Engine and Transmission Tech

Carl - I'm only installing a flame trap on left side - pcv already installed on right side. Seems to be the consensus?

Don

Right. I got hung up on Fred's suggestion of a crankcase depression regulator & forgot that you were only looking for a flame trap. :)

I am intrigued by this CDR. Not sure I really understand the difference between it & a PCV. I have read that a CDR is a essentially a PCV for diesel engines. It functions in the opposite manner in regards to vacuum.

Part of a stainless steel pot scrubber pad makes a pretty good flame trap. You can use it in any suitable enclosure. As an example, I have about half of a pad strung out and drawn into 1" diameter length of silicon hose which runs from my mechanical fuel pump block off plate up to the inlet of my Enderlie style intake scoop. You can probably see it in my avatar, the hose is blue which contrasts with literally everything else on the car. Rover uses a canister on the valve cover similarly filled.

I'd like to see an explanation of that regulator compared to the TR4 pcv. Is there a difference in the way they work?

Jim

Quote:

I'd like to see an explanation of that regulator compared to the TR4 pcv

Looks similar to the PCV that was used in ''65 - '67 MGB's , Spitfires and who knows what else - I know my '64 never had one.
(photo courtesy of Moss)




Edited 1 time(s). Last edit at 08/03/2021 08:26AM by ex-tyke.

It also has one inlet and one outlet.

Jim

The "TR4" pcv is essentially the same as the cdr system.
It's biggest flaw was that it was prone to ingesting oil due to the limited drain back from the cylinder head. (try filling the TR engine with oil. The valve cover fills almost immediately)
It also doesn't have big enough plumbing, probably due to the drain back issue.
The rear crank scroll seal was also a miserable thing that allowed air (and contaminants) to enter the engine, defeating the pressure drop and exacerbating the drain problems with the upper engine.
It's biggest problem however, was that it was different.
Most didn't understand how it was supposed to work and hobbled it with catch cans, road draft tubes, crankcase vents, etc. They then removed the valve because the engine wouldn't idle properly.
It gained an undeserved reputation as a bad design.
That problem seems to continue to this day. With almost any engine or unconventional system falling into disfavor.
Many "fixes" for engine breathing issues still recommend catch cans and open breathing mods.
None of that is required with a properly designed and operating system.

I had this exact issue with my GT V8. Oil pumping out every possible seal. After I got the CDR installed, no oil on the floor after a spirited drive. And no oil on the Offy valve covers around the oil fill openings. Best $50 I’ve spent yet (CDR part exactly as shown in this forum above). Look on ebay or Amazon etc.

I am working on a Rover 3.9 that is having a similar issue with oil leaks. I plan on fitting the CDR, will have it on Friday. My understanding is this provides a controlled constant negative pressure in the crankcase so oil is not being forced out under pressure.

So If I understand this correctly, I need to connect the o-ringed side to both rocker cover ports and the other side goes to manifold vacuum correct? Do I use the pvc vacuum port on the carb or do I need to use the port (currently blocked) under the carb on the manifold?

I have the old style Rover valve covers, so just an oil cap, and one vent tube on each cover.

Previously was running a standard PVC from one cover to the carb and a filter on the other cover, but still seeing pressure causing the oil leaks. Looking for how best to run the lines to the new CDR to eliminate the problem for good. Appreciate the help.




Edited 1 time(s). Last edit at 02/01/2023 06:36PM by dherr2.

The crankcase needs an air inlet otherwise it can't be scavenged. So that's whichever rocker box you currently have as the inlet, which may have a little filter on or not.

What you're scavenging is the crankcase, and both rocker boxes are connected to the crankcase so only one of them needs to be connected to the o'ringed side..

For the CDR, I would use the connection point to the manifold rather than the PCV port.

My own RV8 is vented from the original flame trap to the underside of the air filter, no PCV. Mind you, it's not parked over a clean surface so I couldn't tell you whether there are any leaks, but the inside of the rocker boxes is nice and clean.

Ivor

With oil leaks the problem is not pcv but blowby. Blowby is the thing that creates positive crankcase pressure and it will always exceed the capacity of any pcv system under full throttle. The more power the engine produces, the more blowby it makes. So the answer is a means of routing the blowby to the intake.

Ever wonder why drag race engines used as many as 4 breathers on the valve covers? To vent the blowby, they certainly weren't for looks. If they weren't needed they wouldn't be there. That should give you a small hint of what you are dealing with. And the more worn the engine is, the more the blowby.

Here's a tip. You use a block-off plate for the mechanical fuel pump right? So drill and tap that plate for the largest pipe thread you can, install an elbow to point it up, and run a big hose to the air intake. Stuff the hose with a scrubber pad for a flame arrester and then plumb the pcv system however you like, making sure there is some sort of a restriction there. A pcv valve is a good idea because it allows full flow at low pressure conditions (WOT) to supplement the blowby tube.

Jim

Thanks Jim, I will definitely try this venting solution from the fuel pump blank off plate. Question for you, do you suggest running this to the air filter inlet? Then a standard PVC system and breather on the valve covers? So basically the PVC system works as intended but blow by pressure is vented to the intake as needed?

That is correct Dave. The only difference between this and a factory setup is that the factory connected the breather line to the opposite valve cover. Aside from increasing the line size.

Jim