... also the pvc needs unrestricted flow to carb. so take any check valve that might be present out. breather thing, if you have one ditch it. basically your putting vac on your manifold. so make sure oil fil plug seals. that has worked for me. ...
That's fine as long as nothing ever fails. We need to look at PVC venting further.
The purpose of the PVC is to provide a venting of positive air pressure when there's blow-by past the pistons (and in an emissions acceptable manner).
- You have to provide a way of getting rid of that positive pressure or it will eventually blow something, like the valve cover gasket.
- It doesn't require a huge amount of blow-by; a tiny bit of blow-by can build up pressure too.
The PVC valve has two functions: to close when the carb isn't pulling when the engine is off (to contain emissions), and to limit the amount of airflow when vacuum pulls it open so it doesn't act as a vacuum leak.
- Unrestricted pull (vacuum leak) can mess with the available vacuum pressures, hence with everything running off them.
- A working PVC valve is the superior way of handing it, but they can fail - and you usually won't know until there's a problem.
- Another way of handling it is to replace the PVC valve with the fitting (plastic elbow #47057) that is always open (no valve to fail closed) but with a smaller hole for the required airflow limiting.
- In some jurisdictions, or since they already have the failed PVC valve, people have drilled out the PVC valve with a smaller bit, so it appears in place, but is always open, yet still provides the required airflow limiting.
Deleting the PVC breather, the sealed oil filler and having unlimited pull by the carb, is relying upon limiting that vacuum pull by all of those remaining sealed, so it doesn't become a vacuum leak. And if there is a big blow-by event, there's nothing to handle the increased pressure - something will have to give/blow. Good enough - as long as nothing starts to fail.
The Eagle PVC setup allows for fouled air emissions to go to the carb and be burnt off, and higher pressures can get out through the breather, buying you time to detect that something has gone wrong. The problem with the Eagle PVC setup, is it doesn't adequately manage oil shooting up the breather line or up the venting line, nor the high incidence of a fouled PVC valve sticking closed or having a too restricted airflow. Various methods have been tried/developed to catch and drain-back any oil that goes up where it's not wanted. Sometimes that's a small chamber for oil to gather and flow-back (and sometimes with a metal mesh to catch oil droplets), sometimes a length of hose running upwards for a length is enough. search...
So you'll have to do some thinking about how the whole combination of components will work as a system that can/will vent positive pressure (both when it's low and when it's high), keep the oil where it belongs, and limits airflow to the carb and filters particles out of the breather air going in (contaminate engine oil). And how those will work as a system when components fail: consequences and how will you detect that failures are starting to happen.
Topic: Oil leak pan or valve cover??? (Read 2968 times)