Street/Strip Crankcase Vacuum using a PCV Valve
No vacuum pump at all with the 2nd picture setup, just a pcv valve sucking against a sealed crankcase. Crankcase vacuum is essential for my low tension rings on the street, an earlier version of this engine only got around 250mi to the quart before I sealed it's crankcase and added the pcv valve.
The pcv valve has been modified to make it work similar to adjustable orifice, currently set to draw around 12-15"Hg in the crankcase while cruising down the highway. Here's a RacePak graph showing crankcase vacuum during a 6.25sec long WOT 3rd gear pull with the pcv valve as the only vacuum source. Nitrous system was NOT turned on, this pull was NA.
...Red line- engine rpm
...Blue line- WOT switch
...Yellow line- crankcase vacuum
The pull started out with 12.6"Hg @ 2600rpm. When the pull ended at 6250rpm, even without the electric pump running the crankcase still had 3.9"Hg of vacuum left. I should add that the 355" engine is well sealed, no dipstick (oil level sight glass), Total Seal gapless top rings, and a 114 LSA nitrous cam.
When blowby exceeds the volume of the pcv, the check valves un-seat and any pressure is vented thru the breathers.
Grant
No vacuum pump at all with the 2nd picture setup, just a pcv valve sucking against a sealed crankcase. Crankcase vacuum is essential for my low tension rings on the street, an earlier version of this engine only got around 250mi to the quart before I sealed it's crankcase and added the pcv valve.
The pcv valve has been modified to make it work similar to adjustable orifice, currently set to draw around 12-15"Hg in the crankcase while cruising down the highway. Here's a RacePak graph showing crankcase vacuum during a 6.25sec long WOT 3rd gear pull with the pcv valve as the only vacuum source. Nitrous system was NOT turned on, this pull was NA.
...Red line- engine rpm
...Blue line- WOT switch
...Yellow line- crankcase vacuum
The pull started out with 12.6"Hg @ 2600rpm. When the pull ended at 6250rpm, even without the electric pump running the crankcase still had 3.9"Hg of vacuum left. I should add that the 355" engine is well sealed, no dipstick (oil level sight glass), Total Seal gapless top rings, and a 114 LSA nitrous cam.
When blowby exceeds the volume of the pcv, the check valves un-seat and any pressure is vented thru the breathers.
Grant
