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Ok I just came in from the monster lab with yet another example. I don't call it a test because I already new the outcome. The gage will not hold the highest pressure attained so you'll just have say well this guy went this far I'll take his word. I spun a new BBC pump as that's all I have to use. I used 2 springs both with adequate pressure against the retaining pin. The weak spring had 35psi the stronger spring had 55psi. This is turning it by hand with a speed handle with the gage dead headed to the cap. I know this works as years ago we didn't have a different drive for all of the different engines i.e. Ford Chyrsler so I see an extension with an Allen head on it to prime them and they will go straight to bypass pressure. This is obviously at bypass pressure as there is no where to bleed off. You say well you turned them at different speeds. Nope when they get to bypass you cannot spin it faster and produce a different reading.
if it has/had always been that; yes. if it deteriorated to that, I would go looking for the cause....
Bill
You've got way bigger chahonies than me then. When I built ms LS1 for my GTO I didn't stretch the spring because I said it will be fine it's just a stock motor and I'll never run it hard. After its at temp it has 30 idling and 40 at cruise and scared me to death. I've got 10,000 miles on it now so I'm not so scared anymore but I still don't like it.
As a former GM engine mechanic, retired now, I fixed low oil pressure problems by installing a high volume pump with a standard pressure (55-60psi) spring. The high volume pump could keep the low side pressure usually above 25 psi at a low idle, most of the time better than 30 psi. High side pressure, of course, was unchanged from stock. This prevented the dash oil pressure guages from pegging the needle at higher rpms.
Engines that idled at very low pressures for extended periods could damage themselves by not getting oil up on the higher parts of the engine, like cylinder walls, cam bearings, and rocker arms. Lifters starved for oil will tap, I don't think running dry does them any good. Cam bearings starved for oil will wear excessively, opening up their bearing's oil clearance and leaking out the oil that is supposed to go to the lifters and up to the rocker arms. You almost never hear worn cam bearings, only low oil pressure points to a problem there.
It is true that GM accepted the low oil pressure as normal, but some customers didn't buy into it, and I didn't either. I was happy to offer my customers a relatively inexpensive solution to their problem. It was also true that GM would not warranty this kind of repair, I had a shop at my home where I did a lot of engine building for racers, and repairs that customers couldn't get done at the dealership.
I still don't understand why they would've made the block like that. But Johns explanation goes a long way.
Another basic engineering mistake in the Cole/Engineering Staff design - the differing thermal coefficient of expansion between the open-deck aluminum block and the cast iron cylinder head, aggravated by the nearly non-existent 12" x 12" radiator (note one-handed assembly line installation in photo below), resulted in extreme sensitivity to overheating, followed by a degraded, then failed head gasket seal, and more frequent overheat cycles that literally killed the block casting in short order.
Another basic engineering mistake in the Cole/Engineering Staff design - the differing thermal coefficient of expansion between the open-deck aluminum block and the cast iron cylinder head, aggravated by the nearly non-existent 12" x 12" radiator (note one-handed assembly line installation in photo below), resulted in extreme sensitivity to overheating, followed by a degraded, then failed head gasket seal, and more frequent overheat cycles that literally killed the block casting in short order.
There may be other engines with the open deck but I haven't seen one. When I first laid eyes on an LS aluminum block I had flash backs of the Vega block with the amount of unsupported cylinder at the deck. I know 2 different situations.
Exactly where is this spring and where can you get this pink spring?
We have mentioned it in previous posts but I wanted to emphasize if you are going to use a high pressure spring get an intermediate shaft with a steel sleeve. You can order it from summit as well or AutoZone carries them. This is the oil pump drive shaft.
My 66 350 hp 327 was reading low oil pressure at idle. Idle was set at 750 rpms. It turned out the person I bought it from replaced the gauge. When he installed the tubing line onto the back of the gauge i believe he didn't hold back on the 1/2" brass block attached to the gauge when he tightened down the 1/8" ferrule. What happened was the block rotated slightly counter clockwise moving the needle to the left. The fix was simple. I used a 1/2" open ended wrench and a mirror to move the block back. You want to make sure the block is aligned vertically on the back of the gauge.
You've got way bigger chahonies than me then. When I built ms LS1 for my GTO I didn't stretch the spring because I said it will be fine it's just a stock motor and I'll never run it hard. After its at temp it has 30 idling and 40 at cruise and scared me to death. I've got 10,000 miles on it now so I'm not so scared anymore but I still don't like it.
I mentioned that in post 37. And he is correct, but you shouldn't have to have a high volume pump in a stock engine. It's a quick easy way to get more pressure but unless the engine has abnormal internal leakage the stock pump is more than adequate.
