Gold Founding Member
Join Date: Aug 1998
Location: the Seasonally Frozen Wastelands
Re: What is normal Blow By
1. Beware of using leakdown percentage. The indicated leakdown in percent is as dependent on the leakdown tester as it is on the actual leakage. A leakdown tester with a small orifice will show high percentage numbers, a leakdown tester with a large orifice will show smaller numbers on the same engine.
2. While not as useful for WFO problems, my standard for blowby is to run the engine at fast idle--1200--1500 rpm. Stick my thumb in the vent side of the engine--opposite to the PCV valve, and hold for ten or fifteen seconds. When I pull my thumb off the vent, the crankcase should have vacuum, not pressure. The vent will suck air into the engine, not blow smoke out.
Do you have a WORKING PCV valve? Is it the right one for the engine?
Finding the "right" PCV valve is trial-and-error, since there's no listing of orifice sizes, spring tensions or any other specs that would help to compare two PCV valves. You can't even go by part numbers like you used to be able to do with spark plugs.
I know there was a thread many years ago about leaking front seals; the cause was...shiitty front seals made in India combined with front covers that mis-located the seals so they ran off-center on the damper hub.
A quality seal, combined with assuring the seal is concentric to the hub (and the hub doesn't have a groove cut in it from the previous seal) might go a long way toward fixing your leakage.
The 454 in my boat uses a front cover that is not drilled for the alignment dowels. Aligning the seal requires installing the damper hub through the seal while the front cover is still not fully bolted down. Once the damper aligns the seal, I finish tightening the cover bolts.
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