I have a 350 in my 72 and now in the last few times I've driven my car I have some blue smoke coming out the tailpipe when accelerating from a stop .The engine temp never reaches 150 F by my temp gauge so Im thinking that it's probably rings rather than valve seals because when it's on the warmer side of 150 it's not as much smoke than when its' cold .Im going to change the thermostat to a 165f to make it run warmer.Time to put money aside for a rebuild ??

 

Taking the temp out of this equation .....

I was gonna go with valve seals.

But I think you should get an infrared thermometer & try to confirm what temps you are running.

What's the oil smell like ?.

How does it run ?.

Does it seem cold natured (like it's not warmed up) ?

If you have really been running at those temps for some time .....

You may not be burning off all your fuel which ultimately contaminates the oil ... especially if it's not changed often.

Contaminated oil = very bad things start happening.

I'd also stick with a least a 180 t-stat IMHO.

 

i was thinking valve seals first but then i thought with valve seals it would smoke all the time not just from acceleration.Oil was just changed to castrol high mileage .I have had a
lot of little items that have had to be taken care of ,vacuum leaks ,cracked vacuum lines,
clogged pcv and breather and now the carb base gasket was shot ,replaced it ,now it runs
and idles beauty,i think i'll stick a old thermometer in the rad after driving it to see if the gauge is correct or not .what temp thermostat would be stock from the factory ?

 

When valve seals leak, typically you will see smoke during accelleration after having idled a while. The longer you idle at a light, the bigger the cloud upon accelleration. My Ford's 2.3L goes through valve seals every 10 years, so I am pretty familiar with the issue.
Add a 180* t-stat and use 15W-40 oil in summer. I doubt the "high mileage" formula is actually doing much for the engine.
Stock t-stat is a 190*, but 180* has been my choice and have been happy with them for 20+ years. 190 was used to lower emissions.
An IR thermometer would be faster, more accurate, and safer. They cost as little as 10 bucks. Trying to open a hot radiator is dangerous, no matter how carefull you are with it. Also, you would be measuring the coolant AFTER it has been cooled, giving a false reading.

 

Thanks Rob ,how you just explained does make sense in the way that the smoke cloud
appears ,I guess a valve seal job is in my future ,MAW pull the heads add bigger valves
3 angle valve job ,roller rockers ........lol

 

My first car had the Ford 2.3L, I know what you mean...

 

I have been having the same problem, smoking upon accelaration after idling, or sometimes while idling, a large "puff" of smoke comes out for about 10 seconds.

I changed the valve seals last weekend. Not a fun job. I did it with the heads on the engine. If the heads were off, it would have been relatively easy. If you are going to buy a spring compressor, don't buy the one from
Autozone, it sucks. The one from Oreilly was much better and it was roughly the same price.

I haven't got the car started up again yet (still doing some other work on it), so I don't know if this fixed the problem. I sure hope it does, that will suck if there is a problem with the rings or the pistons.

Good luck man.

 

I'm going to try this too. Thanks Rob!!!

 

Yea ... I'd recommend the infrared & definitely see what the temps are.

That would be a priority if it were me.

Your seals are probably questionable ...

But oil with a potentially high concentration of unburned fuel from running too cool ... certainly wouldn't be helping.

That just thins out the oil & makes it lose its ability to lubricate properly.

Get a 180 t-stat in there & switch over to the thicker oil recommended & see what happens.

How are you're valve cover gaskets ?.

If they are leaking you can always pull a MAW & take that opportunity to check out the oil returns in the heads while the VC's are off.

Especially since you mentioned prior breather/PCV issues.

I saw a head so caked up with sludge one time ... the motor smoked 24/7.

Cleaned out the returns & voila ... no more smoke.

Every lil' bit helps.

 

Well, put on your anti-MAW helmets (pointy-side up!) and join me in the virtual adventure of valve seal replacement!
Disassy:
https://classicoldsmobile.com/forums...tml#post317189

Reassy:
https://classicoldsmobile.com/forums...tml#post318371

I found this job to be easier with the inner fenders out, brake booster out, AC box out, etc, etc.....

It is a great idea to clean / check the oil return holes in the heads as a mini-MAW. I did not even know I HAD drain holes in mine!
https://classicoldsmobile.com/forums...tml#post294407

I figure if that is the only issue I have with that car, it is worth keeping. The rest of the drive train is still factory and working well!

