Is the LS Right for my Project?

[Psyekl]

My project vehicle is a 1967 Chevy Series 60 tilt cab. It originally had an 18-foot flatbed with a liftgate that has since been removed. This is a fairly large truck with a 14,000 GVWR and 42" semi-tires, dual rear wheels on a 2-speed axle. The original engine is a 327 cu in small block mated to a 5 speed manual transmission linked to a 2-speed rear end. Doing my research, I discovered that the largest Gas engine available was a 366 cu in. This particular model was intended for city and farm work. The larger 366 gas and available diesel engines were supposed to manage highway travel.

My plan is to equip this truck with a 16-foot box and convert it into a Recreational Vehicle for cross-country touring. I have no intention of loading it down with heavy cargo other than what an RV would carry, and I do not plan to tow anything. My goal for the engine is to maximize efficiency and reliability while maintaining the power to negotiate hills and other rugged terrain. I don't need a "hot rod" or to consistently exceed 65 mph, but I do plan on dressing it up a bit with mild performance mods and "look pretties" for the occasional car shows I come across.

I'm no expert as far as engine selection, so here I am checking with the gurus and those who potentially know far more than I do on the subject:

I've been looking at an LS swap since it would require the least amount of fabrication, but I don't know if these engines would be adequate for this vehicle, particularly when mated with their accompanied transmissions. In particular I was favoring the 6.0L or 6.2L (L92/LQ4/LQ9?) since I rather liked the idea of the Variable Valve Timing (VVT), and they tend to come mated to a 6L80E transmission that looks to be pretty robust and offers good overdrive.

Any information and advice would definitely be appreciated.

A bit of background on my self: I am confident that I can manage the engine swap. I have spent several years working in a fabrication shop assisting with the construction of hot rods and race cars, including my own. I am experienced with wiring harnesses, fuel systems, EFI systems, and the other basics, but my duties at the shop were basically as a wrench-turner and computer geek/CNC nerd/CAD designer. My knowledge with the actual engines and engine performance requirements is definitely lacking- I know how they work (I can even teach a class on the science)- but I just bolt 'em in and get 'em going. I don't fiddle with the specifics: the customers or my partners always chose the engines.

[LS short box]

With a rig that size I would go 6.2 or maybe a stroked 6.0. You are going to need all the torque you can get.

[ls1nova71]

I actually can't believe I'm saying this, because I have been an LS guy since before being an LS guy was cool, and the fact that I can't stand diesel engines, but a diesel would probably be the way to go if you are really going to make that thing an RV and drive it across country. In my opinion you would need at least a 6.0 if going LS, but that is going to get horrible gas mileage in something that heavy and as aerodynamic as a brick.

Ok, gotta go now, feeling a little sick that I suggested someone not do an LS swap!

[AussieinNC]

IMHO....only choice is diesel....plenty to choose from...

Cummins comes to mind....add some boost for more fun...

Add an auto trans for drivability....

Just my 12 cents worth.

[mongocanfly]

I'm like Eric and Aussie...im a LS fan and I hate diesels, but that needs one..
Cummings,,, or I wonder if you can get some bigger in it?...dont know how much room you have to work with..
A gas burner is gonna suck for mpgs...and you'll need all the torque you can get
Btw...that is a cool truck...hope to see more of it..do you have a build thread for it?..

[jessemthompson]

I’m with the rest of the crowd here. I love the LS platform, but not for this application. I would definitely go diesel in this. An LS would not be economical at all.

[fourspeedwagon]

No idea how much space to play with down there but the always popular Cummins (no g on the end please) is a bit long. If there’s room it’d be the way to go - if not there are V8 format diesels. Also, you may check out other “box truck” engines. Isuzu, Mitsubishi, Mack, International, Hino, Freightliner and on and on. Nothing terribly traditional but if we’re going for useful these are options. Available parts out on the roads too.

[JJH Jimmy]

I agree with the rest that say a diesel would probably be best but if you are opposed to a diesel what about an 8.1 with an Allison tranny? They put them in plenty of RV’s. Fuel mileage is going to suck either way.

[Rich84]

Everyone who posted above knows way more then I do. But my 6.0 & 4L80 came out of a gigantic box truck (Isuzu).

[amberkalvin]

I was going to say it is all going to depend on the gearing you have as well. Maybe I missed it but if you have some super low gears I would imagine something with a 6 speed and maybe a 6.2 L86 would be enough to suffice?

If you're not trying to burn rubber I'm sure it would be fine plus the 6 speed would help you cruise anyhow.

I do also belive that diesel would be better though.

