Supercharging a 251

[cerial]

I have a 67 WDX 100% stock with a rebuilt(done 30 years ago) 251 and 420 with less then 1k drive time on them. This thing fires right up and runs great up to about 40mph.

I have owned over 100 vehicles and out of that 100+ only 4 have been dodges(Magnum, D150, shadow, and this PW). Part of that is the fact that dodges cost more to buy & run then the others, another part of that is parts scarcity of the older dodge engines. I can build 2 GM trucks what 1 Dodge will cost. I just always wanted a flat fender PW so when this one came along I pounced.

I always like to run propane any time I can also. The higher octane, improved engine life, and lower cost gives me something to flaunt to the diesel guys that can get 30% more mileage at twice the cost. Propane takes years before it goes bad, requires 3 wires to run, and because it scares people is actually safer to run due to the DOT guidelines in place.

I don't do diesels. I do do low rpm dauntless style torque monster gas engines running on propane though. In most cases I can make more power/weight with a gas and proper gearing then I can with a diesel at a lower operating cost. NA diesels are dogs compared to NA Gas engines etc. Alright, enough telling you why I do not want to use a diesel back to the supercharging topic.


After quite a bit of time looking I am finding very little in regards to this engine and forced induction except that due to the low compression ratio it would be a ideal candidate.

I have always shy'd away from superchargers or turbochargers due to the cost. But, from a sheer coolness factor and all that room above the engine to work with this thing is begging for a blower.

Where would I even start as far as considering a supercharger on this 251?
How much safe power/torque can I expect?
How much can I bore this thing before I run into issues and where would I look for modified engine internals once it was bored?

I am willing to toss $4k into this engine to make a supercharged 251 a reality. Remember me talking about the GM thing? Yea, 4k into a GM engine will equal a lot more power. This is more about keeping the flat head then anything.


For 4k though I would want more then 350 ft pounds of torque around 2500 rpm. That is not a lot of torque considering this is a "big block" inline engine.
I have a 350 engine right now with $1500 invested that puts out 370 ft lbs just over 2k and will be going into his if the 251 is not a suitable option. I will find something along the rat rod lines to put the NA 251 in if the 350 takes its place in the WDX.

Part of me does not want to ask this because I will just look stupid for asking it. While the frosted side really wants to see a blown 251 under that hood.
With this engine around so long it seems like someone would have tried it?

Where is all the performance write ups on this 251? Seems like people toss a intake and exhaust on it and call it good or junk it for a v8.

Someone give me the heads up. There has to be some good info out there on how to go about placing a blower, routing, numbers, and the parts to make this work.

[JStinson]

This thing fires right up and runs great up to about 40mph.



I am willing to toss $4k into this engine to make a supercharged 251 a reality.

If what you're trying to accomplish is more speed, a supercharger will not help you. You can toss the biggest blown 454 you can imagine in your truck and it will still max out at 45-50mph. The only difference is the time it takes it to get there.

For 4k, you would be much better off re gearing both axles and finding an overdrive for it.

Though, the thought of a 251 with a turbo on it is fascinating, in a bizarre kind of way.

I'm really interested to see other replies on this.

[Charles Talbert]

For what it's worth, you do not have a '67 WDX, that would be a WM300.

[cerial]

This is a civilian.
It is more then a matter of gearing. This truck is very heavy. I plan on installing the .72/1 brownie behind the 201 for 4.19 gearing. Without any power increase this thing will be a major dog up any kind of incline. It will not be able to pull its own weight let alone a trailer and buggy.

How many rpm is that 251 pushing with the stock gearing at 45 mph?

The 350/465 with a .72 brownie behind the 201 running 5.83 gearing will be running 2700rpm at 70mph.

While I know the low end torque would be severely reduced I imagine I could install a cam in 251 to increase the torque higher up power range. I would then install a blower to increase the overall total power output of the engine. This would increase the compression and stress on the entire engine possibly leading to damage.

Once again I have no idea where I would find these parts or what works and what does not work to make power with this engine. I would much rather follow the leader on this then estimate and wonder how long the block will last with one off parts.

[Charles Talbert]

Who said it wasn't a civilian?

