Oil Pressure Troubleshooting

[87sierra]

There is a crush the crush is made when installing new bearings into either mains or rod every new bearing slightly protrudes from the cap and block or rod this is purposely designed by bearing manufactures to ensure perfect contact with the housing it is installed in that's why you never reuse bearings that have been removed also plastiguage is inaccurate due to losing the crush on bearings

 

[austinado16]

I've built a lot of engines over the years, and been inside countless others. I've used plastigauge often. It is accurate. I've also reused bearings in situations where the bearings were still perfect. I've never had a problem.

 

[shortboxchevy77]

There is a crush the crush is made when installing new bearings into either mains or rod every new bearing slightly protrudes from the cap and block or rod this is purposely designed by bearing manufactures to ensure perfect contact with the housing it is installed in that's why you never reuse bearings that have been removed also plastiguage is inaccurate due to losing the crush on bearings

No such thing. The bearings are exact and when installed form a perfect circle, any type of crushing would warp that perfect circle causing a bind with the crankshaft. Tolerances are too tight for what you are thinking of, you cant even swap rod bearing caps without creating a bind. Each rod and cap are unique, that is how perfect the circle has to be.

The crushing you are thinking of is when the bearing is pushed into the rod and cap as tightly as it can possibly be causing full mating between the rod and bearing surfaces at all points. This is why the mating surfaces have to be so impeccably clean, I was taught that a single dirty fingerprint on the backside of a bearing can cause the wear equivalent of 10k miles.

I've spent my entire life around engines on the farm and in the oilfields spending the last decade as a professional working on high dollar CAT engines. I've been into and built dozens of sbc's for trucks and dirt track cars, I like to be humble most of the time but you'll have to get up pretty early if your gonna teach me something about the inner workings of an internal combustion engine.

 

[theblindchicken]

I don't know what y'all are referring to with "crush," but it sounds like it's the force needed to overcome the force of friction when pressing the bearings into the block?

Anyway, I tried to install an aftermarket oil pressure gauge today. Didn't go so well. It was cheaply made and the threads on the back of the gauge stripped completely off. Ended up breaking the gauge through frustration.

So! Would it be possible that the oil pressure dropped simply because the oil was completely changed and given all brand new oil? The oil hadn't been changed in a while and it was a bit dirty. Just kept adding more to replace what was leaking out/being burned.

 

[austinado16]

Nope, not possible.

Sorry that happened with the cheap gauge.

 

[shortboxchevy77]

I don't know what y'all are referring to with "crush," but it sounds like it's the force needed to overcome the force of friction when pressing the bearings into the block?

Anyway, I tried to install an aftermarket oil pressure gauge today. Didn't go so well. It was cheaply made and the threads on the back of the gauge stripped completely off. Ended up breaking the gauge through frustration.

So! Would it be possible that the oil pressure dropped simply because the oil was completely changed and given all brand new oil? The oil hadn't been changed in a while and it was a bit dirty. Just kept adding more to replace what was leaking out/being burned.

No, would have nothing to do with it. Regardless, you still need to confirm oil pressure with a second gauge before moving on to the next step of diagnosing the issue.

 

[theblindchicken]

Alright, thanks.

When I was installing the gauge, I tested it while it was still all hooked up in the engine bay. With a small leak at the base of the gauge and the block, it was reading 34psi on startup.

Got the block leak fixed. Still read 34 psi. Then I brought the gauge into the cab since I was gonna go for a spin and check the pressure. That's when it stripped quite a bit, became unusable and made good friends with the trash can.

 

[bobkyle2]

The numbers don't sound bad. Get get a good gauge on it. You said you had the pan off, Did you disturb the pickup?

 

[austinado16]

If it makes you feel any better, mine's got 285k on it now and even with 10w/40 only makes 30ish on cold start. Hot idle is maybe 20. Super hot, climbed a 20mi hill towing the camper in 95*F temps at 35mph, maybe 12-15lbs. Running down the road at speed, 28ish.

Switching to 10w-40 from the 5w-30 that I'd always run bought me about 4-5psi super hot.

I installed a mechanical gauge and it reads exactly what my factor dash gauge reads.

