1940 Desoto Flathead 6 Engine Rebuilt. 237?

[40desoto]

The casting numbers on my 1940

Engine have been replaced with a VIN number starting with CAL. The motor is 25 in long and finally took the head off and the pistons measure just a pubic hair larger than 3 4/10 in. I guess that makes it 237 engine not a 218??

A good friend of mine dad owns very rebutable engine rebuilding shop and they will rebuild the engine for me at a huge discount..... But as I spoke to them today I cant seem to tell if they are familiar or experienced in rebuilding flathead engines. Is it really that different than rebuilding any other engine? If it was just rebuilt without anything customization would it provide enough highway power? given that I will be running an S10 5 speed tranny and a newer rear end? A buddy of mine swears that it takes someone with flathead experience or i will regret it. Do you guys recommend going to a person specilaized with flatheads and doing some work on it such as Machine crank to counter balance, recarve cam, shave head, redo head chamber, machine block to use newer style bearings and main seals, etc etc. any opinions?

[Andydodge]

Firstly have you a workshop manual?.........these engines use mains & bigend bearings that are the same style as current engines, and depending on exactly what is in your engine the rear main seal may or may not be a neoprene style seal. As far as upgrading the engine, machining the head to increase the compression is a good thing but I wouldn't go playing with the head chamber.......you could chase up a finned Edgy head that would bump the CR up to about 9:1 which should make it pop....a twin carb intake, Edgy cam, good overall balance job on the reciprocating parts, upgraded ignition, headers and a free flow exhaust should all help together with the T5.........if its a 25" engine why not chase up a later version....Chrysler/DeSoto used a 250 cube and even a 265 version......nothing beats cubic inches....lol.........any competent engine machine shop SHOULD be able to do the work....., decide on what engin you intend to use if you go for a larger capacity version and get the appropriate workshop manual and maybe lend or copy the engine section to the machine shop to read thru......Mopar 6's are just like a flathead Ford V8, but better so try that tack.........lol........dunno if this helps....regards, andyd

[52b3b Joe]

The casting numbers on my 1940

Engine have been replaced with a VIN number starting with CAL. The motor is 25 in long and finally took the head off and the pistons measure just a pubic hair larger than 3 4/10 in. I guess that makes it 237 engine not a 218??

A good friend of mine dad owns very rebutable engine rebuilding shop and they will rebuild the engine for me at a huge discount..... But as I spoke to them today I cant seem to tell if they are familiar or experienced in rebuilding flathead engines. Is it really that different than rebuilding any other engine? If it was just rebuilt without anything customization would it provide enough highway power? given that I will be running an S10 5 speed tranny and a newer rear end? A buddy of mine swears that it takes someone with flathead experience or i will regret it. Do you guys recommend going to a person specilaized with flatheads and doing some work on it such as Machine crank to counter balance, recarve cam, shave head, redo head chamber, machine block to use newer style bearings and main seals, etc etc. any opinions?

 

It should be a 228ci engine I believe from the factory. The mid-late 40s Desotos had a 236ci in them. I'm guessing you have a 236ci. I would think you would have plenty of power with a fresh engine and higher compression. With the overdrive transmission, if you change to a "modern" rear end, you may want to stay with about the stock ratio. As far as the shop, I'd have your friend do the work for the discounted price. As said previous, any competent shop should be able to do the work. 

Edited April 5, 2013 by 52b3b Joe

[40desoto]

Thank you for the advise...   Wow!  I need to stop posting stuff while Ive been drinking..  It barely makes sense to me after reading it again.

The reason I do not want to swap motors is that the VIN is stamped on the motor and nowhere else on the car.  Im dont want to go through the California DMV to hassle with that.

I think Im am going to stick with my buddys shop and keep the motor fairly stock. 

 

Any more advise as to what I should consider since I will be rebuilding?  Thank You in advance

[Tim Keith]

The reason I do not want to swap motors is that the VIN is stamped on the motor and nowhere else on the car.  

You can use the 236 block with a 251 or 265 rotating assembly.   The 265

crankshaft requires slight clearancing to clear rod bolts.  I expect you might

have trouble finding a 265 crank and rods(the 265 was used in cars in '52-'54),

but 251s are common and your current block would not need clearanced. The

236 is a fine motor, some say it is the longest lasting of the flathead sixes.