This is a civilian.
It is more then a matter of gearing. This truck is very heavy. I plan on installing the .72/1 brownie behind the 201 for 4.19 gearing. Without any power increase this thing will be a major dog up any kind of incline. It will not be able to pull its own weight let alone a trailer and buggy.

How many rpm is that 251 pushing with the stock gearing at 45 mph?

The 350/465 with a .72 brownie behind the 201 running 5.83 gearing will be running 2700rpm at 70mph.

While I know the low end torque would be severely reduced I imagine I could install a cam in 251 to increase the torque higher up power range. I would then install a blower to increase the overall total power output of the engine. This would increase the compression and stress on the entire engine possibly leading to damage.

Once again I have no idea where I would find these parts or what works and what does not work to make power with this engine. I would much rather follow the leader on this then estimate and wonder how long the block will last with one off parts.

Never said it wasn't a civilian, the WDX was the early civilian series that came immediately following WWII in 1946. The much later '67 model would be several years after the later WM300 civilian series went into production. In fact if yours is a '67, that is only 1 year prior to the end of the so called "flat fender" power wagon production run for domestic sales which ended in 1968.

On another hand, you sound a bit far out, but since I have no clue about you other than reading what you have written here, and you aren't aware that your truck is a WM300, I could be fooled by a simple first impression, and I'll leave that there.

I'm an admitted diesel enthusiast, which is common knowledge around this forum. We also do a lot of back to original rebuilds and restorations. That said, I love working with diesels, (40 years under the belt) like you have spoken of dealing with propane power; but one never knows when someone may happen by that has propane experience. I have no idea whether what you mentioned has ever been done since I've never read of any such upgrades, (or possible downgrades) using a basic 251 engine. You seem to have it together with all the possible options; I'd suggest that you make it happen, then enlighten the rest of us as to what we are missing.

[JStinson]

I'd suggest that you make it happen, then enlighten the rest of us as to what we are missing.

x2

[cerial]

I came off as a bit cocky there and I am sorry for that.

After talking to a few shops about this engine the conclusion is less then I hoped for.

While the engine has low compression the bottom end and internals are not up to the task of any kind of boost. The engine can be bored to 30 over safely while upgrading the valves and rings. The oiling and cooling issues can be fixed with remote pumps. The shared port design is a serious flaw that I knew about before even considering any type of forced induction. The block can be machined for additional ports at smaller sizes. Edgy seriously can grind on this and make power just not the kind of power that I need for my application. Any type of forced induction would be a novelty producing less then 5 pounds without dropping some serious machine work into this 251.
In a lighter rig with the proper gearing this engine is a great contender. The torque curve is very impressive in stock form and I do not plan on messing with it. If I get my hands on a older dodge cab to make a slammed runner this engine will be a great asset.
But, in order to make a tow rig out of this power wagon I simply will be better off going with larger displacement. This is a lot like the 2.5's that I have worked on in the past. You can make impressive power using a turbo in moderation. But, from a longevity standpoint it makes more sense to go with a larger engine with proper gearing.

For now a NA350 and 465 mated to the 201 with a brownie overdrive is the plan. This is being done basically because I have everything already as well as tons of spare 350 and 465 parts.
I will put this engine in place and decide if I need more power. At that point a big block will be mocked up. I am more a fan of the 460 then 442 or 440 in that category due to the power per dollar I have gotten out of these in the past.
A Buick 350 dauntless engine may be a compromise option between a Chevy 350 and big block. It is considerably wider then a 350 with tons of potential while being lighter then most big blocks.

With respect to the diesels they are great for forced induction and longevity. But, this will be a rig that will sit and get used randomly. Because it will be used ramdomaly it will sit for months on end I can not but think of algae. After personally going through a 818's fuel system and a few tractors I have grown to hate algae. Yes I know there are additives and other developments. But, from a simplicity standpoint as well as a "cleaner" standpoint I would rather use propane. From a longevity and maintenance outlook a gas engine makes more sense to me. It will not get to three hundred thousand miles. But the cost of maintenance, fuel(propane in bulk), and rebuilding or replacement a gas engine will be my choice in most cases.

[maineSS]

Ford V8 flatheads have been supercharged with Eaton units quite successfully, upper end is around 300 HP, check out Roadrunner Engineering.

