Need help with 85 GMC.

[irishman999]

I am devoting the time to ask multiple questions about an 85 GMC but I dont want to share pictures of it with other enthusiasts.

First off, its old and has been sitting for a really long time with rust and old gas in the tanks as well as a bunch of worn out ignition parts. I have not tried forward thinking about diagnosing problems or google yet, figured I would ask the experts. The engine does not run perfect and makes popping noises and stumbles. When I accelerate it pops out of the carb and out of the exhaust AT THE SAME TIME. I have narrowed it down to either the carb or the distributor, WHAT DO YOU GUYS THINK?. IS IT THE QUADRAJUNK?!?!?!

Other problems: This thing needs paint, I cant figure out what color I should paint it. Its a K1500 single cab long bed with a 305, what color should I paint it?!?!?!

Its stock height, I for the life of me cant figure out if I want it to be 3 inches taller or 4. This question is driving me nuts, its a really hard decision. This one inch of lift with the same amount of effort and money involved but I cant figure out if it should be 3 or 4 inches taller. WHATS THE BIGGEST TIRE I CAN FIT?!?!

What exhaust can I order off the internet will make a stock low compression 305 sound AWESOME?! I have looked at numerous youtube video's featuring redneck hack jobs with every glass pack muffler made and cant figure out what muffler will make this truck sound GREAT! Currently It has a rusted out stock system and was wondering if there is a muffler i could buy at Autozone retro on to make it sound great.

I cant figure out what wheels I want either, I have no clue about backspace or bolt pattern so can you guys identify these wheels for me and decide weather or not they will bolt on?

http://reno.craigslist.org/pts/2774794774.html

[raws67]

Well here is my 2 cents for you. I wouldnt just jump on the quadrajet calling it junk because there could be a lot more going on here than just the carb. If it were me and I am just saying if it were me I would start with making it safe and reliable before I would start throwing money at a lift and big wheels. Check the timing. If the timing is good throw a vacum gauge on it and see how the gauge responds. If the fuel tanks are that bad put an inline filter between the pump and tank to keep junk from your fuel pump and replace the small filter in the Quadrajet if its still in there. You could have some internal engine problems that need fixing before anything. After you get the engine running right verify that the brakes are good and bleed the old fluid out. How is the wiring? Ive bought a few trucks that were a fire waiting to happen. As for exhaust you my freind are right next to the largest Summit facility on the west coast. I have bought a couple exhaust systems from them ON THE CHEAP and they worked great. The main thing to remember here is to take your time and concentrate on one issue at a time with safety and reliability at the front. Good Luck

[Restrorob]

Originally Posted by raws67

You could have some internal engine problems that need fixing before anything.

Popping out the carb AND exhaust sounds like valve issues (gummed up/sticking), A compression or leak-down test will show the condition of both the rings and valves......

[notyo_cheez]

My $0.02, and purely my opinion based on experience:

Running - always start from the source and work forward from there. As stated you mentioned the condition of your fuel tanks, I'd address this first otherwise you'll always be dealing with it. For my project I'm strongly considering poly replacements so I won't have any issues with E10 fuel. Like yours mine hasn't been on the road in over 10 years and I'm not wasting my time breathing life into something that's sat forever. My crap box will get a Goodwrench crate 350 and rebuilt TH350 tranny from jegs.com. I don't trust anyone locally to rebuild the engine and tranny that's in it so when it gets pulled it will become a freebie core to whoever wants it.

If you do a compression test and find you have rockers/valves sticking you can try this: get a quart bottle of Marvel Mystery Oil, pull off the vacuum hose to the brake booster and insert the hose in the bottle, start engine and let it run at idle. Try half of the bottle, and reconnect the hose. You'll make a LOT of white smoke and your yard will smell like peppermints for a little while. If you don't want to do it this way pull your valve covers and with a spray bottle of MMO saturate the top of the heads, reinstall the covers, change your oil and substitute one quart of MMO for motor oil and run as normal. Add a pint to your fuel tank as well. Gramps used this stuff quite a bit, somehow it managed to borrow time for engines that were on their last legs. Also works great as a tool cleaner.

Wheels: find some stock rallys or steelies and pop some baby moon caps on there. Dare to be different.

Paint: this is a matter of personal taste. For myself I'm debating on chalkboard black or cobalt blue.

Again, it's my $0.02. You can take or leave it, won't hurt my feelings.

[74 stepside]

To answer your questions, it kind of depends on your budget. I would drain the fuel tank, install new fuel filters. Do a compression ck and then look into your carb. Nothing wrong with a quad and they can be rebuilt cheaply. A new distributor isnt expensive either. Also, new plugs and wires. With a 3-4 inch lift, you should be able to squeeze 35" or 36" tires. Might rub front fenders on turns. As for color, it depends on your style. Id choose a color that will go with your interior unless you plan on changing it. If you choose a color other than original, you have to do interior paint too. That gets pricey unless you do it all yourself. With a 305, probably a 2" exhaust. 350 use 2 1/2". Flowmasters and Magnaflow both offer good products. Hope this helps.

[1LowToy]

Sounds to me like a plug wire is crossed, a bad distributor cap, or a flat cam.

Check plugs wires, firing order, cap and rotor.

Good luck

[allchevy58]

Think I would start with a compression test. Then drain, clean and refill gas tank and change fuel filter. Then tune-up, spark plugs, cap, rotor and wires. Check and set timing. It would hurt to change oil and filter and add some Marvel's Mystery Oil. I prefer Q-Jet carbs. Dual 2" or 21/2" exhaust with turbo mufflers would be just fine, Summit has some good deals like raws67 said, I have my own pipe bender so I do that myself. Wheels, lift and paint is your preference. On the paint, I would stick to the stock color or something that matches interior. Unless you paint jams, when you open the door you'll see the old color.

[wildwln]

I have a 85 GMC SWB 4x4 i bought bran new off the show room floor back in 85..its been a daily driver every day since right up through today..its ready for its third new paint job which is black with gold flake- highlighted with red and silver pinstripping...i replaced the 350 on it one time but guess what?..still has the original Quadrajet Carb on it as the day it left the factory...never had a bit of problem...never had a bit of problem with the entire truck other than i ran over 350,000 miles on the first engine and just plain wore it out...the 85 is a sharp classic looking year and model...i have a 4" lift on mine which i had on about a week after i got it..for mufflers i use chevy small block long tube headers with strait pipe all the way to the rear end..sounds like a stock car banking hard on turn 4 sometimes but i like to listen to that Hummm as i go down the road...good luck~

[irishman999]

I Feel bad now that you outstanding dudes took time out of your day to offer advice for my problems. This thread was a shot at humor about alot of posts I see here. I should probably be banned for trolling at this point.

[Restrorob]

Just goes to show, No matter what the issue is there's members willing to help !!!


PS.... Glad I didn't type as much as the others....

[GmtGmt]

didnt you have problems with it had a stuck valve when you first got it?

[irishman999]

Originally Posted by GmtGmt

didnt you have problems with it had a stuck valve when you first got it?

Yeah! That was over 2 years ago, I am surprised you remember that. Its still running perfect, I even got the broken piece of push rod out of the lifter valley when I did my intake swap.