Crankcase Ventilation in a GT, and Holley Carbs
JM,
This is one of Opel's little mysteries that wasn't solved for me until I started hanging around these Opel sites. Actually it was the
[email protected] site, and I think it was Otto Bartsch who provided the answer. Opel GT's do not have a PCV (Positive Crankcase Ventilation) valve, so if yours has one, it was installed by a PO (Previous Owner). Possibly created ALL kinds of engine leaks when he did that.
Instead, a small vacuum hose is meant to suck crankcase fumes OUT of the engine, and the big hose allows filtered air IN to the valve cover to replace air in excess of blowby gas.
This is what happens in detail. Opel uses a metered vacuum port on the side of the intake manifold, just below the brake booster vacuum hose. But NOT the small one that angles back to the rear, which is the distributor vacuum retard (versus the vacuum advance, which is attached to the carb base; on the Solex, it is outboard, while my Weber is inboard; not sure where it is on your Holley). This small vacuum hose (1/8 inch ID on my GT) connects to the small hole in the top of the valve cover.
The metered vacuum port sucks crankcase fumes into the manifold to be combusted. But the engine case would also be subjected to a "vacuum", except there is a big hose (probably where your PCV valve is connected) that draws air into the valve cover. (By the way, a PCV valve is a check valve, which is designed to only allow crankcase fumes to flow OUT of the valve cover. OPPOSITE to what an Opel system should do). This big hose should be connected to the "inside" of the filter housing so that it draws filtered air in, but that can be tricky on an aftermarket filter housing. On my GT, I drilled a hole in the filter base and installed a right angle fitting and a barbed connection, and then used 3/8 inch hose. I tapped the valve cover with a 1/2 inch NPT tapered tap and bought a 1/2 by 3/8 brass barb fitting to connect the hose to. I did the same with the vacuum hose (1/8 by 1/4 I think). But I believe the factory solution is to just jam the hoses into the valve cover holes. Sorry I can't just show you a picture, but the digital camera hasn't been approved yet by management.
I hope that helps. But I now have a question about the carb you are using. Common wisdom around here is to replace the stock Solex (aka "Slowex", or more often "Piece of S--t") with a Weber, usually a 32/36 DGAV (water choke) or DGEV (electric choke) with a progressive mechanical secondary. The serious folks with high compression pistons, wilder cams and more displacement (2.0, 2.2 and even 2.4 litre) use the 38 DGAS, which opens both barrels simultaneously.
I happened to find and install a Weber 32/36 DFM (manual choke), which has a reversed throttle, and requires some fancy linkage modifications. But I believe the reversed orientation may result in cylinder leaning, especially the middle two cylinders. The same problem exists with the Ford Webers ('70-71 Cortina GT with a Weber DFAV?) and Pinto carbs. But I hadn't heard about the Holley from the ubiquitous 2.2 litre Caravan. Tell us about it, and how did you connect the cable versus the standard mechanical linkage? Do you happen to know which model it is? How well does it work, or have you really tried it out yet ? Curious minds, especially those with the crummy old Solex, want to know!