So... this was in my oil drain pan...

[Locobob]

https://www.zr1.net/forum/picture.php?albumid=432&pictureid=4547
http://www.zr1.net/forum/picture.php?albumid=432&pictureid=4547[/url]

pretty sure it wasn't there before I drained the oil

[Locobob]

Right before I changed the oil I noticed the oil pressure was a bit low at idle and the oil temp was a bit higher than usual. I have a bad feeling this is an oil control plug of some sorts but I'm not having much luck IDing it in the FSM. Anyone have a guess on where this came from?

[Jagdpanzer]

looks like one of the crankshaft oil gallery plugs

[A26B]

I agree with Phil. Ties in with your oil pressure observation.

[Locobob]

I found the crank diagram in the FSM, looks like there are 4 plugs in the crankshaft. Is this doable from the bottom by removing the oil pan? Looks like it might be.

[Locobob]

I agree with Phil. Ties in with your oil pressure observation.

I was just talking to Petey about it. Looks like I'll be ordering a plug and a oil pan gasket from you Jerry

[Hib Halverson]

Make sure you install that with Red Loctite and if you can access any of the others, remove them and Loctite them, too.

I've never heard of one of those coming out and, man, with that missing, I'll bet the oil pressure was low.

Interesting that something 5.25-in in diameter would fit though the drain plug hole, but then, I guess I don't remember how large it was.

[Locobob]

Make sure you install that with Red Loctite and if you can access any of the others, remove them and Loctite them, too.

I've never heard of one of those coming out and, man, with that missing, I'll bet the oil pressure was low.

Interesting that something 5.25-in in diameter would fit though the drain plug hole, but then, I guess I don't remember how large it was.

I was actually mentally debating that... removing all of them and re-loctiting. My idle oil pressure was about half of normal, luckily I was close to home. And yeah it must have just barely fit through the drain hole, and I'm sure glad it did or I'd have no idea what was going on. It's .525 btw, 5.25 would surely be a no-go lol

[Jagdpanzer]

The front crankshaft throw has a 1/4" npt pipe plug on the forward side and a 3/8" npt plug on the aft side. The remaining 3 throws have 1/4" npt plug on both fore and aft sides. I use hardened steel plugs from the hydraulic supply store. Stay away from the soft plugs you find the local hardware store.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[Jagdpanzer]

All plugs are easy to get at once the pan is dropped. While in their might check to make sure the press in plugs are still fully seated. Very lucky the plug came out through the drain hole.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[Locobob]

All plugs are easy to get at once the pan is dropped. While in their might check to make sure the press in plugs are still fully seated. Very lucky the plug came out through the drain hole.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

Yeah I'm still debating messing with the other plugs. I've often shot myself in the foot with preemptive maintenance attempts lol. I'll take a look once I get there I guess. This is the first I've heard of a screw in plug coming out like that.

[Jagdpanzer]

First time for me to


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[A26B]

First time for me to


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

Didn't Yun have a plug come out of his new engine build too? Seems like he drove it around for a bit too with low oil pressure but no harm. Just goes to show how robust the oil pump is.

[Locobob]

Well the mystery continues... Marc tells me that the crankshaft oil plugs are too big to make it past the oil pan windage tray. So not sure what to make of the plug I found. Did it come from somewhere else on the engine? Was it already laying in the oil drain pan from some other project and I didn't notice it? Do I need to put down the crack pipe? I guess before I start tearing things apart I should drive the car a bit with its fresh oil and new filter and see what my oil pressure looks like.

[Jagdpanzer]

Could be a plug from one fo the cylinder heads located in the cam chain space that seals off the end of the lifter oil gallery drilling 13974


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[secondchance]

Didn't Yun have a plug come out of his new engine build too? Seems like he drove it around for a bit too with low oil pressure but no harm. Just goes to show how robust the oil pump is.

