Positive Crankcase Ventilation - Rover V8 with Holley Carb

[Veritan]

Hello everyone, my first foray on this forum, though I've had my Stag for 3 years now.

Positive crankcase ventilation (PCV) seems like a really good idea on an oily old Rover V8, and I believe it was originally fitted on many. However, mine currently vents to atmosphere through a catcher. PCV requires a flame trap, pressure control valve and hose to the carb vacuum after the throttle, My Holley carb only seems to have a tube there for the brake servo, but I'm wary of teeing into this line.

Has anyone got any experience of this. I realise it's a bit niche, being non-standard engine and carb.

[Phil S]

had this on my range rover with a holly, don't cut into the brake line, if you have an adaptor or carb spacer drill onto that

[Veritan]

Thanks Phil. Unfortunately there's no spacer and the carb and pancake air filter only just fit under the bonnet as it is.I agree that teeing into the brake servo line seems like a bad idea, so it looks like I'm stuck.

[richardthestag]

I would avoid t'ing into the servo hose also.

You do not mention what inlet manifold you have fitted.

On all the carb'd range rover v8's (including the Edelbrock one I have with the holley) there is a threaded hole in the top of the inlet manifold about half way between carb and thermostat housing. This should be for a non return valve for the brake servo.

Then behind the carb also on the top face there should be is a similar sized threaded hole which provides the vacuum feed for the diff lock. there is no non-return valve. Obviously non Range Rover installations do not need this so there is often a blanking bolt fitted.

Does your inlet manifold have that blanking bolt? you might be able to do something with that, on early range rovers there is a banjo fitting that might be a suitable option for the vacuum feed you need.

[jakesmig]

If you plumb in on the inlet side how would you control the air volume going through the vent pipe and still draw the correct air / fuel mixture trough the carb at tickover. I use injection which is positive fuelling so air volume at tickover is balanced by air valves therefore positive venting to anywhere in the inlet works, but carbs need the air volume passing through them to draw the fuel. If an uncontrolled volume of air bypasses the carb then getting this mixture right must be the work of genius.
In the dim and distant when I used an Edelbrock the crank case vent fitted into the pancake filter. I also beat the base of the filter down so that it was effectively dished on the underside, which increased the room below the bonnet, without adversely affecting the performance.

John

[richardthestag]

If you plumb in on the inlet side how would you control the air volume going through the vent pipe and still draw the correct air / fuel mixture trough the carb at tickover. I use injection which is positive fuelling so air volume at tickover is balanced by air valves therefore positive venting to anywhere in the inlet works, but carbs need the air volume passing through them to draw the fuel. If an uncontrolled volume of air bypasses the carb then getting this mixture right must be the work of genius.
In the dim and distant when I used an Edelbrock the crank case vent fitted into the pancake filter. I also beat the base of the filter down so that it was effectively dished on the underside, which increased the room below the bonnet, without adversely affecting the performance.

John

understand your issue but servo is not open to the elements. the hose from inlet to servo is closed and the vacuum inside the servo is protected by a non return valve to allow for safe braking in event of engine failure. so servo and hose become part of the inlet manifold.

similarly the OP requested a vacuum feed for the PCV valve which I am guessing is both a closed circuit and also only intended to operate when the engine is running.

Unless a hose splits I cannot see how this will effect engine tuning