Bobbed deuce engine swap

[JasonS]

I spent the last week swapping out my OA331 for a completely overhauled later model OH200 engine. The OH200 is a later generation gas engine incorporating numerous improvements over the OA331:
Larger mains (3.125") and rods journals (2.30") with hardened journals.
Larger oil pump (15 vs. 7.2gpm) with full flow filter and oil cooler.
Larger capacity water pump (150 vs. 70gpm) with larger bearings and shaft and ceramic faced water pump seal surface.
Chrome faced top piston ring with steel insert for top piston ring groove.
Bypass-type thermostat (same as multifuel), improved cooling/ water distribution.

The OH200 has 365 ft-lb torque at 1200rpm and 200 HP at 3400rpm. It is 400 cubic inches, 4.25" bore and 4.7" stroke with a 7.5:1 compression ratio. The flywheel, clutch, and flywheel housing from the OA331 bolt up to the OH200. I had to use the air cooled air compressor as the water cooled one wouldn't clear the thermostat housing. The OA331 exhaust manifold was re-used but the top capped off as the OH200 doesn't have exhaust heat. I designed an adapter to mate a Mack/ Cat type spin on oil filter to the OH200. Oil filters are available with combined full flow/ bypass type elements. The oil pan is a center sump. I rotated the oil drain plug 180 degrees to put it on the drivers side. This adds needed clearance and makes for easier oil changes. I changed the armature in the starter to 12V (kept the rest 24V) which spins the engine over nicely. The distributor has a tach drive; I am using a 3krpm military tach and a stock deuce speedomeer cable. I am in process of modifying a 1481 pertronix ignition module from 8 cylinder to 6 cylinder.

Overall, it's is a nice improvement in horsepower and perfectly fit my requirements for a bobbed truck.

 

[JasonS]

Some pics of the entire truck. Needs some paint...

 

[WillWagner]

I thought you put an OH200 in it, not a cat?? (see 4th pic in sequence)

 

[SasquatchSanta]

I Like it!

Please post your fuel mileage.

Propane anyone?

 

[oldshep]

Nice. gas sixes are cool

 

[spicergear]

Hey, that's a cool swap! ...weighs 1/3 of any of my swaps too! I like it!

 

[emr]

Man , that is one SWEET Ride!! Very Very nice!!! Randy

 

[JasonS]

Thanks for the comments!!! I haven't driven it enough to know fuel economy yet; will post that when I have some idea. I am expecting somewhat close to the original engine (hoping that the increase in displacement will be offset by the increase in compression ratio).

There are five new kittens on the farm and they are all over everything. We had to be very careful not to run over any of them.

 

[Barrman]

Looks good!

So, if it produces 200 hp at 3,400 rpm, what is the redline? Matter of fact, what is the red line of the OA331?

 

[Monty]

So is the OA331 different then a 6cylinder out of a 5ton?
By the way it's looking good. Keep us posted on the progress.

 

[m139h2otruck]

The 5 ton gasser is a much bigger engine (602 cid) with two separate 6 port heads, aluminum intake and 3 piece exhaust "header" with a 4" exhaust and a big Holley or Zenith 2 barrel carb. Horsepower is either 205 or 226 depending on source and torque is somewhere over 500 ft-lb at about 1,600 rpm. Red line is 2,800-2,900 and you better not exceed it or you will be doing an engine change! The R6602 is also much longer than the "little" duece engine, about the same as the Mack ENDT used to replace it. It also weighs about 2,000# without the transmission.

 

[JasonS]

Looks good!

So, if it produces 200 hp at 3,400 rpm, what is the redline? Matter of fact, what is the red line of the OA331?

There is a little specsmanship at work. The maximum gross horsepower is 200 at 3400 rpm (redline) but the governed rpm is 3200. The literature makes it clear that the engine should not be geared such that it is operating against the governor at all times (the cruising rpm is supposed to be between 2800 to 3000 rpm). This appears to be a fairly common sales tactic; lots of engine's horsepower is rated at speeds which cannot be maintained indefinitely.

I don't know if the military OA331 is exactly the same as the civvy. The civvy OA331 is stated as having 6.4:1 compression ratio and 3200 governed rpm whereas the military TM's list 6.73 and 3400 rpm maximum governed speed.

 

[JasonS]

The 5 ton gasser is a much bigger engine (602 cid) with two separate 6 port heads, aluminum intake and 3 piece exhaust "header" with a 4" exhaust and a big Holley or Zenith 2 barrel carb. Horsepower is either 205 or 226 depending on source and torque is somewhere over 500 ft-lb at about 1,600 rpm. Red line is 2,800-2,900 and you better not exceed it or you will be doing an engine change! The R6602 is also much longer than the "little" duece engine, about the same as the Mack ENDT used to replace it. It also weighs about 2,000# without the transmission.

All of the R6602s that I have seen have cast iron intake manifolds?

 

[m139h2otruck]

I'm not sure about other engines, but our M139's intake is aluminum. May have been a running change, or the non-mil engines were iron. Good question anyway. Also, good job on the bobbed truck repower. Should go real good with 200 hp and the gearing as it is. Is the trans still a non-OD?

 

[Monty]

The 5 ton gasser is a much bigger engine (602 cid) with two separate 6 port heads, aluminum intake and 3 piece exhaust "header" with a 4" exhaust and a big Holley or Zenith 2 barrel carb. Horsepower is either 205 or 226 depending on source and torque is somewhere over 500 ft-lb at about 1,600 rpm. Red line is 2,800-2,900 and you better not exceed it or you will be doing an engine change! The R6602 is also much longer than the "little" duece engine, about the same as the Mack ENDT used to replace it. It also weighs about 2,000# without the transmission.

Well at 602 cid that explains the bad gas mileage, thanks for the information.
Chad