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Oil passages to main bearings - different diameters


Bryan

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I wonder how far past the restriction turbulence continues?

Also, what if volume is reduced right before the restriction? You aren't trying to force as much fluid thru the restriction, so it shouldn't waste as much energy on turbulence. Every galley that leads to a bearing is reducing the amount in the system, so that at the end, it is much less than what the pump is initially picking up.

 

What if they are deliberately causing turbulence and reduced pressure right in front of the mains so that they have 'time' to get more oil?

 

I think you have a few options

 

1. Leave it be. It will be as good as it ever was. It will be fine.

2. Drill the passage to .33, all the way to the cam, so it matches the early block. Possibly your cam will get more oil than needed. It will be fine.

3. Drill past the main feed, but leave a smaller section to restrict the cam. Possibly mess up some long forgotten innovation from the engineering department of 1950s Mopar. Possibly reduce turbulence and pressure drop at the mains. It will be fine.

 

4. Use a taper reamer to blend the two sizes together. Risk of breaking reamer and likely high cost of tool makes this a poor option. 

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1 hour ago, James_Douglas said:

The rear cam "bearing" being the block itself is known to wear. Back in the day there were restriction devices that were sold so that oil pressure would not drop off due to that wear. They come up on ebay now and then.

 

I would spend more time, money and effort into making sure that the diameter of the rear cam bearing was correct than worrying about the gallery size. When I do my next flathead, I plan on drilling and busing the rear cam "bearing" area so it is back to factory spec. I have wondered what that "slop" at the rear of the cam is going to the valve geometry over time. I know it is not a lot, but the pressure of the valves on the cam must cause the ass end of the cam to "wobble" a very little bit due to the clearance.

 

I have measured a couple of blocks and some at almost at spec and some are way over.

 

My 2 cents worth.  James

Will do, if I ever get my cam back.   Thanks.

If you have a block could you look if the side oil passages change diameter going to the cam bearings? My 48/49 block is the same .33" size all the way back.   The 53 Dodge block  goes from .33 to .25 right before the vertical junction to the mains.  I'm trying to first see if it is unique to my block or standard after a certain year.

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2 minutes ago, FarmerJon said:

I wonder how far past the restriction turbulence continues?

The restriction starts about 1/2" before the mains junction and continues to the cam bearings.

 

Also, what if volume is reduced right before the restriction? You aren't trying to force as much fluid thru the restriction, so it shouldn't waste as much energy on turbulence. Every galley that leads to a bearing is reducing the amount in the system, so that at the end, it is much less than what the pump is initially picking up.

There are no branches before the passage reaches the junction. Volume wouldn't reduce.  

What if they are deliberately causing turbulence and reduced pressure right in front of the mains so that they have 'time' to get more oil?

It would decrease flow to the mains as much as I can tell from researching.  Having a restriction right after the mains T junction seems like would allow oil to go to the path of least resistance (up the T).. 

I think you have a few options

 

1. Leave it be. It will be as good as it ever was. It will be fine.  Not this time.  For me it has to make sense.  They have the front and rear mains holes & T junction with the same larger .33 diameter.  If I had 5-6 people telling me their blocks were the same, maybe.  I still remember the block 1/2 filled with casting sand. 

2. Drill the passage to .33, all the way to the cam, so it matches the early block. Possibly your cam will get more oil than needed. It will be fine.   We know the cams are over oiled, and all the cam holes (not the bearings) are the about .25".

3. Drill past the main feed, but leave a smaller section to restrict the cam. Possibly mess up some long forgotten innovation from the engineering department of 1950s Mopar. Possibly reduce turbulence and pressure drop at the mains. It will be fine.  I'm torn between drilling the front and rear passages to the rear of the T-junctions, vs doing all that way. What is making me hesitant about all is the dished out portion below the cylinder bore on the #2 & 3 mains. See pic. Need something to find wall thickness (measuring tongs?)

 

4. Use a taper reamer to blend the two sizes together. Risk of breaking reamer and likely high cost of tool makes this a poor option. 

 

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Found some measuring "tongs" caliper I'm going to order on Monday to get some idea of the wall thickness on # 2 & 3.    Wonder if a regular metal drill can bore out a passage 1/2" deep?  Have 2 1/2" of shaft to hold the bit in line.

