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

Quote from: rwollman on May 03, 2018, 08:10:48 AM
...  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)

I'm looking for one of these also.  The original is pot metal and crumbled when I removed the dash.  I found something I can use at Hershey Show last October but still looking for same.

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.

Not to highjack Dave's Resto Thread I started a new topic for Oil Pressure and Vacuum Fuel pump.

Interesting observation and question.  I kind of considered the vacuum side of the oil pump like the opposite side of a diaphragm fuel pump.  It would make sense that if one side was restricted the other side would be proportionately effected.  I think there would be two considerations, pressure and flow.  Each of these might be effected differently when you also consider the pressure release valve in the block and where the pressure is measured.  I would think that this relationship between vacuum and engine RPM to provide metered fuel flow across both high and low RPM periods would be a delicate equilibrium where even vacuum line ID would also effect the balance.  Obviously Chrysler had it figured out in that no overflow safety measures were put into place. 

It's really a very simple design that appears to work well when everything is in spec.  Traveling at the moment but something to check into.  Will be heading down this path in the near further. 

Hi Dave,

Prior to the rebuild when I started my car I would have a black spot on the ground from the soot that blow out of the exhaust pipe.  I didn't notice a lot of smoke coming out the back when I drove the car, just at start up when cold.  Also I didn't get many tailgaters. I think I burned/leaked a quart of oil every 100 miles.   Compression was about 50 across the four cylinders.  I am interested to see what compression I get out of the new rebuild.

What are your plans for the restoration.  Mechanicals or aesthetics or both.

Cheers,  Chet...

 Nice Car !!!

PS... I would think that the water pump was used on other cars of the time. If you could research that you might find another market to search in.

Keep checking eBay something might pop up that you could have rebuilt as a spare.

My 2'5 cents

Makes sense to me.

Not a Model Q,

Model U = GP-583-W   GC-499-L from the Windsor Plant Canada.  GP-992H would fall in this production run.

Currently traveling and do not have access to any additional info. 

http://www.1948plymouth.info/1929/support_pages/FEDCO_Information.htm

Thanks Dave,

Is the rear window moldings fabric covered wood or metal.  It looks like wood to me.

Great Question,

There was a $50.00 increase in price from the 4 dr to the 4 dr deluxe.  I assumed esthetics, pin striping, fabric, and interior detail ? but I don't know for sure.  Maybe somebody can school us on the known differences.

Chet...

Wow!! great pictures.

Do you believe the headliner to be original ?

Pictures of the interior and the headliner.  Mostly at the windshield and at the back of the car where the headliner meets the back wall.  Doesn't matter about the condition.

Tks,  Chet...

Also Dashboard and hinge pillars are painted body color !!