308 oil pressure

ShaneStone1964

Can you kind folks tell me what oil pressures you normally seeing on your 308s? Just installed a new VDO gauge and its showing 45-55 lbs at idle. Just wondering aloud.

Thanks all and be safe driving to Chattanooga.

shane

Frankvintagefullflowcom

Shane,

That's pretty danged high, especially at idle. You should be seeing about 40 at speed and, with an overall healthy engine, about 30 at idle. Deviations within reason are ok. I suspect you have a stuck regulator or someone has "adjusted" the regulator spring force under the false belief that more is better. Higher than spec isn't helping in any respect and can increase wear on the pump drive gear. That's already a common problem, so there's no point in aggravating it.

What's the history of the engine?

Frank

Uncle Josh

Get a mechanical pressure gage and screw it in to check your VDO gage.  Electronics are not guaranteed when new...or any other time.  If it checks, Frank is right.  What oil are you using?  Should be 10W30 or straight 30.  The pressure regulator is the large bolt between the distributor and dipstick and under the filter if you have one.  Make sure it's not cruddy and that somebody didn't add a washer to increase the spring pressure.  Clean the spring, ball and seat.

Frankvintagefullflowcom

Shane,

Although the correct oil viscosity may be a factor, the regulator should react and control pressure regardless of what you are using....within reason. You need to tell us more detail about when the high pressure occurs. All the time? Only when cold? Does the pressure continue to rise as engine speed climbs? Has the system been altered in any way? Has the engine been in constant/occasional use or recently been "awakened" from a long sleep? Have you switched from long term non-detergent oil use to detergent types? (that will get some argument)

Usually the plunger sticks (if that's the case) in the "open" position, causing low pressure at less-than high rpms. High flow rates push it open but the spring can't push it back to maintain pressure at lower rpms (lower flow rates). Don't look for a ball.....there isn't one in the pressure-lubed Hudsons, nor is there a seat, per se, but the plunger must move freely in its bore. 

There is a small diameter relief passage (~1/8th") just inboard of the regulator bore-plug threads, drilled at an angle downward/inward so that it intersects the regulator "blow-off" passage. This little passage must be clear or the system will operate in an unregulated mode, causing the pressure to rise uncontrolled. The latter wouldn't be true at idle, though.

More clues please. 

Re-reading your original message, I see that you have said that it 40-55 at idle. The regulator isn't in play at idle, so I'm now suspecting the gage/sender itself, esp. if electric. The 40-55 is about double the normal idle pressure. Check per UJ's suggestion.

F

ShaneStone1964

Thanks, gentlemen. I don't have all of the information you requested as yet. We recently bought the car. While it did turn over when we bought, and would run for a few seconds with starter fluid, I had to rebuild the carbs before it would "really" run. I've now rebuilt the carbs, It fires right up and can run for a minute or two. I'm awaiting the alternator bracket I'm having manufactured in order to get the water pump operating and to take it out on the road. The engine was, as was told to me, started a few times a year, but the car hadn't been road driven in quite a few years. So, yes, right now the pressure reading s just from idle. The new oil gauge is a mechanical gauge replacing an older, uglier one that wasn't really mounted anywhere. I should have it road worthy by next weekend. Maybe I should revisit this question once I can get in running for more time. Sorry if this was a little too premature. Just didn't want to do any damage if this was too abnormal. Shane

Frankvintagefullflowcom

Something else is in play here, 'cause the oil flow rate at idle isn't sufficient to even bring the system up to the rated pressure of 40psi. This isn't a fault. It's typical of most, if not all engines, Hudson or not.

F

ShaneStone1964

Again, Thanks! I'm on my way to follow up on Uncle Josh's suggestion.

shane