[old66tiger]

The only one that was not consistent was #1 cylinder. The other ones with low compression yielded high leakage. I spoke with Wayne Schicantek yesterday and he agreed with me that the high leakages are not good. He figured that a new motor should have less than 10% across the board.

This is just the start of my troubles. I pulled the motor apart and some of the shot peen that was left in the motor from the original build made it's way to the mains and the rods and the cam bearings. As it stands, the motor has to be honed, new rings installed, the crank turned, and new cam, rod and main bearings installed. The fun never ends.

[gtofreek]

Leakdown tests are good for finding real issues in an engine. Ring seal is greatly dependent on combustion pressure. If someone were to do only a compression test on this engine, they would say it's fine. Yet the leakdown suggests it has real issues. If the compression test is good but the leakdown test shows bad, I would go with the compression test over the leakdown test. Unless the leakdown test showed leakage coming from other than the rings.
When doing a leakdown test, if you put pressure on the crank like your trying to turn it, and you add pressure and relax and add pressure again, you can watch the leakdown numbers go down as pressure is added and they go up when pressure is relaxed. Rings that don't seal real good stationary, may seal fine when the engine is running. I think if the rings were as bad as they seem, the compression test would have showed it low also.

[old66tiger]

If that is so, why am I burning through oil? Also, the oil gets dark really quick AND I have blow out through the breather.

[pugslyx234]

Originally Posted by Irish68Firebird

This may surprise a few people as it runs against conventional wisdom on a number of fronts, so don't kill the messenger. I am just reporting my bonafide results.

I recently rebuilt my engine in my 68 bird convertible. It is a 468 with all high quality parts:

Forged crank and rods from Butler
Forged Arias pistons and moly rings from Butler
325 CFM KRE Aluminum Heads
Comp Hydraulic cam w/rhoads lifters - 240/246 @.050 and about .560 lift
Edelbrock RPM Manifold
Modified 800 CFM Quadrajet
Hedman 1 3/4" headers
Aluminum flywheel

Block was bored and honed with a torque plate and received first class machine work and assembly by a well respected local shop in business more than 30 years.

The engine was then taken to a local dyno operator I know where it made 538 HP at 5400 RPM and 586 lb. ft. of torque at 4000. It received at least 20 full load passes on the dyno after breaking in the cam.

I then installed it in the car. To my amazement, it initially used a quart of oil every 100 miles. I couldn't believe it. The car ran hot and showed all the signs of the engine still breaking in, even after the dyno session. I drove it about 600 miles this way. After some research, I found that the Butler valley pan was very poor in preventing oil going through the PCV system. I redesigned the system to use the driver's side valve cover. Custom baffled the valve cover and used a small air/oil separator from jegs in between the PCV and carb port. This totally eliminated oil going in through the carb PCV port.

Result: Oil consumption gradually decreased to about 1 quart every 800-900 miles. Engine gradually began running cooler and by about 3000 miles SEEMED fully broken in. I still thought the oil consumption was too high, but oh well and was resigned to living with it. Plugs still looked too dark to me but mixture readings were right were I wanted on my LM1 O2 sensor. So I thought maybe the heat range in the plug was a bit cold. I also noticed I would have oil on the threads of the plug and at the washer every time I pulled them. Again, I thought this seemed like rings haven't seated, but everything else seemed o.k. Plus, all I ever hear anyone say is that moly rings SEAT ALMOST IMMEDIATELY. As you will see this is not true, at least on my motor.

At 6000 miles I changed to Royal purple synthetic 10W-30. Same weight as the conventional oil I was using and took a trip to Indiana (I live in Florida). On this trip oil consumption went up to 1 quart every 400 miles. I was very surprised and got it out of there on the return trip, so it was in there maybe 1000 miles. After the change, the consumption did not go down and continued to use 1 quart every 400 miles. Now I was really pissed.

When I got back with the engine now having 9000 miles on it, I went through everything. Compression test WAS GREAT with 220 psi per hole and only 5 psi max difference between lowest to highest. Plugs looked too dark to me though, but not wet. Still oil on the threads and washer. I concluded that as wacked as it seemed the rings in this thing had not seated completely, or at least the oil rings hadn't. Took A VERY DEEP BREATH and decided that before pulling the engine I would try the BonAmi trick and see what happened. I took 1/2 a teaspoon full, held the engine at 2000 rpms and added it alternately to each carb bore a pinch at a time until gone. I noticed as I did this that the engine RPM actually came up slightly. When done, I took the car out ran the piss out of it with accel and decel for about 15 miles, then changed the oil and filter.

Result: Engine compression came up 3-5 psi a hole and oil consumption is COMPLETELY gone. This obviously means the rings were not seated after 9000 miles, moly or not and that the oil rings in particular were not seated at all even after 20 dyno pulls and a lot of mileage. I would also caution anyone contemplating running synthetic oil to make sure the engine is fully broken in as mine apparently went backwards and glazed the cylinder walls or something after having over 6K on it!

