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Rebuilding My 218? 230? 1940 Desoto Flathead Suggestions


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#1 40desoto

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Posted 09 July 2013 - 10:01 AM

Im currently have my flathead at a friends machine shop and planning in getting the motor rebuilt.  I know its a 25in block, and according to the previous owner its the original engine for the car.  The numbers have been replaced so there is not telling what the size of the motor is?  I took of the head to measure the bore size but was unable to get an accurate measurement.  Is there any other way of telling what size motor is is?  Im very impatient and want to know whether to keep this motor (if its rebuildable) or purchase a larger 50's mopar flathead six.

 

Here is what my question is,  I saw this post omn the hamb and was wondering if this is really a big issue on these motors and how I can go about mentioning this to the shop..

 

"That the bad thing about Plymouth/Dodge six cylinder engines is that the oil line from the main gallery is drilled straight through. So as much oil goes to the cam bearings as the mains and rods. The fix is to tap the feed to the cam and install a restriction. Maybe with a 1/16 hole. Then the crank gets what it needs.

 

 



#2 TodFitch

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Posted 09 July 2013 - 10:21 AM

The quote was about a Plymouth/Dodge engine but the 25" engine, at least in the US, was used for DeSoto and Chrysler. But I don't think there is a big difference in the way the oiling system is designed (other than possible provision for full flow oil filter).

 

I'm only a shade tree mechanic and I've not built up an engine for high performance, so I am probably missing something. But if the pressure in the main gallery is sufficient then it seems likely that the crank main bearings should be getting enough oil regardless of how much oil is going through the cam bearings. And the pressure in the main gallery is what is measured by the oil pressure gauge on the dash. So I would take that quote from the HAMB with a grain of salt.


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#3 P15-D24

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Posted 09 July 2013 - 10:33 AM

I think this is referring to the fact that out of spec cam bearing can be responsible for low oil pressure. Their were aftermarket gadgets that would be bolted into the oil gallery hole to restrict the oil flow to the cam bearings and help maintain pressure. They were tube about 3 inches long with different size tips on the end for each cam bearing.

 

The obvious solution is if you are getting the engine rebuilt replace the cam bearings. I don't think the original statement "... is that the oil line from the main gallery is drilled straight through." is actually bad! 



#4 Don Coatney

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Posted 09 July 2013 - 10:34 AM

What numbers have been replaced? Do you have a service manual for your car? Per my book if your engine is original you have a 228.1 CI engine. I would think that your friend at the machine shop would be able to measure your engine and tell you if it is worth rebuilding.

 

If what you read on the HAMB posting were true I would think that the streets would be lined with dead mopar flathead engines. The factory engine oiling system works well unless you plan on spinning your engine above the red line for extended periods.


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#5 Plymouthy Adams

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Posted 09 July 2013 - 10:43 AM

a set of inside mics will be needed to measure the bore..the stroke can also be measured to see if the engine has been upped in CI by way of rod/crank swap..


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#6 40desoto

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Posted 09 July 2013 - 09:21 PM

I think this is referring to the fact that out of spec cam bearing can be responsible for low oil pressure. Their were aftermarket gadgets that would be bolted into the oil gallery hole to restrict the oil flow to the cam bearings and help maintain pressure. They were tube about 3 inches long with different size tips on the end for each cam bearing.

 

The obvious solution is if you are getting the engine rebuilt replace the cam bearings. I don't think the original statement "... is that the oil line from the main gallery is drilled straight through." is actually bad! 

Thank you for some clarification.  Do you think ist worth telling the rebuilder to add these aftermarket gadgets in the oil gallery hole? or should I even worry about it and just clarify to him to replace the cam bearings? 



#7 Dave72dt

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Posted 10 July 2013 - 06:11 AM

A stock engine should have little need for those aftermarket pieces.  Cam bearings need lube too.  New  brgs and mike the cam journals for wear.  Out of spec journals, replace the cam.  Make sure the oil pump is in good condition.  Every brg is a controlled leak and the pump must have adequate flow to compensate for them.  Worn parts increase the leak flow.  Owner suggested lube system mods MAY void your warranty.



#8 greg g

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Posted 10 July 2013 - 06:28 AM

Perhaps your over stamp is a attempt to match a non factory engine with registration owner documents as lots of jurisdictions used the engine number for vehicle ID.  Usually a commercial rebuilder would have affixed a tag to the engine with some sort of indication what was done internally.  Desoto engines during the 40's were either 228 or 236 cu in, the stroke was the same.  3 3/8 for 228, 3 7/16 for 236.  Oversized pistons resulting from and overbore during a rebuild are usually stamped with a size indicator on the top of the piston. Getting good micrometer reading of the rod a main journals will also tell you if the journals have been cut necessitating non standard bearings.  All of these measurements should be easy to attain. 

 

Now unless some one swapped in 251 rotating components (crank and rods) your stroke measurement should be 4 1/4 for engines built in the 40's regardless of bore.  251 engines had 3 7/16 bore with a 4 1/2 in stroke.  Your factory oiling system should be find unless you are building an engine that is gong to operate consistently above 4000 RPM, but with any of these log stroke engines, building on that way is usually not the way to go for street operation. Long stroke equals torque, which is what gets a vehicle moving..   Basically you are rebuilding 6 Briggs and Stratton engines in a row, its best not to over complicate the process.


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#9 shel_ny

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Posted 10 July 2013 - 07:39 AM

I think this is referring to the fact that out of spec cam bearing can be responsible for low oil pressure. Their were aftermarket gadgets that would be bolted into the oil gallery hole to restrict the oil flow to the cam bearings and help maintain pressure. They were tube about 3 inches long with different size tips on the end for each cam bearing.

 

The obvious solution is if you are getting the engine rebuilt replace the cam bearings. I don't think the original statement "... is that the oil line from the main gallery is drilled straight through." is actually bad! 

 

 

Pic of some of the aftermarket tubes, with a nifty installation/removal tool.

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#10 P15-D24

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Posted 10 July 2013 - 11:20 AM

Pic of some of the aftermarket tubes, with a nifty installation/removal tool.

Yep, that's them!  Pulled them out of few engine cores. Think the are made by Textron ?  I have a full set with instructions just haven't been able to find them. 






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