1984 Olds 307 V8 / Lots of blowby but no oil usage... (?)

[pfloro]

Although I haven't owned my '84 Toronado (307 V8 - VIN "Y") for a decade, I have been puzzled about this for a long time.

Unfortunately, I never took compression readings or performed a leak down test.

***

At ~150,000 miles, when tuning (air cleaner housing off) and revving to perhaps 2000 RPM, I noticed a tremendous amount of blowby

coming out of the breather pipe which connects to the left side of the air cleaner housing.   Absolutely no oil was being consumed and there

was no oil film in the air cleaner housing.  I always changed it every 4 months (~2000 miles / non-synthetic 10W-40).  I'm sure that compression

was a bit low but all the plugs looked fine, starting was easy, and the idle was rock steady.  I always passed emissions but the HCs were

getting closer to the limit as the mileage rolled up...  Before I sold the car (200,000 miles), the HCs were:  Loaded reading - 117ppm (limit: 220) / Idle reading: 132 (limit: 220).

CO readings were rising but within limits.  Loaded reading:  .63% (limit: 1.2) / Idle reading: .11 (limit: 1.20).

 

Can an engine have lots of blowby but not use any oil...?   If the compression rings and bores are worn causing lots of blowby, can the oil control rings still 

hold back oil usage...?

 

I'm always want to learn so I'm curious about this...!

 

Thanks for your thoughts...

 

Paul

 

 

Edited October 27, 2023 by pfloro (see edit history)

[Rusty_OToole]

Apparently yours did. I don't know how to account for this, a worn engine should burn oil but who knows.

[joe_padavano]

More likely is that the oil use is low enough that you didn't notice it between oil changes.

[Bloo]

3 hours ago, pfloro said:

Before I sold the car (200,000 miles), the HCs were:  Loaded reading - 117ppm (limit: 220) / Idle reading: 132 (limit: 220).

CO readings were rising but within limits.  Loaded reading:  .63% (limit: 1.2) / Idle reading: .11 (limit: 1.20).

Those numbers sound more like the catalytic converter was getting a little tired than any sort of engine problem.

 

3 hours ago, pfloro said:

At ~150,000 miles, when tuning (air cleaner housing off) and revving to perhaps 2000 RPM, I noticed a tremendous amount of blowby

coming out of the breather pipe which connects to the left side of the air cleaner housing.

Was that a new sudden thing?

 

3 hours ago, pfloro said:

there

was no oil film in the air cleaner housing.

Could the hose have been disconnected? Those cars always had some oil film in the air cleaner even when new, just not usually liquid oil until the engine got old and worn. Olds V8s didn't get old and worn as quickly as most other V8s of the period. PCV systems designs are limited by the amount of available air and cannot ventilate 100% of the time. Oil vapors are going to come out of the breather part of the time when the PCV cannot keep up. It is unavoidable.

 

After GM (and others) put the breather up inside the air cleaner, that is where the oil film went instead of out on the valve cover. The idea was that when the PCV could not keep up, the overflow of vapors would get sucked in through the carburetor and burned. It worked, but as the engine wore and the blowby got worse, the PCV kept up less and less of the time, and liquid oil would wind up in the air filter housing.

 

3 hours ago, pfloro said:

If the compression rings and bores are worn causing lots of blowby, can the oil control rings still 

hold back oil usage...?

Yes, because compression and oil are controlled by different rings. The opposite is more likely though.

 

 

Edited October 28, 2023 by Bloo (see edit history)

[pfloro]

1 hour ago, joe_padavano said:

More likely is that the oil use is low enough that you didn't notice it between oil changes.

I always checked the oil level just before a change (engine warm) and for a few days after the change.  My old eyes may have been fooling me...!

 

1 hour ago, Bloo said:

Those numbers sound more like the catalytic converter was getting a little tired than any sort of engine problem.

The cat wasn't original and it probably had only 50,000 miles on it...  The original one rusted out.  That was a long time ago...!

 

1 hour ago, Bloo said:

Was that a new sudden thing?

No... but I must have become aware of the blowby somewhere around 150,000 miles.

 

1 hour ago, Bloo said:

Could the hose have been disconnected?

This engine had a breather filter set into a grommet in the center of the left side rocker cover.  A formed metal pipe then connected to a fitting on the air cleaner housing. 

I changed the filter every year and it was never saturated with oil.  Back in the day, I would raise the hood and check everything over fairly frequently.  

It's funny:  My brother and I never got along too well but he did tell me more than once that "you know how to take care of a car"...  God rest his soul...

 

********

 

I appreciate everyone's feedback.   The Toronado was a good car but toward the end, I got tired of driving a living room sofa...!   A good friend called the car "The Queen Mary"  or  "The Ship"...

 

Paul

Edited October 28, 2023 by pfloro (see edit history)

[arcticbuicks]

are you getting the blow by from the hose on the drivers side valve cover to air cleaner ?...........the passenger side valve cover has the PCV valve inserted in grommet in valve cover........if stuck or plugged would give blow by out the driver side hose.........if you follow the right valve cover pcv hose ........it will end up at the front center bottom of carb........these hoses were known to also collapse usually close to carb.........a quick old fashioned test of the pcv valve is pop it out of valve cover with engine running and put your thumb over it multiple times and should feel a click and very good suction like a shop vac in pcv valve each time ......and notice change in rpm........before replacing.......can clean pcv valve with parts cleaner and blow out with air.......good luck

Edited October 28, 2023 by arcticbuicks (see edit history)

[pfloro]

Thank you arcticbuicks...   The car has been gone (but not forgotten) for over 10 years.  However, I did check the PCV valve for proper operation when I first noticed the large amount of blowby.

 

Paul

[Wascator]

In high-mileage engines manifold vacuum can pull oil and air past the intake valve stems if the  guides are worn and/or seals ate hard; often the first place for consumption to show up. 
I couldn’t stop the valve covers on my ‘85 from leaking oil but it ran great. I had a headliner installed and sold it to a friend. Quite a handsome car in my opinion. GM called it “the sheer look” and supposedly it derived from the original Seville which I also loved. 

Edited November 15, 2023 by Wascator (see edit history)

[joe_padavano]

2 hours ago, Wascator said:

In high-mileage engines manifold vacuum can pull oil and air past the intake valve stems if the  guides are worn and/or seals ate hard; often the first place for consumption to show up. 
I couldn’t stop the valve covers on my ‘85 from leaking oil but it ran great. I had a headliner installed and sold it to a friend. Quite a handsome car in my opinion. GM called it “the sheer look” and supposedly it derived from the original Seville which I also loved. 

I'll add that I've owned five Olds 307s from 1984-86 and all of them have weak valve seals.