Impala Forums banner

1 - 20 of 21 Posts

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #1
Years ago, my 78 had a problem with fouling the passenger side rear 2 plugs with oil and coolant. I figured it was a bad intake gasket, and also figured the problem would be solved when I replaced the intake and cam, at the same time I did that I also had the heads gone through and milled, I put it all back together and re-torqued everything a day later before final assembly. Not too long after that I parked it due to a blown tranny, there it sat for 6 years. Now a couple months ago I brought her back to life, now I'm seeing the same fouling on the same plugs, and I have added 2 quarts of oil and maybe half a gallon of coolant since with no leaks to speak of. So, my question is wtf? Maybe there is a crack in the block? I am kind of at a loss other than that.
 

·
Super Moderator
Joined
·
7,057 Posts
It is possible of a crack on the block between the cylinders at the top of the block.

Now on my 305 I have had a similar problem with the right rear two plugs and it is due to the exhaust manifold. On mine there is a vacuum operated device that closes down the exhaust when the engine is cold to help it warm up faster since the snorkel preheater hose comes from that manifold. The device has a Vacuum Port Sensor on top of the thermostat housing, and if the sensor does not close the port once the engine warms up then a constant rich fuel mixture will foul up those and possible the rest of the plugs on the right hand side of the motor.
 

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #3
...? I did not know the heat riser could do that upon failure. I will look into that, that would save alot of trouble with changing the intake gasket again!
 

·
Super Moderator
Joined
·
7,057 Posts
Look for the one on the exhaust manifold, if yours has it the vacuum motor will be above the rear two cylinders on the right side. The snorkel is controlled by the carburetor through a sensor in the bottom of the air cleaner.
 

·
Super Moderator
Joined
·
7,057 Posts
Here are a some pics to view the device I am talking about. My finger is pointing to the vacuum motor which is mounted right near the heater hoses. If your car has this then follow the vacuum hose to the port switch and when the engine is hot and running pull that line and see if you hear any hissing. If you do then replace the port switch. I bought mine from Auto-Zone.
 

Attachments

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #6
I guess it makes sense. I'll have to try that out, it probably is bad anyway, I've had to replace just about every other vacuum operated doohickey on it. Matter of fact, for awhile I couldn't figure out why the choke wasn't working for crap, turned out to be a bad vacuum choke pull-off.
 

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #7
I wanted to follow up on this, I still haven't assessed the problem, but... Would the heat riser not opening cause oil loss? Because I am going through 2-3 quarts a month with no leaks and no smoke. Sure the engine has about 140k on it, but it had frequent oil changes and there is no cylinder wear that I could notice.
 

·
Registered
Joined
·
371 Posts
I doubt it, though I'm not 100% certain. If you're losing that much oil, it's either leaking out or you're getting blow-by. If that's the case, it's either burning up or filling up your air filter. If it's leaking out, get that engine steam cleaned or otherwise degreased and find the leak from there.

I wanted to follow up on this, I still haven't assessed the problem, but... Would the heat riser not opening cause oil loss? Because I am going through 2-3 quarts a month with no leaks and no smoke. Sure the engine has about 140k on it, but it had frequent oil changes and there is no cylinder wear that I could notice.
 

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #9
The engine is clean top and bottom, I just replaced all the gaskets. Air filter is not getting any oil at all. The oil just disappears...
 

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #10
The engine is clean top and bottom, I just replaced all the gaskets. Air filter is not getting any oil at all. The oil just disappears...
Though I just realized the cat could be burning off enough of it to hide the smoke...
 

·
Super Moderator
Joined
·
7,057 Posts
Two quarts of oil in two months? How many miles have you put on the car? Some cars can burn a quart per 1,000 and would not see any smoke coming out the exhaust pipe and not foul the plugs.

Does your car have the coolant overflow bottle still? Once it goes into the bottle and the engine cools all the way down then the radiator will pull what it needs back in from the bottle. If it is not there and you only put the coolant in the radiator then yes it will become low as the coolant heats it expands and some will go overboard if not into the overflow bottle, and then when the engine cools it is low on coolant.
 

·
Banned
Joined
·
95 Posts
Well first I will ask how many miles are you driving a month?Before my rebuild I was going through a qt every 100 miles or so.Might be best to do a rebuild.If your burning oil you can run a heavier weight oil to get more miles out of the engine with a slightly less consumption of oil.I would do a compression check on all cylinders just to map things out.You can also run a hotter plug to help out on the plug fouling.You can band aid the problem.With that said your engine condition will not get any better to say the least.
 

