251 flathead truck engine Compatibility

[Bill from SE WA]

I am working on a 251 to replace the stuck 230 in my 52 dodge pickup.  The engine I found is a rebuilt 251 that was in an M-37.  I know this is a 25 inch motor instead of the smaller 23 currently installed in the 52.  When I got the 251, it didn't come with a starter so I put the 230 starter on it.  This is before I realized the 251 could have a different flywheel tooth count.  Anyway putting the 230 starter on was no problem and it worked fine - didn't bind up and sounded ok.  So is this normal?  The M37 that I got this motor out of was an ex brush fire truck from central Oregon. The front mount was welded to the frame instead of bolted.  I am betting the M had a 230 originally and it was replaced with the 251 at a later date.  The serial number on the block is from a 48 to 49 truck. So I now have a few questions.  First - could the 230 flywheel fit on this motor (explaining why the starter didn't get bound up)?  The 52 has a three speed fluid drive. Will I be able to bolt the fluid drive to the 251? 

I'm pretty excited about getting this motor installed it the 52.  I fired it off briefly and it sounds really strong. Can't wait to get it cleaned up and ready to go.  I have it on a run in stand so it will be easy to work on and get running before being installed.  Any help you can provide would be great.  Thanks for letting come here and ask questions.  The 52 is going to be treated a dropped front axle, new brakes, and a higher geared rear axle.  I have not decided what I want to do with the body. For now I just want to get it on the road with a good reliable engine and updated suspension.

[NiftyFifty]

I'm sure someone will be able to tell you 100%, but I believe there is something different with the crank in the fluid drive engines.  The flywheel will work between both, I used my 218 on my 251 and fit just fine...230 should be no different.

[55 Fargo]

The US built 218 short engine flywheel is 4 bolt, the 230 and the long block engine are 8 bolt.

Canadian engines are all 8 bolt cranks, to the best of my info.

Now a 218 4 bolt flywheel may bolt to the 8 bolt crank flange, this I am not sure of, but the reverse would might work too, but again have done personally tried this.

Enjoy your 250 engine in the truck, with the right gearing it will be enjoyable.

Correction the big blocks and the 230 engines are 8 bolt crank flanges.

Edited November 14, 2016 by Rockwood

[Young Ed]

1 hour ago, Rockwood said:

The US built 218 short engine flywheel is 4 bolt, the 230 and the long block engine are 6 bolt.

Canadian engines are all 6 bolt cranks, to the best of my info.

Now a 218 4 bolt flywheel may bolt to the 6 bolt crank flange, this I am not sure of, but the reverse would never work.

Enjoy your 250 engine in the truck, with the right gearing it will be enjoyable.

I've got a 218 with an 8 bolt crank with a 4 bolt flywheel attached. However that is non fluid drive. While it would probably bolt up I don't think it would be wise to not use the full amount of bolts the fluid drive originally came with.

[Plymouthy Adams]

218 engines with 8 hole cranks have three sources, the early Dodges with the fluid drive, the later trucks with the fluid drive and the hy-drive with the first true torque converter.

[NiftyFifty]

He has a 230 going to 251....he already has the flywheel bolted up....issues is fluid drive to non fluid drive engine

[Plymouthy Adams]

2 minutes ago, 4mula-dlx said:

He has a 230 going to 251....he already has the flywheel bolted up....issues is fluid drive to non fluid drive engine

yes I read this and as it is bolted up and man states no issues I could not truly get the question as asked...he has already proven what he was asking..I made the crank comment in response to the application of a 8 bolt 218 crank mentioned in another person's reply....

so yes, it is confusing...

[wayfarer]

The 'big' difference between the 201-208-218 and everything else is the distance that the crank flange projects from the face of the block; 1" vs 1-3/16". It may not seem like much but it can cause major alignment issues with the starter pinion to ring gear depending on which ring gear is used on which flywheel.

 

[59bisquik]

Bill,

   Nostalgia Sid did a great job on my dropped axle and let me know if I can help out with any questions you have with that. Also consider flipped WIlly's shackles in the back to level her out. They are definitely priced right at $10 each from Rockauto.com!!

[NiftyFifty]

Maybe I read wrong....the motor is in...but the transmission isn't...he wants to know if the fluid drive system will bolt to a 251 engine that wasn't meant for fluid drive...lets just drop the flywheel  question....its in and working fine from what I can read.

 

Somewhere I thought I read the crank was different on engines meant for fluid drive to accept the input shaft..and it was actually a bit longer then a standard crank...but it's been a lot of years and a lot of beers between then and now

[Plymouthy Adams]

I understand that as long as the matching components went forward it was a no brainer...but if mixing and matching you have a depth issue with the starter/flywheel..

[Bill from SE WA]

Sorry for all the confusion.  The 52 pickup seems to have a 52 Plymouth 230 (based serial number) and it has a fluid drive. This motor is seized and will be removed.  Not sure how it's all hooked together because I have not taken it apart yet.  The 251 out of the M-37 was obviously a replacement motor, and I am sure replaced a 230 based on the modified front motor mount in the M-37.  The one common thing I noticed is that the starter from the 52 pickup works fine on the 251 which makes me believe someone might have left the 230 flywheel in the M-37 when they installed the 251. 

I know a 2 1/2 ton 251 truck engine never had a fluid drive but was hoping to keep it in the 52 pickup and wondering if anyone had any experience making a combination like this work.  I hope this explains what I am trying to do a little better.  Seems like it should work based on everything I see, just wondering if I am missing anything.

Thanks

[Plymouthy Adams]

two error in all that...in the US the 52 Plymouth did not come with a 230 and if stamped P23 would be a 218, it could easily been upgraded with crank and rod to make a 230 but by series/design it is a 218  Plymouth first got the 230 in mid-year production of the 54 model and is denoted with a diamond stamped in the number and in 55 forward the Plymouth 6 was 230 with no further need for a special symbol to denote size..  Second the Plymouth also never came with fluid drive...the Plymouth did however get a torque converter in 53 in form of the hy-drive set up that shared its engine oil with the converter.  This converter allowed two things...the added torque allowed them to change the 1st and 2nd gear ratios to running taller along with the added taller rear axle ratio for a overall boost in performance.

[wayfarer]

I am working on a 251 to replace the stuck 230 in my 52 dodge pickup.  So far so good.

When I got the 251, it didn't come with a starter so I put the 230 starter on it.  This is before I realized the 251 could have a different flywheel tooth count.  The engines that you have in front of you should all have 146 tooth ring gears. The 172 tooth ring did not appear until 1957.

Anyway putting the 230 starter on was no problem and it worked fine - didn't bind up and sounded ok.  So is this normal?   Yes.

 First - could the 230 flywheel fit on this motor (explaining why the starter didn't get bound up)?  Yes.

The 52 has a three speed fluid drive. Will I be able to bolt the fluid drive to the 251?  Yes.

As previously mentioned, there is a difference with the 201 cranks and flywheels in terms of 'depth', but there is also a difference in the number of bolts, also previously mentioned.

All of the fluid couplers and torque converters will have and require 8 bolt attachments. There are 4-bolt and 6-bolt cranks/flywheels in some of the older 23" engines but not in the 25" engines.

 

...clear as mud, eh?