So last night a buddy and I take my 68 442 out to the local county fair. Its only about a 20 mile drive, but with all the driving we do cruising around we probably clocked in over 60miles (or more). Anyways, the motor is a 400G block, rebuilt last year and only has about 2000miles on it. I don't play rough with it since I blew the motor a couple years ago and never wanna do that again.

Long story short, we are in the Taco Bell drive through at 12am and get stuck idling for almost 15 mins because the line is so FRICKEN long. Anyways my buddy goes, I smell something hot, and I was like ya, that smells like coolant. I pull off to the side and my coolant is boiling over and my temp gauge is at 250+.

I was able to let it cool off and filled it with more coolant and once it started it up the gauge dropped to about 160 until it warmed up. Got it home fine and everything; the temp gauge never went back up even to 200.

What's the deal? Can anyone help me out? Needless to same i'm worried about my baby lol

 

Was it possibly low on coolant to start with?? Possibly a thermostat not opening?? Engines generally don't overheat after a long period of time of operating correctly for no reason! Did it act up before??

 

MY theory was maybe the thermostat is stuck closed. Haven't been able to check that out yet. But when I did fill it up with more coolant I had to use up almost the whole gallon and it definitely didn't spill a gallon onto the ground.(I dont have an overflow tank hooked up)

But before it overheated it was driving beautiful, and like I said, after the incident it drove beautiful.

So i'm not exactly sure here.

 

If it had stuck closed you'd have had problems after you got it started back up.

Do you have a clutch fan and if you do is all the shrouding in place? Did you hear it engage? I'm thinking it was because you got stuck idling with poor airflow.

How about your timing and vacuum advance? Do you still have the distributor thermal vacuum switch and if so is it working? It should have switched to manifold vacuum about 225 degrees and advance the timing a bit if it is- you'd have noticed the idle speed pick up slightly.

What antifreeze mix are you using? 50/50 antifreeze/water is deal, maybe as much as 70/30, but it has to be mixed with water to raise the boiling point.

Also- has that engine been bored? You probably already know the G block is Oldsmobile's poorest engine design and one of the poorest of anyone's- it would have been much better suited to a logging truck than a high-performance car.

And finally, Logan, my young friend- you love Taco Hell a lot better than I do to sit in a drive thru 15 minutes waiting for their food! First your car shyts, then the next morning you do!

 

HAHA I was contemplating leaving that line mind you but my friend realllly wanted it lol

I'm using a 50/50 mix. But like you said I think it may have been do to poor airflow, plus I think there may have been a low amount of coolant to begin with.

I know the G-Block is HORRIBLE lol I'm working on a 455 to replace it. But for now that's in there, and will be kept in a corner some where since it is the numbers matching motor to my car.

Also I will check on the other stuff you listed later today.

Do you think you guys could help me with a couple more things? (Sorry, I'm still learning this car one problem at a time )

Problem one, whenever I start the car there seems to be a thick white smoke that puffs out right when it starts. But after that it doesn't smoke at all.

Problem two, when I turn the car from like a dead stop, so like a turn off from a stop sign or light, there is like banging or clunking or something going on with the rear end like it's catching something weird, only when im turning though or going up a steep hill. Also, when I'm in reverse it makes like a pfft pffft pfft noise, and then makes the noise while im decelerating. Any ideas on what that's about?

Any advice is much appreciated, like I said, I learn about this car one PROBLEM at a time lol

 

The white smoke could indicate a head gasket problem (which if you're losing coolant would be a good place to start looking, do a compression test and all that) but I see a lot of cars do that on startup with modern gasoline.

Does the car have a Posi rear end? If so you need to find some of the special positraction additive and put in there, I guess you can still get it. You may need to run the car 50 miles or so to work it into all the clutch packs. If the additive doesn't quiet it down, you'll need to look into the rear end itself and see what's worn.

A Posi should have a metal tag on one of the rear end cover bolts indicating its presence.

I think you're doing pretty good for a guy with a car more than twice his age!

 

White smoke is probably valve guides - they get brittle from age and fall off.
Clunking could be from some worn front-end parts - see if a grease job [cheap] changes anything, as those get skipped.
And, yes, the rear end needs posi additive if it's posi, but change the gear lube, too!
Could be the original, as hardly anyone changes it, ever!!
If it's not posi - look for another rear end, as the spider gears are probably going away!

 

Engine is a fairly fresh rebuild. If the valve seals were replaced then, I'd hope they haven't failed in 2000 miles. Wouldn't that show up as blue oil smoke instead of white? White smoke always indicated coolant or trans fluid in my experience, but since it goes away, I'm still leaning toward fuel.

 

Alright guys we got the heads pulled, and to my surprise the gaskets are good. So now I'm wondering what the white smoke was?!?!?!?! I know why it overheated, which was my own error not checking my fluids. My radiator didn't(does now) have an overflow tank. So, especially on really hot days, my coolant was basically just pouring onto the concrete. I didn't keep up on the fluid level and it bit me in the ***.

As far as the clunking goes in the rear end, it just needed some more posi fluid.

But any more ideas on the white smoke? I haven't started her back up yet, still finishing up some stuff but I'm not sure what would of caused that then.

 

Why did you pull the heads?? Did the compression check fail??

Is it a big puff of white smoke? Raw fuel - float too high, choke not set right, too many pumps on the gas prior to starting, internal leak on carb...

 

Long story lol

Anwyways, thanks for the list. Might just be a carb issue or gas issue. I'm gonna start it up here in the next couple days and see what happens. The exhaust definitely has a heavy gas smell too it when it smokes. But like I said, I will try her out and see what happens.

Thanks for the help guys!

 

When you get it running again go over your tune!

Look down into the carb while its running and make sure you don't have fuel dripping out of the jets while its running. Also look down in there after you turn it off when it's completely warmed up to see if there is fuel dripping. Make sure your choke is operating correctly and is fully open when running after it warms up! Also make sure its closed when cold!

A puff of smoke at start is somewhat normal for older cars, however a big cloud is not!

 

Will do! Thanks for the tips!