Center main pressure oiling

Dick Deegan

Dick Deegan

Well-known member
Happy Halloween to everyone.

Firstly thanks to everyone who answered my questions on my earlier post on the Center Main Bearing. The information was very helpful and, as always, I learned some new things. I really appreciate the help.

My car is a 30 Coupe. I has a full flow oil filter mounted on the valve cover. I have finished checking all bearings (mains and rod) and they all look very good except the center main which is showing some signs of wear. I removed a shim from one side and it is now in spec. As mentioned before I use the tin foil method of checking and adjustment.

I have read previous posts about presuure oiling of the center main and I think I want to do this, but I have a few questions.

1. Can I switch the front cap with the center main cap in order to prolong life on the center main or should I just leave them as is? The object would be to use the cap with the least wear in the center. The chamfers etc look the same on both. I realize that, if I do that, I will have to reshim and adjust. Thoughts.

2. I see that there are several ways of picking up oil pressure - drilling into the oil galley in the block, drilling into the pan gasket area of the block as per Piranio's website (how do they get oil there?) and going into the pump. It would seem to me that the easiest way is to go into the pump as 48 Rob did. Is this adviseable? Any downside of doing this? Is there pump vibration doing normal dirving that may cause a fatigue failure? Thoughts please.

3. Is there anything I should know before I drill into the cap? Do you take the hole for the fitting straight through the babbit? I don't want to screw this up, so any advice will be much appreciated.

Thanks for now

Dick
 
Dick Deegan said:
Happy Halloween to everyone.

Firstly thanks to everyone who answered my questions on my earlier post on the Center Main Bearing. The information was very helpful and, as always, I learned some new things. I really appreciate the help.

My car is a 30 Coupe. I has a full flow oil filter mounted on the valve cover. I have finished checking all bearings (mains and rod) and they all look very good except the center main which is showing some signs of wear. I removed a shim from one side and it is now in spec. As mentioned before I use the tin foil method of checking and adjustment.

I have read previous posts about presuure oiling of the center main and I think I want to do this, but I have a few questions.

1. Can I switch the front cap with the center main cap in order to prolong life on the center main or should I just leave them as is? The object would be to use the cap with the least wear in the center. The chamfers etc look the same on both. I realize that, if I do that, I will have to reshim and adjust. Thoughts.

2. I see that there are several ways of picking up oil pressure - drilling into the oil galley in the block, drilling into the pan gasket area of the block as per Piranio's website (how do they get oil there?) and going into the pump. It would seem to me that the easiest way is to go into the pump as 48 Rob did. Is this adviseable? Any downside of doing this? Is there pump vibration doing normal dirving that may cause a fatigue failure? Thoughts please.

3. Is there anything I should know before I drill into the cap? Do you take the hole for the fitting straight through the babbit? I don't want to screw this up, so any advice will be much appreciated.

Thanks for now

Dick
Click to expand...



You really are not going to get any pressure to the center main, by running a line from the pump, or block. You might get oil there faster, but no pressure to speak of. Yes the pump does move around, and if you use a copper line it will work harden then break if you drive it long enough.

No you should not move the caps around. It was bored for that location, if you move it you will not get full contact, you will have to scrape it in. I would just adjust the bearings and move on.

If you really want pressure you will need to run lines to all the mains, and re-plumb the oil pump.
 
I have done the center man oil pressure thing several times from the oil pump. I always loop the copper tube to alliviate the engine viabration and keep it from cracking. Yes, I drill all the way through the cap and the babbit.
I don't know about exchanging the front and center caps. That might change the alignment of the crank. Interesting question though. Maybe someone else knows the answer.
 
Dick Deegan said:
Happy Halloween to everyone.

Firstly thanks to everyone who answered my questions on my earlier post on the Center Main Bearing. The information was very helpful and, as always, I learned some new things. I really appreciate the help.

My car is a 30 Coupe. I has a full flow oil filter mounted on the valve cover. I have finished checking all bearings (mains and rod) and they all look very good except the center main which is showing some signs of wear. I removed a shim from one side and it is now in spec. As mentioned before I use the tin foil method of checking and adjustment.

I have read previous posts about presuure oiling of the center main and I think I want to do this, but I have a few questions.

1. Can I switch the front cap with the center main cap in order to prolong life on the center main or should I just leave them as is? The object would be to use the cap with the least wear in the center. The chamfers etc look the same on both. I realize that, if I do that, I will have to reshim and adjust. Thoughts.

2. I see that there are several ways of picking up oil pressure - drilling into the oil galley in the block, drilling into the pan gasket area of the block as per Piranio's website (how do they get oil there?) and going into the pump. It would seem to me that the easiest way is to go into the pump as 48 Rob did. Is this adviseable? Any downside of doing this? Is there pump vibration doing normal dirving that may cause a fatigue failure? Thoughts please.

3. Is there anything I should know before I drill into the cap? Do you take the hole for the fitting straight through the babbit? I don't want to screw this up, so any advice will be much appreciated.

Thanks for now

Dick
Click to expand...

Are you running a counterweighted crank? That's the first thing to do for the life of the babbit.
 
