Oil Pressure concerns

[Mr Comet]

I have a 1967 ford 200 cid 6 cylinder engine which came out of a mustang which has been rebuilt and now I have just placed in in my 61 comet. I have a chilton manual which covers the ford 6 engines thru 65. It shows the 65 ford 200 oil pressure should be between 35-55 lbs. Would my 67 be the same? I have a mechanical oil pressure gauge with a thin nylon line only 1/8" OD which I think may not be working well. It's made by sunpro and only costs about $15. I am getting different reading at idle it varies from 0- 16 lbs. Two questions should I get a better quality gauge and if so which is a good quality one to get? I ran a line from the oil sending unit hole on the block so I could see how the oil flowed putting the other end back in the back hole on the valve cover and thru the 1/4 inch tube I got good stream of oil while the engine idled. I believe I have good flow I just would like to know I am getting good accurate pressure reading. Thanks for any and all help

 

[First Fox]

Unless the pump is sucking air from a majorly low oil level, there is nothing I can think of that would cause oil pressure to fluctuate like that. You may have air in the gauge supply line. You can try to bleed the line to the gauge by letting the engine idle, then crack the fitting loose at the back of the gauge and allow any trapped air out of the line. Let it spit oil onto a shop towel for a few seconds to make sure all the air is out, then tighten the fitting back up. I use the very same line of gauges in my daily driver and mine work just fine.

Your oil pressure will likely differ from factory specs depending on the viscosity of the oil you are using. The factory spec is for the grade of oil that they tested with; likely SAE 30. If you are running 10w30, it will be thinner and thus have lower pressure compared to SAE 30 when cold, which is a good thing. Oil pressure numbers are not a huge consideration IMO, as long as the HOT oil pressure is the 10 psi per 1000 rpm rule you should be good.

BTW, how does the pressure react when the engine is revved a bit?

 

[electrorc]

I have a 1967 ford 200 cid 6 cylinder engine which came out of a mustang which has been rebuilt and now I have just placed in in my 61 comet. I have a chilton manual which covers the ford 6 engines thru 65. It shows the 65 ford 200 oil pressure should be between 35-55 lbs. Would my 67 be the same? I have a mechanical oil pressure gauge with a thin nylon line only 1/8" OD which I think may not be working well. It's made by sunpro and only costs about $15. I am getting different reading at idle it varies from 0- 16 lbs. Two questions should I get a better quality gauge and if so which is a good quality one to get? I ran a line from the oil sending unit hole on the block so I could see how the oil flowed putting the other end back in the back hole on the valve cover and thru the 1/4 inch tube I got good stream of oil while the engine idled. I believe I have good flow I just would like to know I am getting good accurate pressure reading. Thanks for any and all help

I have a Sunpro gauge in mine too. My idle oil pressure is generally about 40 psi. If the engine was rebuilt relatively recently, I'd expect higher numbers. 16 isn't too bad, but much below that and I think I'd be getting worried. Make sure you don't have any leaks in the line anywhere. Do you know if the oil pump was replaced?

 

[72maverick]

I have wondered about where it should be. I think I have the same gauge as well. Mine reads from about 35 and goes up fairly fast when revved. It was recently rebuilt too.

 

[Mr Comet]

When I started the engine today it was at 25 lbs but gradually fell off as it warmed up. I bled the line as first fox discribed and will wait until it has cooled to try again. will the oil retrack into the block or should it stay in the line as it cools? I thought I knew some things about engines but I seem to contantly run into things I don't know. Thanks to all.

 

[First Fox]

When I started the engine today it was at 25 lbs but gradually fell off as it warmed up. I bled the line as first fox discribed and will wait until it has cooled to try again. will the oil retrack into the block or should it stay in the line as it cools? I thought I knew some things about engines but I seem to contantly run into things I don't know. Thanks to all.

What happens with the pressure when you raise the RPM? Whats the highest pressure you see?

 

[bubba22349]

" will the oil retrack into the block or should it stay in the line as it cools? "

Yes when the engine is shut down the oil pressure bleeds off, some oil will also drain out of the oil gauge line this is normal operation. If you want you can use a T fitting so that you can have both a low oil pressure warning light as well as your gauge. Good luck

 

[Mr Comet]

ff

When I rev it up the gauge does go up sometimes quick sometimes not so much. This really puzzles me because why do I bleed the line just to have it go back into the block and have air in the line again. I have bled the line at least three times today alone. The pressure was 25 today when I started the car the first time but thats the best I did. I started the car about a hour ago and got 17-18. It always starts to fall off after it starts to warm up. I have bled the line the last two times thinking I must have did it incompletely the previous times. I guess I don't understand the fall off and the weak pressure. I cannot see any reason to repeat the bledding but I am not happy. Tomorrow I'll start the car and track the results until it warm and let you know. When I pumped the oil back into the valve cover it flowed well thru a 1/4 ID tube. Isn't the flow as important as the pressure?

Bubba I had a 1/4 inch tee before but my bro in law thought that was one of the reasons for low pressure. You think I would be OK putting it back on?

