1979 GMC Dually......NEEDS MO POWA!

[Rib Tickler]

Hey guys, My Name is Ron and I`m new here.
It`s been a long time since Iowned a truck that was carburated. Any way my question/questions are What is the best way to give this bad boy more power for towing/hauling.
Here are the specs:
1979 GMC 1 TON Dually
350 4bbl 4 speed (granny low)
original 35000 kms
single exhaust
4.10 gearing

I`ve tuned it up with new accel wires, ac Delco r44t plugs, new vacuum lines, new air filter. It still needs more power, I`m daily towing a trailer that easily weighs in at 6000 lbs which my 07 chevy 1/2 ton easily pulles out to 120 kmh but the truck is way to light for this kind of pulling. My 1 ton I thought would pull this easily but even the slightest hill will make it bog down. The truck runs nicely but just seems to need more power!! I`m sure my ole 71 gmc 1/2 ton would have yarded this trailer around with no problem!
I wonder if the carb maybe needs a good cleaning, it can`t be worn out at only 35000 kms.
I have a heck of a time getting this trailer over 80 kmh, and I sure should be able to.

I`m thinking of dual exhast with an h pipe of course, a cam ( rv cam ) and removing the pollution control junk, maybe headers but I`ve never had any luck getting those darn things to seal at the head, but I know the factory manifolds suck and the ole ram horns are hard to find.

Help me..

[eventhorizon66]

Rams horns are better than any other SBC manifold, but they are still miles behind a good set of headers.  As far as leakage concerns go...look for headers with 3/8" flanges and use quality gaskets.  Use hi-temp (copper) anti-seize on the bolt threads and retighten the bolts once or twice during the first few hundred miles after installation.  Or you could even use a set of locking header bolts from Stage 8.

[SUX2BU99]

Agree with everything event' said. Don't forget that your truck had one of the lowest HP-producing motors ever with it being a 79. Right in the middle of bad-power producing era. I think the 350s then were rated at a whopping 160 HP. I might be 10 or so off. Anyway, it's a 1-ton dually. It's a HEAVY truck. So you have a wheezed-out from the factory 350 pulling around this tank of a truck that probably weighs 5000 lbs if not a little more and THEN pull a trailer. Yeah, it's got it's work cut out for it!

Freeing up the exhaust is certainly a good plan and so is a cam swap but maybe consider a head swap while you are doing the cam to really make some decent extra power. I used Fel-pro gaskets on my truck when I swapped the heads and it has headers and not very fancy ones. No leaks at all. I even re-used the same headers bolts since I figured they were worked in already.

35000 kms, wow that's nothing! Where abouts in Canada are you? With that little mileage I wouldn't doubt there is varnish or gum built up in the fuel system just from it sitting so much.

[Rib Tickler]

Thanks guys,
any recomendations on a cam?
I live in Alberta, and just bought this cab and chassis for $1200 since then I`ve put new tires , new windshield, I built a flat deck for it and just plain ole tuned it up. hey what headers are good headers? like I said I`ve been out of this game for a long time. I used to work at gene`s machine shop in saskatoon saskatchewan, so doing performance mods are in the back of my mind some where, just got to blow the cob webs off..lol

any help is appreciated.

[Dragon]

Definately would recommend a good free flowing exhaust setup(Atleast a 2.5" for Duals, or 3" for a Single)... An X-pipe would balance the system better than an H-pipe would, unless the truck is 4wd, or if money is tight for ya....   For a great price on a Dual System with an X, I would check out what the Site Store has to offer...
http://store.73-87chevytrucks.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=7&Product_Code=SGT80&Category_Code=73-87UHood Note: The setup is sans Mufflers(An additional $50), and it is for a Standard Cab, but I'm sure Chris(Capt. Kaos) can get ahold of the right system for ya (May be an additional charge for the added length).....

The RV Cam would be a good route as well, but if the Pollution Controled Equiptment is working properly, it should be causing you too much of a problem..... Because of the Trucks age, I would replace all the filters(Beyond just the Oil and Air Filters) if it hasn't had them changed in a while(PCV,Crank Case,Fuel,Charcoal Cannister, and Etc)....   Depending on how long it has been, I would rebuild the carb as well...

