Need opinion about this problem (urgent)!!
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 884
Likes: 0
From: Panama PMA
Need opinion about this problem (urgent)!!
Good afternoon all!!
Yesterday I did a couple of dyno runs on my C4 that has 383 stroker and supercharge engine.
Here is the problem:
When we dynoed the car in 4th for example, I accelerate the engine to 6k rpm and boost comes up to 12psi, then when I let off the throttle I notice good quantity of oil comes out from the oil check stick.
The mechanic here says that if that happen, is something bad internally in the engine. Like we need to change the rings on the piston of sometihing. (need open the engine?)
But then I think on something...
Oil pressure is perfect, like 40psi idle and 60psi when reving! And NO oil burned in the exhaust at all. (car feels good power) So I don't think that is the rings? Maybe is that issue normal and what I just need to tu put a security spring in the oil stick and solve the problem? The stick usually use the spring but yesterday we did not see the spring there.
So basically I want to know your real opinion about that.
Or tell me what test I need to do in the engine to be sure what's going on?
The engine has low miles.
Thanks for help!!
Yesterday I did a couple of dyno runs on my C4 that has 383 stroker and supercharge engine.
Here is the problem:
When we dynoed the car in 4th for example, I accelerate the engine to 6k rpm and boost comes up to 12psi, then when I let off the throttle I notice good quantity of oil comes out from the oil check stick.
The mechanic here says that if that happen, is something bad internally in the engine. Like we need to change the rings on the piston of sometihing. (need open the engine?)
But then I think on something...
Oil pressure is perfect, like 40psi idle and 60psi when reving! And NO oil burned in the exhaust at all. (car feels good power) So I don't think that is the rings? Maybe is that issue normal and what I just need to tu put a security spring in the oil stick and solve the problem? The stick usually use the spring but yesterday we did not see the spring there.
So basically I want to know your real opinion about that.
Or tell me what test I need to do in the engine to be sure what's going on?
The engine has low miles.
Thanks for help!!
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 884
Likes: 0
From: Panama PMA
Originally Posted by bogus
What year is this C4? Is this engine L98 or LT1 based?
oil out the dipstick means too much crankcase pressure. That could be caused by blowby from the supercharger, and running a blower at 12psi is pretty sick.
Was the engine built with supercharging in mind? Or was the blower added later on? If the engine wasn't built for it, there is a strong chance that the rings have failed, or, a ring grove is giving up, allowing the rings to walk around too much. Also, if the gap is too wide on the ring, that would cause a problem.
Finally, it could be as simple as a bad PCV valve... I would check it. Do you still have the PCV hooked up? If not, then you have a problem...
oil out the dipstick means too much crankcase pressure. That could be caused by blowby from the supercharger, and running a blower at 12psi is pretty sick.
Was the engine built with supercharging in mind? Or was the blower added later on? If the engine wasn't built for it, there is a strong chance that the rings have failed, or, a ring grove is giving up, allowing the rings to walk around too much. Also, if the gap is too wide on the ring, that would cause a problem.
Finally, it could be as simple as a bad PCV valve... I would check it. Do you still have the PCV hooked up? If not, then you have a problem...
Car is L98 engine. Engine is built for supercharger purpose. It has many custom things doned by Jim's performance shop.
Where is located the PCV valve?
BTW if something bad with the rings, should be smoking oil on the exhaust right? Mine is not doing that.
Let me know what to do, thanks again!!
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
What year is this C4? Is this engine L98 or LT1 based?
oil out the dipstick means too much crankcase pressure. That could be caused by blowby from the supercharger, and running a blower at 12psi is pretty sick.
Was the engine built with supercharging in mind? Or was the blower added later on? If the engine wasn't built for it, there is a strong chance that the rings have failed, or, a ring grove is giving up, allowing the rings to walk around too much. Also, if the gap is too wide on the ring, that would cause a problem.
Finally, it could be as simple as a bad PCV valve... I would check it. Do you still have the PCV hooked up? If not, then you have a problem...
oil out the dipstick means too much crankcase pressure. That could be caused by blowby from the supercharger, and running a blower at 12psi is pretty sick.
