Oil Pressure Questions

[Anonymous]

I rebuilt a 68 200 for a Bronco. 500 miles on rebuild. The original engine was a 170. didnt do anything fancy on the rebuild,, just rings, bearings, oil pump, and timing. Bearings were Standard and the specs were within range. But here is my question. Using 10w-30 oil my pressure at startup is slightly over 55psi but when running down the interestate at rather high rpms. (no tach,, but 3spd manual, 4:10 gears, 31" tires @ 65-70mph) the engine temp runs around 190 or so, and the oil pressure begins to drop to around 30-35 and stay there as I drive. If I park it for a while then get back in after it cools a bit the oil pressure rises to around 45 again. Any suggestions? Im using mechanical oil and temp gauges. Would an oil cooler be the solution? heavier oil? Or am I worrying too much?

 

[ricksmol]

You are worrying too much. 35 PSI is not bad for these engines.
Rick
PS Try going to a K&N filter, expensive but brought my pressure up more than 5lbs. Or get married...guaranteed to raise your pressure..blood that is.
Rick

 

[rbohm]

8) the rule of thumb is 10psi per 1000 rpm, and mathmatically your engine is turning about 2900 rpm, so at 30-35psi you are ok.

 

[Anonymous]

showboat, I have a 66 bronco that I put a 250 that I rebuilt in 2or 3 years ago. I use 10-30 0il, have an oil cooler and a 190 thermostat. Right from day 1 the engine ran about 50# cold at 60 to 70 mph at 190 degrees 2400rpm it runs around 30#(I have an electric and a mechanical guage and they register close to the same) I have a C4 auto with an oil temp guage and it runs about 150 to 180 degrees . When Im making a super tough climb in the mountains on a hot summer day and my engine is running 210 to 220 degrees and my transmission is running 250 degrees my oil pressure sometimes drops to around 20# but comes back up to 30 when things cool down. I have good compression and lots of power the engine doesnt smoke so I have always thought these readings were about normal for this engine. Hope this helps.....Larry

 

[MustangSix]

Most 200's will turn up 55-60# of pressure above 2000 rpm. Rick, I can't explain why yours never did. I've thought about it a lot, and the only thing I can think of is that maybe the oil pump bypass spring is weak or not seating properly.

heat wil definitely cause a loss of pressure as the oil thins and clearances open up. But in any case, 10# per 1000 rpm is normally considered good at normal operating temps.

 

[addo]

Something that was actually pointed out by an honest wrecker... Most Ford dizzies are pretty well cactus after 10-15 years, because of the stress of driving the oil pump off the same shaft. Compared to the separate O/P drives of some GM engines, was his point.

Y/T roller top ends require less "active" oiling; the use of oil-through pushrods is good there, and these can be further restricted if need be, or the excess oiling can be considered to have cooling properties. Even in stock motors, we seem to hear of more heat-induced failures than poor oiling ones.

With coil-on-plug ignition and no distributor, running a HV oil pump with a "dummy" gear would be an interesting exercise. External oil lines would look really trick.

Adam.

 

[ricksmol]

Jack:
With the K&N oil filter mine is running at #40 when warmed up. I am not going to worry too much about the oil pressure as it is. Maybe one day if I take the oil pan out for some reason I will take a look into a new oil pump.
By the way when and if you have some time please take alook at this link and tell me if this is the firewall adjustable cable setup that you had in mind for the T5 clutch. Thanks
Rick


http://www.mustangsteve.com/cable.html

 

[rbohm]

8) rick, just be aware that some oil filters restrict flow, and while you get good pressure reads, you are actually starving the engine for oil. i dont thing K&N is one of those filters though.

 

[ricksmol]

My old Fram used to do that I think. You gets what you pays for.
Rick

 

[rbohm]

yep fram is one that tends to be bad that way, in fact most of the ones that restrict flow are the toilet paper style filters.

 

[Anonymous]

When you did your rebuild - did you replace the cam bearings?
Even if the rod and main bearing clearances were good, the
lost oil through the cam bearings is a common culprit for lower-than-expected pressure.

One way to test for this is to put in 2 cans of the blue-label STP and see how high the pressure goes. If it picks up about 15 PSI at highway speeds and you didn't replace the cam bearings, I'd suspect them.

Another lossy place is the long, long shaft that oils the valve rockers.
It doesn't take much wear under the rockers to lose the flow up there, especially the front few rockers.

When I rebuilt my engine, I replaced all of the above: cam bearings, shaft and rockers. I was surprised how much the PSI went up: it shows the same PSI on 10w40 oil now as it used to show on 20w50 with STP before the rebuild.

 

[ricksmol]

Mark:
I bought from Jack (Mustang Six) a short block . He rebuilt it completely. All the bearings were new. I know because I replaced the cam and saw the bearings (brand spanking new) and replaced the conrod bolts with ARP and saw every bearing in that engine was new.
I think Jack is right when he said that the oil pump might have some bypass spring problem.
Rick
PS: I just realized you were referring to Showboats engine ooops