 

thanks for all the advice guys ,i did change the valve cover gaskets and the drain holes were ok on the pass side a bit of crud in them which i cleaned out but the driver side rear drain hole i could barely get my finger in it ,not sure if it was casting flash or crud was hard to tell but i wasn't about to go jamming something in there to loosen it .I'm going to switch the oil over today to 15w40 and see what happens and get a 180 F in there too ,a compression test is in the works asap ,just to let me know what condition the cylinders are in .I'll let you guys know what transpires .

 

Did the car sit for a long period of time prior to you getting it? I would run some Rislone, Marvel Mystery oil, trans fluid, your choice in the oil system, for about a 1000 miles prior to the oil change. I'd also dump a pint of Marvel Mystery oil in the fuel with a full tank, it will clean up sticky rings, lifters, oil passages, etc...

 

Here is a good explanation on how the holes are designed - they go upwards, not straight down.
If they are full of crud, pick away at it with a screwdriver while holding a shop vac hose right above it to suck away the crud you are picking so it does not make its way into the engine.

 

Changing oil brands can make a vehicle use oil also. I had a customer a few years back that purchased a chevy van from a loyal pennzoil user. When we did the inspection on it, the oil got changed to Kendall and the van statred using oil bad.. to the tune of 3 quarts in 500 miles. He brought it back and we changed the oil again.. the oil consumption got better. The Kendall cleaned the inside of the engine up enough to help the rings seal again.

 

I decided to go with 20w50 oil to put in I figured thicker would be better and it definitely is much better ,still smokes lightly but I'm not fogging the neighbourhood now!The T-stat in there was a 180 so I replaced in anyways ,could have been faulty ,buttoned back up and drove it to my buddies place and discovered that the temp gauge is wayyy off by at least 30 degrees ,it'll have to go at some point .Marvel Mystery oil I don't know if i've ever seen that product up here in Canada ,I've used Restore before in an old 78 Pontiac that i had and it worked like a charm,stopping smoking within a week !Thanks guys for all the input
I can put the re-seal job on the winter to do list now and just enjoy the rest of the summer.

 

soooo.. i just figured out something tonight regarding my blue smoke issue which when i go back to my original assessment of my plugs it all makes sense .the number three intake valve is right where the transmission vacuum line is for the modulator ,my number three plug was the only plug that was wet,i believe that i have a bad modulator which from what i'v e just read may be the source of the blue smoke coming from the exhaust,as the engine will suck up the transmission fluid ,which just recently i've had to replenish with two litres!,as I noticed a slippage one day last week when i went to take off from a stop.
soooo... tommorrow i will get a new modulator , plug her in and see if the smoking bear will cease ! wish me luck

 

But if going to a thicker oil caused the smoke to be lighter, there may still be an issue in the engine. Do see what replacing the mod does. If it is leaking it does need replacing!

 

For sure the engine might still have issues
but I'm thinking that I' ll change the modulator
take a test drive and find out the results and go
from there . I looked at your pics from your
valve seal change Rob , it looks a bit tricky to do!

 

Well got the modulator changed and the tranny topped
up with fluid and it looks like the smoke has
cleared up so far , keep my fingers crossed

 

Great - I'll cross mine, too!
Keep us updated...

 

went for a longer drive today and.... NO SMOKE thanks guys for all the advice.Just shows ya sometimes you have to think outside the box a bit .

 

glad it's fixed =) too bad monday is gonna be a scorcher u got a/c in that bad boy?

 

I am hoping it wont be too bad in Canada. Now down here is another story... Had 107 today.

Great diagnose on the problem; glad you have it fixed now!

 

UPDATE

I replaced the valve seals, still smoking. Then I put in a pertronix, still smoking.

Finally replaced the transmission modulator. Bingo. No more smoking. I told an old GM mechanic about the problem and he asked me if the plugs on the driver side were fouling. Yes they were. He reccomended replacing the modulator. Old guys rule!!!

 

Ah, yes! The bad modulator! Been there. Done that. What a mess!

 

So it was sucking trans fluid? Usually that would result in white smoke, not blue

 

Yes. Could have been white smoke, could have been blue. Don't know for sure. All I know is that it appears to have stopped smoking.

 

This thread has been going on for over seven months now, without anyone giving the lowdown on modulator problems (which may be helpful for other readers).