[40desoto]

You can use the 236 block with a 251 or 265 rotating assembly.   The 265

crankshaft requires slight clearancing to clear rod bolts.  I expect you might

have trouble finding a 265 crank and rods(the 265 was used in cars in '52-'54),

but 251s are common and your current block would not need clearanced. The

236 is a fine motor, some say it is the longest lasting of the flathead sixes.

Just found out from the company curring the cylinder walls that the engine is indeed a 251.  They were able to tell just by looking at the block.  No stamp, no rotating assembly.  Is that possiblethat they can tell with just the block in had and no tag/stamp on the block?

[De Soto Frank]

Just found out from the company curring the cylinder walls that the engine is indeed a 251.  They were able to tell just by looking at the block.  No stamp, no rotating assembly.  Is that possiblethat they can tell with just the block in had and no tag/stamp on the block?

 

It would be difficult to positively ID the block w/o measuring the cylinder bore.

 

Chrysler Corporation had two "families" of flat-head six between 1934 and the end of flat-head production (1959 for US passenger cars):  a 23" long "small block" used in the Dodge and Plymouth cars, and the 25"  long "big block" used in the Chrysler, De Soto, and larger Dodge trucks.

 

Any 1934-'54 De Soto six should have a 25" long block.  Within that range, they had cylinder bores measuring either 3-3/8" (3.375") for 1934-1941, or 3-7/16" (3.4375") for 1942-'54.

Same bore stats apply for 1934-1954 Chrysler Six.

 

Strokes range from 4-1/4" for the 228 & 236 cid six, to 4-1/2" for the 241 and 250 cid six, and 4-3/4" for the 265 cid six, but these are mostly a function of the crank, connecting rod, and piston skirt design,  not the block.

 

You need to have the cylinder-bores measured with an inside micrometer to be sure of which engine you have.

[40desoto]

Just picked up a  Plymouth 230 freshly rebuilt engine. Never been fired up.. The 250 is going in the trash.. 

[Dodgeb4ya]

Wow, a little 230 in a DeSoto! That will be unusual.

[40desoto]

Well see..   Thats what I was thinking as well.  The 230 was intended to be used in a '50 suburban.  would the Desoto Coupe be heavier than the suburban?

[Dodgeb4ya]

Our County prosecuter had a 50 DeSoto woodie wagon that had a 218 in it. I remember the engine was painted grey. He said it was OK to drive but a little weak on the hills. There was a big gap between the radiator and the fan too. This thread just reminded me of that car and engine.he's probably still got it up in thr San Juans!

Edited November 27, 2013 by Dodgeb4ya

[Andydodge]

Don Coatney here on this forum has a P15 with a 25" engine so should be able to give some info regarding the relative varoom of the little & big engines..........theres no replacement for displacement as the saying goes, but that assumes that the $$$$$ are covered as well.........lol..........hey, I've got a 318 Poly in my 1940 Dodge so take what I say with some salt, lol...I always do.......lol..........Andy Douglas 

[wayfarer]

Like Andy says, "no replacement for displacement".   A fresh 230 will get the job done but a fresh 250 will do it easier. If you have space in your shop consider stuffing the old engine in a corner instead of the trash can......someone may have a need. Where are you located?

[Plymouthy Adams]

yeah..I can see the 251 snapping your neck off on acceleration over the 230....get real folks its still antique technology ...and YET..without the rotating assembly ie the crank..how the hang do they (the shop) know the displacement..based on bore you could identify the piston..but crank and stroke determine displacement..

the 251 would be at best 116 ponies as fitted in a stock DeSoto..the 230 anywhere from 105 up to 135 ins stock form dependent on year of the donor in stock build.....base HP was about 110 in mid 50's..so where is the major power difference ??? while there is no substitute for cubic inches...there is a need for a significant amount to make that difference on base builds...given the 230 and 251 I would smoke the 251 on driving just with the earlier fast second with all other things the same..remember, both are 6 cylinder where the peak torque was at a low 1200 rpm the Desoto would have but 18 ft lb over the 230 engine...I do not have the torque curve for this engine but based on most the torque stays rather flat for a bit then drops off at higher rpm and the reserve HP is on tap through the peak HP development at 3600 RPM

[Dodgeb4ya]

Side by side from the factory the 251 is a much better engine. Runs smoother, more power and probably would last longer too given both had top notch maintenence. A 251 for me any day.

