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2K views 19 replies 9 participants last post by  305Guy84 
#1 · (Edited)
305 running like crap!!!

OK, first off, I'm new here, so hi all. I have an 84 Chevy with a 305 CI. just got it a month agoe, used it a little here and there but not lots. today I took it out on the highway for a cruise, and it was awesome to open her up, but when I stop, it idles real slow, and then stalls (new to this truck). to restart it I had to floor the gas as if it was flooded. I thought I did a good job "unflooding" it, but whenever I stopped, it stalled. everytime I restart it, there is a black smoke and a real bad smell, kinda like carbon, if I were to guess. any suggestions as to what is wrong???? PLEASE help!!!. I need this as my transportation

I did look, spark plugs are black, but is that reallly the problem, could it be the carb, heads??? intake??? I am grasping here....Thanks for help in advance....could it be the exhaust??????

I think it may be the spark plugs got fouled when I opend up the 4bbl, now they undercombust...but is that the cause of bad idleing too?????
 
#2 ·
It seems to me like your spark plugs are plugged. i don't know much about intakes and heads and stuff, but I would change the spark plugs. Also check the timing, sometimes a little off timing can mean the diff. between a good runnung engine, and not running at all. I doubt it is your exhaust, if it runs rough at low RPMs, i think you just need new plugs. check fuel and air filters, too. the factory 305 fuel pumps could barely keep up, but i doubt this is your dilemma. worst case you need to rebuild q-jet
 
#3 ·
85silverado said:
i don't know much about intakes and heads and stuff... ....worst case you need to rebuild q-jet

PLEASE tell me these aren't the problems, or that if they are that there is a cheap way of fixing it!!!!

Could the cam timing have gone off a little bit when I floored it and the 4bbl kicked in???!!! OOPS!!!...P.S. I did change the oil recently, and added a fuel additive to clean the engine or some crap... did I screw my plugs when I put that STP crap in?????
 
#4 ·
Doc here, :pimp:

If it is in fact fuel flooding..you probably have a stuck float..

IF It is a Qjet..look at the center of the top of the carb by the choke plate..

you will see a hole there and if you look real close..you'll see its the float..

start it run it at idle or whatever it will run at..and with a small qtip or other tool carefully push it all the way down until gas comes out the top..do that a couple of times and follow up with spray in that hole. Then Tune your Idle screws for best idle..

You really first need to determine if it is in fact flooding OR loosing spark..check for spark first if you can duplicate the problem..if it is good then proceed on to the carb..

Doc :pimp:
 
#6 ·
Stalling

Most the time that I have seen to this problem, is the build up of scale in the fuel tank. If the pig has been sitting for a period of time, plus there is the fact of old fuel, humidity, and all the other factors that sealed tanks develop over time. I have had too pull the fuel tank and dump it out, check it for scale and had to clean it out real good. For the metal tanks there is a kit you can get at your local parts house for re-lining the tank. It is a time consuming process, but if it is required, just do it. When I was a real degenerate and liked to really @1#% with some one, I would put 1" squares of paper into peoples fuel tanks. Once they would slow down, the paper squares would float back to the bottom and cover the fuel pick-up and starve the engine. So, now you have a real viable reason to pull your tank, especially if you might have pissed off someone.
Another possible problem would be weak rings and you are now sucking oil into your cylinders and actually fouling your plugs. Plus if the engine has not been ran for a period of time, depending on your heat temp in the air, your valve seals are dry, and if not kept lubed on a weekly basis, your seals are now cracking and allowing to be sucked into the cylinder as well. Thus fowling your plugs and causing your system to die. Your coil could be breaking down and at lower engine speeds your spark has dropped off and your plugs are being starved, thus the oil is fowling your plugs anyway.
This is one of those things associated with a tired engine.
Time for a real build. Sorry for the worst case scenario. :drunk:
 