The transmission vacuum modulator is the way that the transmission determines how much load the engine is under, in order to decide when to shift - sort of a throttle position sensor. It's just a vacuum diaphragm with a specific amount of spring pressure and travel that translates the amount of vacuum present in the intake manifold into linear movement of a valve inside the transmission.

Because it is a vacuum diaphragm, every modulator will eventually go the way of all diaphragms and develop a hole.
When that happens, the vacuum of the engine will... suck ATF out of your transmission and into the intake, where it will be burned.

Symptoms of a bad vacuum modulator include:

• Smoking, especially of suden onset, in an otherwise good-running engine
  (rings and valve guides / seals don't just decide to suddenly go bad one day).
  If you stand behind the car and smell it, the smoke will smell like ATF and not like motor oil.
• High shifts, like you've got your foot into the pedal too much
  (because the transmission thinks you do have your foot into it)
• Maybe a rougher idle (vacuum leak)
• Mystery disappearing transmission fluid.

To confirm the problem, you don't need to remove the modulator, or even get under the car - just pull the hose that goes to the transmission off of its barb on the intake manifold and push your finger into the end - if it gets wet with ATF, then your modulator's bad.
A further test is to pull a vacuum on the hose, either with one of those hand-pumps, or by sucking on it - if it holds a vacuum, the modulator's good, if it leaks down, it's bad (or you've got a leaky hose or connection).

To replace the vacuum modulator, crawl under car, remove single small retaining screw, pull modulator straight out, remove hose, push new modulator straight in, replace screw and hose.

- Eric

 

Thanks for the great write up Eric!

 

You're welcome, Allan!

Edited because on rereading, I forgot something .

- Eric

 

Ahh, the mystery disappearing ATF. I'd think the clue there would also be after a short while the trans wouldn't go into gear as the fluid gets sucked into the manifold?

Just thought of something else in the 'analysis'. Pull the trans line and plug both intake and line (vacuum loss). See if the smoke goes away. Pretty much the same as what you said though - just from another angle.

 

I had the disappearing ATF symptom. However, I also had a SEVERELY leaking transmission pan so I didn't make the connection. It was after I replaced the pan and fixed the stripped pan holes that I realized the ATF was continuing to disappear. It was then, that an old mechanic put two and two together and postulated that I had a bad modulator. We replaced it and viola, looks like that was it.

Again, old guys rule!!!

 

Now I need to change the oil. I'm sure it has alot of ATF in it. Probably not good for the engine. . .

 

No...

The ATF went into the intake manifold and got burned.

It's all gone now.

The bald eagles and ring tailed lemurs and spotted owls and polar bears and horned toads are all sad now, because they're breathing it in, but your engine is happy .

- Eric

 

The wet sparkplug from the #3 cylinder where the vacuum line draws from for the trannie was the clue for me of a modulator that wasn't doing it's job as my trannie still shifted and it wasn't obvious that it was having any trouble until my trannie fluid started disappearing then i noticed the trannie acting up.MY biggest problem was trying to get that bolt loosened it just wouldn't budge and I eventually broke it off at the transmission .Eric,nice explanation ,I got one question for ya now, how do i fix the broken bolt without taking the tranny out ?

 

That's a very tough one.

If you have enough clearance, I would try centerpunching the screw EXACTLY in the center, and drilling the center out, a small amount at a time, then, when it's almost drilled out, see if you can get an EZ-Out to turn it - there are some nicer ones available these days at places like Sears.
If the EZ-Out doesn't do it, then drill a bit bigger and try to tap the hole to the right size - this might losen the remains enough to get them out. If the remains don't come out, then try using the hole you tapped.
If the hole is too screwed up, then HeliCoil it and you're done.

Of course, if you don't have the clearance to do all that, then it's got to come out.

- Eric

 

Thats gonna be tough Eric without dropping the trannie somewhat to access that bolt ,it is a very tight squeeze in there ,I may just leave it as is for now ,I Mc Gyver'd a replacement to hold the modulator in that seems to be working .
I do believe that vacuum is holding it in there tight enough so it's not loose .

 

i'll give this a try, my car does produce white smoke and I wonder if this is a fix for me as well... did you guys notice a significant amount loss in tranny fluid?

 

Don't waste time gathering opinions and experiences - go out, open the hood, pull off the transmission hose from the manifold, and see if there's ATF in it.

- Eric

 

Yes quite a bit , approx 4 Liters in my situation .