the car junkie daily magazine.


Driveway Tech: Attempt One at Freeing Stuck Piston Rings – Did We Succceed?

Driveway Tech: Attempt One at Freeing Stuck Piston Rings – Did We Succceed?

Everyone says that buying a ganny fresh old car is the best. They are one owner, low mileage gems that granny ony drove to bingo and her Wednesday hair appointment. There can be a problem with driving nothing but short trips. Carbon builds up on the pistons, rings, and valves without longer trips where the engine gets higher rpms at longer periods of time to burn it off. Years later, a new owner gets this great car with a smooth running engine that is also using oil. That is a problem we are having with a low mileage ’73 Monte Carlo we are working on. It’s a great car. It runs and drives fantastic, but it’s 350 is going through the oil nearly as fast as gasoline.

We just replaced the original heads with freshly rebuilt set. We even spent the dough to have the valve guides machines for top of the line Viton seals. We solved the problem with the car smoking like a steam engine every second it’s running, but the oil useage remained. We thought that we’d need to pull the whole engine and rebuild the short block to solve this issue.

But first, we wanted to know what the hell is up. What was causing this. After talking with smarter people than us including our machinest, Garrick Preece at Kelly’s Block Welding, he said that the lack of long trips where the engine gets up to rpm and heat the carbon buildup on the piston rings can cause them to stick and not seal the engine. Add to that, the Monte Carlo sat for long periods of time with very little use; added up to lack of sealing in at least one of the cylinders. The picture below shows the pistons in our 350 as they looked when we changed the heads. Lots of carbon gunk on them.

A look at the Monte's 350 with the heads off

We were looking for a fix that didn’t include an engine hoist and a machine shop bill. We’ve heard of all kinds of remedies over the years to help piston rings seals. From the old tale straight from GM telling service departments to pour Bonami down the gullets of the then new small block V8 to get the rings to seal (Yes, the legendary small block was an oil burner like the Ford flathead.); to the a couple quarts of diesel fuel in the crankcase. We haven’t seen Bonami on the shelves in twenty five years and putting fuel where the oil is supposed to go, frankly, scares us. There were other tried methods we’ve heard over the years. Marvel Mystery Oil in the cylinders, let it sit for a week. Revving the engine to 2000 rpm plus and spraying water down the carb. Transmission fluid in the crankcase. And, transmission fluid into the spark plug holes, let it sit for a few days, and fire it up. We chose the last idea.

But, before we started dumping tranny fluid down the cylinders, we decided to do a compression test to make sure we don’t have a completely dead cylinder. We also thought we might be able to locate the cylinder with the sticky rings. If you have never done a compression check before, it’s quite easy with the right tools. We got our compression tester from Sears toy department, Craftsman. It’s just a gauge and some adapters to fit different spark plug sizes.

Compression tester

First thing to do is to warm up the engine, then pull the plug wires, and spark plugs. We just draped the plug wires on top of the intake, out of the way.

Wires on the intake manifold

Next thing to do is open the throttle of the carburator wide open. We just use the throttle return spring to hold it open like in the picture.

Carb pulled open with spring

Then, screw the proper adapter into a spark plug hole and attach the gauge. Then it’s just a matter of cranking the engine. The gauge will go up with each compression stroke as the engine spins. Keep cranking the engine until the needle on the gauge stops climbing. It usually only take four cycles of the engine to get a final reading. Write down the number on guage and continue the process for all eight cylinders.

Compression test

Compression test
We ended up with pretty good readings on all cylinders. Most repair manuals say the cylinders should be within 15% high to low numbers. Our Monte’s 350 scored the following:

1. 150 2. 155
3. 150 4. 155
5. 155 6. 160
7. 155 8. 165

We didn’t get a low number, or a dead cylinder indication. We should’ve dug out our leak down tester at this point which is a better tool for finding leaky piston rings, but we were running low on time. We were going to continue with our remedy anyways, so we just got on with it. We got a quart of ATF and a flexible funnel and got to making a mess.

Liquid magic?

The funnel’s end is small enough to go through the spark plug hole. We poured about 3-4 ounces of ATF into each cylinder. One cylinder was at top dead center and the fluid just poured back out of the hole. So we clicked the starter a couple times to get the piston down in the hole far enough to take in the fluid. After getting ATF into every cylinder, we put the spark plugs back in. But, before reconnecting the spark plug wires, we cranked over the engine a few times in order to use the compression strokes to force the ATF into ring lands. This is very important. Only use a few ounces and don’t completely fill the cylinders. It can cause the engine to hydrolock if you tried firing it full of ATF.