[dustystrucktoo]

A dually with a 350??
OK, firstly change them heads.  Find a 1990s engine and swap them.  Go to a U pull it.  I think you can handle looking at a center bolt valve cover.  If you find one with roller rockers, grab it and run with it like you stole it.  Or if not, then change your rockers to rollers.  On push rods, get the chrome moly.  On springs, stay with stock style, no double.  You aren't going to wipe out a spring doing less than 5000 rpm all the time.
I am aiming on your truck being better than mine.  I have a 400 small block and can't afford a head reconstruction for it yet.
from them heads, you are going to use the reusable aluminum header gaskets.  Full length headers, Tri - Y if you can afford and if not, then the full length headers  Run a 2 1/2 inch exhaust.  Use the X pipe connector or run two H connectors.  Oh, and make sure you put a heat shield or heat shield wrap on your starter.  If you don't, you are going to wipe it out.  I made my own, but if I had at the time the money, I would have  tried the wrap.  But at least a heat shield.  Mine is made out of stainless.
You want to spend the money and get the Performer Edelbrock Air Gap, not the RPM.  Grab a Holley 500 cfm carb.  (I use a 600cfm on my 400 and need to reduce the jet size to make it smaller.)  600 is too big.  If you were trying to hit high rpms like 7000, then go ahead with the 600 to 650,  but you aren't, so go with a 500 or smaller 4 barrel.  NO 2 BARRELS ALLOWED.  Put on the 8.8 Spiral core wires.  Use at least a Bosch Platinum spark plug.  I myself use the dual prong plug. 
Never use 87 octane.  Always use the 93... The highest octane available.  If you want to give it a treat once in a while, never exceed half racing fuel and half 93 octane.  stay away from octane boosts that auto part stores sell, Waste of money.  Put in a new fuel filter on the line and one before the carb.  On an air filter, I use a blue one.  I think it is called cool blue.  I don't know the name, got it from AdvanceAutoParts.  I am not putting a K&N on, I am not  oiling an air filter.  Gets dirty, gets thrown away and replaced. 
On oil....Yes  it affects performance.  I would advise and use Redline 15w50.  Though only 4 quarts of it.  I also add in one quart of Lucas Synthetic.  I also use the Mobil Oil Filter that is black.  I used to use the PureOne, but I need as large of a filter that I can find that will do the best on filtering without causing any clogging..  My engine don't need cleaning, because I don't have crud built up of old tar oil in my engine.  If you do, you really need to flush out that engine and follw the directions that Gunk gives on the bottle.  That tar like black remnants of oil and carbon keep your parts from being lubricated, and as well affect fuel and air flow, let alone how the oil flows.  Drop the oil pan and clean it out.  Make sure the oil pump filter mesh is clean as well.  I don't suspect you want to have junk up in there waiting to clog up an oil passage.  It is a pain in the wazzoo, but I got the rubber reusable oil pan gasket.  No leaks
OHHHH  not to forget the most overlooked in performance.  Change your tranny fluid.  If you gotto, flush that old oil out and put in some good clean fluid.  Throw in a bottle of Lucas.  I like the synthetic temperature increase of  tolerences, as well as the shock and shearing resistance.  And of course, the rear axle.  Unbolt the cover, drain it out and wipe the inside out.  If you have the time, then teater totter the rear end to get as much out of the axle shaft tubes that you can.  On additives for the axle and the tranny, I do like the lucas.     I do need to look into STP, considering I have a sticker on the  back of the bed.  But, at least you have knowledge of my experience and I don't have a problem with performance, nor of towing.  Not only do I have a 2 1/2 inch exhaust , use the 1 5/8 primaries, and have two H pipes, but I also have a Corvette C5 muffler system.  The mufflers sit behind the rear tires, the inlet and outlets are on the same side of the muffler.  I do have stainless shields wrapped around then so that they don't get damaged from debris and don't heat up my wiring   Corvette Exhaust is not a requirement, but dang it sounds and performs great.