Rings not seating?
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Joined: Dec 2007
Posts: 7,987
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From: Boise, Idaho
Rings not seating?
Hi all,
As some know, I had to do a partial rebuild on my 300. Had the cylinders bored out to 40 over (it was 30). New pistons, rings, etc.
I assembled everything myself and was sure to offset the rings, check end gap, etc. and was very thorough and by the book.
I'm using Joe Gibbs Driven break in oil, and am doing a lot of varied driving with around town, heavy traffic, interstate, hills, etc. the really vary the RPM and throttle.
After the first 90 miles I did a compression test:
1. 130
2. 134
3. 137
4. 135
5. 135
6. 132
Looked decent. Very close together, etc. And with only 90 miles, figured there was a good amount of break in left to go.
However, it's now been 270 miles so I decided to do another compression test:
1. 131
2. 134
3. 137
4. 135
5. 135
6. 132
It's gone nowhere. Literally nowhere.
There's also still a good amount of "steam" coming from the breather cap, so I know it's still getting past the rings.
That doesn't sit well with me.
Am I over analyzing? Or is there an issue here? Do I just need to give it a good couple hundred more miles?
Thoughts? Ideas? Suggestions?
As some know, I had to do a partial rebuild on my 300. Had the cylinders bored out to 40 over (it was 30). New pistons, rings, etc.
I assembled everything myself and was sure to offset the rings, check end gap, etc. and was very thorough and by the book.
I'm using Joe Gibbs Driven break in oil, and am doing a lot of varied driving with around town, heavy traffic, interstate, hills, etc. the really vary the RPM and throttle.
After the first 90 miles I did a compression test:
1. 130
2. 134
3. 137
4. 135
5. 135
6. 132
Looked decent. Very close together, etc. And with only 90 miles, figured there was a good amount of break in left to go.
However, it's now been 270 miles so I decided to do another compression test:
1. 131
2. 134
3. 137
4. 135
5. 135
6. 132
It's gone nowhere. Literally nowhere.
There's also still a good amount of "steam" coming from the breather cap, so I know it's still getting past the rings.
That doesn't sit well with me.
Am I over analyzing? Or is there an issue here? Do I just need to give it a good couple hundred more miles?
Thoughts? Ideas? Suggestions?
FTE Legend
Joined: Nov 2015
Posts: 30,940
Likes: 4,125
From: Angier, NC
Ok you have 40 over holes and 40 over ring set on 30 over pistons or did you go 40 on the pistons also?
What type of rings are you using? Do they take a certain grit of stone for honing to leave a cross hatch pattern?
I ask because I have seen posts they some type of rings need a certain cross hatch grit to get the rings to seal.
Now I hope you have been driving that motor like you stole it to flex the rings.
Just driving it around town & high way is not enough, Do some full throttle starts and run the RPM up there.
Also I would not check it till you got over 500 to 1000 miles on it and even then it could still be breaking in.
Did you reuse your old cam & lifters? If so then why the break in oil as I don't see anything else needing it.
Dave ----
What type of rings are you using? Do they take a certain grit of stone for honing to leave a cross hatch pattern?
I ask because I have seen posts they some type of rings need a certain cross hatch grit to get the rings to seal.
Now I hope you have been driving that motor like you stole it to flex the rings.
Just driving it around town & high way is not enough, Do some full throttle starts and run the RPM up there.
Also I would not check it till you got over 500 to 1000 miles on it and even then it could still be breaking in.
Did you reuse your old cam & lifters? If so then why the break in oil as I don't see anything else needing it.
Dave ----
Thread Starter
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Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Ok you have 40 over holes and 40 over ring set on 30 over pistons or did you go 40 on the pistons also?
What type of rings are you using? Do they take a certain grit of stone for honing to leave a cross hatch pattern?
I ask because I have seen posts they some type of rings need a certain cross hatch grit to get the rings to seal.
Now I hope you have been driving that motor like you stole it to flex the rings.
