1943 Willys MB Halfcab

[Greg]

I was thinking about a more modern 4 cyl for simplicity, weight and ease of working on. I read about a GM 3.0l 181 cubic inch industrial engine, which is also used as a marine engine. It's based on the super common GM 153, but the 181 is a beast, for a 4 cyl. They produce 140 horsepower at 4,800 rpm and 177 pound-feet of torque at 3,600 rpm. Not crazy power, but almost double the HP of the Hurricane engine that's in it.

Parts are plentiful, it has a standard GM bellhousing bolt pattern and I could bolt a SM465 to it, for a deep granny gear and much more robust transmission, compared to the weak T90. Of course, I'd need a $600 adapter to bolt the SM465 to the Dana 18 t-case.

I found a lightly used 181 near by for $500... 🤔

Well, this is the way.... I bought the GM 181 3.0l marine engine previously mentioned, it was in Denver and a good friend took a trip for work and hauled it to GJ yesterday for me (thanks Justin!).

I think this will be a killer engine for the MB, should fit well and offer tons of power compared to a 134. I'll probably piss of the Flatty purists, but fawk 'em. Should fit under the hood well, too. This engine is newer and has around 8k miles on it. Killer deal for $450, IMO!

The intake and exhaust are both on the drivers side, a standard SBC mini starter will fit and it will bolt right up to the SM465 I have sitting around. The engine came with a distributor, plugs & wires, coil and alternator. I will need a rear sump oil pan & pickup, heavy flywheel & clutch, etc. All these parts are easy to source, since this engine shares parts with the very common GM 153 engine. It even has a one piece rear main seal, so no/less leaks! The SM465 will require trans tunnel mods, which sucks but it'll be a big improvement in gearing and strength.

I was comparing the gear ratios of the T90 that it has and the SM465... with the SM, 2nd gear is deeper than first, etc. It should really help the MB crawl with the 6.55 first gear ratio and deeper 2nd for cruising around town.

I'm debating adding swinging pedals with the master on the firewall, a hydraulic clutch and leaning towards EFI. Sacrilege, I know.... but all these things will make it drive better and be more capable offroad.

 

[DesertRam]

I have that engine in my boat. It has been going strong since 1997.

 

[Mouse]

I vote for EFI - do the fuel system now so you don't have to come back and do it again to convert it from a carb

 

[Greg]

I have that engine in my boat. It has been going strong since 1997.

Good to hear, sounds like marine engines are built to last compared to auto engines. It should make for a great little Flatty engine.

I vote for EFI - do the fuel system now so you don't have to come back and do it again to convert it from a carb

I'm leaning the same way, do it now and enjoy EFI.

 

[Hickey]

I was under the impression that the marine motors have different cams for the water system.

 

[Greg]

I was under the impression that the marine motors have different cams for the water system.

My understanding (and I could be wrong) is that they're built to live at 4500 RPM all day long. I believe this engine tops out at 5000 RPM. There is some pretty good aftermarket support for these engines, they're also used in industrial setups, forklifts, etc. Apparently guys also build them for circle track racing, one guy claimed with the right head, cam & other supporting mods he's seen 250 HP out of a 181. Not sure how true that is and it doesn't matter for me.

 

[Hickey]

My understanding (and I could be wrong) is that they're built to live at 4500 RPM all day long. I believe this engine tops out at 5000 RPM. There is some pretty good aftermarket support for these engines, they're also used in industrial setups, forklifts, etc. Apparently guys also build them for circle track racing, one guy claimed with the right head, cam & other supporting mods he's seen 250 HP out of a 181. Not sure how true that is and it doesn't matter for me.

Maybe I’m thinking of this in reverse. I want to say that there is a problem using a automotive 3.0 (or 5.0/5.7) in a boat because of the valves being open at a certain point which would allow lake water to flood the boat.

 

[Greg]

Maybe I’m thinking of this in reverse. I want to say that there is a problem using a automotive 3.0 (or 5.0/5.7) in a boat because of the valves being open at a certain point which would allow lake water to flood the boat.

That makes my head hurt.