The Stovebolt Site Forums The Parking Lot Big Bolts 292 or 350 for 1954 Chevy 6400 grain truck

Hello, I'm new to this forum and antique cars and trucks as a whole. I have a 1954 Chevy 6400 grain truck that I still use to take some grain to the mill and haul about 100 bales of hay between farms. The truck is currently very original with a 261 engine, an SM420 trans (I'm pretty sure, has a 6 digit number starting 59.... on driver's side and a low low first gear), and a single speed rear (stamped 288 with 10 bolts on the pumpkin and dual wheels with 7.50x20 tires and split rims). The trucks runs fairly well but struggles going up hills with a load. It's GVWd at 16,000 and I routinely load it to about 14,000. I would like to put a slightly more powerful engine in this summer while keeping the trans the same--eventually I'd like to find a 2 speed rear for it because she tops off at like 35 mph...So keeping in mind what I intend to use the truck for, what is the most practical swap? I have heard good things about the 292 and the 350 and from my little bit of research it sounds like the SM420 will bolt up to either engine provided I use the 350 style bellhousing ( I think novak sells one with the 4 11/16 center hole, #Kit 3899621-K. The crossmember that supports the bellhousing in the 54' should also work, yes? So that just leaves clearance issues with the radiator and steering box, and front motor mount adaptation, right? I have read that with the correct exhaust you can make the 350 fit without moving the steering box. Will the clutch and associated parts commonly used with the 350 work with the SM420? Overall, which engine would be easier to swap in and which is more suited for the life of a grain dump truck? Thanks all,

Pete Markel

Hi Pete, welcome to the site! I thought the 6400 series all had a 2 speed rear, but, I suppose they could be ordered either way! My 58 viking 6400 has a 327 in it, (and SM420) and a 2 speed rear end. I towed my 35' vintage travel trailer from Seattle, Wa. to Tulsa Ok. and back last fall and even with the 327 in it, it struggles going up the hills. I do run a gallon of diesel in the tank (1 gal in the stock 17ish gal tank) and it has more power than straight gas (trick thanks to Jerry on this forum, a.k.a. Hotrod Lincoln)

My 327 does not have quite the power a 350 will, especially if you build the 350 and not just use a 500 $ engine that was laying around in someone's shop!

That said, my engine compartment is different than yours so, I can't answer about steering fitment and stuff, but I am sure others will chime in soon with more information.

As far as bellhousing, you need a cast iron one from a truck with a V-8 in it anywhere up to 1967. They switched to the SM465 in 1968 and that has the larger bearing retainer so, larger hole in bellhousing. clutch etc from the V-8 will work fine with the SM420.

Most of the time, the 2 speed rear is slow and slower so, verify gear ratios! You may look for an over/under aux trans off a larger truck to adapt in there.

A 350 can be installed. People do it all the time, but It requires moving he steering box. I don't know what your expectations are, but a good running 261 wasn't a bad engine. If it is a single speed axle, I would suspect that it was a special order for a fire truck or government vehicle. Two speed ratios were either 5.83/8.10 and 6.33/8.81 which is not that much difference. We used to use two tons in our business over 60 years ago and they would run 60 all day long. GM used their proprietary Eaton two speed that was vacuum shift. They were a headache when they were new and they haven't gotten better with age. Ford, International and Dodge used electric that worked. 400 series and Larger GMC used electric shift. If I were going change, I would look for an entire axle with electric shift two speed.. I have sold several vacuum 2 speeds for scrap iron.

The 350 would be a much easier swap since a 292 is physically longer than your 261. Bell housing pattern on the 350 and 292 are identical. You DO NOT have to move the steering box if you use a 1955-56 left side exhaust manifold. I would try the V8 before getting into rear end swapping. Since fuel mileage is not a concern with a work truck one could even use a 400ci small block which has a big torque advantage over a 350 and is identical external size. Both the 400 sb and 292 are gas hogs.

Yeah as far as expectations go, I'm not expecting a miracle. I would just like to be able to stay in 3rd gear going up the slight inclines and hopefully not lug the engine down as often. As far as the top end speed, going 60 didn't hurt anything in the drivetrain? On my truck once you get to like 35 or 40 it feels like the drivetrain is overrunning the engine if that makes sense--like a flywheel effect. Maybe that's normal on a 60 yr old truck with such low gearing? Are those 55-56 left side exhaust manifolds still available or sold aftermarket? What's my best bet for motor mounts? Some of the old threads I have read said that some of the kits weren't really strong enough to take the torque of a 292?