[kipps]

I would also recommend a diesel. Being 2wd, it'd be relatively easy to do this, since a complete engine/transmission package can be dropped in. You definitely want an automatic in this case, to avoid the clutch and shift linkage issues with that forward tilt cab. I see Cummins packages showing up for sale for 5k to 8k, that are complete with all the wiring and transmission.

Another thought, is the front axle on that truck won't handle as well as you might like. Drum brakes won't stop as good, etc. It would almost be worth finding a newer diesel powered cabover chassis, and moving that cab over onto it.

[gmc684x4]

I would look for a 6.7 turbo cumm8ns swap with a 6 speed stick

Here is a cab over stacy build back on his old show

https://m.youtube.com/watch?v=H_X9AV1ASAI

[Psyekl]

I had concerns over this...

Diesel has definitely been an option I've had on the table. In particular I've been looking at the lower-maintenance CAT engines used in military surplus LMTV's or GMC Kodiaks/Topkicks. I can actually purchase an entire running vehicle for relatively cheap and have all the parts I need. Swapping the cab over onto a newer chassis to keep the look has always been an idea.

The problem I have is that I no longer have fabrication facilities and I live states away from my friends with all of the build expertise and welding skills. A few years ago this would have been a project that could have been done economically and in short order (I even had my own plasma CNC table and access to machining), but that time has passed. I was hoping a simple GM engine swap would be adequate since it would require the least amount of paid labor for necessary modifications.

Although I have it running, I haven't had the opportunity to drive it yet, but I'm assuming the gearing is low- 1st gear is actually to the far right below reverse as a granny and 2nd gear is where 1st normally appears in the "H" pattern. As mentioned, the rear end also has 2 speeds to shift even lower; essentially providing 10 gear options. I'm including images from factory documentation I procured from eBay; I'm under the impression that this is the equipped with the New Process transmission (manual), the text provides a hint to help discern it but I don't comprehend gear ratios well enough to decide.

I know that typical gas RV's ran with 454's mated to either TH400, TH474 or 4L80E transmissions (according to my research). Typical fuel economy was expected to be around 8mpg. I know a few people with RVs and expecting 8-10mpg is typical. I'm only aiming for "average" 8+ mpg, I just don't want the 6 gutless mpg (or worse) and 55mph top speed that the current engine/tranny promises. My primary focus is that I have the power for climbing any mountains I encounter. Suspension and brake improvements will deal with the downside.

I'm still in the planning phase and saving my pennies, so my options remain open. I'm already considering a fabrication shop about 4 hrs away that shows promise in case I need to go the expensive route. Of course, I'll do as much of my own work as possible to keep costs down. I don't have a build page yet, but once I get going I do plan to keep a log.

I'm including a couple of pics of the engine bay. As you can see, I have loads of room for whatever I want to stuff in there.

For comparison: The Ford moving truck it's parked next to has a 22' box and a 446(?) gas engine. It averages about 6-8mpg fully loaded (or was that 4-6mpg?...).

[fourspeedwagon]

Ok. I’d like to change my vote then. With the information newly supplied, I’d first recommend to leave the 327 and suffer along on the steep hills. Maybe put a throttle body type fuel injection on it. Choice #2 would be big block and a gear vendors overdrive. The 366 that was available was an industrial/truck version of the big block Chevy so it’d be possible without reinventing the wheel. If you are able - 496 or 502. They really mow through the gas but that’s the price you have to pay for not going diesel.
My stupid brother has an Avalanche with 496 in it. Gets about 7 mpg empty but he has over 300k on it (which makes me think of how many gallons he’s burned in it..) but it’d push your rv box along and is a feasible/basic swap.

[Psyekl]

Originally Posted by fourspeedwagon

Maybe put a throttle body type fuel injection on it... and a gear vendors overdrive.

Whatever engine I decide to go with, I'm DEFINITELY swapping over to EFI. There are too many kits available and the prices have become far too reasonable over the years to pass up the upgrade. This truck actually came with a low-dollar EFI setup that the previous owner was installing, I removed it in favor of simplicity for getting the engine up and running.

Ah, yes- Gearvendors. I've already spent time drooling over that option!

Do the big blocks mount to the same position as the small blocks? Would I have to cut and weld new mounts or are adapters available?

[mongocanfly]

any engine/trans you change to from other than what you have is gonna require fitment mods...so id almost call it a wash on that,no matter which engine you choose..
on my C30 i had originally wanted to do a duramax swap , but the high cost of a donor engine quickly made me change my mind....the next choice was LS...which i dont regret....it originally came with a 350/sm456 and 4.10s.....if it got 7mpgs it would be lucky, and even less pulling a load...
the LQ9/NV4500 gets around 16mpg unloaded....but when im pulling my tractor, id be lucky to get 7-8 mpgs
if i had gone diesel i dont think it would have much effect on it....but again, i dont like diesels,,,very expensive to have them worked on if you cant do it yourself...
i would think the diesel box truck donor would be your best option..