Glenn;

Thanks for your reply. Tom brings up a good point about counter balancing. Were the cranks on the engines you did counter balanced?

Thanks

Dick
 
Dick, never change the bearing position! Not front to middle or even turn them around. This affects the alignment of the bearing to crank and will accelerate wear or lock the motor up.
counterbalanced cranks are the way to go. I do many of them both, the Burlington cranks and the weld/bolt on type. This is one of the best up grades you can make.

I also do the center oilers and have no trouble drilling the cap and tapping it for a 1/8 NPT fitting. Just be careful and drill all the way through so you don't push the babbitt out of the cap. This only happens when the cap was not tinned properly but can be a problem. I drill about halfway down in the oil chamber where the pump goes and tap it for a 1/8 NPT fitting also.
 
James & George;

Thanks for your insight. I will leave the caps as they are. I kind of thought that would be the response, but I wasn't sure. I really value your expertise in these matters.

I will look into a counterbalanced crank. Can the bolt on type be installed with the engine in the car?

Dick
 
Dick Deegan said:
James & George;

Thanks for your insight. I will leave the caps as they are. I kind of thought that would be the response, but I wasn't sure. I really value your expertise in these matters.

I will look into a counterbalanced crank. Can the bolt on type be installed with the engine in the car?

Dick
Click to expand...
There is no way to un-bolt it from the flywheel in the car so, NO. Some things just cannot be done in the car.
 
Don't worry about a copper line cracking. A long unsupported line that vibrates will eventually crack, but a short one like we are talking about will last forever. Most older cars & trucks, 40's & 50's, had a small copper line that fed the oil pressure gauge, I was a truck mechanic starting in the mid 50's and rarely saw one that had cracked.
 
P.S. You will get a pound or two of pressure to the main. Model B's used essentially the same pump and got slight pressure to the mains. About 3 PSI when cold and 3/4 pound when hot.
 
Jim Brierley said:
Don't worry about a copper line cracking. A long unsupported line that vibrates will eventually crack, but a short one like we are talking about will last forever. Most older cars & trucks, 40's & 50's, had a small copper line that fed the oil pressure gauge, I was a truck mechanic starting in the mid 50's and rarely saw one that had cracked.
Click to expand...
I did A 28 Chevy this spring that had four originals to feed the rod sluces. None were cracked and all were copper.
 
James Rogers said:
I did A 28 Chevy this spring that had four originals to feed the rod sluces. None were cracked and all were copper.
Click to expand...


Were they soft copper, or were they like the copper tubing we use today. also the oil pressure tubing for the gauge was 3/16 dia not 5/16 big difference.
Why not use steel and not have to worry about it.
 
Engineering question or controversy...a shaft running in a plain bearing drags the oil with it, maintaining a pressure at the bottom where the dynamics make the clearance smaller. There is always a clearance, or serious violence would destroy the thing realdamnfast...the pressure generated at the bottom of the bearing that I am discussing is from the shaft acting on the lubricant forcing it between shaft and bearing, NOT any pressure induced by the pump. In a gravity feed system there is quite substantial pressure down there, and in a pressure fed system said internal pressure between the surfaces is higher than the pressure feeding in the oil, I think by a lot. With existing pressure at its highest at bottom, lowest at the top, oil is introduced to bearing journals at the top whether by gravity or by pressurized galleries in engines that I am aware of. All of this stuff rattling around in my memory seems to be confirmed by the 1935 Ford of England produced "Elementary text book of automobile engineering" I have in front of me. The book, by the way, discusses early modes of oiling as well as the pressurized delivery Ford was using in most engines by 1935...
Doesn't this modification put the oil into the wrong place, a point at which it cannot properly enter???
What am I missing??
Any mechanical engineers around here to sort this out??
 
My thought, and I am no engineer, is that the small pressure that comes from the pump will be more than that generated by 6 inches of gravity from the valve chamber, and more oil will flow into the bearing grooves and parting line reliefs, where it will be picked by the rotating crank to provide the cushion needed. Would like to hear other opinions.
 
The important thing is that the added line will get oil to the main quickly, and not have to wait for the valve chamber to fill.
 
Bruce is entirely correct. Adding the line to the bottom of the bearing cap is of no value. It's the wrong place. Much better to pressurize the existing oil tubes in the block.
 
Two things:
There was a concern about "signs of wear". If it's not 'breaking in', it's wearing out. So a sign of wear is perfectly normal and doesn't mean it needs pressure to the main. The front and rear need it just as bad as the center, why only do the center? If you're not going to do them all, don't waste the time and effort with one.

Second, why do it at all? Have you drastically changed the performance characteristics of the engine? Are you turning high rpm's? Driving under high load conditions? Pressurizing only the center main is a novelty started by backyard mechanics. The need hasn't been sufficiently demonstrated.
 
First question is, what does it hurt? In my opinion and several others in this thread NOTHING. If it hurts nothing then it won't matter if it is done or not so, why not? If it hurts nothing, do it. The way I see it, if it hurts nothing, it may help so just do it. Nothing ventured, nothing gained.
 
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