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Discussion Starter #1
I have a 91 TBI engine that has 28psi @75mph and about 20 @ idle. It also only has about 80k miles but has been sitting alot. Any thoughts on what might cause this? If it is the pump how much room do you need under the pan to be able to sneak it out from the cross member. I only have about 2.5 to 3" of room. Any quick good fixes or ways to check what it may be.
 

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TRY SOME 20/50
 

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Put a mechanical gauge on the engine and check it again..
 

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my bros 350 is the same, also a budies 400 is like that too

both have over a milion miels on them and have mechanicl gadges
 

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20# low???? bahhh I ran a 302 for over 2 years w/ 0 psi I ment zero psi @ idle and 5-10 tops on the road, my 400 runs 65-70 ish in the morning and will range from 15 @ idle to 40 cruzing @ 15oo rpm. I was always told 10 psi @ idle and 10 more per 1ooo rpm, yours sounds normal to me:)

~Nate~
 

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Discussion Starter #6
Yes but at 75mph/28psi it still makes lifter noise. How much room do you need to remove the pan on a chevy? I am planning a trip 3500miles and want to fix it right. Any help on info would be great!
 

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before you do anything drastic, change the oil and use some 20/50. If it still makes noise and has issues then you need to look at other avenues.
 

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I had the same problem with a built 302. I took the oil pan off....... and saw that the guy who had built it had left an oil rag inside the pan. :rolleyes:
 

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damn, if that's "ALL" you're getting than my motor is fawked... and has been fawked for the past few YEARS...
 

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go and dump in 2 quarts of lucas oil stabalizer when you change your oil, you will gain 20-40psi because it is thick as hell, the shit is great for transfer cases:D

 

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Discussion Starter #12
Thanks for the advise. I drained the oil and the sh!t was so thin!!
I put in 20/50 and a new filter and my psi is [email protected] idle and [email protected] cruse rpm. The lifter noise is gone and all seem well. I think it only had 10/30 or something close to it and it sat for a long time so who knows!
 

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Going to a thicker oil is not gonna fix your oil pressure problem. Typical oil pressure on a V6,8 is 40 idle 60 run. If your reading lower on an ACCURATE guage then it means that your motor is wearing out.

If your pressure is uniformly lower throughout the rpm range then it's wear on anything but the rods and mains. If it's low and doesn't change through the rpm range then is the rods and main bearings.

When a motor is new the clearances are tight and resistance to flow is good (pressure). As the lifter bores and bearings wear resistance drops and flow increases. This is your first sign that something is up...soon you'll get to a point where oil pump flow is at a max and you have very low pressure.

Thicker oil will get the pressure up so you think everything is fine, but in reality your not flowing enough oil because the fluid is too thick. You'll hear much more start-up noise and you'll end up spinning bearings if you take the motor to high rev's.

Now, don't go thinking that your motor is gonna shit the bed soon it's prolly got a couple of years in it, but don't be surprised if the bearings spin or it starts sounding like you have rocks under the valve cover.

Correct fix: Rebuild the motor.
Cheap fix: Get a high volume oil pump.
 
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