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Pegging 70??

7

72 Bluz

Guest
My oil pressure guage is almost pegging 70, which is as high as the guage reads on my 72 coupe (still deciding on her name). I have continued to use Castrol 20x-50w as the previous owner and changed the oil last week. The reading dropped a little, but it still concerns me when I see it appearing to max out. I was going to check out the sending unit tonight after Bible study. Does anyone have any suggestions?

72 Bluz

PS: It idles around 50. The oil was about a quart 1/2 low when I changed it and I was losing oil somehow. Later found that a plug wire somehow got under the valve cover and I fixed that. Seemed to drop the oil pressure a bit, but it still seems high to me. Thanks.
 
D

Doug78

Guest
I believe all cars from the 'General' until about 1990 called for 10w40 in an average climate. Unless you drive around in Death Valley I would suggest that you change to 10w40 or 5w30. The 20w50 is thicker and would require more pressure to pump the same volume. Of course it may have heavier weight oil to reduce ticking in the valve train which should be fixed by adjusting the rockers or rebuilding the heads, not by running heavier oil.
 

silver 80

Well-known member
Joined
Jul 9, 2001
Messages
562
Location
madison,wi
Corvette
1980 silver with blk interior 1987 blue / blue
Pegging 70

I agree with Doug that is way to thick for just driving around, maybe if you race, but not for normal driving.
Tom
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Oil Pressure

I don't know if this is a stock or rebuilt motor. You may want to inquire about that. If the previous owner put a high pressure pump it will indeed put up high numbers all the time.

The best kind of pump is high volume, not pressure. This is done by having larger gears in the pump. Most pumps come with a pair of springs that you can install in the relief valve. If you put the stiff spring in you will have ultra high pressure. Some would argue that high pressure leads to premature bearing wear and failure. I always put the softer spring in on a new motor and the stiff spring on a high mileage motor to keep the pressure where it needs to be. The more miles and wear, the lower the pressure as wear in the bearings increases the room for the oil to squirt out.

I also agree with the prior posts. There is no reason to run 20W50 oil. This is only going to cause a loss of power and fuel economy. The thicker oil works best in worn out motors and those that operate in extreme hot conditions.

It is true you may give some valve train noise when switching to a thinner weight in the event the valves were originally adjusted with the thicker oil. It is a pain, but well worth the time and effort to re-adjust them.

Finally, 10 psi per 1,000 RPM is an acceptable range while at operating temperature. You should see higher pressure when the engine is cold. Most of these motors will run around 20-25 at idle and go up to about 40-50 while cruising down the highway.

I would drop to 10W40 or 30. If no change, put an external oil pressure gauge on to see if yours is reading proper pressure.
 
7

72 Bluz

Guest
The previous owner told me the engine has apprx 30,000 miles on a rebuild. I don't know about the oil pump - will ask. It rarely gets below 20 degrees here, but I have always used a 10w40 or a 30 weight oil, was a bit surprised when he told me 20w50.

Thanks.

72 Bluz
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Change the oil back to 30 or 40.

Read the pressure.


If it is still this high, get another oil pressure gauge and temp mount it.

If still this high, go ahead and drop the oil pan and pump. Either buy another pump, or just get the lower pressure spring from you local dealer.

Reassemble and watch the pressure go back to a normal range. At the rate you are going you will push oil out of your seals, wear your bearings, and shorten the life of your engine.
 
7

72 Bluz

Guest
Thanks everyone, but.....

I will probably change to 10w40 tonight, but I have one more (dumb) question about this. Since Xena has only been driven about 20 miles since the Castrol 20w50 was put in, do I also need to replace the new filter as well?

Thanks,
72 Bluz
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Filter

I guess you can take it off and drain as much out as possible and then put it back on. However, I don't know if the dirty and clean side will mix while draining leaving unfiltered material ready to be pushed through the motor.

I would just toss the filter and start fresh from scratch.
 
7

72 Bluz

Guest
Oil pump....

Just confirmed Xena has a high volume oil pump. Previous owner told me he put the high volume pump in on the rebuild about 15-20k miles ago. Think I'll still change to 10w40, but I feel better about the reading now.

Thanks for your help and advice.

72 Bluz
 
7

72 Bluz

Guest
Been out 10 days for vacation. Changed the oil to 10w40 last night and the pressure dropped to around 20 idle and 50 on the road doing about 60 mph. Thanks for all the help, folks.

72 Bluz
 

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