Center main pressure oiling

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
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I agree with James Rogers and have a photo of one of his motors with the oil line. Give me an email address and I will send a photo. Also look at James' web site and you may find a photo plus some good ideas
 
Since I moved away from the Southern Calif. freeways, I seldom drive my Model As more than 35-45 mph on tours. I think I'll skip the center main oil pressure this time. However, I do believe that full oil pressure is the one thing Henry should have included in the Model A engine.
 
We don't know what it hurts or helps, no one has studied the issue in an educated manner. Suppose it truly does not hurt anything, what's the point in doing one and not the other two? They need it just as bad as the center main. To do one and not the others is a waste of time.

Through prep, machine, and assembly work will do more for an engine in reliability and longevity, than the center main. It's the poor workmanship of so called machinists and babitt bearing pours that have done more harm the reputation of the center main than anything else.
 
i think it would possible puts chunks of crap streight into the bearings instead of having them settle out in the lifter valley. just a thought
tk
 
kelley's restoration said:
i think it would possible puts chunks of crap streight into the bearings instead of having them settle out in the lifter valley. just a thought
tk
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And you don't think modern engines live this way for many hundreds of thousands of miles built in just this way? I know they have an oil filter but even in the early days many engines with inserts and pressure oiling had no filter and lived many more miles than dipper engines. Take the lowly 265 Chevy engine for example, no filter and pressure to all crank bearings lived a fairly long life.
 
azmodela said:
We don't know what it hurts or helps, no one has studied the issue in an educated manner. Suppose it truly does not hurt anything, what's the point in doing one and not the other two? They need it just as bad as the center main. To do one and not the others is a waste of time.
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azmodela said:
Through prep, machine, and assembly work will do more for an engine in reliability and longevity, than the center main. It's the poor workmanship of so called machinists and babbitt bearing pours that have done more harm the reputation of the center main than anything else.
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azmodela,
You make some good points regarding workmanship that I agree with. At this point, I also have not seen a study of the piping of oil to the center main, but my experience leads me to suggest that piping the oil to the center main may help.
From my experience of tearing down engines for rebuilding, I find the center main damaged much more often than the front main. The greater frequency of failure leads to my assessment that the center main is loaded more heavily than the front main. FWIW: I also find about equal frequency of failure between the center and rear mains...not combined in the same engine, just the frequency of a bad main. What I am trying to say is that I seldom find the front main the cause for me to suggest new main bearings. I have to believe any help the center bearing can be given by increasing the oil flow to it should allow it to last longer.
I install insert bearings in the engines I rebuild. The feeding of oil to the bottom of the cap fills the integral oil grooves at the center of the bearing and pushes the oil to the parting lines of the bearing shells where it is spread across the entire width of both sides of the bearing. (Take a look at the picture I have included of a typical insert bearing installed in the caps.) At the parting line of the inserts, the oil clearance stays pretty constant regardless of the alternating pressures applied to the crankshaft. So I believe putting more oil through the bearing has to help cool and cushion it. When I build an engine with a target HP in the range of 55-65, I have always piped oil to the center main. I do suggest full filtration of the oil when using inserts and pushing the HP.
James Rogers makes the point that “it couldn’t hurt” to pipe the oil also…we have agreed on this point…more than once in recent threads.
I also have pressure oil to the center main on my stock ’28 pickup with babbitt bearings. The center main cap had an oil groove in it that leads to the parting lines of the bearing. I placed the oil fitting to align with the groove to minimize the loss of bearing surface and to flow the oil to the parting lines where the babbitt is relieved. I don’t have a lot of miles on this engine and I drive it pretty easily…but I would venture to predict that it will more likely be the rear main that fails before the center main. Now…I just hope I did not “jinx” my pickup with that prediction.

Good Day!
Dave in MN (Dave Gerold)
www.durableperformance.net
 

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glenn in camino said:
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.
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Here is a photo of what has been done compared to piping to the oil galley. It would seem that oil gets to the bearing faster than at start up.
 

