Inliners International Forums General Discussion Engines Newbie with 302 questions

Hi, I'm new here and after reading all the topics about 302 engines I think I should tell something about me.
My name is Gerben Faber and I'm from the Netherlands in Europe.
English isn't my first laugage, so excuse me for making mistakes.
I have a militay GMC amphibious truck called DUKW from 1944. Original it came with the 270 engine, but the previous owner Jack Tomlin from Toeele Utah put in a military 302 to gain more power to drive it on the road.
But with nowadays traffic I think it's still to slow. I read somewhere on the web that the civilian 302 has more power. But it needs changing the from enginemount Does any of you guys have more info on this?
There is a civilian 302 from 1955 on Ebay now for $3000. Is that a fair price? Or should I go a different route? I would like to keep the original look in the engine bay.
Thank you for your input, Gerben

Welcome, Gerben, to our international conversation!

Military and civilian 302 blocks are different, but i am not aware of any significant difference in power between the military and civilian 302 engines. Certainly, the power potential is the same.

Does your engine still have the governor that was installed on all GMC 302 military applications? Removing the governor would allow the engine to run faster. The military 302 can be modified for more power in the same ways that we modify other GMC engines. Cylinders can be bored for increased displacement. Four-barrel and multiple-carburetor manifolds are available. Head modifications can make a significant difference in power. The camshaft can be reground.

In your amphibious truck, the greater obstacle to increased speed on the highway is differential gearing. These kinds of vehicles are not built for speed, but rather for strength and endurance in diffcult terrain under difficult conditions.

God's Peace to you.

d
Inliner #1450

Gerben welkom. Uw Engels is veel beter dan mijn Nederlands...

I agree with Don. I don't think there is any difference in RPM potential with a civilian 302. And I also agree that gear ratios are key to top speed. But with a DUKW you have 6 wheel-drive so there are three different gear-ratios that would need to be changed - two differentials and a transfer case!

Sounds expensive to me.

There is a site that specializes in second world war GMC:
The GMC CCKW Site

including a page that talks about going faster:
Going Faster in a CCKW or DUKW

Hartelijke groeten,
stock49

Hi Gerben!

I would suspect that your issue might be more related to a very high output rear end and slow gearbox rather than the engine?
If it can rev OK then the speed limitation is otherwhere in the drivetrain.
I believe the gmc straight sixes were governed up to 3500 RPM, but i'm not sure.
If you are going to change your engine i would be interested in buying your other 302, i'm located in Sweden.
Take care!

Thanks for your replies and advice.
I should have made it more clear that I need more horsepower for uphill speed. The topspeed of the dukw is fine with me, but to reach the top of a hill in 2nd or 3th speed with about 15 to 20 mls/hr is not frustrating for me but more to the modern cars behind me that can't overtake me on the secondairy roads.
We had a amphibious meeting this summer in Norway and sometimes there were about 30 passenger cars and trucks behind me waiting for me to go out of their way, so they could move on with normal speed.
Perhaps it's better to stay on the water, there are no hills

Don, the governor is gone on my engine, so no problem there. I have to look into the engine to get more horsepower. I'm not an engine guy, so perhaps I will get some help for that in my area.

Stock, I know these websites you sugessted, that's where I found the difference in hp for the civilian and military 302.

Gerben

You can't believe everything that you read on websites . . . even this one!

i can tell you that my built 302 military block with a 4-inch bore (320 cid) made 265 horsepower and 362 foot-pounds of torque. That is an engine built for street driving, not racing. A properly built 302 will pull your amphibious rig wherever there is room enough to drive, but with the stock gearing it will necessarily be slower than you would like.

God's Peace to you.

d
Inliner #1450