Just driving it around town & high way is not enough, Do some full throttle starts and run the RPM up there.
Also I would not check it till you got over 500 to 1000 miles on it and even then it could still be breaking in.
Did you reuse your old cam & lifters? If so then why the break in oil as I don't see anything else needing it.
Dave ----
What type of rings are you using? Do they take a certain grit of stone for honing to leave a cross hatch pattern?
I ask because I have seen posts they some type of rings need a certain cross hatch grit to get the rings to seal.
Now I hope you have been driving that motor like you stole it to flex the rings.
Just driving it around town & high way is not enough, Do some full throttle starts and run the RPM up there.
Also I would not check it till you got over 500 to 1000 miles on it and even then it could still be breaking in.
Did you reuse your old cam & lifters? If so then why the break in oil as I don't see anything else needing it.
Dave ----
I have no idea on the type of honing process, since I didn't do it. My machinist did the bore/hone and selected the rings accordingly.
They're Chrome Moly rings.
See, this is where it gets confusing with engine break in. Everyone's process is different. Some say to drive it hard. Others say you have to go easy on it for the first 500 miles. The issue is that those directly contradict each other.
No, I haven't been hard on it. Moderate throttle, 3500 RPMs max.
I'm thinking it needs some hard driving, and I'll talk with my machinist as well and see what he thinks.
Yes, same cam and lifters. The break-in oil was used because its formulated to aid in seating the rings.
Yes. The rings came with specific instructions of how to index them and I followed them accordingly.
Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
I've always heard to vary to load and the rpms. If you baby it you'll build up varnish on the cylinder walls and the rings will never seat, particularly if the rings are cast and you'll have to rehone and try again. For sure have never heard anyone say to go easy on it.
Tuned
Joined: May 2013
Posts: 396
Likes: 5
From: Ottawa, Canada
I thought pistons rings are supposed to be seated by varying rpm and loads with some full throttle in there for sure. Pretty sure that's how I broke mine in with stock bore and just a ball hone on a drill, I'm sure I haven't lost any compression over 50k miles.
Talk to a machinist or google around for some recommendations from reputable sources.
Talk to a machinist or google around for some recommendations from reputable sources.
Thread Starter
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Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
By "easy" I don't mean babying it. I just mean no full throttle, max RPM driving. You don't see what all it's got until it's broken in. I've always heard to never be hard on it until the rings are seated.
That said, I haven't been easy on it. It's been good acceleration, different RPM ranges, engine braking, etc.
This is frustrating, because it's how I broke in my engine last time and it worked great. I had 175 in all 6 cylinders within about 500 miles.
Last thing I want to do is have to pull the engine and start over...
That said, I haven't been easy on it. It's been good acceleration, different RPM ranges, engine braking, etc.
This is frustrating, because it's how I broke in my engine last time and it worked great. I had 175 in all 6 cylinders within about 500 miles.
Last thing I want to do is have to pull the engine and start over...
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Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
I was reading this article https://www.enginebuildermag.com/201...the-right-way/ Makes it sound like chrome moly rings seat pretty easy. They did say that if glazing occurs you should be able to take care of that with a top end cleaner.
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Thread Starter
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Moderator
Joined: Dec 2007
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From: Boise, Idaho
That's what I got out of it. Within 20 - 30 miles.
Why didn't mine seat?
I'll look into the top end cleaner, and discuss the whole thing with my machinist. Last thing I want/need to do right now is have to break the whole thing down and re-hone it. That's probably at least another $300 - $400 in gaskets, materials, and shop work. Not to mention my time....
Why didn't mine seat?
I'll look into the top end cleaner, and discuss the whole thing with my machinist. Last thing I want/need to do right now is have to break the whole thing down and re-hone it. That's probably at least another $300 - $400 in gaskets, materials, and shop work. Not to mention my time....
Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
Well, in my experience, it's always the other guys fault. See what the machinist says, maybe he was having an off day and got some crazy angle on the cross-hatching. Or used some lucas stop leak to aid in piston installation.
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