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Technology changes.  What was done in the past may have worked ok, but that doesn't mean it can't be improved upon.  So let's not just jump on the bandwagon assuming 70 year old engineering hasn't been improved upon, conversely just because it's old engineering doesn't mean it's wrong either.

 

Case in point, me adding an electric cooling fan and removing the original mechanical fan.  Did the mechanical fan work?  In a narrow limited sense, yes it did.  For the technology available in 1951 the mechanical fan was the best choice.  Despite it's power consuming appetite.  Despite the fact that it ran always, needed or not, consuming HP to run and gas to make that HP.   You will note no manufacturer still runs that type of fan.  For a very good reason.

 

If there is a good reason go for it.  If you want to experiment, hey it's your engine.  If it's a bad idea, might want to step back and rethink.  But how do we know it's a bad idea?  Did someone try it and lose an engine?  Did anyone do the calculations?  Does anyone have the original engineer's notes on the change?  Who knows. 

 

Myself, I wonder if the engineers redid the design to limit oil to the cam as I believe they were getting over oiled and production messed up where that change was made.  Maybe it should have been the larger passageway to the mains oiling and the smaller onto the cam oiling.  Odds are we will never know for a fact, those guys are pretty much unavailable to consult.

 

 

 

Edited by Sniper
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4 hours ago, Merle Coggins said:

Why do you want to drill it out? Did it not do a satisfactory job of oiling? Was there evidence of lack of lubrication? 

I'm sure they had a reason for using the bore sizes that they used. Don't try to reinvent the wheel here. 

Because the present situation does not make engineering sense from everything I've read.  I bought this block from someone and don't have any experience with any problems.   Was wondering if you read what I've already posted.  I'm sure there was a reason that the block was 1/4 full of casting sand. There's a reason my old Fluid drive was reinstalled with 2 of 8 bolts cut off.   If 10 people on the forum stated their blocks were just like mine I would be more inclined to leave it alone.   Presently I know my old 48 Dodge/49 Plymouth block was drilled large all the way to the camshaft.  It's all  I know.

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3 hours ago, Sniper said:

Technology changes.  What was done in the past may have worked ok, but that doesn't mean it can't be improved upon.  So let's not just jump on the bandwagon assuming 70 year old engineering hasn't been improved upon, conversely just because it's old engineering doesn't mean it's wrong either.........

 

.....Myself, I wonder if the engineers redid the design to limit oil to the cam as I believe they were getting over oiled and production messed up where that change was made.  Maybe it should have been the larger passageway to the mains oiling and the smaller onto the cam oiling.  Odds are we will never know for a fact, those guys are pretty much unavailable to consult.

 

 

 

Thanks. That's the issue. If I had more information, past tech notes, enough people's info, etc I'd feel better. Presently just going on info from my old block, this one, and the fluid mechanics stuff I posted.  I even asked the Freewheeling Tony Smith on his FB page if he's encountered that.   No answer yet.   It is notable that the holes at the main journals still have the front & rear larger, # 2 & 3 smaller.   All cam journal holes are small. Sense to me would be either to have all the passages large to the T junction of the mains, or just large to the front and back.  

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If it is a 1953 block, there is a chance that it has the block that was designed for use with the fluid torque drive what shared the oil with the "new" converter.

 

They may have made the change in the block to support that even if they did not drill the back of the block with the hole that fed out of the block.

 

James

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Basically it tells us that flow is controlled by the smallest part of the path.  So if the hole in the bearing insert, cam, main or rod, is smaller than the passageways that feed it then that is your flow control.

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48 minutes ago, Sniper said:

Basically it tells us that flow is controlled by the smallest part of the path.  So if the hole in the bearing insert, cam, main or rod, is smaller than the passageways that feed it then that is your flow control.

That's what I'm understanding. It's hard to find basic info without them getting into a bunch of complex equations.  And if there is a restriction in the line before that, it affects flow also.   

 

 I ordered a cobalt drill bit and 8 mm ball hone.

Edited by Bryan
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You know, I got to thinking about the engineering of this engine.

