Miles Posted February 5, 2021 Share Posted February 5, 2021 SBC 350 crate engine with mild cam, Holley Street Avenger carburetor (575 cfm), MSD Street Fire HEI distributor and wires, mild cam, new plugs gapped at .45. No vacuum leaks found. Engine installed in a 72 240z in 2009. Engine ran perfect for over ten years, but started surging at low speed cruise recently. Blocked all vacuum ports and connected vac. gauge to manifold vacuum on carburetor. Reading taken at warm idle. In the video the engine can be heard speeding up and slowing down (surging) as needle moves on the vac. gauge. Other: adjusting idle screws has no effect. Replaced needle valve/seat. Float level adjusted per specs. Went up two sizes on primary jets, but no change. Power valve OK. No vacuum leaks. Quote Link to comment Share on other sites More sharing options...
BJSZED Posted February 6, 2021 Share Posted February 6, 2021 Just a thought, sticking PCV valve ?? Quote Link to comment Share on other sites More sharing options...
Miles Posted February 6, 2021 Author Share Posted February 6, 2021 7 hours ago, BJSZED said: Just a thought, sticking PCV valve ?? Test done with PCV valve disconnected and hose plugged. Also, replaced PCV valve. Thanks Quote Link to comment Share on other sites More sharing options...
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