Any camshaft. torque wrench or oil pressure experts out there?
Retorqued the bolts that hold the front camshaft in place and oil pressure increased.
Idle pressure increased from 20 to 28 psi. Nothing else was done on the car and the gauge is an installed mechanical gauge.Pressure is up throughout the range but by less than 8psi.
I always thought torque on these bolts would not be critical, as I assumed the 'bearing caps will contact the head and once seated there, additional torque would not make any difference. Surely when torqueing the bearing caps one is not torquing the caps onto the cam 'journal' (surely there is a gap, that is why one uses plastigauge, also for oil to flow).Would the fact that the motor has done 250 00 kms make a difference?

ALSO it seems like the noisy hydraulic lifters have gone quiet. Maybe guys with noisy lifters should check the cam torque?

NOW HERE'S THE INTERSTING THING. I have only ever worked on the front cam. I had stuffed valve stem seals and experimented by replacing the seals on the front bank (this cured the problem, so I never bothered with the back bank). Shortly after this I had first problems with hydraulic lifters, but only the front bank and only the Exhaust lifters. So maybe when I replaced the camshft I did not torque the bolts enough, so more gaps, less oil pressure and less oil to the lifters, hence they became noisy.

The reason I re-torqued the bolts is I bought a new wrench and compared it with the old one 17 years old and found the old one compared to new one overreads by about 45%, so head bolts should be 19 to 21 Nm, but if new wrench is accurate, old one had tightened them to only 13 or 14 Nm. I trust the new wrench better, as it's range is only 4.5 to 30 NM AND OLD ONE HAD HUGE RANGE (13.6 TO ABOUT 100Nm).

If cam bolts are slightly overtightened, would it cause drag (and excessive wear) on the cam journals or do the bearing caps push on the head?).Could this also cause loss of oil flow on the journals?

I assume the bolts can be re-used, nothing to the contrary in the manuals I have, or they use once only bolts like many cylinder head bolts?

I compared the 2 wrenches on a wheel nut (convenient and easy to torque up to 100nm).
I would torque with one wrench, then check the torque with the other wrench, then swop over the wrenches and repeat the procedure.

Does anyone know where I can get wrenches checked??

With the motor being 250, 000k old, I'd say it's tolerances have been pretty well worn in.

As the motor warms up, tolerances will change as metal expands. Do you know roughy what the temperature was when you were doing the work?

Torque on camshaft bearing bolts is critical, as bolts that aren't torqued correctly will allow the camshaft to experience play. Even .01mm will have an effect. Camshaft play will muck up all sorts of stuff. If one end is correct, and the other end is out, then uneven wear will occur, and you may even end up bending your cam.

On the other hand, bolts that are over tightened will definetely cause drag, and premature wear.

I did the work in the morning after the car had stood overnight. So temp was about 25 degrees.