Blown out piston rings... I hope.

[enkeivette]

Crankcase is blowing air at me like crazy, oil is still clean. Consensus seems to be that it's a f'd ring or a hole/ crank in my piston. Pistons are forged so I'm optimistic and hoping that it's a ring.

Also, this engine only made 135psi in each cylinder when it was running good. And it's always made less power than it should for what it is, someone hypothesized that my rings were installed upside down. It would def explain things. Either way, pistons are coming out. :D

Also, this would explain the excessive crankcase pressure that I've always had a problem with. Anyone else remember the oil squirting out on dyno day? Maybe it wasn't the intake leak.

Just pray for me that the pistons are still usable and the cylinder is still smooth.

[big2bird]

You have a hole, or a broken land.

[big_G]

And you must find out why it happened so as to not have a repeat occurrence. Detonation is #1 on the list of causes. Too lean next. When you pull the plugs you will know.

[BRUTAL64]

Yea, I blew 4 piston ring lands out with detnotion. Figure worst case here.:(

[joedls]

Do you have a PCV valve on it or breathers? Also, I'd do a leakdown test before I pulled it apart.

[94cobra69ss396]

Crankcase is blowing air at me like crazy, oil is still clean. Consensus seems to be that it's a f'd ring or a hole/ crank in my piston. Pistons are forged so I'm optimistic and hoping that it's a ring.

Also, this engine only made 135psi in each cylinder when it was running good. And it's always made less power than it should for what it is, someone hypothesized that my rings were installed upside down. It would def explain things. Either way, pistons are coming out. :D

Also, this would explain the excessive crankcase pressure that I've always had a problem with. Anyone else remember the oil squirting out on dyno day? Maybe it wasn't the intake leak.

Just pray for me that the pistons are still usable and the cylinder is still smooth.


How big is the cam in the Vette and what's the compression? The Cobra with a 110 lobe seperation and 9:1 has 155psi cranking pressure. Also, how much boost are you running? Did you ever here it detonate? Forged pistons can take quite a bit of abuse. I've had the Cobra detonate quite a bit with the forged pistons and haven't had a problem with them in the 2 years they've been in there. I also have around 30,000-40,000 hard miles on it.

[SeanPlunk]

How big is the cam in the Vette and what's the compression? The Cobra with a 110 lobe seperation and 9:1 has 155psi cranking pressure. Also, how much boost are you running? Did you ever here it detonate? Forged pistons can take quite a bit of abuse. I've had the Cobra detonate quite a bit with the forged pistons and haven't had a problem with them in the 2 years they've been in there. I also have around 30,000-40,000 hard miles on it.

As I recall his compression is 9.5:1? I think his cam has a 111lsa but I can't remember for sure. I think he's running 15lbs.

[94cobra69ss396]

As I recall his compression is 9.5:1? I think his cam has a 111lsa but I can't remember for sure. I think he's running 15lbs.

His crancking pressure should be higher than the Cobra's 155psi with 9.5 and a 111 lsa. To give another comparison, the Chevelle with 12.25:1 and a 110 lsa has 210-215psi.

[BRUTAL64]

Do you have a PCV valve on it or breathers? Also, I'd do a leakdown test before I pulled it apart.

Hey, Joe. Where ya been?

[joedls]

Hey, Joe. Where ya been?


I had a death in the family, then I had the flu for about a week. I've had my head down trying to catch up.

[BRUTAL64]

I had a death in the family, then I had the flu for about a week. I've had my head down trying to catch up.

Sorry to hear about your loss.:(



Good to see you back.:D

[94cobra69ss396]

I had a death in the family, then I had the flu for about a week. I've had my head down trying to catch up.

Sorry to hear that Joe. Hopefully you and your family are doing well.

[joedls]

Thanks, guys. It was my uncle that died. He wasn't that old, but he pretty much drank and smoked himself to death. Even with emphysema, diabetes, chirrosis, and kidney problems that required dialysis, he continued to drink and smoke every chance he had. I inherited my addictive tendencies from that side of the family. Hell, who am I kidding? It came from all sides of my family. I've mostly got it in check now, though, except for my cars.

[BRUTAL64]

You you are heathly? Good.

Hey, try to make the next Motorgen meet. :drink:

[joedls]

You you are heathly? Good.

Hey, try to make the next Motorgen meet. :drink:


Depends on your definition of healthy? :laugh:

When is the next meet?

[BRUTAL64]

Depends on your definition of healthy? :laugh:

When is the next meet?

Apirl 14. It's an AWD dyno day. I don't know if they are meeting at Nicks afterward of not.:huh:


Hey, You're doing Fab Ford Day at Knotts, right???

[joedls]

Apirl 14. It's an AWD dyno day. I don't know if the are meeting at Nicks afterward of not.:huh:


Hey, You're doing Fab Ford Day at Knotts, right???


The 14th I'm probably gonna be depressed about the check I have to write the IRS the next day.

I haven't made up my mind about Knott's. I'll probably go, but I'm kinda over showing my cars.

