Upgrade to Long Block Flathead

[Matt Wilson]

Good evening all,

Thought I'd ask your experiences or observations on this. And since I know there is a fair amount of overlap of subscribership between this forum and Joe's forum, I hope those who already answered this question on Joe's forum won't take offense that I have posted the questions here as well. I'd just like to get it out in front of as many Power Wagon folks as I can.

I'm considering removing the 230 and installing a 251 or 265 into my '49 Power Wagon, with some performance upgrades as well. I'm getting a pretty good understanding of what this swap requires, but one of my main lingering questions is whether the original transmission (original type crash box) and 10" clutch will be up to the task of the extra torque if I install one of these larger engines with some performance goodies installed (two-barrel carb or dual carb setup, split exhaust or headers, cam, etc.). I certainly don't intend to abuse the truck, but there will be the occasional pedal mashing while I'm going down the road, or extra pedal while I'm hauling something heavy.

As I first thought about this, I figured it wouldn't be any big deal, because people install V8's in these trucks all the time, but the more I thought about it, the more I realized that all the V8 or diesel upgrades I see are making use of some later transmission, not the original spur gear type. I don't know how much of that is because of concerns over the stock transmission's torque capability, or if it's because people want easier shifting or overdrive.

I appreciate your input. If at all possible, I'd like to keep the original transmission, as the double-clutching and gear whine are part of the truck's character, and it would be cheaper and easier to keep it anyway.

Again, to those folks who already replied to this question on Joe's forum, please don't take offense that I'm looking for additional input.

Thanks!

[Matthew Welcher PWA]

As I recall the Bellhousings are different, along with the transmission. Using a Late bellhousing and NP420 Transmission behind the long motor. You will have to change the center transmission cover to do this also. I believe they also used an 11 inch clutch instead of the 10 inch clutch.
I will do a little more research on this but you will need to change the lower radiator mount and get the grill extensions to hold a 251 radiator.
the inlet and outlet ports are I believe also different between early Power Wagon and late with a 251.
I myself would stick with the early set up and the 230. You can make a lot of power with that 230 and i really like the early transmission.

[CSCameron]

Iowanogre has it correct. Different bell housing, your crash box will not bolt up. If you upgrade both the engine (251) and transmission (NP420) you'll not only need the transmission hump but also a newer passenger floor board.

Now, if you keep the 230 and want to upgrade the transmission to the later NP420 synchronized version, you can get an M37 B1 transmission and it will bolt up to the crash box bell housing. However, you will need the later tranny hump and passenger floor board. I did this swap in my 55 FFPW and it works well.

Note, the civilian NP420 transmission, available in 56 or newer models, will not bolt up to the 230 bell housing. Only the later M37 B1 (NP420) is compatible with the 230 bell housing. The guts of both transmissions are interchangeable, the cases are different.

Clark

[Matt Wilson]

Well, the plan was to keep the original bellhousing. I've looked into it quite a bit, including talking with people who have worked with these flatheads for many years, and some who have made this conversion, and I'm told that the 251 or 265 will bolt right up to the existing bellhousing and flywheel. Hopefully my sources are correct, and I think they are. One is a man who has been building, driving, racing and otherwise working on 230's, 251's, 265's and other Chrysler/Plymouth/Dodge/Desoto flathead sixes since the late 1940's (yes, he is still doing it, to which I say more power to him!). The others are a couple of different businesses that supply Power Wagon parts and services.

So if all the above is true, then one of my questions is whether or not the original transmission will handle the bigger engine, especially if I do a few power mods to it. As you guys mentioned, the original clutch is only 10", which is also a concern of mine, although I forgot to ask about it in my post. It seems that if anything, the clutch would handle the torque, but would maybe wear out sooner than the 11", and therefore have to replaced more often, but that's just my thought.

As for the later synchro transmission, I would really rather keep the original non-synchro crashbox, if it's up to the task of the bigger engine.

Thanks for the responses! I appreciate any input you and other folks can provide.

[CSCameron]

I believe your sources are correct that the bell housings will interchange (230 <> 251). Not sure about the 265? Most folks are looking to exchange transmissions and do not want to pull the engine to swap bell housings, but you're in a good position to do this.

I can't speak to the strength of the crash box, but I don't see why it wouldn't hold up to the 251 or 265? I'm sure someone with experience will correct me if I'm wrong.

Good luck with the swap, be sure to post pics and details so we all can learn!

Clark

[Matt Wilson]

I believe your sources are correct that the bell housings will interchange (230 <> 251). Not sure about the 265? Most folks are looking to exchange transmissions and do not want to pull the engine to swap bell housings, but you're in a good position to do this.

I can't speak to the strength of the crash box, but I don't see why it wouldn't hold up to the 251 or 265? I'm sure someone with experience will correct me if I'm wrong.

Good luck with the swap, be sure to post pics and details so we all can learn!

Clark

Thanks, Clark. I'm told by these same sources that the 251 and 265 are the same block, but with different crankshaft and rods. Everything else is supposedly the same. In fact, based on my looking around so far, if I decide to go to a 265, I will probably end up buying a 251 block and swapping in the 265 crank and rods, because it seems that complete, rebuildable 265 engines are not all that common, but 251's can be had, and I've found a few places that have them, and I found a place that has the 265 crank and rods.

I have found a couple of references to people who allegedly have larger engines, including V8's in front of the original crash box transmissions, so it seems that it is probably feasible. I've sent an e-mail to one of those folks to ask for his experience on the durability of the tranny.

And yes, if I end up making the swap (I'm not 100% decided yet), then I'll be sure to post updates with photos, and I may also do an article for the PWA.

[CSCameron]

Hey Matt, I finally found my bookmark showing the different bell housings...

http://www.jobrated.com/-bellhousing-id.html

Left: 56 and up (includes the 251)
Right 55 and back (includes WWII)

[Matt Wilson]

Oh, that's a great link, Clark! Thanks.

I don't suppose you have a resource that would tell me if the 11" clutch would work with the old crashbox transmission, do you? I'm wondering about input shaft diameter, spline count, OD of the snout (bearing retainer) on the transmission, not sure what else?

I suppose my existing flywheel could be modified by drilling and tapping holes to fit the 11" clutch pressure plate.

Thanks,

Matt

[CSCameron]

I don't have a link or any knowledge about that. Sorry. Hopefully someone will chime in here. Or post it over on the Power Wagon forum, I'm sure one of those guys will know...

http://www.dodgepowerwagon.com/wwwboard/index.html

Clark

[Matt Wilson]

Ok, no worries. Thanks!