Good memory! Yes, I lost one plug (can?t remember exactly which one) after the first rebuild. My motor barely maintained 15 psi at idle and about 25 at higher rpm. Drove about a year and, I think, about 3-4000 miles. And then, my head gasket went again. We found the cause when Dempsey pulled the motor and disassembled.
Jagdpanzer said something about divine intervention by Corvette God. Or, something like that.:D

[Polo-1]

Hard for me see to it, does the plug have drill hole in it? Not from the rod journal if it does.

[wfot]

I was thinking it could have been a cam plug from the rear of the cams, but I just measured one from a 1991 and it seems to be .5 inch. that is weird? I just looked a bare block and can't find anything like that....

John

[Locobob]

No drill hole in the plug. The plug measures .525 across the threads, and Mark Haibeck is telling me that nothing bigger than about .25 can get through the oil pan windage tray to the bottom of the oil pan where the drain hole is. I haven't checked to see if it fits through the drain plug hole but it should just barely as the drain plug bolt specs as a 5/8's
So that leaves the following possibilities:
The plug is unrelated and was sitting in the drain pan already and I failed to notice it.
The plug fell into the drain pan from somewhere else on the engine
My oil pan windage tray is either bent or modified in such a manner that the plug made it through to the bottom.

I took it out for about a 15 minute drive. On start up and for about the first 5 minutes I'm getting really strong oil pressure, like 65-70psi. Once its good and warmed up I'm seeing maybe 25-30psi after idling for a minute but I'm seeing more like 60psi when I get on the gas.
I finally found the FSM oil pressure specs, they list minimum hot idle oil pressure as 12psi... so perhaps I'm worrying way too much about this. But its odd that it's suddenly lower than it used to read, and its odd that it corresponded with finding that plug in the pan.

[Dynomite]

Since you are now not sure.......I will add another possibility......

The Dash Gauge Oil Pressure Sensor and I had one that all of a sudden showed lower oil pressure.....
after replacement oil pressure was fine (normal) at all Temperatures and RPMs :cheers:

https://cimg8.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/600x600-1/80-soilfilterhousinglabel_zps4cacf14a_1__d0e1c161f9cb 4d877e3c05cb44ccf09b8c61ffd4.jpg

In general the NPT diameter of a plug is 1/4" larger than the NPT size.....

The oil pressure loss depends on where the "open" 1/4 NPT plug is located in the oil path. And depends on which oil path is involved.

[Jagdpanzer]

If it came out of the aft end of camshaft I don't think you would see much influence on the oil pressure gauge. The camshaft oil feed is through a small orificed drilling to one of the cam journals. Oil is then distributed to the other cam journals via the cam rifle drilling.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[Jagdpanzer]

Also, the aft end of the cam is very close to the cam cover sealing plug. Imagine if the plug backed out it would have left some damage behind on the sealing plug.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[Locobob]

It's possible it came from a head... or somewhere else... although its path into the oil pan below the windage tray remains in question.

[Locobob]

I think it being just a sensor issue is unlikely as the drop in oil pressure corresponded with a rise in oil temperature.

[Locobob]

Got a package from Jerry today... and welp... its not a crank plug. The plug I found in the drain pan is .525 across the threads and the new crankshaft plug I got from Jerry is about .662 across the threads. So I can rule that one out


https://www.zr1.net/forum/picture.php?albumid=432&pictureid=4550

[wfot]

I do not know if this is applicable here on your specific engine, your profile shows a LPE 368, I believe that the 368 motors use a stock crank, if I am not mistaken. if that is even the engine in question.

However,

I was looking over my build in process for an answer, I have a bryant crank, specifically made for LPE, it has .525 threaded plugs on all rod journals... except the second from the snout, that one is a little larger.

Again I think you have a stock crank and the rod journals should be plugs, but if LPE modified it, it may have been done in the same fashion as mine, assuming that it did not come from bryant this way. might be worth a call to LPE to see if they may have some insight on it. just a thought since this seems to be vexing a lot of really knowledgeable minds right now. I figured this info would not hurt..

