1986 gmc k1500 4x4 350 tbi swap?

[4Xsquare]

Hey guys I'm new to the forums here, and in need to some guidance on what to do. I picked up a 86 k1500 a few months ago with 4x4 reg. cab long bed, with a carb 305 motor and and th700r4 pushing it. The tranny is in ok condition, from the sound and the feel of the motor the days are numbered on it. So it puts me in the position to start looking for better motor to put in it. The truck was sitting for awhile judging by some of the parts needing to replaced. I would put a carb 350 in the truck with the 700r4 rebuilt but from have one prior to this truck in another truck that motor and the 305 got terrible mpg which we all know gas is going up in price so I was looking for a new fuel induction platform. I began looking at a 5.3 vortec swap with a 4l60e but doing research found that the swap was to heavy for my pockets, so began looking at doing a non oem 350 tbi swap into the truck with a tougher 700 behind it. Now getting to what I need help with, I want to put a 350 tbi with some mods to the motor and convert it over and a cheaper budget. All I rlly want out of it is 300+ hp out of it with atleast 15mpg out of it. I have most info I need for the swap such as a new distributator, new ecu, new wiring harness, fuel rails, exhaust with atleast 1 O2 sensor, for the heads I'm putting vortec heads on it with a eldablock intake manifold with a soup bowl a modified gm tbi with upgraded injectors with a fuel pressure reg. Now that's what I now and want so far I don't no what other parts needed and what to do with my trucks saddle bag tanks. I still want to be able to utilize the 2 stock tank inlets but don't now how to make them work with moving the increased fuel pressure or swap it to a single tank with two inlets. I'm not sure if I want to bore the block and stroke it or just throw a stroke kit in it with good pistons, I want a upgraded cam and parts I like a little chomp to it, I'm thinking to put 35's or 37's tires on it with either 3 or 6 inch. With the unknown motor specs I don't know what gearing to put in the diff. With what I have so far can you with me fill in the blanks any suggestions. Please and thank you.

[gmachinz]

Lots of areas to cover.....I'll suggest an idea for the fuel issue. The mod I would do is similar to what I've done putting an LT1 motor in a gbody. You need to pick up a set of 1987 pickup gas tanks since they have a TBI also (first year for the squares). Now I don't know what psi you need but the late 80's TBI pressures were about 9-12 psi. Now, I think you'll be okay with stock 1987 TBI in-tank fuel pumps. If you need more pressure, you can directly swap out the 12 psi TBI truck fuel pumps with an LT1 (1993-97 fbody) fuel pump which is rated at 37-42 psi.

You may just be better off though looking for a donor 1987 truck to scavenge parts from to run your TBI 350 project motor. And, the 1987 truck would also have all the correct fuel line runs, fuel pump harness, etc.

[nonstop]

Honestly, I would take the money you would use for the conversion and have a quadrajet rebuilt by a reputable shop. I have never had a TBI truck, but from what I read, mileage is not too far different than a quadrajet equipped truck. You will be time and money ahead, and not having to modify tanks or wiring. Just my opinion.

[1976gmc20]

Originally Posted by nonstop

Honestly, I would take the money you would use for the conversion and have a quadrajet rebuilt by a reputable shop. I have never had a TBI truck, but from what I read, mileage is not too far different than a quadrajet equipped truck. You will be time and money ahead, and not having to modify tanks or wiring. Just my opinion.

Yep, nothing wrong with a good running quadrajet.

I've run them from 13,000 feet all the way down to sea level without a problem.

Only real issue is having to let them warm up before you drive.

[gmachinz]

One of my most reliable setups ever was my all stock 91 Burban with a TBI 454 and it was always a flawless running motor. TBI is very troublefree.

[csdineley]

My truck being an 87 had a stock 350 tbi engine. It got 12 mpg on a good day. Ganted it was old and worm out. I replaced the motor with a gm crate vortec 350 with a quadrajet and now I avg 15 mpg everyday. Plus if you lift it and put bigger tires, 15 mpg seems unlikely. A friend had an 87' 305 tbi, 700r4, 6 inch lift and 35" tires. He averaged 5 mpg around town.

[gmachinz]

Yeah....whether cruising or pulling a load, my 454 TBI got 11 mpg flat and was all stock. But, realistically, it wasn't my DD and heck, its a truck.....I didn't build it for mileage....lol But, if I was going for maximum mpg, I'd seriously look at a TPI or an LT1 swap if going FI. I was knocking down 24 mpg in my DD 1995 Roadmaster Wagon fornquite awhile!

[4Xsquare]

Thanks for the reply guys the mpg I forgot to put highway lol but you do valid points it's has a holley on it right now which would probably rebuilt it if I was to stick with carb and if I say with carb honest I'm probably Goin to kick it up to a 383 and there's a pic a part here that I no the owner to pick up some parts. Being gas is Goin up and maintenance wise for the long run which seems more worth the energy between a carb 350 or a some sort of efi 350? Don't mean to be redundant but just want make sure I'm Goin the right direction. And on a side note on the carb 350 is there any positive gain from putting vortec heads on it?

[csdineley]

Simply put about 40 hp

[4Xsquare]

Cause I no the vortec heads have larger channels that in turn would allow for better throttle responsesand maybe better mpg being that better fuel delivery

[csdineley]

Well which way to go depends on want you what. But for me, I'd rather have the simplicity of a carbed motor. I spent to much time casing down electrical problems all the time with all the efi systems I tried over the years. Especially if I tired to change them from stock.

[4Xsquare]

I'm rlly used to carbs or modern motors if I was to go carb what build would u recommend for power and increased mpg for 7 this is not included with the lift or anything

[1976gmc20]

My 1976 GMC had a Holley on it when I bought it 20 years ago. It ran great and got good mpg out on the highway, but started flooding and burping gas all over the top of the engine on two track logging roads. So I got a Q-jet from the junkyard and had a neighbor who was a state mechanic rebuild it. It's still on there now and working fine except the automatic choke never worked right and I never could get a manual cable to work right either because of the geometry.

Before that, I think that I have had three Q-jet 350s and never any carb troubles. The two that were TH350 automatics got terrible gas mpg.

I also currently have two TBI 350s (5.7 L) and they are pretty much trouble free. One of them the module in the distributor died last fall and left me stranded, but otherwise they run great with virtually no maintenance. It is a pain when a fuel pump in the gas tank fails, though.

So I would say either the Q-jet or TBI is a very good system.