Seal old rings
 

I have one bad cylinder that is 125# as compared all the others running 145-155#. I pumped air into the cylinder and its definately coming from the crankcase. I'd like to try sealing them with a product that others have tried with good outcome.

I have a can of bonami( powdered polishing compound) that seems like others have used in the past. If I remember right you disolved a table spoon of the powder in a half cup of water and trickled it into the carb and let the car run till the smoke disappeared. Then changed the oil after.
I thought I would also try one of the additives that profess to re-seal rings in old motors. I hate to have to spend a thousand on a motor that barely gets driven a thousand miles a year.

I'm open to suggestions.
BTW. This is not one of my pontiacs.

Sounds like snake oil to me.

To me, this is what I would use as my guide. If it gets driven that little I would leave it alone. I certainly wouldn't introduce a scouring agent into it!

BEFORE you screw with abrasives, try a couple of solvents. The first solvent is water. The second is GM/Delco Top Engine Cleaner, (my preference) but some folks have good luck with Seafoam, or other combustion-chamber cleaners.

Run the engine to proper operating temperature. Remove air cleaner, drizzle a "urine stream" of water back and forth between the two primary carb venturis at ~2000 rpm. I sometimes use a soda bottle with one of those push/pull "sports drink" nozzles screwed onto it. Anything worth doing is worth over-doing, I use about a gallon of water. It doesn't take very long. You want to swing back and forth between the primaries fast enough that the engine doesn't misfire. Water does a fabulous job of steam-cleaning the combustion chambers. You'll get rid of any soft carbon, and a fair amount of baked-on carbon. When you're done, let the engine run a little while longer to assure all the water has boiled out of the intake manifold, and that'll take water vapor out of the crankcase via the PCV valve also. Shut off the engine, let it cool.

Loosen all the plugs when cold (especially with an aluminum head. Maybe even put anti-seize on the threads.) Put 'em back in, start the engine, warm it up to full operating temp. then shut the engine off. Remove the plugs hot. Use a pump oiler or funnel or whatever is needed to put about two ounces of GM Top Engine Cleaner in each cylinder. Turn the engine by hand (Not the starter motor) with the plugs out, at least two full revolutions. Put the plugs back in loosely to keep crap from falling into the cylinders. Let it soak overnight.

Next morning, tighten the plugs, crank engine at least two revolutions by hand to assure the engine isn't hydro-locked. Start the engine, (it will smoke like mad!) and then dump the rest of the bottle of Top Engine Cleaner into the carb primary barrels, slowly at first, but using the last of the product dumped in rapidly enough to stall the engine. Again, let it soak overnight. Next morning, start engine (clean plugs if needed) and take it out for a drive. Ideally, you'd run it hard in high gear for lots of cylinder pressure, then let it coast down as if you were seating rings on a new build.

With the easy-to-remove carbon and deposits gone, the Top Engine Cleaner solvents away the remainder of the crap sticking the rings. If the water treatment (first) then the Top Engine Cleaner doesn't help the rings to seal, you're probably looking at engine disassembly.

When the two-phase process is done, you might want to change oil and filter.

We have an AC Delco product available here (maybe outlawed in the first world, I don't know) that comes in an aerosol. You direct a stream into the carb at fast idle until it's nearly finished then stream it fast enough to stall it. You let it sit fifteen minutes then start it and rev it. Huge clouds of black smoke and your neighbour will hate you but it sure cleans out the crud. Probably causes cancer just by looking at the can.

Sam

If the motor is stock then it has a Moly faced top ring , if the motor has been rebiuilt then it likley has a Moly faced top ring and maybe even the second compression ring has a Moly face also.
What this means is that if you put any fine grit into that bad cylinder like Bonami it will only serve to distory the rings Moly face and then you have even more leakage from that cylinder!

The Bonami trick worked on old type Chrome faced rings that needed a corse cylinder wall finish to bed in on and as such took a long time for that type face ring to seat up.

