Boosting a SBC for towing

[Randy67]

Basically I am wondering about the feasibility of boosting my 350 in my 79 GMC Dually standard cab longbed. I am towing a 28ft Horton enclosed v-nose trailer with this truck and would like to improve its power. Either that or would an engine swap be a better choice. Here is the truck and trailer I am dealing with:


The 350 does a decent job but does struggle a bit on hills. The truck has the SM465 transmission along with 3.73 gears. Truck weights 5400 lbs, trailer is probably 8 to 9000 lbs loaded (GWR is 10K), haven't had a chance to weight it yet.

I am looking for improvement in the idle to 4500 rpm range, currently it tows best at 2800-3000 rpms, which is 65-70 mph per GPS. No plans for an overdrive yet as the 350 just won't pull the trailer in OD. Here are the options I have currently see:

1. Supercharger, either a roots style which would give good low end power, or a Centrifugal style, which would probably work better in midrange.

2. Turbos. This interests me, but could end up being a more expensive build. I believe it would give me the best towing power for a gas engine, but I could be wrong.

3. Throw in the towel and put a BBC back in the truck, it originally was a 454 before I got it. I helped my buddy I got the truck from swap it to a small-block, he was looking for better mileage and wasn't towing heavy stuff. He suggested a 402, to get more power without totally killing the gas mileage.

4. Swap in a late model Diesel, Duramax or Cummins. This would be my favorite, but it would be cheaper just to sell my truck and buy a Diesel truck.

For the sake of this discussion only, swapping an LS motor is not in the mix. Again, at this point it would be better to just get a newer truck with a 6.0 or 6.2L. I do enjoy the cheap tag and insurance on the 79.

The one thing I do worry about boosting the SBC, is on long hills (like Mont Eagle in TN and hills around North GA) that the constant boost may be hard on the bottom end, leading to a short engine life. Maybe it isn't a problem, but I don't want to overlook anything. So let me know your thoughts, this isn't something I am doing anytime soon, more of a brainstorming session. Randy

[srh3trinity]

You could consider a cam and gears. There is a guy in my area that swaps bodies onto older rams with Cummins. I have talked with him about doing a square bodied crew cab one day. That would be my pick.

[Randy67]

Forgot, the 350 does have a mild cam in it, just not sure what it is. Also has 492 angle plug big valve heads, with exhaust manifolds and dual exhaust. Originally we thought the truck had 4.10s but found 3.73s when I changed the gear lube.

[SLO_Z28]

Never tow in overdrive. If it were my truck (and smog exempt), I would throw a set of vortec heads and a comp cam in it. For ~$1000 you could have 450# to play with, and that should be sufficient for that trailer.

[Chevelle598bb]

Throw a 454 in it and be done. Zero deck, 9 to 1, small cam (210-220 at .050), stock intake or performer, exhaust manifold if you don't want to run headers and peanut port or large oval port heads. It will make massive torque from idle to 3500 and pull the trailer better than a boosted 350. You could build a close to stock 454 for less than you could buy a blower. As far as the 402 gas mileage over the 454. It would be so close you probably couldn't tell but would be loosing 50 ftlbs or so.

You may run into detonation issues with a boosted small block under high load and low rpm. Especially with the standard trans.

[Randy67]

I figured the 454 was the best option, just wanted to explore other options. Budget is thin as well. It will be at least next year before anything happens though. The 350 will have to do for now, but I have considered the Vortec heads.

Don't worry James, I would have to have an overdrive to use it.

[BrianP]

I've always thought it would be neat to plop a 472 or 500 Cadillac motor in an older truck. Their 4.25 stroke cranks and small combustion chambers help create a lot of low end torque.

[TheJDMan]

Did you say is has exhaust manifolds? The first thing I would do is install a set of 1 5/8 primary tube headers preferrably a set with a 3/8" thick flange.

[jokerswild454]

Go for it and just swap in a Duramax. You'll get the mileage you need and the power in one package.

[TheMeat]

Did you say is has exhaust manifolds? The first thing I would do is install a set of 1 5/8 primary tube headers preferrably a set with a 3/8" thick flange.

+1 ^

[LS1NOVA]

$1000 used Miniblower.

[Randy67]

Headers may be in the future, depends on what I decide to do. As for a Duramax, I would most likely just buy a newer truck with one. I would like to have 4-doors too for the extra room. This truck fit my budget very well and does what I need it to do. Plus the parts are cheap for it and readily available.

Nathan, a buddy had a miniblower for a good price a while back, but he sold it before I got this truck.