More engine power in dukw

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Joe Gopan
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Re: More engine power in dukw

Post by Joe Gopan » Sat Apr 07, 2018 8:27 am

Any input from those who have installed the 50's Civilian engines in a DUKW?. Got a feeling it is not worth the cost. It's still a DUKW with all its handling warts.
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Re: More engine power in dukw

Post by Dodgeguy1942 » Sun Apr 22, 2018 3:33 am

Anything to help it up the hills will be good

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Re: More engine power in dukw

Post by johne504 » Sun Jul 15, 2018 6:31 am

I installed a 302 in my Dukw years ago. I am very happy with it.. it can be ran up to 3500 rpm to shift from 3rd to 4th, which is a good improvement.. I also installed a Paxton supercharger, with a m135 intake manifold and carb. I’m not sure how much the supercharger helps, but it sounds cool.!!! Haha... no major modifications to the Dukw are needed for this swap, could easily put the original motor back in if wanted... going from 91 hp to 160+ is a huge improvement...!!!! I’m thinking about shaving the head 100 thousandths now also. Ive been told by m211 owners that doing this will greatly improve power. I will not go back to the 270 after driving the Dukw with the 302... no longer hold up traffic in town, and can pull hills so much easier now!
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Re: More engine power in dukw

Post by johne504 » Sun Jul 15, 2018 6:42 am

I would look for a civilian 302, as Ive been told the military version had castings that would need to be removed, and also fuel pump blocked off. I will say, that in order to use the original Dukw air compressor driveline, crankshaft pulley, etc, you will need to cut the end of the crankshaft off about 1 inch in order for the original Dukw crankshaft pulley to work correctly with the compressor drive shaft. This was easy, but making the decision to do it was not... it worked out perfect though... my Dukw I made a bracket to run a additional 12v alternator, and 12 volt electrical system just for the starter... the 6 volt starter has a hard time starting the engine, and when your in the water, you need reliability...!!!! I added a 12 volt gauge, extra 12 volt battery, 1 wire alternator, etc... the 12 volt system only runs the starter, gauge, and any other 12 volt accessory, (like a cigarette lighter to charge your phone, marine radio, etc, etc,). Like I said, I would never go back to the original 270, unless it was only a static display Dukw.... they are gutless...but the 302 upgrade makes them practical to drive in city/town traffic c... and on the Hiway, doing 50mph is no problem.... although the running gear is really spinning fast, so I usually keep it around 45mph, seems to be the right speed for my Dukw. Transfer case growl gets loud after 45-50 mph... I have had my Dukw up to 60mph once or twice, but that’s just too fast for something not made for speed....
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Re: More engine power in dukw

Post by Dodgeguy1942 » Mon Jul 16, 2018 4:29 am

I have sourced a later civilian 270 which I believe are around the 145hp mark. Should be a big improvement. But it has an auto tranny on the back so I will need to find a flywheel for it. Looking forwRd to the power increase

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Re: More engine power in dukw

Post by Joe Gopan » Mon Jul 16, 2018 5:07 am

The later 270/302 GMC engines came with different intake ports and carburetor mounting options, make sure that you can locate the correct later carburetors and mounting patterns that match your new engine. The later intake manifolds are scarce.
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HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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Re: More engine power in dukw

Post by Dodgeguy1942 » Tue Jul 17, 2018 4:26 am

This motor is a complete runner. Just need to sort out the flywheel

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Re: More engine power in dukw

Post by Steve Greenberg » Tue Jul 17, 2018 6:16 am

Hello,
I may have a spare DUKW flywheel. I will look around my shop today.
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johne504
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Re: More engine power in dukw

Post by johne504 » Sun Nov 18, 2018 7:51 am

Dukw flywheel will not work for the 302 upgrade. It is a 4 bolt, and the 302 needs a 6 bolt.
45 dukw
41 cckw closed cab cargo
45 cckw open cab cargo
44 cckw open cab leroi
43 weasel
41 ben hur trailer
45 ben hur trailer
43 M-6 bomb truck
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mark III bomb/torpedo trailer
53 GMC XM-215
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mark 5 bomb trailer

johne504
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Re: More engine power in dukw

Post by johne504 » Sun Nov 18, 2018 7:59 am

Doing the swap on the Dukw is not that big of a deal. Parts are available... intake manifolds are readily available on eBay (NOS M211’s), which are a two barrel, even better. I ended up using the bell crank also that mounts to the intake on the M211’s, it worked out good for the stock M211 carb I used. If you wanted to use a stock 50-60’s Gmc two barrel you can use the original throttle linkage set up. Really the only main issue is getting the clutch/flywheel set up right for the newer engine. And like I said, you will have to cut the front of the crankshaft to fit the crankshaft pulley off the original 270 for the air compressor. Everything else is easy to make work. Newer Gmc exhaust manifolds seem to fit perfect for the exhaust system in a Dukw. You may need to keep the original ring gear if you stick with the 6 volt system, but the original ring gear will fit on the newer flywheel. I have had my original engine, a newer 270 engine, and now a superchaarged 302 engine in my Dukw. After you pull the engine out once or twice, its not that hard. With two people... I’m not so sure I would do the Paxton supercharger again, but its already done, and seems to help. I would estimate my 302 is pushing min of 160hp, and maybe as high as 200 with supercharger (at certain rpms)... If you want to call me to discuss, I can help you get through any issues.... John Engelke. 5095540526
45 dukw
41 cckw closed cab cargo
45 cckw open cab cargo
44 cckw open cab leroi
43 weasel
41 ben hur trailer
45 ben hur trailer
43 M-6 bomb truck
45 M-6 bomb truck
mark III bomb/torpedo trailer
53 GMC XM-215
66 CJ-6
mark 5 bomb trailer

uglydukwling
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Re: More engine power in dukw

Post by uglydukwling » Wed Nov 21, 2018 4:13 am

It sounds like you already have what you need, but just in case, I have a couple of take-out 302s on stands and 3 or 4 more still in trucks. I also have some new engine parts. I'm in southwestern Ontario (in US terms, about 50 miles east of Detroit).

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Re: More engine power in dukw

Post by Dodgeguy1942 » Wed Apr 24, 2019 4:05 am

Finally got the newer 270 in but not a great deal of improvement. Still running original carb and manifolds though


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