Anybody know what thread the oil pressure sensor thread is on a black-top zetec? 1/8" or 10mm?

Sure it's 1/4 NPT

Now you say it 1/8" seemed odd when I typed it but I put that as I'd looked for sensors for a VDO gauge in Europa Spares and they listed 10mm and 1/8" as options.

Also any idea what max pressure on black-top? Not my car and the gauge I've been supplied with us 0-5bar

Most gauges go up to about 5 bar (70psi). Probably be that or higher on a cold start with max when hot about 50-55 assuming it's got a std oil pump etc.

My smiths mechanical gauge goes to 7bar/100psi, cold idle is 60psi, cold 3000rpm+ is 100psi, hot idle is 40psi, hot 3000rpm+ is 90psi.

I have run 5w40 fully synthetic oil for about 6 years, previously with 5w30 it used to be 80psi cold & 60psi max when hot, however that was with a 100k mile block that was foobard, the current short block has only covered 10k.

Dave

Mine reads high when cold on 5/30 fully synth - 115psi+.

When hot about 40 at idle and 80 as revs rise.

As above, its 1/4 NPT

Looking at Dave's figures, we might have an issue with the supplied 5bar gauge. That's 72.5psi and so well under what he's seeing at 3000rpm hot. Looks like 0-10bar would be needed.

Funny how you can maintain these engines day in day out in tin-tops but then find a whole load of details you don't (need to) know once you put one in a kit.