The exhaust change didn't have much effect on the crankcase pressure, but today I figured out the problem! I had switched out the OE oil cap for a Mr. Gasket one, but found out the crimp seal didn't seal worth a crap and that was killing the ability to pull any vacuum in the crankcase. So my solution? A quick trip to the hardware store.
Which resulted in plenty of crankcase vacuum! However, it seems to now generate a seal whistle at around 8inHg vacuum. D'oh. I'll figure that out later. It still generates pressure at WOT and low rpm. I haven't tried WOT and high rpm yet. Cruising down the highway at 60mph it was pulling decent vacuum. :thumbs: I have noticed a change to the oil pressure to the lash adjusters though, so I have to give more thought on what to think about that.
As a reminder, I'm taking a reading from the crankcase at the brass fitting under the red tube.
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"How I learned to stop worrying and love the OHC Pontiac L6"
The Silver Buick- '77 Skylark coupe w/455, SPX, MegaSquirt 3 & TKO-600 (Drag Week 2011, 2012 & 2015!)
1969 Firebird with a turbo'd Pontiac L6 controlled by a MegaSquirt 3 and backed with a microsquirt controlled 4L60e and 4.56 gears! (Drag Week 2018!)