Oil pan pressure

I am going to fit a 0-5psi pressure sensor to measure/log engine crankcase pressure (blowby). Purely as a tool to reduce downtime for leakdown testing and enable me to check after each run for early detection of issues. Got the idea from a nitro dragster, but didnt get the chance to get more detail from the owner. Where would the best place be to mount sensor - sump above oil level, or rocker cover? Or maybe valley cover? Engine is turbo LS drag engine. It does not run any engine vacum pump.

Good idea! I would expect the upper sump/crankcase to be best, as that's the first area the blowby goes. If your logger allows it, a high sampling rate may even show spikes that would indicate a individual cylinder issue, rather than relying on an average reading of all.

You may find 5psi is too low, depending on how poor the ring seal is, and how good your breather set-up is at drawing off the crankcase and rocker-cover's accumulated gases - if you find you're getting significant oil in the catch can(s), that would indicate you need to do a lot more investigation in oil drainback and/or vent position in the cover and/or separators and/or actual crankcase venting - rmember, all those drainage passages from the head are doing two things, draining the oil and venting the crankcase, and those flows are in opposing directions which compromises both.

You may even find crankcase pressure is lower under higher loads as the rings are forced harder against the bores and higher under a little less load and/or higher rpm where the rings are freer to move in the grooves and bore.

If you haven't done so, I'd also suggest monitoring the coolant pressure to pick up early signs of head gasket leakage.

Thanks for the reply Gord. I also managed to contact the owner of the nitro car. He has fitted it to the front of the block, into the valley. Just for interest, they record 1.6psi @7100rpm over the finish line. This is a N/A engine, so I would expect a bit more from a boosted motor? I do have a 0-15 psi sensor too, so if the reading exceeds 5psi without evidence of engine issues I will swap it out. Thanks for your help.

Crankcase may be better than the valley, as some valleys have restricted passages to the c-c and so will have a poorer signal.