Customs Flathead 6 or Slant 6 Swap for 55 Dodge Truck

Hey Guys, Squirrels Old Skool Valve job thread fired me up a bit...lol
I have a 1955 Dodge Fargo truck.
It has a very tired 228 long flathead 6 with dual carbs and exhaust, T 98 Acme 4 spd trans and a Mopar 8 1/4 3.23 diff.
This engine is okd and tired and never been open.
Compression 85- 90 across, wet or dry no difference , cyl leak down test most leaking big time. I only hear air rushing out the oil cap not out carbs or tailpipes.
Vacuum is steady 17 but had to advance timing to get there.
I have a 265 combine flathead 6 but if needs at least rings, honing and valve lapping.
It has a slight cyl ridge too but quite clean.
I also have a 225 slant 6 supposedly low miler was running in carbtil fall of 2017.
Dirty inside rockers and oil pan I cleaned it up cyls have nice cross hatching and by hand it feels good on compression.
I have a rebuilt A833 overdrive and bell for this engine.
Swapping it in is not too complicated but things like the clutch pedal linkage might be.
It has no performance parts.
So thats my choices right now have not 100% decided on my direction yet.
Here are a number of You tube vids on this.

 

My buddy Love's them Damn Slant's, has every configuration of intake's made, even has a drag race one, he just put one in a 32 Essex he just finished

 

I would rock the flatty. Go thru it and plastigage the bearings, hone the cylinders. Small pits in the cylinder will do no harm. Think of a 2 stroke and the holes they have in the cylinders. Pits will soon fill with carbon and polish smooth. Lap valves and check valve guides for wear. If everything checks out good it should be good for 100,000 miles.

If you plan on a hop up now would be the time to install a cam, shim the valve springs, lighten the flywheel. Your 228 head should fit and give you higher compression.

With a little of this and that you will have an engine with more power than the slant six and a lot more torque which is handy in a pickup truck.

A good running 265 will give twice the power you have right now or at least feel that way. Flathead Chrysler engines are very well mannered and continue to run without bangs or knocks even when worn out. You could be down on power quite a bit and not know it.

 

Not familiar with the Acme trans, is that a heavy duty truck trans? The A833 should work a treat behind the flatty if it will fit.

 

Hi Rusty it would need an adapter plate and it will fit.
T98 Acme in all CDN M37s after 55 and heavy duty trucks too.
A very tough full synchro trans.

 

265 is a great engine for torque. I used one in an M37 and was well pleased. It is 2 inches longer as you know than the 218 and you will have to move your radiator forward and fab up your front mounts but well worth that. Twin carbs and dual exhaust would add a little power and looks good. Tom Langdon has manifolds and other goodies. Slant six will give you more rpm's and hp but I doubt any more low end torque. Rebuild parts for the 265 a little pricey.

 

Hey Tim, all Canadian engines are 25 inches long no shorty 218 or 230s.
Mine is a 228 in truck now.
I already have dual carbs and exhaust too.
Yup 265 with right cam can rev too.

 

Vintage Power Wagons has parts for the old flatty and they are not expensive. Set of NOS pistons 6 for $75 how good do you want it? Most parts can be ordered from your local parts store.

 

You have probably seen this but it never gets old. Original owner's experience of a 51 DeSoto Suburban 8 passenger that he drove 185,000 miles with the original 251 flatty, later taken out to a 265 during a rebuild. My favorite quote "at high altitude at 70 MPH it smooths out like a perfectly balanced turbine". This in a 3 ton car with 4:11 gears and Fluid Drive, towing a trailer. If the old flatty can make it in that whale it can make it in your pickup truck.
https://www.allpar.com/cars/desoto/suburban-1951.html

 

I would do the slant / Great engine's lot of them still around, lot's of hot rod parts for them.
I have one in my '38 Plymouth would not trade it......Good luck.
Did I mention that it has 300Hp in it. and it gets lots of look's

 

Heres a video just shot.
Sorry about poor camera work.
I was by myself and shouldnt be doing this alone or without a GoPro.

 

225 slant six 145HP @4000RPM and 215 ft lbs of torque @2400RPM

265 flatty 119HP @3600 and 218 ft lbs @1600RPM

So, HP advantage to slant six but not a huge one, but the flatty actually develops more torque and both torque and HP at lower RPMs.

BUT the OP is no square. He already has twin carbs, dual exhaust, and with a cam his flatty should handily outperform a slant six at all speeds from idle to 80MPH. The /6 may rev a little higher but remember it has a long 4 1/8" stroke which is shorter than the flatty's 4 3/4 but not exactly a short stroke engine.

With all the goodies the flatty should develop 150 to 175HP on regular gas.