The ATF heads for the spark plug hole


Then it was just a matter of waiting a few days. The detergents in the transmission fluid should break up the carbon build up. Hopefully, the rings will get unstuck and seal the cylinders better. After a few days, we started up the car. As you can imagine having that much oil in the cylinders caused a bit of smoke. The car will smoke for a while. In order to get the car to clear up the billowing smoke faster, we took a 15 mile jaunt down the freeway. The first mile no one behind us could see through the smoke screen.

She's a smoker

Here’s the Youtube video of the car as a gross polluter. Thankfully, most of our neighbors were at work so they couldn’t call CARB on our asses.

What was the result of this freebie fix? The jury is still out, but it looks like it’s a fail. We still see smoke when we are hard on the gas pedal. And, the oil level was down after a 80 mile trip on Sunday. But, we didn’t check the oil before the trip, so we’ll have to see. If it looks like a bust for sure, we’re planning to spray water down the carb with the engine running as a next step. This comes from noticing that cylinders with a blown head gasket always have sparkling clean pistons. We’ll keep you updated.

The Monte lookin' good


  • Share This
  • Pinterest
  • 0

19 thoughts on “Driveway Tech: Attempt One at Freeing Stuck Piston Rings – Did We Succceed?

  1. jack pine

    Did you notice the ‘first puff’ pressure reading for each cylinder? This is usually a good indicator of the quality of the ring-to-cylinder seal. It’s the first swing of the rod from TDC to BDC. I can’t wait to follow this thread. Lots of suggestions about how to un-stick rings

  2. Robert

    Try some GM Top Engine Cleaner
    part# 88861802. Start the engine and get it up to temperature. Then suck some up with a small vacuum line disconnected and inserted into the bottle of cleaner. Shut the engine off and remove the spark plugs. Squirt some cleaner in each cylinder. Let it soak for 1 hour. Crank the engine with the coil disconnected to clear the cylinders. replace the plugs and start and run at 1,500 -2,000 rpm until engien gets up to normal temperature again then do 2-3 full throttle acceleration runs from a slow roll 10-20 mph up to highway speed in a safe area. GM techs rely on this stuff.

  3. C1BAD66

    Please keep this subject open. I have a friend with a 4 or 5 year old “Goodwrench” 350 which goes through a lotta oil. He claims it doesn’t smoke or leak. It gets short-trip usage, only. ‘Sounds like the same problem.

    Introducing water into the intake system causes leanness, hopefully burning off carbon deposits. What effect it has on ring seal, I don’t know…

  4. dieselgeek

    … that the oil isn’t coming past the rings? Compression looks fine, what about other possible sources?

  5. OldMachinist

    Usually when rings are leaking oil, the oil will clean the outer edge of the top of the pistons. It’s hard to tell from the pictures if this is happening.

  6. 428FE

    That GM top engine cleaner Robert talks about is some good stuff. I have used it and it works. I poured it down the carb while working the throttle instead of pulling a vacuum hose.

  7. pro1

    Make sure that you don”t have a intake leak which can suck oil out of intake valley. Try spraying some WD40 into cylinders and leave it sit a couple days. Also you can check compression again take your baseline that you have now spray some WD into cylinder and see if compression gains or stays the same which will determine piston or valve problem, if compression increases normally ring seat issue .

  8. Chevy Tech

    In my experience this problem is usually caused by carbon blocked oil drain holes behind the oil rings, you still have good comp from the top rings but the oil drains for the lower rings will be mostly blocked.
    The only sure cure is to pull the pistons and open up these holes with a handheld drillbit

  9. b3m

    I agree with chevy tech..and for rings to get that bad, there is something else in the oil..bad headgasket is number one. the carbon will be as hard as plastic..no dissolving, it created a real product, not just got dirty. At least the engine is iron.. those are easy. Forced to use this engine..marvel in a long term, I mean months does good..but that is on non-siamese bores. the iron 8s are stuck when they are stuck. no mircales.

  10. efi-diy

    The shop I used to work at used Karb-Out – get the engine hot (220F or so) Rev the engine up and dump the whole can down the carb as fast as you can and let the throttle close – the engine will stall which is what you want. If doesn’t shut it off immediately after the can is empty.

