Would a turbo system help a 1 ton, carb'd, GM truck that hauls heavy?
We're talking about 10-12000 lbs total weight. Would it help mileage and power?
What system or turbo would you reccomend?
This is for a friends truck, not mine.

 

Which motor/trans?

 

Mileage no, power yes. The issue you need to manage is thermal load. Most of the guys here are wide open for 8 seconds then shutting down. You're pulling a trailer over hills, you're going to need a good intercooler, oil cooler and radiator. I'll get back to you with more details...heading out for dinner.

 

Which would work best? He has 454's and 350's. TH400's and 4L80E's. The truck is 4X4, with low gears.

 

The simple answer to do what your friend wants to do is to pick up a used factory turbo-diesel truck. This would be the easiest path to achieve the objective reliably. This would be the common sense approach. If he wants to keep his truck, put some money into a warmed over big block, it will suck fuel, but it can tow the load reliably. If he's looking to play around with a turbo, and doesn't mind spending a lot of time and money putting everything together and is undeterred by the very real possibility of destroying a motor...then read on.

What does your friend have and what is his budget? Since GM went TBI fuel injection in the trucks in '87, I'm guessing you've got a pre-'87, probably worth $2500 or less depending on condition...so this is sounding like a budget build but reliablility is key. Correct me if I'm wrong.

Unless he's modified the truck, he's got a TH-400 3 speed auto or a Muncie 465 4 speed with a granny first gear and full floating rear end (if it's a dually, probably a Dana 70; if single rear wheel, corporate 14-bolt). If it has 4 wheel drive, likely an NP205 t-case and a Dana 60 up front. Aside from the 465, these are all beefy parts, suitable for moderate levels of boost if in decent condition. Not saying the 465 is weak by any means, but I'ld rather run the TH-400 with a turbo. If the trans is tired, it may need a freshening before throwing some power at it.

I'm guessing he's not looking to build a $5000 forged motor for this project so the big question is what's under the hood? 350 or 454? In either case, it's probably low compression (good) and if he got lucky, some of the 1-ton motors have forged cranks. If he's got a low compression 454, this would be the best starting point. The crank, and rods are beefier than the 350 and the extra displacement can make more power with less boost and less rpm. Yes, you can get insane amounts of power out of a small block, but for how long? Push 6 to 8 psi through the big block with the right tune and you should see a 40-50% increase in power and the engine should be able to live for a while if it was in decent shape to start with. Same goes for the small block, just less power for a given level of boost.

The truck motors were cammed for low end torque and economy. The intake valve closes shortly after bottom dead center and there is not a lot of overlap....should actually work pretty well with boost. Probably has a fair amount of miles on the engine which has worn the bores a bit which helps to open up the ring end gaps. The bearings have worn a bit and have looser clearances which can be a good thing.

So without spending a lot of money, he might have a suitable motor for low to moderate levels of boost. The thing that will kill the rings, pistons, and bearings fast is detonation. Too much timing, not enough fuel.....boom, this motor will need a rebuild. A fresh, purpose built forged motor can't take much detonation, a worn stocker with hyper pistons, much less. He might want to get a knock gauge and plan on spending time and money upgrading the fuel delivery system, fuel lines, fuel pump, etc. He's going to need a carb set up for boost. Yes there are things he can do himself, but unless he's a carb genius, spend the money and go with a CSU or something similar so you have a chance of getting it to run right. These carbs are not cheap. He'll have to figure out the spark curve. Find a reputable tuner to get the carb and timing right. This will be money well spent. Also he will need to make some changes to the pcv system to get it to work under boost, check valves, etc. Do a search, there are some good articles on this site pertaining to this issue. Many of the one-tons had hydro-boost power brakes. If so, great. If not, there may be issues with the vacuum assist.

Now you've got to turn to plumbing the hot side and the cold side. The one plus is you've got a bunch of room under the hood of these old GM trucks. The next question is what kind of fabrication skills do you have? Are you good with a welder? If not, you're going to need to find someone who is because it is unlikely you are going to find an off the shelf kit for this beast. (That used turbo-diesel is starting to make sense isn't it?) You'll need to decide to run twins or a single. Aside from runing a cross over, a single is usually cheaper and easier (one turbo, one wastegate, one downpipe, one compressor outlet to route to your intercooler. Intercooler for 6-8 psi? If you're towing, yes. You're going to have to work to make it fit and the IC may adversely affect the cooling efficiency of the radiator. You may find that towing in the heat under boost will overburden and overheat your cooling system. Now your looking at a larger/better radiator, more fans etc. As temps climb, back off on the boost, or upgrade the cooling system.

The details of turbo, wastegate and bov selection have been covered pretty thoroughly on this site. Use the search button to come up the curve. This application will be a bit different than most. For towing, he'll want a tight converter, and a turbo that will deliver more on the low end. After doing a fair amount of research, contact some of the turbo vendors that help sponsor this site. They can help make a proper turbo recommendation for this vehicle and its use as well as supply many of the parts needed to put this project together.

 

I realize you said carb, but if you've got access to used GM parts which it sounds like you do, you might want to look at going EFI to control fuel and spark under boost. Check out www.dynamicefi.com. You can take a GM TBI truck computer and convert it to port with tables to control fueling and spark up to 15 psi. You can do it cheaper than getting a blow through carb set up and you've taken care of spark as well. Lots of options for port manifolds and injectors for 350s and 454s.

I converted an '87 Suburban from TBI to port with an EBL from Dynamic EFI and ran a RamJet 350 with it. Currently, I'm running a 502 with it and it works great. VE learns, datalogs, instrument panel on your pc realtime...it's an incredible value at around $350 to $400 depending on which options you go with. He modifies the guts of the factory computer and you can set all the parameters for spark and fueling by hooking up your laptop. EBL Flash means no burning chips, very slick. The only thing it won't do is control a 4L80E if that is what you are planning to run.

 

WOW, thank you very much Torqued. I will print that and give it to him.
A little background on him. He's in his 70's, was a hotrodder/dragracer/dirt oval racer/sledpuller in his time, with championships, so he's no stranger to performance. Was a GM mechanic, and automotive shop teacher (where I met him). Has personally met or spoken on the phone to some of the icons of motorsports.
BUT, he's oldschool and doesn't understand the electronics. Thats the main reason he has the older GM's. He rebuilds them and uses them in his salt brine business, spreading brine for ice and dust control.
I think he's mostly looking for mileage gains, but power is always welcome.
We really appreciate the time it took to type all that out, thank you.