Author Topic: Oil Pressure and Vacuum Fuel pump.  (Read 237 times)

chetbrz

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Oil Pressure and Vacuum Fuel pump.
« on: May 03, 2018, 03:37:08 AM »
There were some great questions and observations concerning the Oil Pump from Dave's Resto Project Thread.  So we don't highjack Dave's Thread.., I started this new thread as a continuation from that discussion.

rwollman,  I am not familiar with the Model Q - Maxwell engine.  I am attaching a picture of the Model U Chrysler engine showing the pressure release valve. 



This is a picture of the Oil-Vac pump on the Model U engine.  It appears that Oil-Vac are created as a combination of the total volume of both that is moved by the pump.  So it would be logical if you capped the vacuum side you would make up the difference by pulling more oil.  Also if the ID of the vacuum opening was bigger than designed you would logically pull less oil.  What the ratio is would take some experimentation. 



It appears that there is a very precise balance between all these items to come together to create the correct result.  I would think that oil viscosity could also play a role. 

Any thoughts.
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rwollman

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Re: Oil Pressure and Vacuum Fuel pump.
« Reply #1 on: May 03, 2018, 02:10:48 PM »
chet - is the oil pressure adjusted at this relief valve pictured? On the 28 it is adjusted inside the engine after removing the base.  The oil vac pictured is identical to the 28. Since the oil pump is a vane pump oil viscosity would play a factor.  I don"t believe worn bearings would be as much a factor as a worn pump.  I believe vacuum for the fuel canister is created by an venturi effect.  Line size to the fuel pump would not create more or less vacuum, only effect the time it takes to reach max vacuum in the canister..  I didn"t check signal strength on the vacuum line, wonder if anyone has as I have never found any specs regarding this.  A good service manual on these engines would be worth its weight in gold.  LI believe you are  having your engine redone, did you ever take a compression test or cylinder leak down test on it?  The one I am working on carries about 60 psi compression but cylinder leakage test shows app 80% leakage past the rings therefore either rings/cylinders are worn or rings stuck/collapsed.  Going to run it a bit then retest to see if any changes take place. 

chetbrz

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Re: Oil Pressure and Vacuum Fuel pump.
« Reply #2 on: May 03, 2018, 04:25:15 PM »
...  I believe vacuum for the fuel canister is created by an venturi effect.  Line size to the fuel pump would not create more or less vacuum, only effect the time it takes to reach max vacuum in the canister.. 

I agree with your statement about a venturi effect.  When I was speaking about vacuum line size, I wasn't implying a change to vacuum but a possible decrease to oil flow.  Similarly capping the vacuum port on the oil pump increasing the oil flow/pressure.

As far as my engine goes I believe it was in pretty bad shape.  As the rebuilder told me the engine was never rebuilt.  When I first got it I pulled the head and the cylinders had a pretty significant edge ring.  Also compression was pretty low I don't believe it hit 50psi wet.  The engine ran but knocked at 40mph with significant oil usage.  Also hard to start.  I to am very interested in the rebuilt compression numbers.  Unfortunately the rebuilder is using pistons which have an additional ring which I believe will increase the compression numbers.  Also cyl bored to .060 over. 



Pressure release valve can be adjusted after removing the dust cap but is generally changed by adding a different weight spring.  This is the same as my 6 cyl P15 (1948 Ply)
« Last Edit: May 03, 2018, 04:31:11 PM by chetbrz »
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rwollman

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Re: Oil Pressure and Vacuum Fuel pump.
« Reply #3 on: May 03, 2018, 05:53:33 PM »
Chet: could you list where you located os pistons - I could only find standard and was considering sleeving block if necessary - thanks

chetbrz

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Re: Oil Pressure and Vacuum Fuel pump.
« Reply #4 on: May 04, 2018, 12:45:01 AM »
I didn't find the pistons J&M Machine did.  They were new old stock.  The newspaper they were wrapped in was dated 1966.
Normally J&M would have pistons made to fit the purpose.  Basically got lucky.

See link to online engine rebuild progress:

https://www.facebook.com/pg/J-and-M-Machine-Co-Inc-270076059772640/photos/?tab=album&album_id=1467684380011796
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rwollman

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Re: Oil Pressure and Vacuum Fuel pump.
« Reply #5 on: May 04, 2018, 09:52:55 PM »
Chet - U were lucky your machinist found the pistons - looks like beautiful work.  Man, that rear thrust bearing in the block sure looks like an insert - is your machine shop doing the Babbitt work or is it farmed out?

chetbrz

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Re: Oil Pressure and Vacuum Fuel pump.
« Reply #6 on: May 04, 2018, 11:12:07 PM »
Yes J&M specializes in antique engine repair.  They do the Babbitt work and any parts they can't find they make.  I have great expectations for this motor and I am glad I went this route.  Its nice that they photograph the progress as they do the rebuild.  Really keeps the customer in the loop.  Big shop and two brothers John & Michael who care about the work they do.
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