Was the engine built with supercharging in mind? Or was the blower added later on? If the engine wasn't built for it, there is a strong chance that the rings have failed, or, a ring grove is giving up, allowing the rings to walk around too much. Also, if the gap is too wide on the ring, that would cause a problem.
Finally, it could be as simple as a bad PCV valve... I would check it. Do you still have the PCV hooked up? If not, then you have a problem...
Melting Slicks
Joined: Jun 2004
Posts: 3,253
Likes: 2
From: Castro Valley CA
It sounds like a compression test is in order to determine if there is a ring sealing issue. Even if it has low miles and was built with 12 psi in mind; a fractured ring or piston land can occur on a boosted engine pretty quickly. Do you use pump gas or racing fuel?
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 884
Likes: 0
From: Panama PMA
Originally Posted by bogus
What year is this C4? Is this engine L98 or LT1 based?
oil out the dipstick means too much crankcase pressure. That could be caused by blowby from the supercharger, and running a blower at 12psi is pretty sick.
Was the engine built with supercharging in mind? Or was the blower added later on? If the engine wasn't built for it, there is a strong chance that the rings have failed, or, a ring grove is giving up, allowing the rings to walk around too much. Also, if the gap is too wide on the ring, that would cause a problem.
Finally, it could be as simple as a bad PCV valve... I would check it. Do you still have the PCV hooked up? If not, then you have a problem...
oil out the dipstick means too much crankcase pressure. That could be caused by blowby from the supercharger, and running a blower at 12psi is pretty sick.
Was the engine built with supercharging in mind? Or was the blower added later on? If the engine wasn't built for it, there is a strong chance that the rings have failed, or, a ring grove is giving up, allowing the rings to walk around too much. Also, if the gap is too wide on the ring, that would cause a problem.
Finally, it could be as simple as a bad PCV valve... I would check it. Do you still have the PCV hooked up? If not, then you have a problem...
Car is L98 engine. Engine is built for supercharger purpose. It has many custom things doned by Jim's performance shop.
Where is located the PCV valve?
BTW if something bad with the rings, should be smoking oil on the exhaust right? Mine is not doing that.
Let me know what to do, thanks again!!
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
I have no clue what the compression should be... you really want to run a "leak down test." this tests the cylinders ability to maintain pressure over time.
I would hope that with such high boost, the compression ratio is rather low... like 8.5:1 or so. This is an issue with the build, it's not something you are going to measure now.
PS: I think the system clock freaked out earlier today.
I would hope that with such high boost, the compression ratio is rather low... like 8.5:1 or so. This is an issue with the build, it's not something you are going to measure now.
PS: I think the system clock freaked out earlier today.
Instructor
Joined: Dec 2005
Posts: 188
Likes: 0
From: Riverside CA
R . U Running a valve cover breather?
At 12 PSI you will have some blow by even if the rest of the engine is in order. The PCV valve will not do anything to relieve this presure!
Remember, the PCV valve is hooked to the intake. If the intake is under Boost, how could we expect it to suck out the blow by pressure?
It is better to run double check valves for PCV to insure that the boost pressure is not blowing back through the week little valve.
I Unhooked mine completly to eliminate the possibility.
You need a breather.
At 12 PSI you will have some blow by even if the rest of the engine is in order. The PCV valve will not do anything to relieve this presure!
Remember, the PCV valve is hooked to the intake. If the intake is under Boost, how could we expect it to suck out the blow by pressure?
It is better to run double check valves for PCV to insure that the boost pressure is not blowing back through the week little valve.
I Unhooked mine completly to eliminate the possibility.
You need a breather.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 884
Likes: 0
From: Panama PMA
Originally Posted by Sidney004
It sounds like a compression test is in order to determine if there is a ring sealing issue. Even if it has low miles and was built with 12 psi in mind; a fractured ring or piston land can occur on a boosted engine pretty quickly. Do you use pump gas or racing fuel?
What comprension numbers should be show in a good cylinder?