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97 chev 305 v8 oil Q

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I have a 97 chev with a 305. When I got it the oil was junk, very very old. I have changed it and filter 3 times. Oil presure was kinda bouncing all over the place and then going very very low 5psi. I replaced the sending unit and that did nothing. So I installed a mechanical gauge, now it still reads low. Oil has not actually made it to the gauge yet, but it looks like it reads normal when cold then drops down to 5 psi again. I would believe it, but the valve train makes no noise. Is anyone knowlegeable enough to give me a hint on what the problem is? I was thinking the oil passage going to the gauge could be plugged, I am really hopping the oil pump is not bad, cause I will be looking to rebuil the motor if it is. Thanks for any info.

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I have a 97 chev with a 305. When I got it the oil was junk, very very old. I have changed it and filter 3 times. Oil presure was kinda bouncing all over the place and then going very very low 5psi. I replaced the sending unit and that did nothing. So I installed a mechanical gauge, now it still reads low. Oil has not actually made it to the gauge yet, but it looks like it reads normal when cold then drops down to 5 psi again. I would believe it, but the valve train makes no noise. Is anyone knowlegeable enough to give me a hint on what the problem is? I was thinking the oil passage going to the gauge could be plugged, I am really hopping the oil pump is not bad, cause I will be looking to rebuil the motor if it is. Thanks for any info.

It is possible that the oil gallery leading to the sending unit is goobed up-try using a pipe cleaner to probe it out.

Pull the valve cover and see if there is oil gettin up there-if it looks like you're gettin oil up there, it very well could be a blocked passage.

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Are we talking 5psi while driving or 5psi at idle?

5psi at idle is expected (and even somewhat acceptable) on a older engine. If you're seeing 5psi at 3000+ rpms you have something to worry about.

How many miles are on the engine?

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Are we talking 5psi while driving or 5psi at idle?

5psi at idle is expected (and even somewhat acceptable) on a older engine. If you're seeing 5psi at 3000+ rpms you have something to worry about.

How many miles are on the engine?

Dittos what C/C said. I know even Toyota sais 4 psi at idle is minimum, but even then, its a sign of trouble. But any engine RPM, it needs to climb right up, especially being as it will be under a load then, and the loads will easily overcome 5PSI of oil pressure. Visualize the cranshaft, floating on a cusion of pressureized oil, not metal to metal contact. Now under a load, the this layer of pressure is overcome, the engine will be short lived. I suspect if the vavle covers reveals no signs of neglect, ie sludging/gelling, then you have excess clearances which basically measn an internal oil leak from the rod and main engine bearings. I have an 88 GMC C3500, at idle, even warm, its 45 psi, and at throttle, it goes up to 60 PSI. You dont want to see much fluctuation between idle and 2500, the wider the gap between idel vs 2500 means extra clearances inside the engine. Get it fixed or you will become a pedestrian

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5-10 PSI at idle is normal.

Add 10 PSI for every 1000 rpm.

Synthetic oil will lower those specs by 5 PSI sometimes.

If you're close to those specs just run it. If not........just run it. Small block Chevys are a dime a dozen. Replace it when it starts knocking but before you put a rod through the block and ruin your core.

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as long as its building up 25-30psi at highway speed it'll stay together for years. If ya start seeing 10-15psi at RPM you better start shopping for a motor, Or a bearing kit.

The 10PSI per 1000RPM's is a guideline for racing engines... daily driven street engines will run for years on quite a bit under that.

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as long as its building up 25-30psi at highway speed it'll stay together for years. If ya start seeing 10-15psi at RPM you better start shopping for a motor, Or a bearing kit.

The 10PSI per 1000RPM's is a guideline for racing engines... daily driven street engines will run for years on quite a bit under that.

A little confused with your numbers.

You say 10 PSI per 1000RPM is only a guidline for racing engines, yet you say at highway speed which is roughly 1500-2200 RPM (depending on ratios) 25-30PSI is acceptable.

Isn't your spec much higher than my "racing spec"??

Yes, an engine can run for years at a lower spec, however a truck engine that gets worked should fall in closer to the 10PSI-1000RPM rule, IMO.

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What weight of oil are you running? Thicker oil can help to boost the pressure on a marginal engine.

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A little confused with your numbers.

You say 10 PSI per 1000RPM is only a guidline for racing engines, yet you say at highway speed which is roughly 1500-2200 RPM (depending on ratios) 25-30PSI is acceptable.

Isn't your spec much higher than my "racing spec"??

Yes, an engine can run for years at a lower spec, however a truck engine that gets worked should fall in closer to the 10PSI-1000RPM rule, IMO.

Well I guess engine speed while driving completely depends on the driver. I tend to wind one out to 3500+ RPM's before shifting, and I've been known to dip into the 5500 range occasionally :bonk: On a stock or near stock engine, 25-30psi is more than enough to get into the 5-6000 rpm range safely, 55psi would be complete overkill unless it was a race engine.

