RV8 rocker cover / oil breather set up
Discussion
I have realised that my Chim does not have the usual rocker cover / breather / flame trap set-up. Any thoughts on these ...
The engine has apparently had some head work in the past, but unsure what exactly, and may or may not be a 400 block. I wonder if the rocker covers were changed for some reason at the same time. It runs and pulls really well, but I am getting a bit of oil in the plenum and some smoke on start up from time to time.
Not sure whether I need to change back to the normal set-up or any other suggestions?
Cheers, Chris.
The engine has apparently had some head work in the past, but unsure what exactly, and may or may not be a 400 block. I wonder if the rocker covers were changed for some reason at the same time. It runs and pulls really well, but I am getting a bit of oil in the plenum and some smoke on start up from time to time.
Not sure whether I need to change back to the normal set-up or any other suggestions?
Cheers, Chris.
Normally the oil filler cap is on the opposite side. There looks like there's a direct feed from the rocker cover into the plenum to help vent the crankcase; however, without the flame trap to catch some of the oil & vapour, I should imaging that this will fill the plenum and trumpet base full of gunge after a while. Is there a mushroom filter on the rocker cover with the filler cap?
Interesting fuel pressure gauge and PAS reservoir cap!
Interesting fuel pressure gauge and PAS reservoir cap!
I'm not an authority on this, so I'm sure somebody will be along to correct me soon!
The RV8 uses a PCV based system (positive crankcase ventilation). A mild vacuum is created by the air being sucked through the plenum. The hose from the plenum (where yours is connected) is normally connected to the flame trap on the offside (driver's side) rocker cover, not to the nearside rocker cover as in your car. The vented gasses from the crankcase that are vented out of the flame trap are normally drawn into the plenum (due to the drop in air pressure/ vacuum) and 're-burnt' with the fuel. Normally, the flame trap has a steel wool type pad in it that helps filter the vented gasses and catch some of the oil from the vapour. What is left travels up the hoses and back into the plenum. This includes any oil not caught by the steel filter in the flame trap. The mushroom valve normally located on the nearside rocker cover is fitted with a foam filter and draws air into the crankcase. It is an essential part of the crankcase breathing system from what I understand.
Crankcase breathing is essential, otherwise crankcase pressure will build and basically begin to force oil out of various gaskets. The valley gasket is a common one.
I should imagine if your car is leak free, then it is venting okay. There's more than one way to do things. However, the lack of anything to filter the vapour vented into the plenum is likely to put loads of oil deposits into your trumpet base/ plenum. But as I say, if it isn't broken, don't fix it!
Here's a few pics:
Flame trap on rocker (from top)
Flame trap removed (from underneath) showing steel pad/ filter
Rocker cover with flame trap removed.
Trumpet base, with oil collected.
Breather Hoses & Mushroom Valve
The RV8 uses a PCV based system (positive crankcase ventilation). A mild vacuum is created by the air being sucked through the plenum. The hose from the plenum (where yours is connected) is normally connected to the flame trap on the offside (driver's side) rocker cover, not to the nearside rocker cover as in your car. The vented gasses from the crankcase that are vented out of the flame trap are normally drawn into the plenum (due to the drop in air pressure/ vacuum) and 're-burnt' with the fuel. Normally, the flame trap has a steel wool type pad in it that helps filter the vented gasses and catch some of the oil from the vapour. What is left travels up the hoses and back into the plenum. This includes any oil not caught by the steel filter in the flame trap. The mushroom valve normally located on the nearside rocker cover is fitted with a foam filter and draws air into the crankcase. It is an essential part of the crankcase breathing system from what I understand.
Crankcase breathing is essential, otherwise crankcase pressure will build and basically begin to force oil out of various gaskets. The valley gasket is a common one.
I should imagine if your car is leak free, then it is venting okay. There's more than one way to do things. However, the lack of anything to filter the vapour vented into the plenum is likely to put loads of oil deposits into your trumpet base/ plenum. But as I say, if it isn't broken, don't fix it!
Here's a few pics:
Flame trap on rocker (from top)
Flame trap removed (from underneath) showing steel pad/ filter
Rocker cover with flame trap removed.
Trumpet base, with oil collected.
Breather Hoses & Mushroom Valve
Edited by chris1972 on Thursday 16th May 21:21
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