The good news is it runs fantastic now and appears to have suffered no ill effects from the bonami. Oil pressure has not changed and I have the bypass blocked in the filter housing which probably helped prevent any getting back into the motor after initial treatment.

Mike

Any recent news from when this was done?

[rtanner]

Glad you posted this, i beleive we had a thread like this years ago, my 455 in my bird smoked pretty heavy, so when i had the head off on one side, i found the cylinders were slick as glass, so bought bon ami, poured it in my hand and i rubbed it around in those cylinders, what the hell right? well sure enough its not smoking on that side now, hey im not promoting it as can of overhaul powder, and this is a on the trailer off the trailer down the track car, but i did see a noticable improvement.

[Stuart]

Originally Posted by pugslyx234

Any recent news from when this was done?

The original poster hasn't been back here in nearly five years, so chances are they aren't going to respond.

[i82much]

Originally Posted by Stuart

The original poster hasn't been back here in nearly five years, so chances are they aren't going to respond.

Maybe this will be just the thing?

[Schurkey]

Originally Posted by Tom Vaught

What the testing done "Dry" Try with a very small amount of oil in each sparkplug hole, reinstall the gage, and report the results.

Tom V.

Leakdown testing with oil? I'd expect the air pressure to blow the oil past the rings in short order, leaving no difference with or without oil added to the cylinders.

[pugslyx234]

Rtanner which bon-ami did you use ? I only find the powder cleanser and not the polishing one.

[rtanner]

it was just the powdered, think it says bar cleaner on the can, looks like a can of comet kitchen cleaner, product is a different color than comet, but is same type of powder

[rtanner]

Originally Posted by Schurkey

Leakdown testing with oil? I'd expect the air pressure to blow the oil past the rings in short order, leaving no difference with or without oil added to the cylinders.

its the way its done,

[hurryinhoosier62]

Originally Posted by Schurkey

Leakdown testing with oil? I'd expect the air pressure to blow the oil past the rings in short order, leaving no difference with or without oil added to the cylinders.

You use the oil to seal the rings AFTER you have established a base line reading. IF the pressure goes UP, the rings aren't sealing correctly. If it stays the same or DECREASES, start looking for leaking valves(especially exhaust valves). We've been doing this for DECADES on recip aircraft engines. I know many here will not agree, but cylinder glazing is the prime reason why I DO NOT use engine oil on the pistons and rings when assembling an engine.

[Schurkey]

Originally Posted by rtanner

its the way its done,

Originally Posted by hurryinhoosier62

You use the oil to seal the rings AFTER you have established a base line reading. IF the pressure goes UP, the rings aren't sealing correctly. If it stays the same or DECREASES, start looking for leaking valves(especially exhaust valves). We've been doing this for DECADES on recip aircraft engines.

1. How can adding oil decrease the pressure? What in a combustion chamber leaks MORE when oiled?

2. The FAA does not suggest a "wet" leakdown test where oil is added to the cylinder via the spark plug hole. They do accept an "oiled" re-test that involves running the engine in "CHAPTER 8. ENGINES, FUEL, EXHAUST, AND PROPELLERS; page 8".
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2043.13-1B/$FILE/Chapter%2008.pdf

Originally Posted by FAA

recheck the readings after operating the engine for at least 3 minutes to allow for sealing of the rings with oil.

My concern still stands: Does added oil via the spark-plug hole just blow out the ring gaps or other ring leakage points when the cylinder is pressurized? The result would be no difference in "wet" versus "dry" cylinder leakdown testing once the oil has moved down the piston.

[rtanner]

Originally Posted by Schurkey

1. How can adding oil decrease the pressure? What in a combustion chamber leaks MORE when oiled?

2. The FAA does not suggest a "wet" leakdown test where oil is added to the cylinder via the spark plug hole. They do accept an "oiled" re-test that involves running the engine in "CHAPTER 8. ENGINES, FUEL, EXHAUST, AND PROPELLERS; page 8".
http://rgl.faa.gov/Regulatory_and_Gu...apter%2008.pdf


My concern still stands: Does added oil via the spark-plug hole just blow out the ring gaps or other ring leakage points when the cylinder is pressurized? The result would be no difference in "wet" versus "dry" cylinder leakdown testing once the oil has moved down the piston.

Do it however you want then! Thanks for the FAA info come in handy if I ever work on a airplane.

[madokie]

i agree with hurrinhooser62, i don't use engine oil when installing piston w rings in bore, oil is like water is wont compress, i have seen in car mags a pan full of oil and piston dunked in oil and then assembled in bore, not needed !!!!, a light spray lube in bore and on piston is all you need for assembly.