[RandyW]

I've seen the Bon Ami trick used for 45 years, never seen it fail, or rather never seen it cause more problems. If it's just a seating issue it will work 95%+.

[styx169]

There is also a BonAmi health drink that is supposed to cure all kinds of diseases and ailments. I'd hate to see someone putting a health drink in their engine.

[old66tiger]

Which Bon Ami was this? Powder or Polish?

[old66tiger]

I tried this method and it did not work. My leakage on number 2 was 29% before the bon ami and 26% after the bon ami. I took it for a thrashing between the bon ami and the test.

I did not put it in each cylinder but rather got it up to 2500 rpms and dusted it into the cylinders.

Looks like I get to tear down an engine this winter.

[steve25]

If your oil ring rails where bent on install, or you compression ring faces where beat up and scratched on install( which I have seen alot from novist builders using a band compressor type ring install tool) or if your walls where honed too course, than the Bon Ami thing will not help!

[old66tiger]

Unfortunately, this was not a novice builder. I guess I will see what is wrong when I get it apart. My forst motor had a wrist pin walk on me....hope this isn't the case here.

I am putting the motor together this time. WHat ring compressor do you suggest?

[Transam Stripper]

I saw a old timer mechanic use it once and that was back in 1980. He put down thru the carb though. That was the smartest mechanic I have ever met to this day. He is probably with the Lord now. Tajunkman thought I was a total retard when I told him that story 10 years ago.

[steve25]

The safest type to use is a adjustible tapered model, they only adjustible in a narrow range of sizes so you have to know which one to order for your bore size.

[Murf'sDad]

I used a band compressor on my first build and will use one on my latest build. As long as it is well lubed and you are careful installing the pistons you won't have any problems. Get sloppy or lazy though and watch your back account disappear and your hp drop.

JMO, Stewart

[Firebob]

I haven't really checked oil consumption on my rebuild but I do seem to be getting a bit of blow-by. I used moly rings and compression is fine but when making a hard pass it tends to blow a bit of oil out the dipstick tube. Not a lot but a bit of spray. I've got probably around 8-9K miles on it so far.
Does this sound like something that might be cured by the Bonami trick?

Robert

[GT182]

It seems the folks at Bon Ami have heard of this use for their product. On a whim I email the link to this thread to them... and, I even received a reply. LOL Here's their emaill address if you want to do the same to let them know it works..... good, bad, of indifferent. [email protected]

BTW, I've used BonAmi for many things and have never had a bad thing to say about it. It is great for cleaning windows and windshields.

"Dear Gary,

Thank you for your recent email regarding your interest in our Bon Ami products. We always appreciate consumer correspondence.

This is a use for the product that we have been introduced only through our consumers. We have not tested it in this application and therefore cannot speak to the efficacy of its use.

Should you have any other questions, please feel free to contact us again.

Sincerely,
Annie Blackman
Consumer Specialist"

[steve25]

If your oil level is not over filled and you are pushing the dip stick tube out, or have oil coming out of it, I can tell you for a fact from a friends motor that we just leak down tested and honed and re-ringed, that you probibly have 15% or more leakage and thats way too much!
His race motor started to push and oil out the dip stick also.

[old66tiger]

Not over filled and not pushing the dipstick tube out. However, I am running an extension tube on the breather to deal with excess pressure making a mess out of my valve covers.

Here are my numbers

CYL --COMP LEAKAGE%
1 ----> 150 ---- 8
2 ----> 145 ---- 29
3 ----> 155 ---- 10
4 ----> 155 ---- 7
5 ----> 150 ---- 22
6 ----> 150 ---- 16
7 ----> 155 ---- 5
8 ----> 155 ---- 8

[Firebob]

Mine is not overfilled(in fact it was about a qt low) and not pushing the dipstick out either but I must be getting a bit of spray out of the tube because there is bits of spatter on the plug wire boots to the rear of the tube and a bit of smoke from oil burning off the ex manifolds after a hard run.
Just wondering if the bonami trick might help with this situation. Guess there's one way to find out.

Robert

[Jack Gifford]

Originally Posted by old66tiger

... here are my numbers

CYL --COMP LEAKAGE%
1 ----> 150 ---- 8
2 ----> 145 ---- 29
3 ----> 155 ---- 10
4 ----> 155 ---- 7
5 ----> 150 ---- 22
6 ----> 150 ---- 16
7 ----> 155 ---- 5
8 ----> 155 ---- 8

Nothing wrong with those numbers.

[Will]

Really? Nothing wrong with three cylinders having over 10% leakage, two as high as 22% and 29%?

[Jack Gifford]

Really. You need to understand the leakdown tester.
The industry-standard orifice in leakdown testers is a round .040" diameter hole. If a cylinder were to read 50% leakdown, the "leak" would be the equivalent of the air passing through the .040" aperture. So 29% leakdown indicates a leakage path of significantly less area than a .040" diameter circle. Air can't move very quickly through a tiny passage. See for yourself- even at cranking speed, you only show about 5-10 PSI less- about 3-5% lower than cylinders with "good" leakdown numbers. Even at idle, piston speed will be 4-5 times as fast as when cranking. And the impedance of fluid (air) through an orifice increases as the square of its velocity. Without doing the somewhat difficult math, I estimate that the 29% cylinder will suffer about 1% pressure loss- at idle speed!

[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.

[Will]

Originally Posted by pontiac jack

Really. You need to understand the leakdown tester.
The industry-standard orifice in leakdown testers is a round .040" diameter hole. If a cylinder were to read 50% leakdown, the "leak" would be the equivalent of the air passing through the .040" aperture. So 29% leakdown indicates a leakage path of significantly less area than a .040" diameter circle. Air can't move very quickly through a tiny passage. See for yourself- even at cranking speed, you only show about 5-10 PSI less- about 3-5% lower than cylinders with "good" leakdown numbers. Even at idle, piston speed will be 4-5 times as fast as when cranking. And the impedance of fluid (air) through an orifice increases as the square of its velocity. Without doing the somewhat difficult math, I estimate that the 29% cylinder will suffer about 1% pressure loss- at idle speed!

Yes, I understand that the leakdown doesn't greatly affect cylinder pressures, that much is obvious. But what about other issues, such as oil consumption and crankcase pressure?

[Geoff]

PJ,
The percentage leakdown figures in post #53 are also puzzling to me. I would think the leakdown percentage would be the same, or close, for cylinders with the same compression reading. Cyls 3, 4, 7 & 8 all measured 155psi but LD perecentage varied from 5 to 10%. Even greater discrepancy with cyls 5,6 & 1 which each measured 150psi, but LD varied from 6 to 22%. Am I missing something or are the figures wrong?