What's normal oil pressure on a '66 390?

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TbirdIntender
Posts: 55
Joined: Sat Jun 27, 2020 11:56 pm

What's normal oil pressure on a '66 390?

Post by TbirdIntender »

My oil gauge does move, but it doesn't move very far--never gets anywhere near the middle of the dial.

Thankfully, I see no sign of a problem, but I'm wondering what's normal on these gauges?
1966 Town Hardtop in sapphire blue
JamesR
Posts: 196
Joined: Sat May 11, 2019 7:47 pm

Re: What's normal oil pressure on a '66 390?

Post by JamesR »

Hi, good question. You may not have received any replies because you're asking about a 66 in the '67-71 forum. You have other posts in the '64-66 forum, so I presume a '66 is what you have.

With my '65, the actual oil pressure was way off from what the factory gauge said it was. And I don't think that there's a formula you could rely on to translate the non-numerical factory gauge readings into actual pressure. I.E., you should probably assume that the factory gauge is off, but you can't know what direction.

In my case, I installed an aftermarket gauge to find out the actual readings. It so happens that I had access to TWO aftermarket gauges of the exact same type, so I'm reasonably sure they were accurate, as I installed them both - one after the other - and they gave the same readings.

Strangely, my factory gauge - like yours - was giving me indications that my pressure might be a bit too low, but when I tried the aftermarket gauges I found that my actual pressure at startup was much higher than normal rather than lower than normal, as the factory gauge led me to believe. Consulting with local experienced engine expertise, it was determined that my engine had been rebuilt with a HV oil pump installed.

A similar thing happened with my '54 Ford Ranch Wagon: for years I thought the engine ran hot, per the factory non-numerical electric gauge. A good quality mechanical/thermal gauge told me that my car had actually been running too cool all that time! I had to put in a warmer t-stat.

So, the takeaway FOR ME is that those old Ford factory gauges shouldn't really be trusted. I've opted to live with aftermarket gauges on my fairly stock car. If you insist on keeping original gauges and not using aftermarket, one solution would be to hook up some quality aftermarket gauges temporarily so you can compare and reference the readings from the original gauges (to determine what their "normal" ranges are.)
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