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Discussion Starter · #1 ·
Update to this link earlier today:
http://forums.vintage-mustang.com/forums/showflat.php?Cat=1&Board=forum&Number=463304&page=5&view=collapsed&sb=5&o=&fpart=
I just checked my oil pressure with a mechanical guage screwed right into the sending unit extension tube.

Cold idle (in gear) = 30 psi
Cold 2500 rpm = 45 psi

Hot idle (in gear) = 18 psi
Hot 2500-3000 rpm = 35 psi

I have 1500 miles on my rebuilt 289. My guage seemed to drop from halfway at normal cruise to low end of "normal" at cruise this past week. Hot idle shows a little under "normal" range on original guage.

I get a little lifter/rocker tick tick tick at hot idle as well. Car is not overheating, 185 degrees checked with a digital thermometer on a hot day. Also using 10w-40 Valvoline. Just changed oil and filter today to see if it would change. Was using straight 30 w with same exact readings. Sealed Power standard volume oil pump with chromoly driveshaft.

Do these pressures sound correct? I revved it up when it was hot to 4000 - 5000 rpm and the pressure went to 45 -50 psi. I think that is adequate, just concerned about the idle pressure. Thanks for any input you can give. Hopefully I'm just worried about nothing and need to quit looking at that 36 year old guage!
 

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im not sure but i think your sapost get more pressure with higher oil weight
 

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My thoughts are that your oil pressure is low for a fresh 289 with a new pump. Especially concerned that it seemed to drop all at once from mid-scale to the low end as you noted. Who did the rebuild ? And the install labor ? If it was a pro job I'd get a read on some warranty work. If you did it, well, you get to decide..

For reference, Lolita's current all-original 289 with 118,000 miles has 45-50 psi cold idle, 28 hot idle and 50 lbs hot at 2500 rpm.
 

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I have the same concerns about my new 289-2v in SWMBO's '66. It was professionally built by a local race engine builder with a very good reputaion. Was broken in and tested on a dynomometer before it ever went in the car. Showed 48.5 PSI on the dyno printout. Car has only about 200 miles on it now and I am seeing numbers almost exactly like yours with a mechanical gauge.

Maybe this is correct with a standard volume pump. Any comments appreciated.
 

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You're in my area, climate-wise...

Drain (filter too) and re-fill with 20W-50 and re-check pressures.

Likely your rod and main clearances are on the big side of normal and/or you might have a sloppy standard volume oil pump. I wouldn't know without dimensioning the bearings and pump but that's my guess...

If, upon examination, your clearances are a bit big but the crank and bearings look OK, switching to a HV pump should cure your problem. I prefer blueprinting them but know lots of guys who run them stock with no problems. M68HV is a typical pump which I've run on the race car....think I paid 28 bucks for the last one....it checked out pretty good on the gerotor radial clearances but the thrust was a bit loose; had to lap the housing about .003".

Have fun!
 
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