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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..



#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. 



#11 De Soto Frank

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Posted 24 July 2013 - 08:27 PM

Greg's on-target with the bore/ stroke info...

 

'37-'41 De Sotos originally came with a 228 cid engine:  3-3/8" bore x 4-1/4" stroke.

 

'42-'50 (at least) had a larger bore: 3-7/16" x 4-1/4" stroke, for 236 cid.
 

I have heard that 3-3/8" pistons are getting hard to find, and expensive, so you might want to have your shop measure the bores and check parts avails before committing to machine work on your block.

 

It might be a little cheaper to find a decent 236 De Soto or 251 Chrysler six, that uses the 3-7/16" pistons, and re-do that one.

Good luck !

 


 



#12 40desoto

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Posted 25 July 2013 - 01:49 PM

Thanks for all the input guys!!   I shared most of these comments to the shop doing my engine. 

Desoto Frank,  Are you sure 34-41 desotos all came with the 228 cid engine?  when I have called places that carry the parts they state that they either came with 228 or 236 cid.  I guess Ill know when the bore gets measured. 



#13 De Soto Frank

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Posted 25 July 2013 - 05:17 PM

The 236 didn't come along until 1942.

 

The 1941 and earlier De Sotos going back to 1934 or so used either the 228 cid, or a few years used the 241 cid that Chrysler used in their big sixes through 1941: this engine is also a 3-3/8" bore, but with a 4-1/2" stroke.



#14 40desoto

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Posted 26 July 2013 - 10:59 AM

Thank you Frank.. The shop is currently checking the bore size before ordering the parts for a complete engine rebuild.  Any recommendations on rebuilding a 1940 228 ?  head milling,oil gallery hoe restriction, etc etc  that I should consider doing since the engine is being rebuild?

I plan on ordering a Deluxe rebuild kit from Kanter or ordering all the parts included from Andy Bernbaum   any recommendations?  Im trying to catch the Andy Bernbaum %10 off special through the end of July..

 

In case it matters Ill be using a 1986 S10 5 speed transmission (non-world class) and a rear end from a 1973 Plymouth Satellite



#15 De Soto Frank

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Posted 26 July 2013 - 11:42 AM

I don't think you need to worry about making oil gallery restrctions.

 

Properly re-built, the Flahead MoPar is a sturdy, durable engine.

 

Make sure the coolant passages are thoroughly rodded / cleaned-out ( all freeze-plugs removed, all rust & sludges raked/flushed out of the water jackets).

The other caution is with setting the end-gaps in the piston rings.  The spec in the MoPar and other period shop-manuals is suspect.

The period shop literature suggests a ring end-gap of 0.007".  Many modern rebuilders feel that this is way too tight, and the the engine comes-up to operating temperature, the ends butt, the ring continues to expand, causing binding, scoring, and possible ring / ring-land breakage.   Most flat-head MoPars were reb-built and rebored before 50,000 miles... probably from this original set-up.

Most modern authorities recommend allowing  0.0035"  end-gap per each inch of bore diameter.  The stock bore on a 228 six is 3-3/8", or 3.375" x 0.0035" = 0.0118" minimum end-gap, or 0.012", rounded.

Check-out the following from Hastings, a manufacturer of quality piston rings for over 75 years:

http://www.hastingsm...s/ring_gaps.htm
 

 

Beyond this,. the usual careful attention to cleanliness and careful re=assembly and pre-lube should put you in good stead.

After break-in, running the engine on good, modern detergent oils should result in good, long engine life.

 

The 228 is modest in terms of power, rating somewhere around 105 HP @ 3600 RPM,  but should have decent torque.

 

 

Let us know what the shop tells you on the bore sizing...

 


 


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