Thanks guys

 

[Mr Comet]

Oh another thing. while I am bledding the line the gauge falls to 0 of course but after bled and tightened down the gauge never reads more then 5 # until the turn off the car and restart it later.

 

[bubba22349]

Mr Comet, a T installed correctly will have no effect on the oil pressure. Is the top end oiling correctly? It's a bit tough to diagnose without being there to see it or with out some pictures but these are some of the areas that can cause low oil pressure (in no particular order).
1. Bad oil pump or pressure relief valve (IE gear clearance, scored gears or cover plate, relief valve sticking open, weak or wrong spring).
2. Oil pump pickup tube setting too close to or too far from the bottom of oil pan sump
3. Wrong amount of oil volume in the oil pan.
4. Dented in oil pan
5. Oil pump pickup tube not sealed at pump IE missing gasket
6. Bearing clearance that is excessive
7. Cam bearings installed incorrectly
8. Missing oil galley plugs

Every engine has zero oil pressure due to oil drain back for a short time until the oil pump starts turning again. If you wanted you can make a coiled section of the line behind the gauge that will stop some of the drain back. I would not bother to bled the line. The depth of the gears in the oil pump control the oil volume supplied to bearings and other moving parts engine RPM along with bearing clearances control the oil pressure. Is the oil pressure reading rock solid at a steady idle or dose the gauge swing between a range or it's bouncing? X2 as FF said yes you should see a rise in oil PSI as RPM goes up. It's normal for the PSI to go down some with engine warmed up but 5 PSI on a new rebuild is a sign of a problem. Good Luck

 

[stu in wichita]

I recommend you don't spend any more time worrying about air in your oil gauge line. The air doesn't change the reading. Pressure is pressure, whether oil, water or air. The only thing the air bubble in that line will do is delay changes in the readings by a fraction of the second - not perceptible without sensitive monitoring equipment.

Same thing for tube size going to the gauge, there isn't any flow to speak of, only pressure. It will take a fraction of a second more to pressurize a 1/4" line than a 1/8" line, but again, not perceptible. The tube size doesn't matter - period.

If I were you, I'd spend 100% effort on the pressure loss after the engine has run. The above suggestions are all good. Another possiblility, is debris in the oil pan getting sucked up to block the pickup screen. After you shut it off, it falls back into the pan until the engine is running again. Not likely, espectially on a fresh rebuild, but over-use of silicone can leave a lot of stuff floating around an engine.

Good luck.
-Stu


.

 

[Mr Comet]

Thanks stu, can I buy a oil pressure gauge or perhaps rent one to see what the pressure is? This morning I started the car got 22-23 from the start rev it a few times and the pressure went up slightly never even 30 lbs. so I let the car idle and warm up. as it got warmer the pressure dropped off. by time the car was 160 deg by water temp press was like 5#. So I decide to go back to my tee coming off the block. Put teflon tape on all of the threads except the compression fitting for the nylon line. The one 180 end of the tee is nippled into the block on the other end of the tee is the sender unit. the 90 end of the tee is sticking up and that is where I installed the line for the gauge. However once again that line was pinched bringing into question whether the line is plugged again or not. One problem I have is Sunpro does not sell the replacement brass ferros for the nylon line. I have tried to use regular compression ferros but they are designed differently and seem to twist and then kink. I said all of that for Bubba since he said the tee needed to be installed correctly. Upon starting up the engine the light went out right away but I am not getting any pressure in the gauge. There is no dents in the oil pan. The oil is up to the full marks. I don't want to buy a new gauge just to find the one I have is fine but I need to know I am getting an accurate reading from a gauge I know is working. No use moving on until I know I have the correct pressure.

 

[stu in wichita]

Sorry if this is long-winded, but we need to get this figured out. A drop in oil pressure when the oil gets warm is normal, but it should increase as rpms increase, at least to the point that the relief valve in the pump prevents it from going up and up and up. I imagine that is the 55 psi mentioned in the Chilton's book.

Gauge accuracy - Even a cheapy gauge should be within maybe 10-15% accuracy. If it isn't physically damaged, it's probably not the problem. Just to be sure you can test it for apporximate accuracy with a regulated compressed air supply. If it's even close to correct, it should be good enough for trouble shooting. With your symptoms, you're looking for BIG variances, not an exact number. In other words, it's less important if it reads 5 pounds when you should have 10 than to show 5 pounds when you should have 40!

Gauge plumbing - As long as the lines are unobstructed without kinks, they'll be fine. Don't obsess about sealing threads - a little sealant or tape should work well. If you do have a leak, it'll be apparent.

Oil viscosity - It sounds like you're running 10W-40, right? I'd be tempted to change it to straight 40W just for testing. It'll still thin out as it gets warm so the pressure will drop, but not as far as a light oil. As a real long shot, change the filter too, it could be restricted somehow.

After you're sure the above are okay, the problem can only be caused by a few of things:
1. A restriction or leak in the oil supply to the oil pump - plugged or restricted screen, or maybe a leak in the pickup tube that lets it suck air.

2. The oil pump itself - this includes the gears,housing, mounting surface, gasket, and relief valve.

3. Last, is the "worst case" possibility - the downstream components can't hold the required pressure - usually excessive ckearance main bearings, rod bearings, or both.