Earlier someone suggested an engineering drawing or a cutaway. I provided that. Then I went as far as trying to show the setup for showing a pump getting on the bypass spinning only by hand which is certainly much lower than idle speed. I seriously doubt any of these guys telling me I'm wrong have ever switched or altered the pybass spring, I would have no way of knowing this. If they had they would know what does and doesn't work. If we could post videos I would post testing the pump but we can't and I'm not going through the trouble of posting a YouTube video, don't really care about this that much. If I post pics of testing the pump they'll just say I manipulated the results to show what I wanted. I can tell you there is a difference between education and experience. Education= you've studied it. Experience= you've done it.
I mentioned that in post 37. And he is correct, but you shouldn't have to have a high volume pump in a stock engine. It's a quick easy way to get more pressure but unless the engine has abnormal internal leakage the stock pump is more than adequate.
Earlier someone suggested an engineering drawing or a cutaway. I provided that. Then I went as far as trying to show the setup for showing a pump getting on the bypass spinning only by hand which is certainly much lower than idle speed. I seriously doubt any of these guys telling me I'm wrong have ever switched or altered the pybass spring, I would have no way of knowing this. If they had they would know what does and doesn't work. If we could post videos I would post testing the pump but we can't and I'm not going through the trouble of posting a YouTube video, don't really care about this that much. If I post pics of testing the pump they'll just say I manipulated the results to show what I wanted. I can tell you there is a difference between education and experience. Education= you've studied it. Experience= you've done it.
yes, you can post videos, but they must fall within the forum's size guidelines; or maybe a Utube link
Here are pics of the test setup. I ran these at 500 rpm which is the same as the engine running 1,000. And yes this is not representative of the actual engine as there is no leakage or temperature involved. This only shows what happens with a spring change.
Here are pics of the test setup. I ran these at 500 rpm which is the same as the engine running 1,000. And yes this is not representative of the actual engine as there is no leakage or temperature involved. This only shows what happens with a spring change.
As a former GM engine mechanic, retired now, I fixed low oil pressure problems by installing a high volume pump with a standard pressure (55-60psi) spring. The high volume pump could keep the low side pressure usually above 25 psi at a low idle, most of the time better than 30 psi. High side pressure, of course, was unchanged from stock. This prevented the dash oil pressure guages from pegging the needle at higher rpms.
Engines that idled at very low pressures for extended periods could damage themselves by not getting oil up on the higher parts of the engine, like cylinder walls, cam bearings, and rocker arms. Lifters starved for oil will tap, I don't think running dry does them any good. Cam bearings starved for oil will wear excessively, opening up their bearing's oil clearance and leaking out the oil that is supposed to go to the lifters and up to the rocker arms. You almost never hear worn cam bearings, only low oil pressure points to a problem there.
It is true that GM accepted the low oil pressure as normal, but some customers didn't buy into it, and I didn't either. I was happy to offer my customers a relatively inexpensive solution to their problem. It was also true that GM would not warranty this kind of repair, I had a shop at my home where I did a lot of engine building for racers, and repairs that customers couldn't get done at the dealership.
I am certainly not taking issue with your statements about how you treated the symptoms of low oil pressure with a pump that produces more volume than a stock low volume 45psi pump BUT.. you treated the symptom and not the cause. If you go to the extent to remove a engine oil pan to install a high volume pump why would you not check the main and rod bearings in a attempt to find the cause of the low pressure.
That being said I understand the simple cure may be as you did but IMO if GM did not think low idle pressure was a problem then it's just your opinion that 10-15-20lbs. at the gauge is not enough for a camshaft the spins at half crankshaft speed. There are three passages for oil to travel, one for each bank of lifters then the center for the cam bearings then down and on to the main and rod bearings. With 10-20 psi at the gauge why would this be a problem with a engine at resting idle speed.
Please don't tell me the 1970's camshaft lobe wipe problem was a result of low oil pressure.
Respectfully, I think we beat this one to death but I am not buying the argument that the pump relief spool moves to the bypass port at idle pressure and the argument that these low oil pressure issues are really a problem. My 1963 Corvette shop manual specs main bearing clearances at .0008-.0034 and rods at .0007-.0028 so that is a wide margin and I bet makes a huge difference in the leakage shown up as low pressure at idle.
FWIW, I remember a discussion a long time ago over at the NCRS site that stated GM would use one half of a under size bearing to bring things in spec at Flint.
Butch, I believe that you anyway, where did I say low oil pressure hurt anything. I posted pics of my Briggs engines that run with zero oil pressure. I said I don't LIKE low oil pressure. And when I was in the business customers don't like it. I simply posted examples of how to cure it and many here chose to take exception. That's fine everyone is entitled to there opinion. As far as you not buying the pybass at idle if the last pics don't show you nothing will. All that is envolved there is th bypass spring. I showed those with the mill turning 500 rpm. They show the same when I spun them yesterday with a speed handle. Having blueprinted engines for the last 44 years I'm very well aware of bearing clearances and using different undesize to obtain the correct clearance. I didn't bring up Firestone tires, Vegas, pintos, wiping cam lobes, or any of the other stuff that pops up in these threads. You or anybody else don't have to like or buy my opinion, but I back my opinion with the years of hands on experience. At 19 years old I was doing the valve jobs on John Lingenfelters SS engines what were you doing?