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I have spoken many times of the long tours my wife and I do in our Phaeton. When I built the engine for that, I bought a new (Burlington) counterweighted crank shaft and new rods, all of which run on inserts. There are other things too like HC head, cam shaft etc but to stay relevant to the topic of this thread, I pressure fed the middle main bearing with a 1/4" copper tube from the pump direct to the bearing cap. I built a pressure relief valve (25 psi) into the elbow at the cap. I kept the tube s short as I could. To install it is a bit tricky. I have to twist the pump while holding the tube in place because it won't fit between the elbow and pump when they are in their final location. After 60 or so thousand miles at a steady 50 mph with a trailer in tow, I decided to "adjust" the bearings before our most recent trip. That involved nothing more than replace the inserts which I did with the engine in the car. The crank has nitrided journals so wear on them was ignored.
I now have more like 70,000+ miles on it and it is running just fine. I put that down to a counterweighted crank shaft and a harmonic balancer. I know of a fellow in Arizona who has well over 125,000 miles on his engine but with solo car only.
The middle main bearing is the weak point of the Model A engine so anything you do to help it will help your pocket. IMO, fitting counterweights and/or a harmonic balancer on a rebuild are non negotiable must do's.
 
Grab yourself Jim Brierley's book "4 Bangers And Me". It's got all the tricks and even if you're not building a hot rod they'll help your stocker live longer.


jimb4e4@gmail.com
 

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nkaminar said:
Excellent.
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SAXBY2 said:
Here is a photo of what has been done compared to piping to the oil galley. It would seem that oil gets to the bearing faster than at start up.
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Good gosh this is an old post. Kinda sad looking back at names that posted above who are no longer here, -or above ground for that matter.


With regard to how this is plumbed in your picture, my vote is this method poses some issues that could/will be catastrophic.

To begin with, the size tubing is way too large IMO. The size tubing we use is 1/8th". Your larger size tubing is going to cause a significant volume of oil to be diverted to the center main which will cause a loss in head pressure to push oil on up to the valve chamber. That center main does not need that amount of oil.


Number 2, from experience I know that the size hole that was drilled into that pump housing has compromised the structure integrity of the casting. It is going to fail (crack) at some point due to harmonic vibrations as the engine is operating. When it does crack/break, the pump will no longer be pushing oil up to the chamber, ...so how long do you anticipate the engine will live after that? When tapping the block and installing the fitting there, even if you have a line failure, the fitting only has a 0.125" diameter hole which will still divert enough oil to the chamber to allow the engine to live.
 
Here is piriano's set up.

Also, evidently the Burtz blocks have the oil pump housing drilled for a pipe or pressure reducing valve, not sure which. Perhaps that is comparing apples to oranges. What would be used to replace the steel bent pipe with a flexible line ? Some posters don't like copper pipe.

This precludes removing the pipe altogether and somehow plugging the holes where the brass fittings are. Could permanent locktite and plugs be used in the bearing cap and housing ?
 

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My engine is getting new insert mains soon. Pressure oiling the center main is interesting to me. I have a cracked block that I don't mind experimenting on, so I measured it to understand the Piriano's setup. The connection seems to be close to the oil pump hole centerline.

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For this to work, there would need to be an oil passage under the fitting as shown. The outer wall of the crankcase looks like it is only .25" or .3125" thick there, so I don't see how oil would reach there. I left a voicemail at Piriano's asking for a copy of the instructions, even if they don't sell the setup anymore.

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On the other hand, I'm 77. how many miles am I really going to drive the car?
 
Bruce of MN said:
My engine is getting new insert mains soon. Pressure oiling the center main is interesting to me. I have a cracked block that I don't mind experimenting on, so I measured it to understand the Piriano's setup. The connection seems to be close to the oil pump hole centerline.

picture.php


For this to work, there would need to be an oil passage under the fitting as shown. The outer wall of the crankcase looks like it is only .25" or .3125" thick there, so I don't see how oil would reach there. I left a voicemail at Piriano's asking for a copy of the instructions, even if they don't sell the setup anymore.

picture.php


On the other hand, I'm 77. how many miles am I really going to drive the car?
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Lets see 77, I am guessing 9,000,000 Miles. So how's that!
 
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