#7 ·
LordMaximo said:
Most the time that I have seen to this problem, is the build up of scale in the fuel tank. If the pig has been sitting for a period of time, plus there is the fact of old fuel, humidity, and all the other factors that sealed tanks develop over time. I have had too pull the fuel tank and dump it out, check it for scale and had to clean it out real good. For the metal tanks there is a kit you can get at your local parts house for re-lining the tank. It is a time consuming process, but if it is required, just do it. When I was a real degenerate and liked to really @1#% with some one, I would put 1" squares of paper into peoples fuel tanks. Once they would slow down, the paper squares would float back to the bottom and cover the fuel pick-up and starve the engine. So, now you have a real viable reason to pull your tank, especially if you might have pissed off someone.
Another possible problem would be weak rings and you are now sucking oil into your cylinders and actually fouling your plugs. Plus if the engine has not been ran for a period of time, depending on your heat temp in the air, your valve seals are dry, and if not kept lubed on a weekly basis, your seals are now cracking and allowing to be sucked into the cylinder as well. Thus fowling your plugs and causing your system to die. Your coil could be breaking down and at lower engine speeds your spark has dropped off and your plugs are being starved, thus the oil is fowling your plugs anyway.
This is one of those things associated with a tired engine.
Time for a real build. Sorry for the worst case scenario. :drunk:
well it did sit for 2 years, only started up once every month or so, i changed the fuel filter, son of a ***** plugged on me. I have 2 locking gas caps, ain't nobody puttin no **** in my fuel tank, i already pissed off 20 too many people (LOL)...i think that a bunch if **** got loose in the carb and fouled the plugs, cause it happened after i gave her more gas than usual (LOL) there is new gas,i will check ofr flooding, thanks so much for the info
 
#10 ·
I found a problem in the Q jet

i found a gas leak near all the choke crap whenever i start it of pump the gas while off. I already changed the gasket between the carb and intake manifold. I cannot tell where the leak is from, I think probably just old, dried out seals. so what i am going to do is have the Q jet rebuilt... any other suggestions
 
#12 ·
305GUY84,

There are two plugs at the bottom of the fuel bowls that come loose and leak fuel into the intake manifold and cause this problem. You must take the base plate off of the body of the carb and check these plugs. There is a repair kit for these plugs. It looks like a big piece of hard rubber. When you put the baseplate back on the body this "plug" gets pushed up against the leaking plugs and seals them.
If Doc is correct and there is something in the fuel supply like a bit of rust or something, then the float will not be able to close the needle against the seat causing the engine to flood out. What I do in a case like this is disconnect the fuel line at the carb and PLUG it off. Then start the engine. Let it run until it stalls because it runs out of gas. Then re-install the fuel line and then start the engine again. Because the float is down to the bottom of the fuel bowls the needle is WIDE OPEN and when the pulse of fuel from the fuel pump hits whatever is in there it gets washed right out.

Let us know what cures the flooding out.

Scholman
 
#13 ·
well, I pulled the q-jet from an old piece of **** , this thing is nasty, the 4bbls stick open sometiimes, and it stumbles if you give any amount of gas from idle, but hell it makes my truck run, roughly, any help on tuning it here???
but how difficult is it to do a rebuild on my leaking one??it is not the float,,,i already checked that out ut maybe it is the gasket in the carb, or, because it sat for 2 years, maybe the seals dried out in the carb, andit leaks...thanks for the suggestions, i will try them, but i am not advanced in tuning carbs,,,does anyone know of any good websites that have like a manual for that carb???


I was also considering repacing th Q-Jet with a Barry Grant, but, i was told there would be little if any advantage over the Q-jet because GM used the Q-Jet on most engines, even 500CI caddys, and it has a multi CFM displacement depending on what the engine can handle... it is like 750 CFM??? does anyone think I should repace the carb???open to ideas on a new intake manifold as well.
 
#14 ·
305Guy84,

These carbs can be touchy but not that hard to rebuild. But first check the throttle shaft to see if there is very much movement. If it wiggles around don't even bother trying to rebuild it. Turn it in as a core on a rebuilt unit from SummitRacing.

I am not sure of the web site you are looking for but there is one I remember seeing it posted before. Maybe Doc knows?

Scholman
 
#15 ·
Doc is correct, if you have fuel comming out of the top of the carb, either the float is stuck or the needle and seat have a piece of crud that is keeping it from sealing properly. My guess is the needle and seat is bad from sitting for so long. It is a fairly easy fix.
 
#16 ·
Doc here, :pimp:

Here is EXACTLY what I'd do if I were you...

Go to the bone yard..Get a Q~Jet off your era car..preferably A runner..so you can monitor leakage and drivability issues (sounds great in a perfect world..huh?) Anyway, get the very best one you can find..

Next take it to your local Napa Dealer, and get a TOTAL rebuild kit..not a cheesy $19.95 kit that is a few gaskets and a primary pump..You'll spend up to $79.95 For a GOOD kit with all the parts and destructions ( uhh..I mean Instructions) you will need .