 

[chengny]

If you find that your oil pressure is truly lower now than prior to the recent work, here are a couple of things to think about:

1. How old was the filter you pulled out? See if you can dig it out of the trash and cut it open. To my knowledge Fram oil filters are not fitted with a by-pass valve. And BTW - DO NOT depend on the engine's internal by-pass around the filter:

You must be registered for see images attach

(about %75 of the ones I test when doing a rebuild are stuck closed).

Consequently, it may have become so fouled over time that one or more of the pleats burst open. This would do a couple of things:

Number one; it would have allowed the oil to pass through it completely unfiltered - bad enough.

But here is another effect of a blown filter (deals with your issue): because the flow of oil from the pump to the system would be unhindered by any pressure drop through the filter - it would actually increase the oil pressure as indicated by the gauge.

Installing a new filter (with intact media) would slow the flow through the filter and result in an apparent drop in pressure.


That's it for the filter.

More likely this is what happened:

While you were stuggling with dropping the pan, scraping the old gasket off, re-installing the new gasket and replacing the pan - is it possible that you disturbed the oil pump's pickup tube and the attached screen?

If that screen is moved even 1/2" down it is going to be jammed right up tight against the oil pan floor. When that happens, the required clearance is gone and the pump is basically trying to suck the bottom of the pan into the inlet tube. It is starved for oil.

On the other hand if the pickup tube got knocked upwards far enough the opposite happens. The screen can be above/or right at the level of oil in the sump. In that case the pump the pump suck in a considerable quantity of air along with whatever oil it can grab. The aerated oil will not pressurize the system as effeciently as pure oil. Pressure at the gauge will be lower.

That pickup tube it just pressed into the pump housing and it doesn't take much to knock it free. Once it has broken the factory fit, it can move all over the place. Get a new pump if this turns out to be the issue.

 

[89Suburban]

Jerry is that you making those photos with the cut oil pan?

 

[chengny]

HAH - yeah it's me. I was putting an engine together last spring and was interested in the actual pan to screen clearance . I was bored one night and also got fed up with going by what everybody "knew" was the correct distance between the pan and screen. Measuring down from the rails is a pain and my kids ate all my Play-doh - so I made that jig.

I took my sawzall to a pan that was junk - it got hit a little bit too hard with the Black Beauty while being sand blasted - and found out for myself what exactly the deal was. Now I have a tool that to allows me to see and set the clearance any time I do a bottom end.

I also found a much simpler way to lock the pickup tube into the pump housing. Drill and tap the pump inlet where the tube inserts, for 10-32 set screws (90 degrees apart from each other). Jam the pipe home, set the gap where you want it. Then just tighten the set screws and peen the ends of the holes over.

The images below show the gap (as compared to a piece of 1/2" round stock) and my method to save the cost of a new oil pump due to a loose pickup tube:

 

[89Suburban]

That's good stuff

 

[shortboxchevy77]

HAH - yeah it's me. I was putting an engine together last spring and was interested in the actual pan to screen clearance . I was bored one night and also got fed up with going by what everybody "knew" was the correct distance between the pan and screen. Measuring down from the rails is a pain and my kids ate all my Play-doh - so I made that jig.

I took my sawzall to a pan that was junk - it got hit a little bit too hard with the Black Beauty while being sand blasted - and found out for myself what exactly the deal was. Now I have a tool that to allows me to see and set the clearance any time I do a bottom end.

I also found a much simpler way to lock the pickup tube into the pump housing. Drill and tap the pump inlet where the tube inserts, for 10-32 set screws (90 degrees apart from each other). Jam the pipe home, set the gap where you want it. Then just tighten the set screws and peen the ends of the holes over.

The images below show the gap (as compared to a piece of 1/2" round stock) and my method to save the cost of a new oil pump due to a loose pickup tube:

We tacked our pickup tubes onto the pump housings with a MIG welder for our dirt track AMX race cars (imagine motocross racing with cars). Worked well, they never budged.

 

[chengny]

There is a widely accepted engineering school of thought that strictly precludes this practice. It states in part, there shall be no joining, by welding, of any parts; that are to be used within the block of internal combustion engine.


Aw - I'm just fuggin' with ya - real reason for the set screws, I don't have a welder.