[BRUTAL64]

The 14th I'm probably gonna be depressed about the check I have to write the IRS the next day.

I haven't made up my mind about Knott's. I'll probably go, but I'm kinda over showing my cars.

I'm going. It'll be great to actually be among the GOOD cars.:thumbs_up:

[Vettezuki]

The 14th I'm probably gonna be depressed about the check I have to write the IRS the next day.

I haven't made up my mind about Knott's. I'll probably go, but I'm kinda over showing my cars.

We will be meeting at Nicks after the Dyno Day. Hey, I set a new record for owing the IRS without paying any penalties this year. :penguin: Now if I could just figure out how to get the total burden down to something civilized I'd be smok'n.

[BRUTAL64]

We will be meeting at Nicks after the Dyno Day. Hey, I set a new record for owing the IRS without paying any penalties this year. :penguin: Now if I could just figure out how to get the total burden down to something civilized I'd be smok'n.

So you are helping with the bail outs?:sm_up_there:

[joedls]

So you are helping with the bail outs?:sm_up_there:


:rant::rant::censored::censored::bang::bang::barf: :barf::suicide::suicide:

[Vettezuki]

So you are helping with the bail outs?:sm_up_there:

Anybody who pays Federal Income Tax and is not receiving redistributed plunder, I mean tax money, is. My goal is to eventually slip the surly bonds of earned income tax, create progressively more, and give away progressively less (to the government). :drink:

Anywho, back to blown out piston rings. What's the difference between:
- checking cranking pressure
- compression test
- leak down test

[big2bird]

Do you have a PCV valve on it or breathers? Also, I'd do a leakdown test before I pulled it apart.

Why. It's broken. Out it comes.

[big2bird]

Anybody who pays Federal Income Tax and is not receiving redistributed plunder, I mean tax money, is. My goal is to eventually slip the surly bonds of earned income tax, create progressively more, and give away progressively less (to the government). :drink:

Anywho, back to blown out piston rings. What's the difference between:
- checking cranking pressure
- compression test
- leak down test

A compression test should reflect near identical pressures in all cylinders. Lower numbers in adjacent cylinders identifies gasket issues. If the introduction of oil increases pressure, the rings are worn.

A leak down test identifies ring wear/failure to hold pressure.

[big2bird]

I'm going. It'll be great to actually be among the GOOD cars.:thumbs_up:

You mean there will be some real Cobra's there?:D

[joedls]

Why. It's broken. Out it comes.

If he has a defective or plugged PCV system, it can cause excessive crankcase pressure.

Also, a leakdown test can help pinpoint where he is losing compression and exactly how much.

If he can clearly hear a whooshing/howling by listening at the oil filler cap during the leakdown test, he's losing compression through the rings.

If he can hear it (or even feel puffs on his hand) at the tail pipe, then it's his exhaust valve on that cylinder.

If he can clearly hear a whooshing/howling by listening at the carb/intake manifold, then it's his intake valve on that cylinder.

If he can see it bubbling in the radiator, it could be a head gasket, although it doesn't sound like that's it.

[big2bird]

His crancking pressure should be higher than the Cobra's 155psi with 9.5 and a 111 lsa. To give another comparison, the Chevelle with 12.25:1 and a 110 lsa has 210-215psi.

The 454 engine I just refreshed for the Winnebago has 175lbs cranking pressure with 8.5 CR. Other than "relative" numbers, it means very little.

[94cobra69ss396]

The 454 engine I just refreshed for the Winnebago has 175lbs cranking pressure with 8.5 CR. Other than "relative" numbers, it means very little.

The cranking pressure is dependent on the compression ratio and the cam timing. More overlap equals less pressure. I'm sure your 454 with 8.5 also has a lobe seperation in the 115 or higher range which would give you good bottom end torque with your low compression. My 454 has a 110lsa that bleeds off some pressure but with 12:25 still has a high cranking pressure.

Ben, the whole point of the compression test, which is what gives you the cranking pressure we are talking about, is to determine if all cylinders are in the same range. Say you have 150 on all cylinders except one that is only at 80. Then you know that low cylinder is causing the problem. As Joe explained, by then doing a leak down test you can determine what the possible cause could be.

This is why I asked Adam what his compression and lsa were after he said he only had 135psi cranking pressure. If he only had an 8.5:1 compression ratio and a 106-108lsa I would say 135 could be an accurate range. However, if he does truely have 9.5:1 and a 111lsa 135psi is low.

[enkeivette]

9:1 with my thicker MLS
Hyd Roller .576 in .594 ex Lift 239in 245ex Duration @ .05 110LSA

Motor made 135 at 9.5:1 And it's always seemed to me like it's made about 20% less hp than comparable setups. It only made 520 crank with 5lbs, granted it was with a 14:1 afr, but still it should have made close to 500 without boost.

Once I sealed up the intake gaskets and tightened the belt after dyno day, it made 10lbs.

Not going to do any testing, time to pull the heads, and then the pistons. Pistons are coming out for sure, I can only hope that the cylinders are ok. I'd like to do this without pulling the motor. If the pistons are ok, I will resuse them. If not. I will get some blower slugs and drop my CR and order a smaller pulley when funds allow. It would be awesome to run 19lbs...