[greg g]

The 40 had a 228,100 hp, and the 41 was stroked out to 236, 105 HP.  The 230 splits the difference, don't see it as a big deal power wise.  If its a 50's motor it's making at least 103 and perhaps as much as 135.  Seat of the pants won't notice any difference unless its a higher hp later engine. you will need to do something with the front motor mounts but that should be easy.  And it will get him out and driving and perhaps a long block will become available, as folks see the car out and about.  I can;t recall the number of times I have been at a show or a cruise in and been offered that old engine from the back of the shed.............

[40desoto]

I was being sarcstic about throwing the 251 away.   The cylinders where worn out beyond what they have rings for.  .060 max?  It needs to be resleeved.  I have sources to get a rebuildable '25 or '23 block for about $100.. 

It had to do with cost.   I picked up a nice rebuilt 218 bored and 230 rotating assembly. Never been fired. Dual exhaust, electronic ignitions,all  powder coated parts, automatic transmission and adapter for less than have the $$ to get the 251 rebuilt..

That was the reason for using the 218/230 in the Desoto

 

Im fairly new to these flatheads but one thing that I found interesting....   If the 25" inch block was a 'much better' engine  why dont they make speed goodies for them?  Aluminum heads, Dual carb intakes, headers, etc...Is there no market for them in the 25" option?

Im looking forward to getting this car on the road.   I do still have the 251 with all parts and was thinking if I can ever find rings larger than .060 I would love to tinker in rebuilding that engine sometime.

 

The thing that worries me the most is that my Engine VIN number was stamped on the 251 block.  Started with the letters CAL...  ???  Ill save this topic for another thread.

 

Thank you all for all your input

[Don Coatney]

I have dual carburetors, dual exhaust, dual points. a high lift cam, and more on my 255 Desoto engine. There are parts available. George Asche makes a new aluminum 3 carb manifold for the long block Desoto engine and I believe Edgy makes an aluminum head.

 

[greg g]

There was a 2X2bbl edmunds long block intake that a guy was asking about on the HAMB a couple weeks back.  He may have it listed in the classifieds there now that he knows what it is. Also Egge will make you just about any piston you can come up with.  I believe you can overbore the DeS/Chrysler block to .090 over, before you need to consider sleeving.  Your block is not necessarily a goner.

[40desoto]

Thank You..  Something to look forward to..   Don, so the dual intake and dual exhaust was purchased from a manufacturer?  Ive seen this picture before and though you had cut and brazzed yourself.

That engine looks killer!

[martybose]

I was being sarcstic about throwing the 251 away.   The cylinders where worn out beyond what they have rings for.  .060 max?  It needs to be resleeved.  (snip)

 

I wouldn't jump to that conclusion just yet.  It might be worth having someone with an ultrasound gauge measure all of the cylinders.  When we found my 230 block was a worn-out .060" overbore, we checked the wall thickness and found the the bore was concentric with the casting and had lots of meat left.  My motor is now 0.072" oversize ( I used a modern metric ringset and had pistons made to match).

 

Marty

[Don Coatney]

Thank You..  Something to look forward to..   Don, so the dual intake and dual exhaust was purchased from a manufacturer?  Ive seen this picture before and though you had cut and brazzed yourself.

That engine looks killer!

The manifolds on my engine are modified factory. I sent them to George Asche and he did the drilling and welding. I believe George Asche has also gone as big as .100" on an overbore. On one visit to his place he was working on a Dodge (pictured below) that had a long block with a displacement of 283". Also pictured below is his 3-carb intake manifold for a long block. And lastly a picture of the engine in his 29 Desoto.

 

 

 

 

[40desoto]

Three and a half years later, I've purchased a 230 23" block, sold it to purchase a 250 from a 1950 Windsor.   A couple months back I picked up a fresh 265 Chrysler engine  with spitfire head, an Edmunds aluminum head, as well as ordered a triple AOK George Asche intake and dual  exhaust from George can't wait to get it all together..

[neil and ethan]

not to be dumb , but what is the horn like thing on the right side of the block,  

and the large diaphragm to the rear   ?   thanks

   love the pics

[Don Coatney]

The horn is a wolf whistle. I do not know what the diaphragm thing is. There are so many bells and whistles on this car it is over kill. There is even a pull out sink under the dash.

https://www.amazon.com/46128-Vacuum-Wolf-Whistle/dp/B007NBC6OM/ref=sr_1_6?ie=UTF8&qid=1493715629&sr=8-6&keywords=wolf+whistle