    Wait a day or so. Then fire it up (it’ll smoke bad) and get it hot then with the engine at RPM (3000 ish) run a 1/4 stream of water into the carb. The steam will clean the engine out.

    Then fill it up with super and go run the snot out of it on the highway – it’ll clean any residual crud out.

    Change the oil and filter – before you do get the engine hot and put in a quart or so of kerosene into the oil and run the motor at fast idle for 10 min’s (don’t put any load on the engine) then change the oil. You’ll be amazed how well the kerosene cleans all the crud out of the bottom end. Repeat after 500 miles or so until the oil stays clean.

    Best if you can let the oil drain for 1 hour with the car tilted to get the most oil out of the pan.

    Prefill the new filter with fresh oil and turn the engine over with the plugs out to prime the motor.
    If this fails then its tear down time.

  11. Anonymous

    Fill the cylinders with carb cleaner – it will dissolve the carbon. You want the gnarly stuff that eats paint. GM top end cleaner works well also. Take the plugs out and fill the cylinders and let it sit for a couple of days to work. Then take all the plugs out and turn it over to clear the cylinders.
    Make sure you change the oil after you do this.

    Throw the plugs back in and fire it up and run it down the highway. It will smoke like a crazy at first but should clear up.

    I had an old 318 mopar that had all the oil rings stuck from sitting and no maintainance. This cleared it right up.

  12. Tuning Nerd

    The GM cleaner, or a Marine top end cleaner work. To really free up the rings in the lands, the rings have to be loaded and the cylinder subjected to higher bmep. An automatic transmission in drive will not do this, you must shift to a lower gear and run the engine at a higher RPM to get the power up. This will work the rings and hopefully loosen them up. The downside to this is the deposits may score the cylinder walls, especially if thereis trapped silicate material.
    Stuck rings should also make the oil black and the engine oil temp hot as the combustion gasses sneak past the rings. I’m wondering if the engine sat in one position for a long time if the cylinder walls were etched and corroded, and that is where the oilis getting by. It could also be due to such high crankcase pressure that oil is being pushed out the breather in a mist. I find Marvel mystery oil works well in the FUEL to clean combustion chambers, as the combustion process vapor blasts the.piston, valves and head. The contaminants head out the exhaust. I wonder if the breather recircs to the intake snorkel or air cleaner, that right there could be the cause of your smoke machine and oil loss.

  13. TheSilverBuick

    I like this Drivewsy Tech. Great write up and pictures as usual Scott.

    I agree with D/G, IMO the compression is that far off for a ton of oil consumption unless the rings never really seated or the cylinder walls are all worn out.

    Any chance of an intake leak into the lifter valley? How are the plugs looking afterwards?

    I’ve done the water spray down the carb with 305’s and 307’s before. Cure’s the dieseling for a while. Though I also usually follow it up with going out on an empty highway or industrial road, load the carb with SeaFoam and then run hard from a stop to redline in first gear a few times to keep the engine loaded and hammering the carbon.

  14. Scott Liggett

    Thanks for all the ideas and theories. I’m going to try a few of these out and show the results, good or bad.

  15. John Brown

    Where I used to work, we got a lot of “old lady” driven Olds And Caddies. We would pour a can of BLASTER TVF in the oil when they complained of a dragging starter or heavy oil usage. By the time for the next oil change, the oil burning and dragging starter complaints were usually gone. BLASTER used to have a couple of thousand words on the old funnel top cans, and one of the things they claimed was disolving carbon behind stuck piston rings.

  16. Mark

    Use Seafoam and Deep Creep. WIth the engine at idle, spray the Deep Creep (Seafoam in an aerosol can) down the carb until the motor quits. NOw, remove the plugs and pour some Seafoam into each cylinder (or spray Deep Creep in) put the plugs back in and let sit overnight. By letting it sit overnight the carbon is reduced to a goo that will blow out the next day when you start the motor. Plus, you won’t see a mosquito for miles! I have used on both 2 and 4 stroke engines and this works!

  17. lee sherman

    Don’t forget to check the trans. vacuum modulator for a split diaphram. This will pull ATF from the trans. straight into the intake on the motor. Badly overlooked item.

  18. Mark W

    Vote # 2 on SeaFoam, that stuff is the bomb. Buy two cans. put one in the gas tank (on half a tank) and split the other in the crankcase and through the intake (after warming the car up, and while its running). It’ll smoke more than a Vegas slot whore, but the stuff works great. Run it a 100 miles at highway rpm then change the oil and filter.

Comments are closed.