BTW, broken rings or not, I slaughtered the guy that I was racing. And I'd do it again, 60 psi in several cylinders or not. Watch out suckas!

[BRUTAL64]

If he has a defective or plugged PCV system, it can cause excessive crankcase pressure.

Also, a leakdown test can help pinpoint where he is losing compression and exactly how much.

If he can clearly hear a whooshing/howling by listening at the oil filler cap during the leakdown test, he's losing compression through the rings.

If he can hear it (or even feel puffs on his hand) at the tail pipe, then it's his exhaust valve on that cylinder.

If he can clearly hear a whooshing/howling by listening at the carb/intake manifold, then it's his intake valve on that cylinder.

If he can see it bubbling in the radiator, it could be a head gasket, although it doesn't sound like that's it.

When I blew my 4 pistons, I'd take off the beather cap and it looked like a steam engine.:rolleyes:

I did a leakdown just for grins. Man, you could hear it hissing thru the whole engine. Just plain sad. Yea, the engine just lasted 16 years.:(

[BRUTAL64]

You mean there will be some real Cobra's there?:D


Describe a real Cobra for me.:pot_stir:

[BRUTAL64]

9:1 with my thicker MLS
Hyd Roller .576 in .594 ex Lift 239in 245ex Duration @ .05 110LSA

Motor made 135 at 9.5:1 And it's always seemed to me like it's made about 20% less hp than comparable setups. It only made 520 crank with 5lbs, granted it was with a 14:1 afr, but still it should have made close to 500 without boost.

Once I sealed up the intake gaskets and tightened the belt after dyno day, it made 10lbs.

Not going to do any testing, time to pull the heads, and then the pistons. Pistons are coming out for sure, I can only hope that the cylinders are ok. I'd like to do this without pulling the motor. If the pistons are ok, I will resuse them. If not. I will get some blower slugs and drop my CR and order a smaller pulley when funds allow. It would be awesome to run 19lbs...

BTW, broken rings or not, I slaughtered the guy that I was racing. And I'd do it again, 60 psi in several cylinders or not. Watch out suckas!

I blew 4 piston's ring lands out of mine. The cylinders were fine, but I stopped running the motor right away.:)

[big2bird]

Describe a real Cobra for me.:pot_stir:

http://www.prc68.com/I/CSX3282.shtml

[BRUTAL64]

http://www.prc68.com/I/CSX3282.shtml

Yep, that's the "Cobra" I grew up with.:drink:

[BlacknBoostn]

If he has a defective or plugged PCV system, it can cause excessive crankcase pressure.

Also, a leakdown test can help pinpoint where he is losing compression and exactly how much.

If he can clearly hear a whooshing/howling by listening at the oil filler cap during the leakdown test, he's losing compression through the rings.

If he can hear it (or even feel puffs on his hand) at the tail pipe, then it's his exhaust valve on that cylinder.

If he can clearly hear a whooshing/howling by listening at the carb/intake manifold, then it's his intake valve on that cylinder.

If he can see it bubbling in the radiator, it could be a head gasket, although it doesn't sound like that's it.

:hail::hail::hail:

Good to have you back Joe, sorry for your loss! My condolences...

[enkeivette]

I think my low engine vacuum might be another sign that my rings are upside down.

[TimAT]

Did you ever get the autopsy done? I've been watching and haven't seen what exactly happened.

[big_G]

I think it's a secret...:pot_stir: BTW Einkeivette...I have an appointment tomorrow with Dr. Dyno. Need to play with my F.A.S.T. fuel injection, do some laptop tuning and get things optimized. It feels freekin strong compared to how it ran with the Holley.

[big2bird]

Did you ever get the autopsy done? I've been watching and haven't seen what exactly happened.

I have the pics. However, my computer upgrades have taken a beating. I believe I have to update my Motherboard Bios, whatever the hell that means. Tomarrow maybe.:huh:

[enkeivette]

I have the pics. However, my computer upgrades have taken a beating. I believe I have to update my Motherboard Bios, whatever the hell that means. Tomarrow maybe.:huh:

I forgot my piston slept over at your house. There is another thread around here with the blown piston in the hole.

[BRUTAL64]

I have the pics. However, my computer upgrades have taken a beating. I believe I have to update my Motherboard Bios, whatever the hell that means. Tomarrow maybe.:huh:

Bios is the start up protocals for you computer. What some people call instincts in a human being.:smack:

[BRUTAL64]

I forgot my piston slept over at your house. There is another thread around here with the blown piston in the hole.

"slept over"? Gosh, Bird, you never had me over for a sleep over.:(

[enkeivette]

"slept over"? Gosh, Bird, you never had me over for a sleep over.:(

Are you made of forged aluminum!? ...Then you're not worthy... humans... with their inferior organs. Ha!

[BRUTAL64]

Are you made of forged aluminum!? ...Then you're not worthy... humans... with their inferior organs. Ha!

I'm carbon based.:sm_laughing: