PDA

View Full Version : Piston ring install.

enkeivette
06-16-2009, 08:51 PM
Got my new piston pressed today. In the process of removing the old rings, and I've snapped several. Is there a trick to installing the new ones without snapping them? :nuts:

Also, setting the gap at .022, did the Total Seal math and I get .022165 for a blown gas engine.

Old rings were not installed upside down. :(
enkeivette
06-16-2009, 08:54 PM
Also, are would the thick black rings be the second rings? The other thick ones are gray.

Also also, a brass brush and hydrochloric acid works wonders on steel cylinder walls coated with melted aluminum.
94cobra69ss396
06-16-2009, 08:58 PM
There's a special tool for installing them. If you don't have one like I don't you can use the old fashion one which is your thumbs. Spread it just enough to slide it over the piston. Make sure you spead it evenly and don't twist it because that is when they usually break.
Vettezuki
06-16-2009, 08:59 PM
Do you plan on putting them on upside down this time?
enkeivette
06-16-2009, 09:00 PM
Do you plan on putting them on upside down this time?

I was hoping to find a reason for the always low cylinder pressure.
Vettezuki
06-16-2009, 09:02 PM
I was hoping to find a reason for the always low cylinder pressure.

Did you? Can't recall.
enkeivette
06-16-2009, 09:02 PM
http://i43.tinypic.com/10p7lmx.jpg
http://i42.tinypic.com/2qbcepd.jpg
Vettezuki
06-16-2009, 09:05 PM
Now how are you supposed to have cylinder pressure without a damn cylinder. That just don't make sense. . .
enkeivette
06-16-2009, 09:05 PM
Did you? Can't recall.

Nope. Although the old rings look kinda funny, I'll let you know what it pumps out this time.
Vettezuki
06-16-2009, 09:06 PM
Nope. Although the old rings look kinda funny, I'll let you know what it pumps out this time.

IRQRIUS
94cobra69ss396
06-16-2009, 09:10 PM
Were they all low before or just the ones that were broken? If they were all low before I don't see how they won't be now. Are you sure you have as high of a compression ratio as you thought? What type of pistons do you have, flat top or dished? If dish what's the cc? How thick of a head gasket are you using? What the deck height on the pistons?
enkeivette
06-16-2009, 09:22 PM
I've done the math before obviously, but feel free to double check.

Standard deck height which is 20 or 25 down, -5cc reliefs, 74cc heads, 61 HG, 4.03 bore...

I get about 9:1, with a 110LSA I guess I shouldn't expect much dynamic.
BRUTAL64
06-17-2009, 10:05 AM
Got my new piston pressed today. In the process of removing the old rings, and I've snapped several. Is there a trick to installing the new ones without snapping them? :nuts:

Also, setting the gap at .022, did the Total Seal math and I get .022165 for a blown gas engine.

Old rings were not installed upside down. :(

I've been doing the ring install by finger and thumb since the 70s. I'd have to show you how it's done. I don't think I could explain in words.
BRUTAL64
06-17-2009, 10:22 AM
I've done the math before obviously, but feel free to double check.

Standard deck height which is 20 or 25 down, -5cc reliefs, 74cc heads, 61 HG, 4.03 bore...

I get about 9:1, with a 110LSA I guess I shouldn't expect much dynamic.

Just ran your numbers thru the engine program I have. I got 8.49 ratio.

I did it three times.:rolleyes:


I used the same program on my engine.:bigthumbsup:

I ran that for a 350.

For a 383 it is 9.17
94cobra69ss396
06-17-2009, 10:41 AM
I've done the math before obviously, but feel free to double check.

Standard deck height which is 20 or 25 down, -5cc reliefs, 74cc heads, 61 HG, 4.03 bore...

I get about 9:1, with a 110LSA I guess I shouldn't expect much dynamic.

What's the bore on the head gasket?
BRUTAL64
06-17-2009, 10:42 AM
What's the bore on the head gasket?

I used 4.060 bore for the head gasket.


With a 4.030 hg bore the cr is 8.50.

Again, that is for a 350.


383 with 4.060 hg bore is 9.17
94cobra69ss396
06-17-2009, 10:46 AM
I used 4.60 bore for the head gasket.

He has a 383 with a 3.75 stroke, correct?
BRUTAL64
06-17-2009, 10:49 AM
He has a 383 with a 3.75 stroke, correct?

Shit that is right. Ok, I'll redo it.:o

383 is 9.17:o
enkeivette
06-17-2009, 01:10 PM
Knew I forgot something, 4.166 bore HG, 3.75 stroke. 6" rod if that matters.
BRUTAL64
06-17-2009, 01:34 PM
Knew I forgot something, 4.166 bore HG, 3.75 stroke. 6" rod if that matters.

I got 9.12 cr.:bigthumbsup:
94cobra69ss396
06-17-2009, 02:08 PM
Are you sure the compressed thickness on the head gasket is.061? I'm trying to find one that thick but can't. Do you have the P/N of the gasket you're running?
big_G
06-17-2009, 02:08 PM
Stop being a cheap bastard and by the tool: All of $4.95 at Summit.
http://static.summitracing.com/global/images/prod/large/wmr-w80575_w.jpg
94cobra69ss396
06-17-2009, 02:11 PM
Is this the head gasket you are using?

http://www.summitracing.com/parts/FPP-1144-061/
Vettezuki
06-17-2009, 02:17 PM
Stop being a cheap bastard and by the tool: All of $4.95 at Summit. . .