[Psyekl]

Originally Posted by mongocanfly

any engine/trans you change to from other than what you have is gonna require fitment mods...so id almost call it a wash on that,no matter which engine you choose.

Supposedly, there are adapter plates to make the LS mate to the 1st gen mounts. I do assume that I may have to modify the transmission crossmember, driveshaft and I'll probably go with a rear end that incorporates the e-brakes unless I can get a truck-style on the driveshaft like it has now.

I know there will definitely be some fabrication required, I'm just trying to see what I can avoid.

[mongocanfly]

Having done several swaps with adapter plates, I can say it isnt cheap to do some of them..that's why unless your really set on a certain combination, youd be money ahead to get a engine trans combo already assembled..
If the LS is what you want, I'd go with at least a 6.0 and 4l80 ...min...
The 4l80 has a od..which trying to see your current trans numbers in your pic, you may only have a 1.00 final trans ratio..
I'd get it running and stick with the axle you have at 1st...see how the ratios do with the od...at least it would let you know how your current ratio will be.

[kipps]

After you clarified a little more, I'll modify my vote too.

I suggest leave the drivetrain intact, and look for a used EFI kit. If you buy it used, you should be able to sell it used for the same price. I see them pop up on Facebook from time to time.

Build out the box you want, and when the budget allows, move the box and the cab to a newer chassis. Most likely, your truck has a 34" frame width, which should match any newer box truck. You'll likely need to lengthen or shorten a new box truck chassis to fit your box and cab, but that's not impossible.

This method will let you get started on the box immediately, and do some limited camping nearer home. Fuel economy may still prevent you from traveling further afield.

The box truck chassis will definitely give you the best improvements in ride, fuel economy, power, braking, legality, and serviceability. I would suggest treating your current drivetrain and chassis as a make-do option for now, and just plan on discarding them in a few years.

[Psyekl]

Great advice so far.

I was researching Duramax diesel options as suggested and ran across Banks: I guess mortgaging the house for a car project isn't too uncommon among the community, right?...

https://www.bankspower.com/i-2556-en...0l-diesel.html

[Psyekl]

OK, a new option just popped up that nobody mentioned:

What about a turbo 4.8L?

The HP and torque looks decent, and fuel economy might be acceptable as well when driven reasonably. Stock bottom ends apparently handle 7-8lbs of boost and turbo kits are readily available.

I'll look more into this option to see if it's viable, but input is definitely appreciated. So far the advice has me seriously considering sticking with the 327 until I can go diesel, but I would much rather have the ease of serviceability of a gas engine if possible (really the ONLY reason I would choose gas over diesel).

[kipps]

Originally Posted by Psyekl

OK, a new option just popped up that nobody mentioned:

What about a turbo 4.8L?

I've wondered about that for a towing rig. Instead of chasing after cubic inches like the conventional wisdom would recommend, add boost to a smaller engine. I've done quite a few google searches for "towing with turbo 5.3." It's been proposed quite a few times, but there's very little info from anyone who's actually done a lot of towing with one. There's some question how well the LS platform would handle staying in boost for hours on end. Cooling would definitely need to be up to snuff. One positive comparison, is the Ford ecoboost engines have done very well at this, when using a smaller boosted engine in heavy applications. On the contrary, a lot of small Chevy sedans that have tried tiny boosted engines have not fared well. So I'm not sure how to guarantee a long-lived setup.

[LS short box]

So this may be a bit out there but how about a salvaged RV with a diesel pusher drive train? Moves the engine towards the back of the vehicle. Less noise in the cab. I have a couple of friends that started out with gas big block GM/Ford RV's and I wouldn't say they hated them power/mpg wise but after ponying up for RV's with diesel pushers they said they would never go back. COPART has many salvaged RV's
Small cube 4.8 turbo? Same cost to do a 6.0/6.2 turbo with more cubes. I would be more inclined to do a super charged 6.0/6.2. No spool up time unlike a turbo.
Just my .02.

[kipps]

Originally Posted by LS short box

I would be more inclined to do a super charged 6.0/6.2. No spool up time unlike a turbo.

Fuel efficiency would favor the turbo over the blower. Anything you can do to profitably extract heat out of the exhaust is going to benefit the overall economy of a power plant.

[truckdude239]

Consider doing an 8.1 gm swap its not an ls per say but same kind of platform