I'd keep the original engine and install a 3 speed Brownie. The 261 has enough power to keep the truck moving- - - -it just needs enough gears to keep the engine in its best torque band. With 12 speeds instead of 4, and an OD top gear to improve the road speed when running empty, you've got a lot more gear options with a lot less work and expense. There are usually a few available on Ebay, and some of the older truck salvage yards might have some stashed away.
Jerry

I have a '59 Viking 40 with a 292 and a '69 C50 with a 350. The 350 has a lot more power. I would choose a 350 over the 292 if I were swapping engines. A 350 will be easier to find parts for if needed. It's not going to be the easiest swap either way. If you want the simplest solution maybe rebuilding the 261 and changing out the gearing like Jerry suggested would be the way to go.

If you are up to the challenge, I would go 350 or 400 as Evan had mentioned.

John

From the perspective of those of us who tried to keep those 400's running back when they were new, it would be difficult for somebody to give me one of those things. Putting 400 cubic inches into a small block is a step too far. That 4 1/8" bore size makes them hard to cool, and blown head gaskets were a pretty common failure.
Jerry

I agree with HRL, the 400 small block would not be my choice for a hard working truck. It would provide a nice torque range but not at the price of other issues it historically has. A well built 350 or 383 would be the least expensive and very reliable.

Yeah I think that's the direction I would like to go. Now maybe this is a dumb question but are all 350 sbcs the same or do they differ based on application-- is a 350 out an old car the same as a 350 out of a truck? Also what exactly.is a 3 speed brownie and how is it mounted in the driveline?

A "Brownie" is slang for a Brown-Lipe auxiliary transmission that mounts on crossmembers between the main transmission and the rear end with two short driveshafts. There is a separate shifter in the cab. Other auxiliaries are made by Spicer, Dana, and a few other manufacturers. Most of them have an underdrive, direct, and overdrive ratio, so each main box gear has three ratios available. When the engine starts to lug down in direct drive, you can shift down a little instead of dropping a whole gear. It's much simpler to drop half a gear and keep the engine in the right torque band, with 12 forward speeds instead of 4 to pick from. You'll also have 3 reverse ratios.

Yes, car and truck 350's are basically the same, except for the 4 bolt main bearing engines used in medium duty trucks and factory hot rods.
Jerry

Is a brown-lipe durable enough for a 16000 gvw?

The block casting in my 1978 Corvette is the same casting number that was in my new 1976 K20, that was a 4 bolt block. I built a 383 from a 1977 block with the same casting number that came out of a C10 and it's a 4 bolt, I'm betting the Vette has a 4 bolt block but I've never dropped the pan for any reason. I built the 383 to transplant into the Vette but now have decided to leave it stock. Any 350 should do you just fine as long as it's built correctly and to stroke it to a 383 adds great low RPM torque. The iron could contain some different percentages of tin and nickel but other than that and 2 or 4 bolt mains all of the parts are cheap, plentiful, and interchangeable.

The stamped engine serial number ahead of the passenger's side cylinder head will have a letter code at the end of the number containing a "T" on most, if not all of the 4 bolt main bearing blocks.
Jerry

Pete,

Brownies come in sizes dictated by torque rating of the engine: 5500, 5800, 6200, 7000, by dropping last number of model, I. e. 5800 unit capacity is 580 ft.
lbs. of engine alone. Ratios can be found by googling, denoted on unit by letters after the torque rating. Uses standard bearings, no output shaft seal, reverse threads, not a problem. Standard Speedo output on rear.

I have several that had larger engines and running gear larger than stated, one concrete mixer truck with big GMC V-6 engine with 5500 Brownie.

No ‘speed shifting’ these, unsynchronized, but are easy to shift using common knowledge!

Search yard oneself, if call, they will not know what you are talking about. Look for extra shift lever in cab. Make sure and get shifter and rod ends, rods are easily made with water pipe or EMT.

7000 and 8000 models are semi truck size, 5000 and 6000 are big enough for most common size trucks unless a ‘hot rod’ truck. They are heavy, use rubber mounts, one mount is circular, other mount handles the torque. True-Stop disc brakes were integral from factory, pad relining is available in Denver, CO area. Most were removed with the advent of Spring Brakes, so spare discs are uncommon.

