We have an 84Z28 305 w/38k miles - it was garaged for over 15 years. Replaced gas tank, fuel filter & had carburetor rebuilt. Fired it off and it ran ok for about 15 minutes. Shut it off, started again, sputtered and wouldn't stay running. I think it fouled out plugs, as there was an "oily" coating on them. Engine is clean - do I rebuild the carb again or take out all pollution control hoses/emission hoses and replace with a Holley w/adapter for carb? Originally thought I wanted to keep it stock, OEM - would it devalue the car if I replaced it?

 

I have a factory one for sale in the classifieds section if you want to keep stock, it came off an running 82 originally 305 but had it running on my 350, removed it last november so it will not need to be rebuilt. Has 58,000 miles on it. If you change out carb to aftermarket you will probably have to ditch most emissions related stuff, but the biggest issue is the tv cable for transmission will not work properly without proper adapters. let me know if interested.

 

More questions than answers....

Did you pull the plugs to determine if they're fouled?
If there was an in-tank fuel pump was it and the sock changed when the new tank was installed? Is the correct fuel tank cap being used?
Is there a mechanical fuel pump? Was it changed as well?
Did you check the little fuel filter in the carb inlet?
Is the carb properly adjusted?

It ran for 15 minutes, then stalled and won't stay running. Is the carb still running with an ECM or was it removed?

The car has only 38k miles on it. Why had it been parked for 15 years?

 

Don't just continue to throw expensive components at it; start troubleshooting and find the cause of the problem.

As far as devaluing the car by stripping off engine components and adding non-stock parts, that depends on the state/condition of the car as it is now. If it's completely original and unmodified, and in very good condition, any change away from stock will be likely to decrease it's value. A vehicle is only original once, especially one that's 36 years old.

 

Keep it original! Once you change one thing, you need to change something else- change to the Holley and you need to change the distributor cap, etc... I know problems can get frustrating, but go step by step and figure things out. This forum is a great resource... use the "search" function and you will find most answers to your questions.
BTW, who rebuilt it? Can they tune it? What part of the country do you live in? Maybe someone locally can help you out.

 

I spent the day reading and informing all possible options - this truly is a great resource Glad we found it

 

Well, the car was a garage queen - Hubby bought it off the showroom floor when he was in college - it's never driven in the snow and used only for fun. Life happened (way too fast) and since it was having some issues running rough/bogging out, it got parked and sat covered in the back garage. A couple of years ago, he pulled the gas tank and had carb rebuilt. Last year finally had the time and $ to try and get it running again.

Yes, we pulled the plugs - there was an oily substance on them and the carb was removed and rebuilt
There is not an in-tank fuel pump and yes for the correct fuel tank cap
No to the mechanical fuel pump
Yes, the little fuel filter was changed when the carb was rebuilt.

When this happened last year, he was worried if he kept trying to get it running he would toast the motor...they say the motor is clean and no damage was done and looks good for it's age. I think we need to keep everything stock like it is and revisit the carburetor issue - did the shop we took it to, rebuilt it correctly? Thank you

 

There's no way any of us out here can know whether they rebuilt the carb correctly. Although, there's really not much to it... take it apart, dunk it in solvent to dissolve the crud, brush it or use an ultrasonic cleaner to get everything out of all the nooks and crannies, epoxy up the plugs that always leak (likely to be the problem here), put it back together. As long as it's assembled right, they probably did it "correctly"; whether they have the finesse to fix the leaky plugs, who knows.

These carbs suffer GREATLY from dissimilar-metal electrolysis. The carb castings are some kind of chinesium, basically the cheeeeeepest thing they can find that won't dissolve in gasoline; but various other parts of it are made of other metals. Steel screws, various brass things, spun-in plugs made of aluminum. Every place that every one of those other metals touches the chinesium, if it gets wet (electrically conductive) even just from moisture in the air that condenses a little bit, sets up a tiny battery. The current that it generates causes metal to erode. Specifically, the chinesium turns to a white powder. Where it's worst is the plugs in the bottom of the main casting, the bottom of the bowl that the fuel sits in, where they drilled holes through the outside of the bottom so they could drill all the little passages in it; then after they were done, they put in these plugs. The casting erodes around the plugs and leaks. The bowl is full of fuel, and with the engine running, there's vacuum on the outside of the plugs, trying to suck the fuel through the leak. A leak that's too small to see can let an UNBELIEVABLE amount of fuel through, which makes the thing idle WAY rich, smell bad in the exhaust, wash the rings down with fuel to the point it sometimes even causes oil consumption, and makes it get half the miles per gallon OR LESS than what it should. Carbs that have sat around for long periods of time not running are PARTICULARLY susceptible to this. If they didn't fix it, … well, you do the math.

If I EVER take one of these things apart and the screws have white powder on them (no not that kind of white powder) then I KNOW WITHOUT ANY QUESTION that the carb will have this going on, and will need the plugs sealed. And since about 80% of all of them that I've ever taken apart had the white powder, I don't even bother looking any more; I just epoxy up the plugs NO MATTER WHAT. Every one I work on.

Here's the plugs in question. The ones that cause this are 3, 4, 5, & 6; 1 & 2 CANNOT, because they're inside a gasket-enclosed area.



See this post. https://www.thirdgen.org/forums/carb...4-trans-2.html It's REAL long; this guy had a whole laundry list of issues; by the time he gets around to this one, it's about post #60 or so. It turned out that his particular carb had rotted through the casting completely and wasn't salvageable, but the photos and descriptions and symptoms and whatnot should be instructive. And of course all his arguing about "but it was just rebuilt, it can't be bad". Yeah right. Don't be "that guy" and argue with people that have been there and done that OVER AND OVER and are trying to GIVE YOU the benefit of their hard-won knowledge of something obscure but critical.

 

I should add also: if it takes A REAL LONG TIME of cranking to start up after it has sat for acoupla days; and then if it's REAL HARD to start after you drive it for awhile and then stop for 10 or 15 minutes and get back in, like going to the store or something, and then blows out clouds of black smoke and runs real rough at first when it FINALLY does start; then it has this problem. No further questions even need to be asked. Once you have processed and absorbed this knowledge, you can spot cars that have this problem from a quarter of a mile away or more, it's SO OBVIOUS. There's another fuel-related hot-start problem that it can have as well, that ISN'T "caused by" the carb although that's where the symptoms show up, and is even more obscure; but, one thing at a time. We'll cross that bridge if/when we get to it.