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'46 2 ton - 350 swap advice?
#1375424 Mon Aug 31 2020 06:23 PM
Joined: Mar 2020
Posts: 3
D
Moderated
Hi everyone. I joined this site when I got my 1946 Chevy 2 ton dually back in March. It has a 235/4 spd in it right now that runs pretty well. But, being a college student for diesel mechanics, my mind is always taking the next step further. So I went ahead after a little research and bought a 1990 GMC Sierra with a 350 TBI/700R4. As far as I know, the hardest part will be figuring out the exhaust manifolds and mounting everything, as well as fitting a driveshaft onto it. My plan is to use the gas tank/hangers off the '90 and mount it on the side of the frame to keep the in-tank fuel pump the TBI requires, as well as swapping over the master cylinder/brake booster. I'm hoping I'll be ok with the stock steering system with the added weight of the 350. I'm very familiar with TBI systems and all the wiring included. Any advice is appreciated. I'm looking forward to starting this project!


1946 Chevy 2 Ton Dually - 350 Swap Project
-235 I6 Loadmaster, 4 Speed Bolt Action, 2 Speed Rear
1990 GMC Sierra 1500 - PARTS
2002 Subaru Forester - Daily Driver
Re: '46 2 ton - 350 swap advice?
Darth Plasma #1376548 Wed Sep 09 2020 10:24 PM
Joined: Mar 2020
Posts: 3
D
Moderated
Anyone?


1946 Chevy 2 Ton Dually - 350 Swap Project
-235 I6 Loadmaster, 4 Speed Bolt Action, 2 Speed Rear
1990 GMC Sierra 1500 - PARTS
2002 Subaru Forester - Daily Driver
Re: '46 2 ton - 350 swap advice?
Darth Plasma #1376590 Thu Sep 10 2020 07:17 AM
Joined: Mar 2000
Posts: 1,391
Red dot, center of chest ...
The 350 weighs less than the 235 (about 575 lbs vs 630 lbs [gomog.com]) and the 700r4 weighs a little more than the 4spd, so weight shouldn't be a problem. The two combinations are about even weight-wise. You can get a driveshaft made up once you have the dimensions figured out, so that shouldn't be a problem. I assume you're changing the rear end out, because the original torque tube isn't going to work at all. So, you might want to look at mating up the rear end off that Sierra to your '46's new drive train. (Check the axle length to make sure it will line up. You may have to have the axles shortened. The older trucks had a shorter overall width.) You may be able to roll the Sierra rear end with springs and shocks under the '46 frame and fabricate mounts for everything, but you need to check all your measurements carefully. You don't want the rear tires rubbing on the fenders.

To do all this is going to take some fabrication. You'll need engine mounts, a transmission mount, and axle and shock mounts for the rear. The original front steering would probably work, but you may find you prefer power steering, in which case you could rob the Sierra for that as well. Brakes are a different issue. They didn't use dual master cylinders back then, and they were shoe brakes (not disc) all the way around. You may want to convert the front brakes to disc, in which case you would have to have a dual master cylinder, but none of that stuff is all that hard to find. You might even be able to figure out how to use the Sierra setup, although space under the hood will be at a premium. (My master cylinder is mounted under the floor on the frame, where the original one was.)

With enough money and/or ingenuity, you can do almost anything you want. I'm sure some old hands with a lot more experience than me will come along and give you the straight scoop.


Paul Schmehl CI 12
geek@stovebolt.com
Stovebolt Staff: Geek
1948 Chevy 3100 Five Window [stovebolt.com]
Re: '46 2 ton - 350 swap advice?
Darth Plasma #1376610 Thu Sep 10 2020 12:23 PM
Joined: Apr 2005
Posts: 9,023
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
Paul is pretty much on point with his advice. You are going to be challenged by the exhaust manifold interference with your steering. There are manifolds that will work with a little creative routing. Good luck.


Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne 4dr 230 I-6 one owner (I’m #2)
‘39 Dodge Businessmans Coupe
USAF 1965-69 Weather Observation Tech (got paid to look at the clouds)


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Re: '46 2 ton - 350 swap advice?
Darth Plasma #1376621 Thu Sep 10 2020 01:38 PM
Joined: Nov 2005
Posts: 5,768
3
3B Offline
Master Gabster
Hy Guys, this is a two ton truck he is asking about, I'm pretty sure it is an open drive setup, and anything less than a 3/4-1 ton rear axle should not even be considered as swap bait for this project.

Re: '46 2 ton - 350 swap advice?
3B #1376637 Thu Sep 10 2020 03:52 PM
Joined: Mar 2000
Posts: 1,391
Red dot, center of chest ...
Originally Posted by 3B
Hy Guys, this is a two ton truck he is asking about, I'm pretty sure it is an open drive setup, and anything less than a 3/4-1 ton rear axle should not even be considered as swap bait for this project.
That's why I depend on the experts. First, I assumed (yeah, I know) his Sierra would be a 1 ton at least, and second, I wasn't aware that '46 trucks had open drivelines. That being said, he'd still probably have to have a new driveshaft made because the location of the tailshaft on the 700r4 is going to be different from the original manual tranny. And I'm pretty sure that rear end is going to have to be shortened to fit under the '46.

All of this can be done. It just takes a lot of work and a lot of fabrication to do it right. And, as Justhorsenround points out, he'll probably have to fabircate headers to fit around the steering, especially if he goes with power steering.


Paul Schmehl CI 12
geek@stovebolt.com
Stovebolt Staff: Geek
1948 Chevy 3100 Five Window [stovebolt.com]
Re: '46 2 ton - 350 swap advice?
baldeagle #1378087 Tue Sep 22 2020 05:49 PM
Joined: Mar 2020
Posts: 3
D
Moderated
Thank you, Paul. I should have mentioned that the Sierra is a 1/2 ton, and I intended on using the original 2 speed rear. Indeed I will have to get a custom driveshaft made up, id like to keep the 2 piece driveshaft setup too. I was curious about the weight of the swap setup when deciding on power steering, but I’m hoping it’ll be fine keeping the stock steering. Any resources on front disk brake setups or upgrading the rear drums? I’m thinking of a way to use the Sierra master cylinder under the cab where the stock one is mounted


1946 Chevy 2 Ton Dually - 350 Swap Project
-235 I6 Loadmaster, 4 Speed Bolt Action, 2 Speed Rear
1990 GMC Sierra 1500 - PARTS
2002 Subaru Forester - Daily Driver
Re: '46 2 ton - 350 swap advice?
Darth Plasma #1378140 Tue Sep 22 2020 11:55 PM
Joined: Feb 2004
Posts: 21,033
H
Boltergeist
You're pretty much on your own on disc brake conversion parts on anything bigger than a 3/4 ton, and even 3/4 T systems have only been developed recently. Obviously, any 1/2 ton brake parts on a big rig will be way under capacity. What's the fascination with disc brakes in the first place? Most of our big bolt guys just rebuild their original brakes to "as new" condition. Unless you're planning to go into the trucking business on the side, it's unlikely you'll ever have the kind of a load onboard to make use of all the brake capacity you've got right now. My grandfather's drivers hauled beer from Milwaukee and St. Louis to Nashville with 1934 Chevy tractor-trailer rigs, with vacuum-boosted mechanical brakes on the trucks, and NO brakes on the trailers. In the 1930's practically all the roads were 2-lane, and some of them were unpaved. "Interstate highway- - - - - -what's that?"
Jerry


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