Have you ever witnessed the engine running warm with good oil pressure? It sounds like you bought it from the guy who had it rebuilt. Any chacnce Can you contact him and find out if he ever ran it, and how was the pressure? How many miles are on the engine? Don't get discouraged.
-Stu

 

[Mr Comet]

Borrowed a gauge from a local auto repair shop guy has done work for me in the past. Started out about 10-12 lbs just guessing because gauge goes from 0 to 20 no numbers in between. as I revved to 2000 rpm the pressure went right up to almost 20 lbs but not quite. As the engine got to 175 degrees the oil light came on so I shut the car off. The sun pro gauge is working pretty well as you said its close. What's should I do next? I have never installed an oil pump before so it's my first time but then installing the rebuilt engine is new to me as well. Everyone has a first time somewhere. The oil is pennzoil 10-30w zttp additive and an STP oil filter. I am open to all help I can get. I have never heard of using 40w oil in a car. Doesn't that put added pressure on all the parts?

 

[thesameguy]

Oil pump is easy. Remove the pan, undo a couple bolts, replace pump, assemble. If you've got a cherrypicker you can use to lift the engine off the mounts to give you some excess clearance, you should be good! Worst part about this job is probably the oil pan gasket and rear seal, but if the engine was recently rebuilt it shouldn't be a big deal. Old, baked-on gasket kinda sucks.

 

[Mr Comet]

The steering cross member frame support member and front suspension piece get in the way as well. Thanks for the encouragement. I am just waiting to be sure they didn't already change it in the rebuild but it is not listed on my invoice so I think not. If the rest is new I would like it to be new too and to insure esle is wrong inside the pan. Any other suggestions while I am in there?

 

[stu in wichita]

Yeah, it looks like you're gonna have to pull the pan. On the plus side, with the pan off, you have access to almost every possibile cause. It may sound scary, but don't let it overwhelm you. Just cross each issue off the list as you check it, one by one. Once you find the problem, you don't need to go any deeper.

If you haven't done this type of work before, remember: the first consideration is safety. You can pull the pan with the engine "dangling" from a hoist, but you definitely want some additional rigging before you spend time underneath it. Some of the guys on here will have some ideas on additional supports, chains or other methods of securing it. But don't just count on the hoist holding it up.

Once the pan is off, check the pickup screen and tube. Make sure it is located correctly the pan. Remove it and check for junk inside, cracks, leaks, blockage, etc.

Move on to the oil pump, but don't just replace it with a new one. The pump is relatively cheap, but it would be a shame to replace it and find out that wasn't the problem. Try to determine what's wrong with the old one, if anything. Look for wear or damage to the pump itself, stuck relief valve, etc. Again, this forum will provide details on what to look for.

You also have access from below to the main bearing caps. You can remove them one at a time and check for damage. While each cap is off, use some Plasi-Gage, a cheap, easy and accurate way of checking bearing clearances. It's possible that the crank was machined too small, or the wrong bearing size was installed.

Inspect and check the clearance on the rod bearings next, using the same process.

I hope you find the problem early in the process and don't have to disassemble the bearings. But if it comes to it, you WILL find the problem, as this covers the entire oiling system, except for the cam, lifters and rockers, which would exibit some distinctive symptoms. You are now intimately familiar with the business end of your engine. Keep us posted as the investigation progesses.

-Stu

 

[bubba22349]

X2 you can check most everything with it installed though it may end up to be better to pull it out again. Especially if you paid to have your engine rebuilt you might want to check with the shop before you take much of it apart it might void your guarantee if you have one. Are you over tightening the oil line fittings? They should just be snug if your tightening the fitting enough to pinch the line thats way too tight. Many auto parts house have gauge line kits seperate like NAPA and also the ferals and other fittings. I used to prefer to use a copper line kit, but the nylon is fine as long as you keep it away from heat like the exhaust. The 200 engines used a straight 30 weight oil back in the day. Good luck

 

[Mr Comet]

Thanks Bubba,I think I will go with Autozone the manager and asst manager have been good to me. I do not believe I have any warantee because I bought it on E bay. The company I bought it from is Fastime Racing out of Wyandotte, MI if any of the forum members know about them. They are two and a half hours from me. I'll try and see what's wrong first and go from there. Sure hate to have to take the engine out run it down there and then have to go get it when their done.

 

[Mr Comet]

The pump is out and here are what I have found:
One of the bolts holding the pump to the block seems to loosen rather easier then the other. Is there specs for the torgue upon replacement? Also the gasket between the pump and the block has a tear in it. Nothing in my paperwork shows that this gasket was replaced upon the rebuild. this tear is between the outside of the pump flange and the bolt hole. Screen does have from caking in one corner of cludge. Not alot but I don't know what is normal just stating it I guess. At Autozone the gentleman said I needed to know what size plasigauge. Any ideas? I am not in a hurry to reassemble everything. I can't tell if the pump is good or not by turning the shaft. It looks prestine but it's been bathe in oil its whole life. There was two pumps available one 4 5/16 length and the other was 4 5/8. Mine is the 4 5/16. Would that make a difference?

Thanks

Denny