Poor oil pressure ?

[stealthyflatfish]

Anyone give us a clue ? 454 ish originally, put away for winter all running ok, high volume oil pump normaly runs 70 psi cold at idle.
In my wisdom decided to investigate small leak at back of engine and pulled distributor, checked gaskets, tightened inlet manifold etc all ok.
Reassemble, now my oil pressure cold idle down to 35 psi ? Pulled distributor again re checked still the same, only thing I noticed is seems to be a lot of sideways movement on oil pump drive shaft, is this normal ?
Been on American websites and apparently it's a common issue, but know one has said what the problem is. or how they cured it. Any ideas ?

 

[Oneball]

Is the dissy sitting properly? Is there any damage to the tongue and pin on the shaft and drive?

 

[stealthyflatfish]

No, all ok can't see any problems with distributor, no damage, no scuff marks nothing ?

 

[Oneball]

And it’s all the way down in the manifold?

Was the pressure ok after the winter and it might be unrelated to the dissy?

 

[Chuffer]

Just a suggestion but like Oneball said . May well not be dissy related at all . Could be oil pressure sender in the block gone bad during winter shutdown . They are not expensive and easy enough to change so I would start there first .

 

[stealthyflatfish]

All the way down, and this is the first fire up after winter. Sender unit ? assuming this is the brass take off point on the side of the block, is there anything inside the sender, I will have to research, thanks guy's I'll get back to you

 

[Chuffer]

That will be it I guess low down on the block on drivers side . Best accessed from underneath . I say guess because my 1980 has a 1985 Camaro IROC - Z engine installed and the sender is on top of the block roughly behind the dissy . Gus our regional rep had oil pressure reading issues on his 1973 350 cu. in . car and the sender was low down on the side of the block . I fitted a new he had bought and hey presto ! the jobs a good un
The sender isn`t an item you can dismantle and fiddle about with .

 

[stealthyflatfish]

Guy's it's a 71 with oil filled guage, and tube's so is there anything in the brass fitting on the side of the block, it's reading a pressure on start up and releasing a pressure on shut off, so i suspect it's not blocked, just showing lower pressure than normal.

 

[Roscobbc]

No other underlying issues? - like oil dilution from petrol seeping to to the oil?

 

[Oneball]

What sort of dissy is it? Have you got o rings on the bottom?

 

[stealthyflatfish]

No fuel dilution, and no 'o' rings on HEI distributor, never has been from new.
It's a mystery as Toyah Wilcox would say.

 

[Oneball]

Is there vertical clearance between the dissy shaft and oil pump?

 

[stealthyflatfish]

Don't get that one Oneball ?
The shaft must be engaged as there would be no oil pressure.

 

[Oneball]

There should be a small amount of vertical play in the oil pump drive/dissy drive when it’s clamped up so you’re not pressing the pump vane into the face of the housing Can’t see it affecting oil pressure more of a wear thing.

 

[Roscobbc]

Sorry to say it but the usual reason for reduced oil pressure on any engine is an increase in the bearings clearances on one of more of the main, crankshaft or big end bearings. But it usually happens of over a period of time or something else has occurred to give a clue. If just one bearing had excessive clearance I doubt if you'd notice any change in oil pressure (perhaps a couple of pounds or so). Big block engine has camshaft oiling priority (cam gets oil before mains). So oil goes firstly from oil pump to no. 8, then 7, 6, 5, 4, 3, 2 and no. 1 camshaft bearings, pushrods and valve gear. Then feeds mains and rods. Oil pumps don't generally wear-out or leak - they either work or (rarely) break - ask me how I know!.

 

[stealthyflatfish]

Read that one a couple of years ago Ross, but you can fill in the uninitiated if you like.
Clutching at straws here, has the oil pump got a pressure limiter in it, spring and ball , spring broken or ball stuck ?

 

[Oneball]

There is a pressure relief bypass in the oil pump. It could have got something lodged or got stuck. Does the oil pressure change with rpm?

 

[Roscobbc]

Yes, there is a ball valve/spring arrangement pressure relief valve in the pump - very unusual I would have thought for the spring to break or ball become stuck - filter on oil pick-up tube would stop any debris getting-in and jamming the ball...........mind you it didn't stop something getting in the gear teeth on mine and causing the pump shaft to break.
I know its clutching at straws - but have you tried an oil change and new filter. There was quite a lot of chatter on CF forum a couple of years ago about the poor quality (then) of Fram filters I believe - everyone used them (being best rated) but a number of people were having major engine failures (seemingly down to the filters)......Its not such a difficult job to replace the oil pump - it can be done in situ - drop steering linkage and possibly starter motor for clearance - it's 'do-able' if you feel minded..........

 

[stealthyflatfish]

mmmm! Oneball, good call no the pressure doesn't change if I rev the engine Pressure is static at 40 psi .
Ross, good call mine has a Fram filter fitted, and I have a spare Fram, but don't think that will be going back in!
Could this be the answer ?
Think I'll be logging onto rock auto.
a filter change is preferable to dropping the pan.

 

[Oneball]

I’d throw the new Fram one on and see, but then I lack patience!