If your motor is newly rebuilt and has more then 300 miles on it and 2 or 3 full throttle blast on it then that low pressure reading cylinder needs to be addressed on a mechanical basis , not a ring brake in bassis.

might be a bad valve seal.....

He posted that he hears leakage into the crankcase when he pressurized the cylinder, so that's not a valve seal issue .

Oh ok....

The op really needs to pin down what's going on here and soon, because if it's due to a broken ring or piston then it's only going to get worse and in turn cost more to fix as time passes!

If it where me I would want to look into the Bore with a camera with the piston at BDC to atleast see what the walls look like.

I have no idea how many miles are on this motor. It was in the car when I bought it 12 years ago and the 10 years that the previous owner had it. Before that I have no history. It was a parts car for the PO so it didn't get driven much. We've probably put less than 10K miles on it since we've owned it. It actually runs fairly well albeit a little rough at idle and the rpms drop into dangerous territory when I drop it into gear. If not for that I would leave it alone until it was unmanageable. If I kick the idle up higher it slams into gear. So as it is I just have to two foot it a bit at a stoplight.

I'm going to try some SeaFoam in it today and change the oil and add the snake oil that's supposed to help seal the rings up. If it doesn't do anything I'm no worse off than I was( just out a little cash). I'm not totally sure that one cylinder with the low comp is the only reason for the miss but it's my best guess.

My wife came home and asked if an alien ship landed in the driveway. That's because I'd done Shurkey's water and cleaner approach on an old s-series blazer, and the tailpipe was aimed at the ground on my gravel driveway. Hot engine, cold water, used up 2.8 blazer, it was a recipe for a Carbon Celebration. I had nothing to lose, and the driveway suffered as a result. Maybe some rocks got cancer, hard to say. It sailed thru the I/M240 emissions test afterward, and never ran better.

if the engine could PING then it could be a cracked ring.

Otherwise, oil change and run it on the highway; uphill load helps

The Bonami trick is for a desperation situation. An old ford pickup or any other old ford....

You very well may have a flat cam lobe as well.

Pop the valve covers and poke around a little and watch the rockers while running

Throw a can of restore in it.
I had a GMC Jimmy 4WD that had about 150K on it. Had low compression in one cylinder. Treated it with 2 cans of BG Fuel system cleaner, one can of Seafoam in the crankcase, drove it for about 250 miles, changed oil to Valvoline High Mileage and put a can of Restore in it. Stopped the blow by and ran until I sold it with 235K on it.

MMO is your friend. Add 1 qt to the crankcase and run the engine. We used to do this all the time when aircraft recip engine would have low cylinder pressure but no other indications of other mechanical maladies. in most cases the compression would come up enough to put off a top overhaul for a few more hours.

I tried the Bonami trick 20 yrs ago on an engine I rebuilt that washed the ring out on break in. I didnt work at all, and that was a fresh engine. I ended up pulling it and had to rehone and add fresh rings.

Hoosier, what is MMO?
Got some work in on it today. The other day when I was poking around I happened to put my hand over the carb intake and the idle raised right away. Hmmmm. Idea planted. It's getting too much air or not enough fuel for the amount of air. Hmmm. Vacuum leak.? Bought some carb cleaner today and while I was giving it the Seafoam treatment I sprayed it around and got a hit in between the gap in the intake runners. Either the intake is cracked underneath or the gasket slipped. Pulled the intake and sure enough the gasket had moved and created a vacuum leak into at least one of the ports. New gaskets on and it's running much better. Not sure if the Seafoam has done any good or not. I'll change the oil out tomorrow and make the run this weekend up to the concours at Ironstone in Murphys. Probably around a 500 mile weekend. I'll do a comp check on #7 next week. And see if there's any change.
Thanks for all the help and opinions. It helps to hear what others are thinking.
BTW. It is an old Ford

Marvel Mystery Oil.. Old, OLD school stuff...

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