Ed

I’ve got a series 2 ‘55. Years ago I took out the six cylinder and put in a 350. Best decision I made. It is the only big truck I have without the original engine, but that electric choke and the power make me love it. It doesn’t haul grain any longer - scrap truck, post truck, rock ruck - you name it, but no grain. I’ve got three other old straight trucks for that.

Someone told me it was a mistake - that 350 wasn’t built to haul loads like those old sixes. It does great, though. I don’t over-rev it and don’t overload it. If someone gave me another 350 the 270 in my 58 GMC would belong gone.

FYI - don’t swap to a late GMC rear end with the electric shift (like my 58). The shift motor went out, I can’t find another, and it’s stuck on the high side forever. The six does not like that!

Pete Markel That suggestion of 383 sounds good ,the added torque would help you. The brownie is an in-line added 3-speed that would give you 12 ratio's. Think I would try the 383,then you could find a bolt-in 2 speed axle that wouldn't be too much trouble to put in. Give you 8 speeds forward and 2 in reverse LOL .Seriously you will use your 2-speed in reverse if you need to back very far. good luck.

Pete Markel The brownie is made for truck use,shifter take some doing,would use a 2 speed axle that is electric shift for simplicity ,have to study ratio's to get what would work best for your application. With brown-lipe you'll be a "2 sticker" where you run your arm thru the wheel and shift em both !!! You know like the big boys ,hmm glad that's over for me !!

The guy who taught me to drive a Brownie told me if he ever caught me with my arm through a steering wheel he would break it for me- - - -just to show me how it felt for the wheel spokes to do it after hitting a bump or rubbing a curb while shifting!
Jerry

I have several leads on 350 engines in my area for fairly cheap. I also found a number of the 1955-56 V8 exhaust manifolds on eBay. It looks like they were used on corvettes and with 265 engines? I read another thread that the exhaust ports are a little smaller on the 265 manifold. Will that hurt the performance of a 350 or is it a neglible difference?

At any sane RPM the port size won't matter. It's also possible to bolt a 350 exhaust gasket to the manifold and open up the ports with a die grinder.
Jerry

Ok thanks that's good to know. The next question I have is about the flywheel and clutch setup. One of the engines that I can get reasonably is about a 78' I think. The owner used the flywheel for another project. Should I just be looking for a standard 168 tooth flywheel to put on? And should I go with a regular car/pickup style 11 or 12" clutch or could I get a button clutch for something like this. Reason I ask is because we have a button clutch in our GMC topkick and I was told all the big trucks use that type of clutch...

I believe the pressure plate bolt pattern for the 12" clutch is on a wider radius than the 11", but if you can find a flywheel that's drilled for it that's the one to use. That extra 1/2" of facing material radius and the bigger pressure plate makes it much more effective if you're doing real truck stuff. Don't use a flywheel for a small block 400- - - -it is off balance to compensate for the longer stroke crankshaft and it will make a 350 vibrate.

Here's a complete kit- - - -flywheel, clutch, pressure plate, and accessories:

https://www.ebay.com/itm/133795601787?

Jerry

I think my clutch was listed as a 10 1/2 inch, I wanted to replace with the original style, which is a Borg and Beck style, not a diaphragm style. I don't have a bit of trouble with it, had the original flywheel cleaned up at the machine shop. You should be good with a stock flywheel and matching clutch. Dito on the 400 flywheel, can't be used on the 350.

Jerry, thanks for the link for the kit, that should bolt up ok to a 70s engine? Novak sells a new bellhousing that will accommodate up to a 12" clutch so I figure I'd like to put the largest one in I can fit since this truck would be weighing anywhere between 11 and 16k pounds when loaded.

I think so, but it would be worth a phone call or a "message to seller" on Ebay before ordering the kit. Anytime a truck works for a living, "heavy duty" parts are usually a good thing.

I don't know what Novak charges for that 12" bellhousing, but here's a "reman" on an Ebay auction that looks brand new. It's aluminum, so a rear transmission support would be needed to use it safely. Hanging something as heavy as a SM 420 off anything other than a cast iron housing is a little risky.

https://www.ebay.com/itm/154376588517?

Jerry

Pete Would be a double syick

Pete Brownie bolts in drive line with another stick to shift it,truck 350 might be built a little better for truck use. The big blocks even had another piston ring for heavy use !!