 

The "Plymouth 6" as it was originally called was specifically built to a price.  The big deal when it was introduced was that Plymouth gave you a 6 in a low cost car whereas the competitors only gave you a 4.  It was a marketing campaign that pushed Plymouth sales up.  It worked.  But one has to think that the engine was developed with low production costs in mind and not so much building the perfect engine.  So when the claim is made that the engineers back then knew what they were doing we need to understand what it is that they were doing.  I think that was building an adequate engine for a low cost.  Turns out they did a pretty decent job building a durable engine, but even then they did make changes over the years.  

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22 minutes ago, Sniper said:

  But one has to think that the engine was developed with low production costs in mind and not so much building the perfect engine.  So when the claim is made that the engineers back then knew what they were doing we need to understand what it is that they were doing.  I think that was building an adequate engine for a low cost.  Turns out they did a pretty decent job building a durable engine, but even then they did make changes over the years.  

But drilling up to a 1/2" before the mains T junction wouldn't be a way to save cost. Either drilling it to .26 all the way, or .33 all the way would be cheaper.  Drilling 2 times would be more.   I think it might be more of a problem at the factory. Someone drilled it short of the junction. That's why I'm hoping other people that have either overhauled a lot of blocks, or have one sitting around could look and let me know.

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If you read the book on the development of Chrysler's engines...the section on the slant six where they talk about the issues with the aluminum vs the iron blocks...there are references to the issues of drilling the blocks. Problems with long drill bits in production.

 

I suspect that the different sizes may have something to due with the need to not have long bits fail in production.

 

Just a thought...it may have nothing to do with engineering and everything to do with production issues.

 

James

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Wasn't feeling well today, so just did a quick measurement of the 48 Dodge block in the shed on the #2 main where the cylinder bore lessens the diameter of the oil gallery..  The method I used seemed to be consistent.   The diameter I measured was .5845".   .5845 - .33 (present hole) leaves .2545".   1/2 is .127", so say .125" or 1/8" wall thickness.  That's worst case.   Best case would be if I could drill and exact 5/16 hole (.315) leaving .135" wall thickness.

 

I'll have to make more measurements when I feel well but 1/8" wall thickness seems risky.  Any opinions?   How's 1/8" cast iron for strength?

Some other day I'll measure mains # 2 & 3 on both blocks and make sure it's accurate. Then I'll measure front & rear mains.

IMG_6672.JPG

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And thinking about it too much, given that the main journal holes for # 2 & 3 are about .26", might be good to leave these alone. The front and rear journal holes are larger.   There, boring the passage out might help.

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  • Bryan changed the title to Oil passages to main bearings - different diameters
On 6/7/2022 at 10:58 PM, FarmerJon said:

Have you emailed Tim Kingsbury? I believe he has many old Mopar engineering documents, and has lots of hands on experience with the insides of the engines. 

Got an email from them (Peter Hendrickson) that they were CCing Tony Smith but never got an answer.   Nobody seems interested in this subject.

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On 6/7/2022 at 8:19 AM, James_Douglas said:

If it is a 1953 block, there is a chance that it has the block that was designed for use with the fluid torque drive what shared the oil with the "new" converter.

 

They may have made the change in the block to support that even if they did not drill the back of the block with the hole that fed out of the block.

 

James

 

When you look at a HyDrive engine there is a relief valve on the oil pump in addition to the one in the block.

It makes you wonder why they put that there.

Could it be that the Torque Converter generated its own pressure?

Aside from people forgetting to drain the Torque Converter every engine oil change, I wonder what the engine longevity is vs a standard shift.

HyDrive has always fascinated me being the ultimate FluidDrive. If it added to the life of the engine that would be another reason to find one.

 

(one of my modern cars needs to have a transmission oil change every 70,000 miles. The car lets you know its time when the transmission slips going up a hill in high gear. After I had the dealer do the service -once, I only got 55,000 miles and it was slipping again. I talk to a number of friends in the trade and they said, "Nobody drains the Torque Converter". Needless to say I now do that service myself)

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Thought this was interesting and understandable.   Interesting parts are 45 sec - 1:00 min then 2:00 min to the end.

 

Edited by Bryan
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