haven't had any oil leaks since. I'm thinking of testing the Mann Pro Vent with the CDR, but haven't yet.
I would decide what type of vent/CDR/open to atmosphere system you are going to run and then select the vent location that works best with your system. If you go with the stock CDR, its much easier to plumb using the valve cover. Plus, you are using all stock parts. If you choose something else, then maybe the vent tube would work. I think all NA 6.2/6.5's use the oil tube vent, but cannot say for sure.
One more thing, the NA's have a shield over the timing chain. I'm guessing its some sort of splash shield for the oil tube vent, but cannot say for sure.
Here are some pictures of the vents in use:
Here is the oil tube vent, plumbed to the Mann Pro Vent.
And the current, stock CDR setup
I had not changed the vented oil fill back to stock when this picture was taken.
The valve cover style is definately easier to deploy. It seems that those with experience with both systems feel there's no significant advantage. So I believe I'll go with the factory setup. I may try to use something like the the ProVent if I have a lot of blow-by.
bobbiemartin
Author of The DB2 Conversion Guide
If you are undecided, I would install the vented valve cover with some sort of plug. Its much easier to remove a plug than change the valve cover later. The oil fill is no big deal, changing it is a 5 minute job. The valve cover, not so easy.
I'm not sure the Pro Vent would do much for blow-by. It also needs some sort of drain back to the crankcase, I had a fitting welded in my oil pan.
I'm not sure the Pro Vent would do much for blow-by. It also needs some sort of drain back to the crankcase, I had a fitting welded in my oil pan.
bison
Well-Known Member
The CDR is normally open,vacuum applied by the turbo causes it to close(supposed to anyway, but it works only half assed on an engine in good condition).
bison
Well-Known Member
I got a provent on my 98 since 009.It works fine in keeping the intake clean of oil so far on the rebuild engine (30 K),altough at idle there is a slight build up of crank case pressure. I come to think however that when blowby increases as the engine wears the Provent is gonna be as useless as the CDR has proven to be.But time will tell.If you are undecided, I would install the vented valve cover with some sort of plug. Its much easier to remove a plug than change the valve cover later. The oil fill is no big deal, changing it is a 5 minute job. The valve cover, not so easy.
I'm not sure the Pro Vent would do much for blow-by. It also needs some sort of drain back to the crankcase, I had a fitting welded in my oil pan.
The valve cover is the main reason I needed to make this decision now. I don't want the CDR cover on there with a plug in it. If I chose to run the 6.2 style CDR I was going to use a plain cover on the right side when I put things together. I had planned to drain the oil back to the pan by "T"-ing into the turbo drain.