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #13
Yes I still have the overflow tank, and that is where I add coolant. It appears that the coolant level is no longer dropping, so I think it was just air bubbles. The oil would not be air though... Monthly, I guess I probably do about 1000 miles, so I suppose thats 1000 miles per quart. I know that is supposed to be an acceptable rate of consumption, but I'm not pleased. I don't really want to go heavier on the oil because it won't flow as well, I suppose I'll keep topping it off until I can afford the time and money to rebore.
 

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #14
Okay, I have to adjust my timing before I even bother with the rest of this. I remember now that I have it advanced like 12 or 14 degrees because thats the only way it would run before. Now that I have other issues worked out I need to drop that back, I'm still getting knock when I accelerate burning 92 octane.
 

·
Super Moderator
Joined
·
7,057 Posts
That knock may be from the timing being to far advanced.
 

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #16
That's what I meant. What I am not sure on though, is why I needed to do that to begin with. Was it because the choke was hosed up? Maybe I have a rich fuel issue? I am getting terrible mileage... Tell me, does anyone know a procedure for adjusting the idle mix screws without hooking it up to a gas analyzer or anything else? Stock rochester 4bbl.
 

·
Banned
Joined
·
95 Posts
That's what I meant. What I am not sure on though, is why I needed to do that to begin with. Was it because the choke was hosed up? Maybe I have a rich fuel issue? I am getting terrible mileage... Tell me, does anyone know a procedure for adjusting the idle mix screws without hooking it up to a gas analyzer or anything else? Stock rochester 4bbl.
Turn the idle screws all the way in.2 and a 1/2 turns out is a good starting point.
 

·
Registered
Joined
·
828 Posts
That's what I meant. What I am not sure on though, is why I needed to do that to begin with. Was it because the choke was hosed up? Maybe I have a rich fuel issue? I am getting terrible mileage... Tell me, does anyone know a procedure for adjusting the idle mix screws without hooking it up to a gas analyzer or anything else? Stock rochester 4bbl.
Here's my method:
Screw the idle set screws in (clockwise) so they lightly seat. Then screw them out 1 1/2 turns. Start the car and slowly turn each screw out (counterclockwise, which is richer). The car should idle faster and faster as you rich each screw out until a point where there's no speed increase. Then screw each screw, one at a time in (clockwise) until you see what's called a "lean stumble", where the car starts to idle rough. Then screw the screws out a half a turn. That's it.

If you want, you can turn the screws in all the way to seat and count the turns to see where you ended up. More of a learning reference. Ideally the screws are similar (i.e. maybe both end up 2 turns out) but they will usually be a bit different from each other.

They sell flexible shaft tools for adjusting those screws. I bought two (so you can leave them both on when you're doing this) and painted a white out line on the ends of them so you could count the turns easily.

After you adjust the screws you'll need to set the idle screw speed.

The basic thing is to find the lean stumble and then back them out a bit. A bit is a 1/4 to 1/2 turn counterclockwise. You want to rich them up the least you can get away with to not waste gas, but the whole thing doesn't need to be NASA exact because your pedal will make up for it.

Sometimes you can tweak the screws a tiny bit at the end (like an 1/8th of a turn) and get the engine to idle in a more balanced way.

I bought a cheap $50 steam cleaner at Kmart last year and it's great for rebulding carbs.

I always check the 4 bolts holding down the carb because I've seen them be loose and cause leaks. You can use a heater hose up to your ear as a stethoscope and find vac leaks.

I've rebuilt Rochester 4 barrell carbs, set the screws to 1 1/2 turns out and had the car start right up and you could have left the screws where they were with no further tweaking.

good luck!
 

·
Registered
Joined
·
828 Posts
just another basic thing I thought I'd throw in here:

Get someone to hold the throttle pedal to the floor (cinder block?) and make sure that the throttle on the carb is opening all the way.

With swapping carbs and different throttle linkages I've had a few times when holding the pedal to the floor was only opening the throttle maybe 80%, and when I adjusted the throttle linkage (whatever it took - swapping brackets, new cable etc...) the car had, no big surprise, a faster top end.

WOT should be just that!
 

·
8th Gen Antagonist
Joined
·
13,660 Posts
Discussion Starter #20
Well, other than the new intake manifold, nothing exterior to the engine has been replaced. My dad rebuilt the carb since I am fairly clueless to it, but I had it rechecked by a pro just to be sure and he said it was done very well. However, we never went through the adjustments since I had other issues at the time. So I will set my mixture with the procedure you gave me and adjust the idle afterwards. Are there any other adjustments I may need to make besides choke?
 
1 - 20 of 21 Posts
Top