If you tend to baby the RPM's then you're right, my numbers are skewed somehwhat.

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Well I guess engine speed while driving completely depends on the driver. I tend to wind one out to 3500+ RPM's before shifting, and I've been known to dip into the 5500 range occasionally :naughty: On a stock or near stock engine, 25-30psi is more than enough to get into the 5-6000 rpm range safely, 55psi would be complete overkill unless it was a race engine.

If you tend to baby the RPM's then you're right, my numbers are skewed somehwhat.

That poor camaro :bonk:

Do the T.P.Is even make power at 5500 rpm?

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Well it does seem a little on the low side. I have a 4.3 in my s10, and warm engine at idle, the gauge reads 40. At 55 down the road it reads 60-65. I'm running 5w-30 too.

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That poor camaro :bonk:

Do the T.P.Is even make power at 5500 rpm?

:naughty: I was actually talking about my new truck. The stock TPI's tend to run out of power about there, but with some work they'll pin ya in the seat up til 6300 or so. Its currently out of commision though, the motor finally insisted on being pulled for overhaul and I've got more important projects going at the moment so its just sittin in the corner of my shop with the motor on a stand.

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Ok, to try and answer some q's. I run 15-30, 5 psi at idle(some times the mech gauge drops to the peg), 20 psi at all other rpms, havent looked under valve covers, but when purchased oil was junk one part 2 weight one part 700 weight.

Nothing seems bad about the motor except some noise at 3800 rpm, I just purchesed a high volume pump and will install soon. Put some thick stuff, not sure of brand, in the oil well see what happens. And I hope this high volume pump dosent blow out my leaking crank or cam seals :bonk:

Thanks for the help

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I have had this very problem. It was the oil pump. They do not just "go out", they die a slow painfull death. Put some STP, ETC..thick stuff in to thicken the oil untill you have time to change. Drop the pan and change the pump as soon as you can. See if you can get your brother, who may have some experience here, to help you. Changing an oil pump is easy-getting the pan off may suck more than you can possably imagine. Also it makes sence to start with the less expensive stuff. You have already tried changing the oil, and I see you have tried a mechanical gauge, so the pump is next. This will also give you a chance to see what kind of splooge is in the pan.:bonk:

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I put the honey in and it works when cold but no workie when warm. The pump is on order from seattle (?) Will be here on wednessday or thurs. We should be able to finish or friday night? I am getting off work an hour early. That thing I was talking about is the axel, center section bolted to frame should be able to loosen boltes and get more room

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I put the honey in and it works when cold but no workie when warm. The pump is on order from seattle (?) Will be here on wednessday or thurs. We should be able to finish or friday night? I am getting off work an hour early. That thing I was talking about is the axel, center section bolted to frame should be able to loosen boltes and get more room

You'll need to drop the whole diff out to clear the oil pump pickup. Very easy. Just the C/V axle bolts, upper and lower mount bolts, R/H extension housing bolts, vent hose, actuator wiring, pop the center link off the pitman arm for extra clearance, and it will drop out. Takes about 15-20 minutes on a hoist.

Careful with the high volume oil pump if it is a high miler. I've seen slightly worn bearings errode from high volume oil pumps.

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I put the honey in and it works when cold but no workie when warm. The pump is on order from seattle (?) Will be here on wednessday or thurs. We should be able to finish or friday night? I am getting off work an hour early. That thing I was talking about is the axel, center section bolted to frame should be able to loosen boltes and get more room

The fact that the honey does not help once warm means you have real trouble somewere:foul: . I hope it is the pump!:bonk: If not -it is time for a crank job.(NUTZZZZ:banghead:)

What kinda of PSI when cold?

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The fact that the honey does not help once warm means you have real trouble somewere:foul: . I hope it is the pump!:bonk: If not -it is time for a crank job.(NUTZZZZ:banghead:)

What kinda of PSI when cold?

45-50 psi cold, 1-2 psi warm

Hey, anyone out there want to buy a 97 chev pickup. Runs strong, needs little to nothing, SELLING AS IS!!!!!!!

Just kiddin

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Try changing the pump. Doing it sucks:foul: , but it is like a new heart for the truck. If that doesn't fix it, either sell it or put a new(turned)crank into it. :bonk:

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Try changing the pump. Doing it sucks:foul: , but it is like a new heart for the truck. If that doesn't fix it, either sell it or put a new(turned)crank into it. 👍

Ok, new Hugh volume pump is in. When cold 50 psi, warm running rpm 20 psi, warm idle 5 psi. All of these numbers are with 20-50 weight. Motor toast, and if so how long could I have, remember there are no noises comming from the motor

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