Turbocharging backs up too much heat into the exhaust manifold in my opinion- you'd likely have cracks in the exhaust valve area pretty quickly, the casting is thin there.

If you're looking for heavy loads at highway speeds, you'll be better off with a modern engine with an overdrive tranny- the brownie units have straight-cut gears (from what I hear), and will take some finesse to shift in and out of. The Chevy 350 will fit the PW engine bay with minimal hacking, compared with other engines, and can be built into bigger displacements at minimal cost compared to other options.

You will need to address other expensive items like axles, brakes, and tires to safely harness the extra speed on today's roads- figure on doubling your initial estimate at a minimum.

[cerial]

That 4k estimate was towards the motor only. I will be tossing more then that into some 19.5 rims and G rated tires for this build. The rims are being built both for weight and the pressure of the higher grade tires.

For breaks I will go with uglytrucking if they are still available when I reach the axle rebuild step. I will machine my own rotors if need be. A booster, resistor, and upgraded calipers will halt this thing without question. When towing, a tipple axle trailer will do most of the heavy breaking. I plan on retaining the current parking break and simply switching over to a 2 position cable operated lever.

I have a thing for passenger side drop axles. I have a set of International, a few sets of jeep cj, and a few sets of Toyota passenger side drop axles. There are better axles and worse axles then these out there. For what I plan on doing these will work while keeping the overall look of a power wagon. There are a few quirks with these axles that need to be upgraded and addressed. But, once I rebuild it and replace the seals a few times I am sure I will come to like it.

For steering a PSC / Saginaw pump and Box, crossover steering, and hydraulic ram assist are on the checklist. Also a T plate is planned to avoid cutting into the frame. I plan on cutting down the steering shaft and making it a 2 piece to not only make it mate to the Saginaw better but also be considerably safer in the chance of a accident.

The suspension I have not decided upon yet. I will need to see how it handles. I have had heavy 1 tons that rebounded within reason when hitting a pot hole and others that have gotten air on the same pot hole the rear suspension was so stiff. I know I do not want to link this. I could see replacing the spring pack, only running the 2 or 3 new longer leafs, and running bags if need be.

The 350 motor that I have makes a lot of vacuum just off idle so I plan on just sending out the vacuum motors to be rebuilt and running them. I will need to play around with electric motors and maybe redesign the wiper system slightly for a clean look that will give enough torque to break ice. Until this is done I will take it easy and stop during big storms.

I do not plan on "beating" on this truck. As far as the brownie is concerned I have used them in the past. I could see myself simply leaving it in high range when empty. Shifting from 4th(1/1) to 5th(.72) is something that is not a harsh maneuver if done at higher speeds. It is when people try to split the lower gears which requires quicker shifts where issues arise. You just need to remember to double clutch the brownie, keep fluid in it, and it will outlast most other parts on the truck. Shifting this from medium to high range can be done very quickly. I plan on using a 2 position lever with locking tabs and cable to shift the brownie.

First thing is to be able to go 75(top maximum white knuckle speed) without damaging the engine. I plan on running 60-63 most of the time on the highway. This is to save on wear more then anything.
Then the steering-safer and less strain on me(done during engine install)
Then the tires and rims-safer
Then the breaks-safer
Then the body-dents, bed, and weatherstripping
Then the suspension-if need be
Then I will begin towing, fixing, and upgrading the small things as I go.

If I did it all at once it would not be fun.

[maineSS]

I suggest you look at Dana 60 axles for what you have in mind, that will solve a number of problems at once- rims, brakes, and steering. One of the things you will run into is the extreme scarcity of good front axles- most are worn badly in the bushing area, no one is making replacements.

The original suspension is extremely stiff, you'll need at least 500 lbs in the back to soften it a bit- empty you will get air over bumps, it rides like a buckboard from the 1800's. I used to carry a spare front axle in the back of my '49, there was quite a difference when I took it out.

I used a Toyota 4wd truck PS box to avoid hacking the frame, but the stock drag link setup is very short and prone to bumpsteer- crossover steering would be much safer at highway speeds (another vote for D60 axles). It will be a major job to try to make crossover steering work with OEM axles, and your particular state may prohibit welding on steering parts- check into that.