I don't think you realize just how cheap he is. He once had me weld something . . . have you seen me weld. :judge:
enkeivette
06-17-2009, 04:59 PM
So does 140psi with a 110 lsa sound about right?
BRUTAL64
06-17-2009, 05:02 PM
I meant when the engine is running. Or is it like this

Engine off, turning manually, the pressure in the cylinder is "cranking pressure."

Engine running, the pressure in the cylinder is "cylinder pressure."

enkei's motor is boosted, 15psi I think.

Que?

Cranking pressure is "starter" speed cylinder pressure.:drink:
94cobra69ss396
06-17-2009, 05:04 PM
So does 140psi with a 110 lsa sound about right?

With the cam timing you have it sounds about right to me. I'm at 150-155 with the Cobra with 9.2:1 compression and a less agressive cam.
Vettezuki
06-17-2009, 05:05 PM
So does 140psi with a 110 lsa sound about right?

By the way, since your FI, how do you factor boost into cranking pressure? After all, when you're jamming air in cylinders, it must be quite a bit higher right . . . Or am I mixing up terms.
94cobra69ss396
06-17-2009, 05:09 PM
By the way, since your FI, how do you factor boost into cranking pressure? After all, when you're jamming air in cylinders, it must be quite a bit higher right . . . Or am I mixing up terms.

There isn't any boost.
Vettezuki
06-17-2009, 05:11 PM
Cranking pressure is "starter" speed cylinder pressure.:drink:

Ok, that makes sense. Hence the no boost.
Vettezuki
06-17-2009, 05:14 PM
There isn't any boost.

I meant when the engine is running. Or is it like this

Engine off, turning manually, the pressure in the cylinder is "cranking pressure."

Engine running, the pressure in the cylinder is "cylinder pressure."

enkei's motor is boosted, 15psi I think.

Que?
94cobra69ss396
06-17-2009, 05:15 PM
You get cranking pressure by pulling out a spark and installing the gauge. Then you crank the engine using the starter motor until you reach the max psi which is usually after few revolutions. What you are checking is to see that all the cylinders are in the same range.

Like I said before, cranking pressure doesn't tell you much because cam timing can change cranking pressure. I read an article once written by an engine builder who was using the cranking pressure to demonstrate how to choose a cam. He said that for a street engine he doesn't like to see more than 210-215psi cranking pressure. The customers engine he was writting the article on had 250-260psi with the cam that was in the engine. He had a custom cam ground and it dropped the cranking pressure down where he wanted it at around 210. I can't remember what difference in HP it made but it did make more power. I'll see if I can find it online somewhere.
enkeivette
06-18-2009, 03:34 PM
That's the gasket Cobra, and it was a 4.2 bore, my old gasket was a 4.16. That must be the 1/10th difference in compression. I'll bet if you guys do it again it'll be right at 9:1.

Ben, cranking pressure, you got it. By the time the motor is idling the pressue will increase. So I guess you could make the argument that a better starter would increase the pressure. It's really not a good test for anything other than comparing cylinders to look for leaks. But the numbers themselves tell very little.
Vettezuki
06-18-2009, 03:37 PM
That's the gasket Cobra, and it was a 4.2 bore, my old gasket was a 4.16. That must be the 1/10th difference in compression. I'll bet if you guys do it again it'll be right at 9:1.

Ben, cranking pressure, you got it. By the time the motor is idling the pressue will increase. So I guess you could make the argument that a better starter would increase the pressure. It's really not a good test for anything other than comparing cylinders to look for leaks. But the numbers themselves tell very little.

I see, it's just a comparison test, nothing so absolute. Wouldn't a compression leakdown test give the same diagnostic information (i.e., identifying trouble cylinders.)
94cobra69ss396
06-18-2009, 03:47 PM
That's the gasket Cobra, and it was a 4.2 bore, my old gasket was a 4.16. That must be the 1/10th difference in compression. I'll bet if you guys do it again it'll be right at 9:1.

Ben, cranking pressure, you got it. By the time the motor is idling the pressue will increase. So I guess you could make the argument that a better starter would increase the pressure. It's really not a good test for anything other than comparing cylinders to look for leaks. But the numbers themselves tell very little.

The best way to do a compression test is with all the spark plugs removed and crank the engine until max psi is reached. That way there isn't a load on the engine caused by the compression stroke of the other cylinders.

Ben, a leak down test is better but is also more time consuming. It is quicker to do a compression test to see if there is a low cylinder. If there is then you can do a leak down test on that cylinder.
Leedom
06-18-2009, 03:58 PM
Can someone explain to m what a leak down test is?
94cobra69ss396
06-18-2009, 04:35 PM
Can someone explain to m what a leak down test is?

You pump a measured amount of air pressure into the cylinder, and the gauge will tell you the percentage of leakage the cylinder has.

Read this article done by Car Craft. http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html
BRUTAL64
06-18-2009, 05:46 PM
You pump a measured amount of air pressure into the cylinder, and the gauge will tell you the percentage of leakage the cylinder has.

Read this article done by Car Craft. http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html

OR--the ole driveway leak down. Pump compressed air in a cylinder, make sure that both the intake and exhaust valves are closed and listen for leaks. :leaving:

I've done dozens of these--quick way to find broke rings or bent valves.:rolleyes:
enkeivette
06-18-2009, 07:05 PM
On another forum it was recommended that I run a 26 first and 24 second gap.

Doing the math on the chart that came with my total seal pistons, I get 22 first and only 14 second. So what's up?
94cobra69ss396
06-18-2009, 07:13 PM
On another forum it was recommended that I run a 26 first and 24 second gap.

Doing the math on the chart that came with my total seal pistons, I get 22 first and only 14 second. So what's up?

Call them and tell them what you have and get their recommendation. Boosted engines need a larger gap than a N/A engine does.