ZINGER-D95 Posted August 22, 2019 Report Share Posted August 22, 2019 Recently I had gone in for a smog test on my 1978 datsun 620 l20b, the HC and CO levels were way above passing. When diagnosing what the cause may be, he pointed to a valve that Y's off from my smog pump. After research, I found the parts name being a C.A.C Valve. When the hose leading to that was plugged, the emissions dropped. But would cause the truck to back fire. What do I do?? Any way to bypass? 1 Quote Link to comment
datzenmike Posted August 22, 2019 Report Share Posted August 22, 2019 The CAC regulates air flow into the air injection tubes in the exhaust manifold. This air provides oxygen to burn off excess unburnt gas. By passing an emissions device is no way to lower emissions. There is an anti backfire valve, maybe you have them mixed up. 1 Quote Link to comment
Stoffregen Motorsports Posted August 23, 2019 Report Share Posted August 23, 2019 They used to call that a gulp valve , right? Wouldn't be the first time that part caused a fail. 1 Quote Link to comment
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