John

[Locobob]

I do not know if this is applicable here on your specific engine, your profile shows a LPE 368, I believe that the 368 motors use a stock crank, if I am not mistaken. if that is even the engine in question.

However,

I was looking over my build in process for an answer, I have a bryant crank, specifically made for LPE, it has .525 threaded plugs on all rod journals... except the second from the snout, that one is a little larger.

Again I think you have a stock crank and the rod journals should be plugs, but if LPE modified it, it may have been done in the same fashion as mine, assuming that it did not come from bryant this way. might be worth a call to LPE to see if they may have some insight on it. just a thought since this seems to be vexing a lot of really knowledgeable minds right now. I figured this info would not hurt..

John

Yeah its a 368 with a stock crank shaft so the plugs should be stock. I can't think of a scenario where LPE would put a smaller plug in as that would require the plug to be installed in a bushing which makes no sense at all. I'm a little jealous of your bryant crank... cube envy :D

[A26B]

Got a package from Jerry today... and welp... its not a crank plug. The plug I found in the drain pan is .525 across the threads and the new crankshaft plug I got from Jerry is about .662 across the threads. So I can rule that one out

I think the one you have is a 1/4" NPT plug. These are used in the rear of the camshafts. Its a tapered thread, smaller on the end, bigger towards the top. In the middle of the plug threads, it would measure abt 0.532" on the thread o.d.

I have heard of new, aftermarket, new & reground camshafts being installed without the plug. I have not heard of one coming out, but would bet this is what you found. If you are lucky, you will pull the correct cam cover first!

A spec plug like this would be abt 0.405" long.

My money is on the rear cam plug.

[wfot]

Yeah its a 368 with a stock crank shaft so the plugs should be stock. I can't think of a scenario where LPE would put a smaller plug in as that would require the plug to be installed in a bushing which makes no sense at all. I'm a little jealous of your bryant crank... cube envy :D

Haha Rob,

I wish there was a way to see it with the engine IN the car, it is such a rare thing, it has a hand stamped number in the front journal... called bryant.. they pulled the build card on it and told me its whole story on it. great company. they told me it was good for 1,500 hp and 12,000 rpm. of course he added that one has not actually broke yet, so those numbers could be higher as blocks/rods fail first.

John

[Locobob]

I think the one you have is a 1/4" NPT plug. These are used in the rear of the camshafts. Its a tapered thread, smaller on the end, bigger towards the top. In the middle of the plug threads, it would measure abt 0.532" on the thread o.d.

I have heard of new, aftermarket, new & reground camshafts being installed without the plug. I have not heard of one coming out, but would bet this is what you found. If you are lucky, you will pull the correct cam cover first!

A spec plug like this would be abt 0.405" long.

My money is on the rear cam plug.

It does match those dimensions and it is NPT, it screwed right into the back of one of my air tools... although its path into the bottom of the oil pan remains a head scratcher. If it is a camshaft oil plug how big a deal is this? Oil pressure is still within minimum spec, am I looking at a rapid wear issue?

[Dynomite]

I say remove the oil pan and check the windage tray to see if there is any place a 1/4 NPT plug can fall through.

If no.......then that plug has been in oil pan for a long time or in your oil drain pan for a long time and nothing to do with your perceived small drop in oil pressure (which you just noticed recently).

If that 1/4 NPT plug can drop through the windage tray........then check that bottom crankshaft plugs are intact. If they are intact......The Cams each have a rear plug about 3/8" OD, 1/8 NPT (.405" O.D.) unlike your 1/4 NPT Plug (.540" O.D).

And.......when you say idle pressure is 25psi-30psi (Hot)....what is your idle rpm?
Makes a difference in oil volume output. And.....what is your oil weight?? (Maybe you are using light weight oil for winter).

[A26B]

It does match those dimensions and it is NPT, it screwed right into the back of one of my air tools... although its path into the bottom of the oil pan remains a head scratcher. If it is a camshaft oil plug how big a deal is this? Oil pressure is still within minimum spec, am I looking at a rapid wear issue?