 

Advantages of the flatty 1) he has a good one in stock 2) it bolts right in with no mods or drama 3) he already has hop up parts for it. 4) In this application should perform better than the slant six.

 

Well in the latter part of the 1950s the 265 in big trucks were 123 hp rated with 1 carb or 136 hp with 2 carbs.
The slant 6 HP rating were way over zealous and more like 110 hp.
Now have no idea if it twere the same for the 265 flattie.
The slants advantage are as follows,
6 intake ports versus 3 on flatheads
Overhead valves
Forged crank and rods but so are the 265s.
Oh you can make slant 6 power but not cheap and not what I can afford right now.
265 warmed up hotter cam more compression and my dual.carbs and exhaust should push 150 to 175 hp.
Much better than my wore out 228s HP which is probably 75 hp now from its 105 HP.

 

I'm currently working on a 46 Dodge pickup. Still not sure what engine I want to go with. I have aquired 3 slant sixes
(2 forged cranks, 1 cast crank), In hopes of putting together one good one. But with all the problems with oil pump gear and dizzy gear on the cam, I am having second thoughts. Can't see spending 4-5 K on a rebuild only to be putting questionable parts back in. Might look into a 4.0 jeep engine. Plenty of parts available and no hassles like the slant. But no cool factor either like the slant.

 

The 265 I put in my M37 was out of a combine I think-came out of the midwest. with single carb and stock exhaust and cam, it was much better than the 230, especially with 4.89 gearing.
Good thread.

 

Yes the nylon dizzy gear has been some problem for people.
Has never happened to me.
4 litre jeep is a good engine.
So is a late 50s beefed up 230 flathead.
And a direct bolt in 4 U.

 

You guys be careful and MEASURE. I have seen slant sixes transplanted into a fifties Dodge pickup and a 49 Plymouth and in both cases they cut the firewall and boxed it so the engine could sit 4 to 6 inches farther back. The slant six is a lot longer than the flatty. I couldn't believe it until I measured for myself.

The Jeep six is a lot longer than the slant six.

I wouldn't use either. If I couldn't use the flatty I would put in a V8.

 

Hmmm 4.89 must pulled like crazy on the bottom end.
Would you hit 65 mph occasionally?
265s can be made to really go.
They are a lot more powerful than 218s or 228s.
I sure hope they are...

 

An inch longer than a 265.
I have both on the floor so it would be 3 inches longer than 218 230 US version.
Yah the older stuff might require surgery to the firewall.
They fit fine in my truck though.
A few guys on hete have slants in C series trucks.
Im veering over to my 265 so far.

 

I had a bad problem with the Clifford cam eating my dist. gears, get maybe 15 miles before it would chew them up. Took the Clifford cam out and put in a Isky and its been fine ever since.

 

Having a good 265 flatty in a person's possession has a huge impact on which way I would go. Especially when they have a dual carb intake and dual exhaust in their possession as well. I also think I would look into the 833, and maybe the 833 OD behind the 265, depending on the rear gear ratio.

I wouldn't waste my time with a slant 6.
If the 265 wouldn't work, a V8 would be the next stop, and that would bring a lot of other modifications with it (if they are not already done). Gene

 

No brainer...after having a really nice running 55 dodge low-box with the original flathead and 3 speed and putting many many miles on M-37s while in Sam's army, I'd have to go with the flathead 6. One of the biggest factors in choosing the flat motor for me is the distinct sound the flathead makes. The slant 6 just sounds too........new.

 

My 265 is need of I dunno yet.
Bores are .040 mains .020 rods .010
Thats a long time ago and gave no idea how long run after that.
Cyls have a bit if ridge.
Good news is I have 2 other 265s in the wings and 1 might be a fresh rebuild.
Western Canada is a trove for 265s in farm equipment scattered all over the western prairies.

 

Cyl taper less than .007 you are good. Make sure it's not just carbon buildup. Vintage Power Wagons has NOS pistons for $75 a set so worst case how much do they charge to bore a cylinder?

 

They only have limited sizes but have .060 which is whete it would need to go.
Pistons rings bearings valve job were near a full on rebuild at that point....lol
Machine work, block cleaning, boring, magnaflux, head milled and block decked is 700 cdn here

 

I vote for the flathead. Swapped too many slant sixes in old Mopars over the years. Speed equipment is expensive and when you do get power, they blow up. In contrast. I put a rebuilt combine engine (think it was a 251) in my '39 Fargo eons ago and loved it. You already have the two carb manifold.

 

LOL! try posting that over on the slant six forum. You will be flammed to hell, even if its an accurate statement.
I still think I am leaning towards a 4.0 Jeep they run forever, and parts will be available until the day my grandchildren die. And yes I know it's not traditional.