Had a slight external head gasket leak under the thermo housing, so I dropped some Bars stop leak into it. The stuff is suppose to be put in after a coolant change and thermo in place ( did coolant and thermo about 500km ago). Chucked it in and the leak stopped. After doing it I noticed the other day when I did a 25km trip on a mid to high 20 degree day the oil pressure guage went down to the 1/4 mark but raised to the half when reved. Temp went to the top of the M and there was a burning smell ( kind of like riding the brakes). Oil is fine, thermo is working and plugs are fine. I need the head to last till the end of the tax year when I will be either doing the head or dropping in a Tickford donk. I also changed the oil about 1000km ago and have not had any problems with oil pressure till now. Please, I need some advise.

Do a compression check for a start, let us know the results.

Gab

compression wont have any effect on oil pressure.

1/4 on the oil pressure gauge would still be around 1bar of pressure =14psi which is still within normal specs..

did you change the type of oil on your last oil change?

I would've thought if oil was severley leaking past the rings/valves/valve guides, seriously causing the oil level to drop, that could have an effect on the oil pressure, but I geuss it'd be blowing smoke too, so you've probably got a point.

Is the oil pickup nice and clean and the oil pump working properley? If the headgasket is blown badly, and some scale/rust/water gets into the sump it could thin the oil and reduce oil pressure, and the rust and scale may also block the oil pickup.

Is the oil milky?

Gab

actually, the pistons, rings and valves are not lubricated by oil pressure, they are cooled and lubed by oil splash off crank and cam rotation,
only things lubricated by pressure are crank bearings, bottom rod bearings, camshaft journals rocker arms and aux shaft ect. then there are things that rely on pressure to stay operational, like lifters, cam chain tensioner ect..

the main things that can effect oil pressure are, oil it self, the oil pump, crank and rod bearings, it may just be the sender is not reading the same as it use to??..

We all know how dodgy the senders can be....

You'll likely find you've reduced the effectiveness of your cooling system, engine is getting hotter, oil temperature is getting hotter, hot oil = thin oil = oil flowing 'easier' = less oil pressure

If enough oil passes through the rings/valves/valve guides/etc for the pressure to drop, I don't think the engine would be running very well and as you said, it'll be blowing smoke, and there would be a hell of a lot of it.

1/4 up the gauge is fine. Mine has been running like that for 2 or 3 years. Only recently when the car has been sitting more than driven (drive maybe once a week) have I seen my pressure go up higher than 1/4 at idle. Pretty sure that might be a sign of oil gumming up some where.

It is also normal for oil pressure to increase with acceleration. Since the pump runs off the crank, the higher the RPM the faster the pump will run the higher the pressure out put. If you used a different oil viscosity grade (lower viscosity) then you may see an oil pressure drop.

The oil was fine before I put the bars stuff in, I am thinking it may be that effalcon is right and the bars s**t has gummed up the head in places. Am going to drop bottom hose and take about half the coolant out and replace it with fresh stuff. Hope that works.
Oil is not milky and before the bars stuff the pressure was excellent. Temp was fine too, just put the bars stuff in to slow a minor external leak and now I have low oil pressure. Might be the smell of the oil cooking I could smell?

Unfortunately I dont have a compression tester, that went with my timing light, feeler gauges and vacuum gauge when the ex cleaned me out. Her old man was in need of tools obviously. Slowly getting the shed back to what it was.
Dropped about 2L of coolant out of the res, disconnected the thermo pipe from top of thermo housing and were it goes into the res. Cleaned and checked for good flow then ran in 2L or so top up coolant (same as what is in the car) / bleeded the cooling system. Temp is not going higher than the A. Coolant is hard to check if it has oil in it as the bars s**t turns it a brown. I am thinking that the cooling system just heated to the R because of me being stuck in traffic for a while ( 20 minutes or so...maybe more). There is no leaks now that can be seen.
Topped up the current oil with a bit of fresh stuff, its very slightly overful at the moment, but not to the point of drowning the block. The mrs has to take the 25km trip tomorrow for shopping, then its not being driven till the weekend. I will drop the oil and filter on Saturday and hope that solves the oil pressure drama. It seriously had Valvoline Engine armour 15/40 put in it with ryco filter no more than 1000km ago. I also drained, flushed with new oil/additive then trained and refilled the oil, would be p****d if its the oil thats packed it in that quick. Might use 20/50 next time until the heads done for added protection.
The oil pressure gauge with the car warmed up sits on the 1st white notch in drive idle and half when in neutral or driving. By the way the engine has only 177000km on it too.

Yeah I always run 20W/50 oil anyway, helps with oil pressure.

Gab

With the head, what would be better fix the stock head on the 177000km motor in it or replace the engine with an exchange tickford ef i6 from the wreckers? I think from memory theres a guy in Smithfield that would drop a tickford i6 block and head into her for around $1500 with supposed low k's ( around 120 to 150 thou), but how can I be certain I wont have to worry about the head on the tickford in 12 months or if the k's are correct? Is a tickford i6 in the ef's much better than stock? Fixing the donk I have would be a safe long term thing, but if the tickford is a better start for modding maybe that would be the better choice....

I'll say. Whats with that? I have a brand new sender on a freshly built motor and it looks like a freaking yoyo. Most of the time its off the dial.. Is it typical of all senders or just another Falcon "charm"?

I have no idea why they are so fiddly. Some issues are sometimes caused by putting an oil pressure switch for a low series dash in a vehicle with a high series dash which requires a oil pressure sender to give readings. The switch simply detects pressure or no pressure whereas the sender is a larger unit with an actual pressure gauge that can give varied pressure readings.

Dropped the oil today and replaced it with Nulon 20/50 and another ryco filter....... pressure problem resolved. I wouldnt have thought having the temp go to the R on the gauge would make the oil fry........ Was going to compain to Valvoline but I would have just got the hand ball. Fully synthetic 15/40 Engine armour oil aint obviously oils. Should have trusted Nulon and not gone the flashy oil, even if John Laws stands by it. Speaking of Johnny, love that ad on the idiot box where he says " for anyone man enough to change there own oils, Valvoline now comes in 6L". I think if Johnny bent over to check his own oil Ray would give him a stiff one up the a**