I should go check this before I start talking about it, but its late & too cold to go down to the shop to verify tonight.

There are 4 oil drain conduits from the cylinder heads, down through the cylinder block and into the oll pan exiting UNDER the baffle. If you will note, one of the 4 conduits is in the far rear corner of the cylinder head, right by the camshaft. The conduit is sealed with the head gasket and the oil pan gasket all the way down to within an inch or so of the very bottom of the oil pan, where an errant cam plug could exit underneath of the baffle tray.

Head gasket
https://cdn10.bigcommerce.com/s-nkg90o/products/1050/images/2767/10106176-77__36840.1599254168.120.120.jpg?c=2

Pan Gasket
https://cdn10.bigcommerce.com/s-nkg90o/products/266/images/554/10106193Oil_Pan__07891.1413935351.120.120.jpg?c=2

and, the Oil Pan (note the exit from the drain back conduit at the bottom of the pan
https://cdn10.bigcommerce.com/s-nkg90o/products/393/images/1443/10225138_U__63653.1439379733.1280.1280.jpg?c=2

[A26B]

Are your cams stock? If not stock, where did they come from?

[Dynomite]

I should go check this before I start talking about it, but its late & too cold to go down to the shop to verify tonight.

There are 4 oil drain conduits from the cylinder heads, down through the cylinder block and into the oll pan exiting UNDER the baffle. If you will note, one of the 4 conduits is in the far rear corner of the cylinder head, right by the camshaft. The conduit is sealed with the head gasket and the oil pan gasket all the way down to within an inch or so of the very bottom of the oil pan, where an errant cam plug could exit underneath of the baffle tray.


That errant cam plug is most likely a 1/8 NPT (.405" diameter).......unlike the 1/4 NPT (.540" diameter) plug found in oil pan.

[Locobob]

I should go check this before I start talking about it, but its late & too cold to go down to the shop to verify tonight.

There are 4 oil drain conduits from the cylinder heads, down through the cylinder block and into the oll pan exiting UNDER the baffle. If you will note, one of the 4 conduits is in the far rear corner of the cylinder head, right by the camshaft. The conduit is sealed with the head gasket and the oil pan gasket all the way down to within an inch or so of the very bottom of the oil pan, where an errant cam plug could exit underneath of the baffle tray.

Head gasket
https://cdn10.bigcommerce.com/s-nkg90o/products/1050/images/2767/10106176-77__36840.1599254168.120.120.jpg?c=2

Pan Gasket
https://cdn10.bigcommerce.com/s-nkg90o/products/266/images/554/10106193Oil_Pan__07891.1413935351.120.120.jpg?c=2

and, the Oil Pan (note the exit from the drain back conduit at the bottom of the pan
https://cdn10.bigcommerce.com/s-nkg90o/products/393/images/1443/10225138_U__63653.1439379733.1280.1280.jpg?c=2

Thanks Jerry! This is sounding like a very feasible scenario. The cams are stock. Sounds like there are differing opinions on the size of the plugs though? Can we get a consensus on the size of the plugs? Anybody have one they can actually put a caliper to? or any other plug in that area that could conceivably make its way down one of those 4 passages from the cylinder head? Judging by the pics of the windage tray and Marks input regarding clearances as well as the fact that the crank plug I bought doesn't match the plug I found I think we can discount the idea that it came from the crank.

[Dynomite]

Thanks Jerry! This is sounding like a very feasible scenario. The cams are stock. Sounds like there are differing opinions on the size of the plugs though? Can we get a consensus on the size of the plugs? Anybody have one they can actually put a caliper to? or any other plug in that area that could conceivably make its way down one of those 4 passages from the cylinder head? Judging by the pics of the windage tray and Marks input regarding clearances as well as the fact that the crank plug I bought doesn't match the plug I found I think we can discount the idea that it came from the crank.


I measured diameter of plug across end of cam.
I also found one more source of the Camshaft Plug Diameter in "Solutions".