Get either 5 cans of berrymans Carb cleaner, or a gallon Bucket of carb dip..if you go with the dip..DO IT outside..away from living beings..wear long rubber gloves and a rubber vest and goggles..That stuff Tears up the skin..AND if you spill just a half cup of it on the garage floor it will stink for months after..no matter how you try to clean it.

Get a Quiet workspace where nothing will get messed with..and begin disassembly of the carb..Get a Styrofoam Flat packing lid..or an old cooler lid..as draw an outline of the air-horn using the new gasket..on it..as you remove screws, punch them through the lid..where about they came out..you'll notice Q~jet uses a million of them all different sizes..remove the air-horn. Remove the secondary metering rods..located on top center on a wishbone that go down inside the top..the rods just "hang there " so be careful not to drop and lose them.

(you need to unscrew the choke linkage at the top of the carb at the butterfly , and the secondary pull-off at the bottom right side to remove the horn..)

place the linkages on your lid approximately where you removed them in the proper orientation. Also shoot a bunch of digi photos before you start taking it apart for assembly reference.

Next remove the fuel inlet, you'll find the spring and an in carb filter here, pull that.

Next you find the primary pump, remove that..

Remove the float and needle assembly, note the direction of the float hold down shaft..If you install it backward, it will work on the bench and hang up in the car..Remove the brass seat from the air-horn.

Put your float in a cup of gas and let it sit while you rebuild the rest..If it sinks..It's bad replace it.

Your air horn should be apart now..(depending on the series Carb..)

Follow your instructions for the main body..there is even less stuff there..

Then remove the throttle body. Remove the jets, place them in your lid..and mark the lid left / right so they get back in the right holes in case one has a "Wear " mark and the other doesn't..

Take the Carb body parts (all the metal parts to be reused ) and dip them in the carb cleaner, Or spray with the Barryman's use all 5 cans, spray all passage ways and everywhere you can see a hole..(wear Goggles..get that stuff in your eye , you'll be blind for a day..or worse..)

While it is dipping & drying or neutralizing..read ALL your assembly instructions..spend at least an hour doing so until you feel confident you understand them..

Reassemble as per the sheet , pay attention to float level and linkage clearances..

That should score you a great running carb after you set the jets when it's running..test of course for leaks..

Doc :pimp:
 
#18 ·
ok, bought a rebuild kit and carb dip, but how do u set the jets??? silly me it is probably in the instructions, thanks for the advice doc, there should instructions that will help me find this airhorn thing (dont use big words, i am not big on the whole lingo stuff,,,,use SMALL words LOL :confused: hahaha hopefully I can rebuild thes Qjet and be done.....is there an intake manifold that supports 2 Q~Jets????? it would be awesome, but use LOTS of gas, bad for a daily driver :spank: LOL thanks again! :D
 
#19 ·
305Guy84 said:
ok, bought a rebuild kit and carb dip, but how do u set the jets??? silly me it is probably in the instructions, thanks for the advice doc, there should instructions that will help me find this airhorn thing (dont use big words, i am not big on the whole lingo stuff,,,,use SMALL words LOL :confused: hahaha hopefully I can rebuild thes Qjet and be done.....is there an intake manifold that supports 2 Q~Jets????? it would be awesome, but use LOTS of gas, bad for a daily driver :spank: LOL thanks again! :D

Doc here, :pimp:

The air horn is the whole top of the Carb..about an 1/8 thick and covers the whole top of the float bowls..

To set the jets to do a first start, carefully turn them all the way in, (DO NOT cinch them down..you'll score them or the throttle body and they won't be useful as a jet anymore..) then back them out 3 turns..

Start the car, inspect for leaks (fuel / Vacuum) and set the jets..Be sure the engine is warm and the Choke is full open.

you want highest idle, to start with..then slowly work between them , giving time for the engine to normalize (up to 30 seconds) burning off excess fuel from last adjustment..and work between them, until you get highest idle, with no random "Pops" out the exhaust..

Then set your curb idle for 650 Man, 950 Auto, and go to the rear..what do you smell? If you did it right, nothing..If not it will be raw fuel. go back and adjust again..

Key is Don't rush the adjustments..allow time to normalize between movements of the jets..and make small movements..Plan on an afternoon to do it right..If you rush it..you'll never find the "Sweet Spot" and either run too rich or too lean..

Doc :pimp:
 
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