I'm working on the venting for my hemi. Its probably under 450 hp with dual quads. I have the PCV valve setup. My question is: How much "intake" is required on the breather side of things? I do not want to cut my valve covers and have no room on my valley cover for mini breathers. My oil fill cap is non-vented. I'm planning on putting a barbed fitting in the vent cap (or valley pan) with a hose to a one-way valve (similar to venting a gas tank). I'm concerned whether or not a small 1/4" vent line is enough.
From my recollection of engines I’ve had a 350 Olds used a tube of about 1/2” ID drawing air from the air cleaner and the 396/375 BBC was a bit larger at maybe 5/8” ID. Your 1/4” seems small, most seem to use a larger size on the fresh air side than the PCV side.
Yep, on my SBC's I use a 1/2" fresh air hose, sourcing from the underside of the air cleaner. On my BBC motors I typically use a 5/8" hose. Both are ID. Bob
I’d like to see a photo of your oil filler. I use 1/2”-5/8” heater hose to a fitting I attached to the rear air filter.
If you look back at 60s-70s setups you will see that the pcv is on the opposite, or at least distant, side of the engine. If you put a pcv at the back of the valley cover and the vent at the front then you will simply pull fresh air across that short distance as that will be the path of least resistance. In the oem Hemi design there was/is a rubber seal separating the oil fill side from the down draft tube side that caused air to flow down around the cam tunnel and back up. In some past projects we have put a vent tube in the side of the front cover above the fuel pump and that seemed to be useful with a pcv in the downdraft tube opening. Nice shop btw. .
Well that’s exactly what I’m planning. Vent the front and pcv the rear of the valley cover. You bring up a great point, but I’m a bit committed at this point. Thanks.
Yeah, for best sludge and corrosion resistance engines should not just be "vented" with a breather or three. Crankcases should be ventilated, and the longer and more inclusive the flow path ( head > crankcase > the other head ) the better. Even some modern engines have gotten it wrong, with sludge related recalls the result. Some Toyotas and Mopar v6 come to mind.
You changed my mind @73RR . I'll run mini Offy breathers on the front side of the valve covers. Seems like a fair compromise.
The Jalopy Journal