See Post #26.........Camshaft plugs (http://www.zr1.net/forum/showthread.php?p=94539)




Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[Locobob]

I measured diameter of plug across end of cam.
I also found one more source of the Camshaft Plug Diameter in "Solutions".

See Post #26.........Camshaft plugs (http://www.zr1.net/forum/showthread.php?p=94539)




Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

Ah thanks Cliff, so the cam plugs are 1/8 NPT... are we sure that applies to all years? Mine is a 91. If its not a cam plug then perhaps one of those head plugs up by the cam chains? Something else on the cylinder head?

[Locobob]

I say remove the oil pan and check the windage tray to see if there is any place a 1/4 NPT plug can fall through.

If no.......then that plug has been in oil pan for a long time or in your oil drain pan for a long time and nothing to do with your perceived small drop in oil pressure (which you just noticed recently).

If that 1/4 NPT plug can drop through the windage tray........then check that bottom crankshaft plugs are intact. If they are intact......The Cams each have a rear plug about 3/8" OD, 1/8 NPT (.405" O.D.) unlike your 1/4 NPT Plug (.540" O.D).

And.......when you say idle pressure is 25psi-30psi (Hot)....what is your idle rpm?
Makes a difference in oil volume output. And.....what is your oil weight?? (Maybe you are using light weight oil for winter).

I was just talking to Petey and he also says the cam plugs are 1/8 NPT

Mark told me he removed the windage tray and cleaned the pan so it wasn't sitting in there.

There doesn't seem to be a path from the plugs that are in the heads up by the cam chains into the bottom of the oil pan that I can see.

Assuming the plug is unrelated and was either overlooked laying in the drain pan or fell off the engine from somewhere other than the oil drain hole... oil weight could be a factor. I usually run about a half and half mix of Mobil 10-30 and Mobil 10-40. I ran out of the 10-40 a while back and have been topping off with 10-30 so maybe... but it seemed like kind of a sudden change to me... to the point where it immediately stood out to me as abnormal. IDK maybe its just 2020 stress and I'm losing it lol
Idle seems about where its always been.

[XfireZ51]

And Bob, your not seeing any oil leaks anywhere?

[wfot]

I suggested the rear cam plug a while back, it does appear to be too small, it is 3/8 roughly across the threads. picture is of the early cams '90 - '92

Also I agree with marc, that tray is pretty tightly spaced, I do not think a .525 plug will make it passed the tray

Also I agree with Jerry that the cam plug can sneak down an oil port

I just do not see another spot where a .525 plug can come from based on looking at my bare heads and block.

Is it possible that some cams have a rear .525 plug?? or are they all identical.

I fear that it is an actual drop in oil pressure and idling and light driving will not pose a problem, but if you lean on it, the lack of pressure will show up as a cam or bearing problem..

John

[Dynomite]

A new oil pressure sensor for the gauge is relatively inexpensive and very easy to replace.

Jerry has 16 in stock :thumbsup:

[Locobob]

And Bob, your not seeing any oil leaks anywhere?

I haven't noticed any

[Locobob]

I suggested the rear cam plug a while back, it does appear to be too small, it is 3/8 roughly across the threads. picture is of the early cams '90 - '92

Also I agree with marc, that tray is pretty tightly spaced, I do not think a .525 plug will make it passed the tray

Also I agree with Jerry that the cam plug can sneak down an oil port

I just do not see another spot where a .525 plug can come from based on looking at my bare heads and block.

Is it possible that some cams have a rear .525 plug?? or are they all identical.

I fear that it is an actual drop in oil pressure and idling and light driving will not pose a problem, but if you lean on it, the lack of pressure will show up as a cam or bearing problem..

John

Thanks for the pics. Yeah Marc just further confirmed the cam plugs as 1/8 NPT and apparently the only 1/4 NPT plugs in the head are the ones up by the cam chains where there is not really a feasible path into the bottom of the oil pan.