excessive blow by, compression and leakdown results inside

[supraguru05]

Well my road race car during the last race last year started to put some oil into the intercooler. i assumed it was from the ct26 not being able to handle my high oil pressures on start up without a restrictor. this year to confirm i installed a turbo feed restrictor. as well as i plumbed in a spin type parker filter, the same one adjuster uses, inline with the hose from the accordian tube to the metal line that ties into the valve covers. figuring if the restrictor didnt fix the problem i at least could rule out the turbo if the catch can took in alot of oil.

this puts us to the current situation. my first race was last weekend. after my first 20 minutes of driving after coming back in the pits the catch can was filled. here is a picture of the amount of oil present. Ignore the oil color thats a long story.

it did this every run. if im not mistaken this means that i have excessive blow by. so in order to confirm this i did some compression tests and leak down tests today and this is where it gets interesting.


Results

Gauge A
Cyl 1 150
2 150
3 152
4 155
5 150
6 150

Gauge B (crappy harbor freight gauge messed up therefore some missing results)
Cyl 1 151
2 145
3 155
4 140 (most likely did not crank engine enough)
5 no results didnt crank long enough
6 150


i gave up on the harbor freight gauge so dont worry about it.

here are the leak down results
1 8%
2 8-9%
3 11%
4 13%
5 17-20%
6 8-9%

the leak down test was ran with the cylinders on their compression stroke about three quarters of the way up

The engine is a 7mge bottom end rebuilt by yours truely two years ago. it has 2 seasons of autocross on it, and one season of road racing. the engine is completly stock running on 10psi of boost with a wideband and no safc or anything since i am just hovering below fuel cut. the base timing is set around 7-8 degrees due to the high compression, and the car is always ran on 93.

1st question. should i rerun the leak down test with the cylinders at the top of the compression stroke? reason i ask is it seemed like when i repeated the measurements there could be quite a bit of variation depending on the piston positions.

2. these results, at least to me, show nothing really conclusive as far as a single cylinder being down, does that seem right?

3. what can i do to determine which cylinder has a bad ring?


anyone have some ideas.

 

[mkIIIman089]

How long (in hours if you can approximate) has it been run? A full season of road racing depending on how long is a pretty abusive thing...

It could just be normal wear and tear, I would retest at TDC for each cylinder.

 

[supraguru05]

ok ill retest at TDC, but if those results come back the same or better then why do i have this much oil vapor in my engine? i have a crank scrapper so windage should be at a minimum. i would say the run time from last year was about 11 hours of racing. im starting to think mybe the engine is just a little loose and i should just get a higher capacity can. the engine makes good power

 

[mkIIIman089]

Only 11 hours... that's not much, it could go 4x that before you even see any power loss. Compression seems to be in within variation specs but low across the board for NA pistons.

If you're happy with the power then my course of action would just be to monitor the can, and the state of the oil and filter for metal particles. If any start to increase a lot then it's time for a tear down. Until then just enjoy your race car.

 

[supraguru05]

what do you think about the amount of oil does that seem high (ive never had a catch can on before so i dont know if thats normal for a racing situation where your foot is down for 20 solid minutes

 

[IJ.]

Describe the PCV system.

#5 leakdown would indicate an issue, GTE?

 

[supraguru05]

Describe the PCV system.

#5 leakdown would indicate an issue, GTE?

its a GE bottom end with full 7mgte electronics and manifolds. so to answer your question no, the pistons, rings, block is all 7mge.

the PCV system is in the factory layout. line from the TB orifice, to the hard pipe over the valve covers. the line that enters the accordion hose has the catch can inline with it. effectively i only filter the air flowing from the valve covers to the accordion hose.

 

[IJ.]

I'm guessing broken ringlands in #5

 

[supraguru05]

let me ask this to. the leakdown tester i have only builds around 15 psi. the way the gauges and orifice is setup is kinda wierd i dont know if maybe i should enlarge the orifice to increase the pressure.

NInja edit:

thanks IJ im going to redo the leak down test now. and ill get you some cleaner numbers.

