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1978 Ford Tbird with 351M/400


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So almost a year ago, I bought a motor that was very clean from a trustworthy car guy.  he said the motor had been rebuilt but never really used, we checked the heads and they were clean, I put on a new mainfold and carb and it was incredibly clean also.  I brought it to colorado and have had many issues that have only ever arisen here in colorado.  My main issue now is after I drive my car for the time it takes to fully heat up, my tempature begins to climb and sometimes goes up to immediately go back down.  Along with that my oil pressure plummets in lower rpms and when im not going 20 to 25 at least.  I have a new thermostat, the wire to the oil pressure sensor is new,  I was told to use 5w-30 (or 40 I cant fully recall)  Then i heard that was to thin for here so I now have 10-w40 in my car.  My car is 6.6L and I noticed only 4 quarts came out and i put that in, and the oil reading was above full. So i am rather confused on that.  My radiator has some leaks, and some shops told me that because it leaks, it cant cool properly and its causing the oil to thin out to much even with the thicker oil.  I have tried additives to thicken it, i have found one that mostly kept my oil pressure in the normal zone but with longer drives it would still seem to act up.  Could a new radiator solve this problem like I am told or is this something else?  The oil pump has never been replaced as far as I know, but its never given me issues and when I start and when its all cold it shows oil pressure quiet high (also a new common thing here in colorado) but it shows pressure.  I am really confused, and quite worried.

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Factory gauges? Not sure if your Thunderbird has it or not, but I suspect that the gauges CVR (constant voltage regulator) could be faulty.

Use separate,  but known working gauges,  to test oil pressure and coolant temperature. This will allow you to compare it's results to the dash gauges (think process of elimination).

Chances are you have multiple issues that need a disciplined approach to solving them one by one.

Best of luck. 

Tom

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My Tbird does have its factory gauges, but they have never malfunctioned or shown worrying signs.  Not until,  not at all exaggeration,  I drove it in colorado.  I heard I could move the sensor down near the oil filter but that would give optimistic readings and not the reading the OEM placement in the rear top gives for the end of the reverse lubrication I hear my motor has.  I could look into a mechanical gauge and see.  I do hear that my motor from factory comes with low oil pressure, just odd how I never had such issues till colorado happened.  before I moved here I did install a 4 barrel edelbrock with edelbrock performer manifold and it has changed the power around some, but none of these problems happened in my last state.  I want to upgrade my oil pump regardless and am just trying to find a proper fit hardened oil pump drive shaft for a Melling high-volume.  on a side note, if you happen to know if that is a good pump to use and possibly a shaft that fits would be fantastic.  I cant find a shaft that directly says it will fit my motor and the year.

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