Generation IV External Engine - Fresh build... Low oil pressure? (mechanical vs. factory)

I recently fired up an ERL 434ci bullet and noticed the pressure was lower than expected (although acceptable), according to the factory gauge. The previous engine had very high pressure, but I had replaced most all of the sensors when doing the 434 build, including the oil pressure sender.

Well, I hooked up a mechanical gauge to the oil port on the side of the block. I already had a "jumper" hose hooked up to the port to facilitate priming the engine before firing it up, so it was simple enough to toss a temporary gauge into the mix.

The factory gauge (and DIC display) showed 40psi on a cold start. At 200 deg. it dropped to 25psi and held steady at idle, rising with RPM increase. No odd noises, knocks, or rattles... it all sounded/sounds great, IMO.

The mechanical gauge? ....60psi on a cold start and 48psi at 190-200 deg.

Crazy. If it wasn't such a motherbitch to swap oil pressure senders, I would reinstall the old one and see what sort of difference there is. But, for now, I will just make a mental note of the difference and proceed with buttoning things up and working on the tune-up.

I beat myself up over this... thinking I might have pinched the pickup o-ring (even after being very careful), installed a faulty cam retainer plate or a junk oil pump, etc. It was too late, the evening I fired it, to get a mechanical gauge, so I picked one up from the local speed shop the following evening and was pleased with what I saw on the mechanical rig. fughkyeah.

random pics...

http://i27.photobucket.com/albums/c151/rlsracing/Mobile%20Uploads/Resampled952012-04-309521-28-2295246.jpg

http://i27.photobucket.com/albums/c151/rlsracing/Mobile%20Uploads/Resampled952012-04-309521-28-4095580.jpg

http://i27.photobucket.com/albums/c151/rlsracing/Mobile%20Uploads/Resampled952012-04-309520-37-5095778.jpg

http://i27.photobucket.com/albums/c151/rlsracing/Mobile%20Uploads/Resampled952012-05-019522-20-4395430.jpg

Hoping to drive it soon...

Its aggravating to install new parts and they dont work . PITA! Atleast you know the oil pressure is good .

That's good to hear it is the sending unit. After I did my H/C/I/E swap my oil pressure started to drop slowly. Acted just like a spun bearing. Ended up being the stock OPSU was going out. I had never seen one act like that. Needless to say I was relieved.

That car should be a beast man.

interesting.. wonder if the sending unit or the dash display is to blame? how does it read on a scan (does it go thru the computer on that car?)

mine is the xact same way on my 408 i was pissed to see my fresh motor with less pressure than expected,only to put a mechanical gauge on it and see the pressure almost 23 psi more!WTF

interesting.. wonder if the sending unit or the dash display is to blame? how does it read on a scan (does it go thru the computer on that car?)

It's the sending unit. The gauge and DIC (digital display) read the same, and it also reads the same in the HPT VCM scanner.

Hook up an autometer mechanical gauge and it has great pressure, as noted.