 

[supraguru05]

results are from a cold motor and apear to me to be a wash

1 18%
2 24%
3 24%
4 26%
5 30%
6 27%

now as just a non quantitative measurement, the amount of blow by is enough where if i cover the outlets of the cam covers with my fingures for a second and then lift one you hear a pop. im pretty sure im going to have to pull this thing and re ring it. im just kind of wanting someone to basically tell me i need to do it.

my plan, if i pull the motor, is to take it apart have a machine shop mic the bores and pistons and let me know if i can simply hone the block and add new rings. ill install a new head gasket and reuse my arp head studs. ill have the block and head surface touched since they probably are a little off from all the heat from racing. ill reuse all the bearings if they are not worn abnormally, which i hope they are not. im kinda working from a budget but if i see a damaged piston this plan goes out the window and i might just bore the block and get probes.

if you want Ian i will re run the test one last time with a warm engine tommorrow, the cars a little apart so it will take a little bit to get it back running. but ill trust your opinion based on the numbers, and the quantity of oil present in the catch can on whether you think a ring is down or not.

 

[IJ.]

Cold leakdown is a waste of time

 

[supraguru05]

then ill have another set of numbers tommorrow :biglaugh:

 

[IJ.]

A valve in my 7M used to not seal for some reason when cold tested and showed 35% leakage, fire the motor for 30 seconds and it was 8% :aigo:
(I had a HUGE panic when I saw 35%)

 

[supraguru05]

warm (not scalding hot) engine numbers

1 24%
2 24%
3 25%
4 25%
5 20%
6 22%

well this test is so inconsistent that its driving me up a wall. so i am pretty sure i am just going to ignore the possibility of a ring being down and get a larger catch can and move on with my other projects before the next race. since the car isnt smokeing except on rare occasion i am going to say that the engine is well seasoned and maybe a bit loose. if the car wants me to fix it, it needs to make this obvious and start smokeing alot.

in the mean time i am going to send the oil out to blackstone for its regular analysis and work on some projects. in a week or so i might re run the leak down test after getting the oil and the engine up to full temperature to see what i get.

thanks for the help Ian its just so annoying when i cant get a clear answer from these tests, i would seriously rather it just drop a ring and smoke like hell so i can fix it. i hate this cat and mouse stuff

 

[IJ.]

20% and up is about at the upper end of what I'd consider "normal" but at least this test was more even.

 

[jdub]

 

[supraguru05]

jDub that picture would be better if someone added like a shockwaves infront of the cat like it was breaking the sound barrier lol

 

[supraguru05]

I hate bumping old threads but since I am still on this same motor and working on the same issue I figured this was best.

So last I left this thread I simply kept running the motor and just emptying catch cans to my hearts content. Now I have upgraded the catch can to be larger so I do not have to worry about emptying it and the car is slowly begining to smoke on decel more and more after hard pulls. This is clearly a ring issue. I got an electronic bore scope and ran it in all the cylinders. It was real tough to check the walls for scaring, but i was able to get a good view of the piston tops. Cylinders 1-5 were all severely covered in carbon and cylinder 6 was clean. That could be do to the crappy flow distribution of my manifold or because of my 20 year old fuel injectors which I have not flowed.

If I am not mistake excessive carbon buildup in the cylinders from running to rich (wideband reads around 10.5 on WOT pulls) could stick a ring. My plan of attack is to use MOPAR combustion chamber cleaner, with my friend who is a MOPAR tech, to attempt to give the cylinders a clean. I will be taking before and after pictures with the bore scope to compare. The other worse case situation is its cylinder 6 running lean and it screwed a ring land. For sake of my sanity I'm ignoring this possibility. I also will probably run some miles with the all hated Seafoam in my oil to help try to free the rings. Since I don't have cats i shouldn't hurt anything trying these snake oils out before my race two weeks from now. When my car is back from getting the exhaust put on next tuesday ill get the current cylinder pictures taken so you all can see what they look like. If anyone has any tips on how to look at the cylinder walls I would love to hear them.

 

[jdub]

#6 could easily be due to a HG - coolant in the cylinder will steam clean it.

If you put Seafoam in the oil, all you will accomplish is to reduce it's viscosity. Don't do it.

The Mopar cleaner is good, but I have always used it to clean piston tops with the head removed. You could try to clean the cylinders by metering distilled water (needle valve) in a TB post that is under vac at idle...use at least a quart. A lot more effective and cheaper.

 

[homeless]

As far as the #6 cyl, it shouldn't be clean. What did your spark plugs and valves look like? Check your fluids for commingling. Run a compression and leak down test. Use a stethoscope to find your leakage. If you have to pull the head then go ahead and re-ring it. If the top end and HG check out, then run the MCCC and use the ATF trick to try and reseal the rings, but don't mess with the SeaFoam.