Chris Case over on www.dodgepowerwagon.com has made up an electric wiper conversion using linkage arms and a modern drive motor that fits- check the archives there.

I would suggest a good 3 or 4 point safety belt before you drive anywhere- you will be badly injured in even a low speed accident that today's drivers walk away from. All you'll hit is steel and glass, and the original steering column will spear you right in the chest as your rigid arms fold the wheel around it. One of the reasons the PW was taken off the market in '68 was that the cab wouldn't meet Federal safety standards- it's easy to see why.

[The Other Ross]

Keystone Turbo makes bolt on kits for gas inline 4 and 6 cylinder IH tractor engines.These engines have much bigger bottom ends than the 251 but it is a starting place.
I've toyed with the idea of a propane powered 440.The technology is out there as Chrysler Industrial provided propane Big block motors for irrigation pumps and such.

[Aaron S]

While I haven't seen one specifically on a Chrysler engine, centrifugal superchargers on inline sixes and eights were not all that uncommon before WWII. Many manufacturers offered them as an option at the time, mostly high end makers like Deusenberg, Auburn, and Cord. But, notably, Graham produced several fairly utilitarian models for the working man with supercharged flathead sixes. The superchargers did provide signifigant power gains in these cars, boosting an 80-90 horsepower engine up into the 110-120 horsepower range. I know it doesn't sound like much but its still about a 40% increase in output. As you have already pointed out, however, a motor like this is pretty much a novelty piece... really cool, but will never match the performance of a modern, naturally aspirated V8. It will easily match or exceed the cost though.

[maineSS]

The 230 engine has a lot more "speed equipment" options than the 251, but with 21 fewer cubic inches, it needs it. One of the problems with straight 6 engines is even mixture distribution to all cylinders, propane might be easier to work with than gasoline in this respect. The disadvantage with propane is locating fuel if you operate outside your local area- it's not easy to find after buisiness hours in many places.

There was a company (Squires) several years ago that made rear-mounted turbo conversions- the turbo wasn't mounted on the engine exhaust manifold, it was just before the muffler. It was basically a low-boost setup, don't know how they handled condensation- fast-spinning compressor blades don't like water droplets much.

[cerial]

The bottom end of this motor can not support boost. Simple as that. If I milled the motor and installed new sleeves, cam, crank, pistons, etc. Basically replaced everything inside the block I could give the illusion of a stock 251 with a supercharger or turbocharger. I have been told enough and am convinced I would crack the block it would just be a matter of time.

It works for what it is.


As for weight in the rear I am looking at a 60 gallon(48 usable gallons) propane tank for in the bed behind the cab. When it is full it should provide around 400 pounds of weight while not being that noticeable.

I have some kid trying to sell me a Dana 60/70 setup right now. I admit that would fix most of the front end issue but totally kill the look. I can hide a engine swap but not axles. That being said the more I look at these axles the better a axle swap seems.

Right now I just want to take the thing down the road. Then put the overdrive behind the 201 and make a checklist of what can be fixed and what can be replaced body wise.
I have had this thing for 2 months and will not be able to get in it for another month due to my job.

I will run the 251 while doing bodywork and deciding the best drive train to move this thing later on.

Thanks for all the help.

[cerial]

Finally got in this truck this weekend that I bought sight unseen. Notice it took a bit longer then a few months. I spent over 2 hours driving through the woods and down some trails by the house. Everything drive train wise worked flawlessly.

I Freaking LOVE it. The cab is tight the engine fires right up. The thing rides like most of the utility trucks that I have. Yes it goes slow but after riding in it I don't plan on messing with the power train it at all. I have a issue where the doors decide to fly open at random times but that seems like a easy fix. The axles do kind of scare me. I will need to find a guru somewhere in Michigan that knows how to work on these axles to keep this thing moving.

Something that totally surprised me was how easy this thing turns. I don't know how many of these are left that are stock. I see no need any more to mess with this. It will be my "golf cart" for heading into town or something. Probably end up one of my restored rigs after a few years that just sits under a cover 360 days out of the year and I'm good with that.

Have had flat fender PW on my "vehicles to own" for years. Now that I have gotten in this thing and drove it I can see why it had such a good run.