First off, I can't see any of the pictures. Just little blue blocks.
The oil pressure is going to be low(er) at idle speed even if the bypass doesn't open.
So someone tell me what is the engineering logic to cause low oil pressure to deliberately be even lower because the spring doesn't sufficiently limit travel?
Or was this just sloppy engineering tolerances on the springs and machining that allow this to happen? It is known that some brand new cars had this condition as well as many didn't.
PS. You can put me in the category of not knowing how much spring travel is allowed to open the relief.
The engines and the oil pumps were mass produced. Some were tighter than others.
It is fact that some engines went out the door brand new with undersized rod bearings.
Some would have just a half bearing changed to a .001 under to tighten them up.
This was not common but it sure did take place.
Even in the Rebuilders market tolerances vary from engine to engine and oil pressure will vary due to the variables. Some pumps are tighter and make better low speed pressure. An extra .001 between the oil pump gears and the gear cover drops oil pressure.
The extent of knowledge on this forum never ceases to amaze me. I didn’t understand it all but I enjoyed reading it LOL
The owners’ manual for my ‘67 says 30 psi at idle and 40 psi moving down the road are normal numbers. But it doesn’t say anything about pressure before the engine reaches normal operating temperature.
My car shows 30 at idle and 45 at speed when warmed up but cold, the gauge reads just shy of 60. Is that normal?
My engine is a 327/350 and is the original engine to the car. I don’t know about any work that may have been done on the engine by previous owners.
The extent of knowledge on this forum never ceases to amaze me. I didn’t understand it all but I enjoyed reading it LOL
The owners’ manual for my ‘67 says 30 psi at idle and 40 psi moving down the road are normal numbers. But it doesn’t say anything about pressure before the engine reaches normal operating temperature.
My car shows 30 at idle and 45 at speed when warmed up but cold, the gauge reads just shy of 60. Is that normal?
My engine is a 327/350 and is the original engine to the car. I don’t know about any work that may have been done on the engine by previous owners.
Butch, I believe that you anyway, where did I say low oil pressure hurt anything. I posted pics of my Briggs engines that run with zero oil pressure. I said I don't LIKE low oil pressure. And when I was in the business customers don't like it. I simply posted examples of how to cure it and many here chose to take exception. That's fine everyone is entitled to there opinion. As far as you not buying the pybass at idle if the last pics don't show you nothing will. All that is envolved there is th bypass spring. I showed those with the mill turning 500 rpm. They show the same when I spun them yesterday with a speed handle. Having blueprinted engines for the last 44 years I'm very well aware of bearing clearances and using different undesize to obtain the correct clearance. I didn't bring up Firestone tires, Vegas, pintos, wiping cam lobes, or any of the other stuff that pops up in these threads. You or anybody else don't have to like or buy my opinion, but I back my opinion with the years of hands on experience. At 19 years old I was doing the valve jobs on John Lingenfelters SS engines what were you doing?
I'm Tim not Butch, but to respond to the above post your test shows a pump dead headed out and of course it's going to build pressure and relieve. The test would need to be done in a engine with all the different leak points (rods, mains, etc.) Am I missing something here, what did you intend to prove dead heading a pump.
At 19 years old I had a few small blocks apart and back together but for the most part still partying hard not listening to the smartest guy I have ever known, my Father. Back then I knew everything... :-)
At 19 years old I had a few small blocks apart and back together but for the most part still partying hard not listening to the smartest guy I have ever known, my Father. Back then I knew everything... :-)
At 10 years old, I had changed a head gasket on a Model A Ford and learned to drive. At 13, I had souped up the family's 1 1/2 hp Briggs lawn mower by taking the head gasket off, installing an 8 hp carb and putting roofing nails in the tires to get traction coming off the corners. At 14, I had overhauled an OHC Crosley engine, a '49 Olds V-8. At 18, I overhauled a buddy's MG TD engine and installed a supercharger using modified SAE size tools. Also built a 312 Ford engine with a factory 2X4 intake and Clay Smith cam. This was after I did a flathead Ford that was bored/stroked, ported, relieved, Johnson adjustable tappets, Edelbrock heads, 2X2 intake with '97's and a Dunn track cam.
I am not a name dropper but even if I was, never worked for anyone important in the engine building business so I guess I'm just another "deplorable" trying to grasp what little knowlege I can here in the short time I have left.
04-29-2018, 08:55 PM
