Oil pressure +misfire on a falcon 7hp

[MartinRaine]

Hi i am just about to drop the body back on the chassis i have rebuilt the engine and had it running for about 2 hours to check things out, I have about 30-40psi at just over tic over, Is this too high. I was told it should be about 20 psi ?. Also it has a slight misfire and a weep from the carburetor any ideas?. Thanks Martin

[george garside]

Jowett's recommended 25 - 30 lbs under 'normal running conditions' so 30 - 40 at tickover seems abit on the high side. Personally I would,t worry at the stage your at but would waait untill you are in a position to run the car on the road & then adjust the pressure relief valve to give something like 20 idling which all being well will give Jowetts figure at around 40 mph

slight misfire could be anything! tracking in distributor, 'leaky' plug lead, crap on anything etc etc. Or worn throttle spindle holes/shaft allowing air in & thus weekening mixture or incorrect idling/progression jets or blockages thereof or blocked passage in emulsion block or again that well know disease of a bit of crap in one of its passages¬!
george

[Tony Fearn]

Hi Martin.

Did you loosen off the nut behind the oil pressure gauge and turn the engine over without ignition so that the air in the oil pressure pipe to the gauge all bled out and oil dripped from the union? When you've got your drips, tighten the nut. Perhaps this might make a difference, but have plenty of rags under the instrument panel when you're doing it or your carpets will not like the resultant oil bath. At least it should give you a baseline so that when you follow George's suggestions the pressure should be correct.

If you turn the screw in then it increases the pressure, and of course the opposite occurs.

Don't overtighten the locking nut on the pressure release valve screw. I did so recently on 'Mary Ellen' and the screw cracked! Mind you it had been there since about 1980.

Perhaps more detail on the 'slight weeping' on the carburettor would help us to suggest a remedy.

Tony.

[Keith Andrews]

turn the engine over without ignition so that the air in the oil pressure pipe to the gauge all bled out and oil dripped from the union

That is a myth..basic school physics..
Any air or foreign body will compress up to the extent of the source of the pressure

The 1st thing to check is that the pressure gauge is reading correct on a known source..be it an air compressor what ever...And check that it moves ..doent stick at any point all the why thru its range.

Weeping any leaks in a carb....100% a no no...dismantle check gaskets, seals ferrels and replace
Hint When replacing gaskets in things like carbs, smear lightly and evenly the gaskets surfaces with oil ...this gives a little better seal and makes any side of the road 'fixes' easy if dont have spare gaskets on hand...the gaskets do not stick and can be reused.

[george garside]

if the needle on the guage is steaady ( and not sticking) then air in the line should not in theory at any rate, have an effect on the reading. This however only applies oncle the air has been compressed and since it is likely to be several short 'bits' of air rather than one long one the result is usually a very definate pulsing backwards & forwards of the needle during said compressing of all the little bits of air one at a time (ish). Obviously the cure for this is bleeding at the guage end as Tony has said ,but if the needle is steady in theory air should not be in the line - but of course elderly Jowetts do not always conform to theory, them being horizontally opposed to everything!

george

[Tony Fearn]

Sorry to have misled you Martin, I stand corrected, but... why do we bleed hydraulic brakes and clutch master cylinders? It would be very interesting to know.

Tony.

[george garside]

? to save having to pump the pedal to compress the air in the pipesevery time brakes or cluitch are used

[Forumadmin]

Air in oil pressure gauge pipe should still give true reading, just it may take some time getting there. Air in brakes or clutch means yyou need to pump the pedal to get the air compressed; but it will still give the same pressure but perhaps not in time to stop hitting the car in front.