What's up Guys'

I have a 1998 C5 ( 96,000 odometer.) that I just dyno'd last month and put down 420RWHP.
It has a Vararam Air system and ls6 ported intake. A set of 243 ported and polished Exhaust side only and an Ed Curtis Cam (Formato called it small). Stainless headers, Xpipe, and serious loud SLP axle overs. I thought everything was great due to the great HP numbers I got with just the little work I had done. Fast forward to about 4 weeks later and my Front Crank seal popped out??
Smelled and seen the oil smoke from the headers when at a stop light. After reading for hrs last night, I went and rented a compression checker and proceeded to run my numbers. Should have looked a little longer because I did the check on cold motor with all the other plugs in and no use of the throttle at all.

But here are the numbers:

1 200 5 238
2 195 6 195
3 195 7 239
4 205 8 195

Oh yeah and it took about 3 turn overs of the motor for about 3 sec each to get these numbers. Can't figure out what is up with cylinder 5 and 7 ??

What I know is the blow by of my stock system is being overloaded with pressure and popping my seal out. My sysem is an updated lS6 valley tray with the drivers side valve cover is blocked. The passenger side has the rear blocked and the front nipple is going to the throttle body. The valley tray line in front goes through the pcv valvle into the intake body.

What do you guys think??
Thanks for all the replies in advance.....This site has helped me do every rebuild of every system that was now working correctly when I bought this STOLEN repo. And as you can guess it was EVERYTHING!!!!

Chad.

 

Just say'n...... maybe it's carbon build up. I would definitely use some techron or similar product before tearing into the engine.

 

^Agree.

When I pulled my heads last week there was a lot of carbon built up in the combustion chambers.

 

Do it again the correct way? I dont really see anything wrong with those numbers. Little high on those two. But that could be a few things.

What made you do a compression test because of an oil leak?

 

After reading the posts on the front seal popping out it led me to believe that there was excessive blow by the cylinders. So I wanted to do a compression test to see if I had a cylinder down or a broken ring letting major crank case pressure build up. I thought it must have been some serious pressure to pop out a front seal? I just had the top end all apart and cleaned the top of the pistons. The engine was bone stock with 96,000 miles and the pistons looked great. Hardly any build up at all on top and the cylinder walls had all the cross hatch still visible. SO it can't be build up unless it has happened in a one month period after the cam and head swap.
What is the correct way to do the compression test? I have a throttle by wire on the vette so do i pry the throttle body open and then do the test with all the other plugs out?
Thanks for the ideas, keep them coming!

 

When you say your crank seal popped out what do you mean? Ive never heard of that happening. Did the Balancer bolt come loose?

 

CRANK SEAL POPPED OUT!?

Was the new SEAL tight in the front cover when you reinstalled it??

Is your PCV Valve working properly? Do you have a metering or FIXED orifice PCV

What is the Intake Vacuum at idle.

Bill

 

Just got back in from doing a recheck with the throttle body open and all the plugs out and here are the numbers:

1 210 5 250
2 220 6 220
3 210 7 240
4 240 8 240

I do not know what my vacuum is at idle as I have my front end torn apart right now for the seal replacement. I have a stock PCV valve for the 1998 system which is I think is a fixed orifice. I went and bought a new one to put back on at autozone for 3 bucks. I bought a new timing cover when I did my head and cam swap because the previous owner had a balancer come off and beat up the old timing cover and oil pan which I also replaced. The seal was already in the cover when it was new and honestly I did not check it. It just at a glance looked seated, but maybe it wasn't all the way. I am looking into getting a catch can set up from Rev Extreme or Bat Car from this forum. I have noticed a black oil film on the exhaust tips and I sure I am now pulling some oil in through the intake. I changed over to the valley pan update as I had read it worked better than the old valve cover style PCV system but maybe it doesn't. My pistons when I took off the heads were really very clean for an almost 100,000 mile car.

Johnny the bolt was fine the seal just popped out of the timing cover and rode up onto the balancer leaving just enough room for oil to puke out the front when RPM's were at 3000 and above!!

Are these numbers acceptable for the compression test? Why such a big flux between the cylinders?
Thanks again for the help...Chad.

 

Can someone please tell me if these compression numbers are OK?? LOOK ABOVE!!!
The front seal I think was just the wrong size. After cleaning the cover well, I then placed the seal into the cover and it just feel into place like it was too small? I then put my new seal up into the timing cover and it fit very tight, I had to use my Sac city crank seal tool to pound it in:-) Hopefully all is well now but I am going to add a Tracy Lewis catch can to the system to keep those oil residues out of the combustion chambers!

 

I am 48 and have been in engineering most of my life.

Half of the stuff you guys do makes no since.

 

What do you mean?

 

The compression test looks ok.. The numbers are all very high... Higher then what you would "think" they should be, however there is a lot of variance in compression testers/gauges so...

You do have a bit of a spread from the low of 210 to the high of 250.. So 40 psi spread is a bit more then the general rule of thumb of 10% but..... I wouldn't worry about it a bit.

You could have a bit of oil leaking into the cylinders from the valve seals, and that oil will increase the cranking psi.

For 96k miles, I'd say it's in pretty strong shape... As long as you aren't consuming a BUNCH of oil or something, I'd let it ride!

If you are really concerned about the blow by, you can get a leak down tester and do a leak down test and see how much compression you are losing and where from.

Honestly, I wouldn't worry about it. Ignorance is bliss..

 

the heads were completely gone thuough and milled 10 thousands with .40 cometic gaskets so compression is somewhere around 11:1. That's the reason for the high numbers but I was just concerned about the difference on each cylinder. I borrowed a leak down gauge set from a buddy today and i'm going to check the two cylinders that read 210 and see where the pressure is going. I'm sure its rings since the valves were checked cleaned and lapped in and the seals are new. Thanks for the reply guys!

 

When you do the leak down, make sure 100% that the piston is at TDC... Otherwise, when you introduce the air, it will try to turn the engine over, rock the piston in the bore and show leakage.

Also, make sure to use a GOOD tester... Don't mess with Harbor Freight testers etc.. You need a good, accurate tester.

I recently bought a new Longacre tester and it was like $120 shipped from summit.. But it worked much better and more accurate then the off brands. A tool you'll keep for life.

I would expect to have some leakage....

Milled heads and thin HGs makes your compression numbers more believable.

 

Yeah the tester I borrowed is top notch, that's all my friend buys is Snap on and Mac. I think his tool bill is a few hundred a month to the truck every month for the rest of his natural life...LOL.
I think I am going to just do like you said and drive it... ignorance is bliss. I am sure its the rings and i'm not going to do anything anyways. Gone to drive it like I stole it and have furn!
I also have to eat a little humble pie because I found out why my crank seal popped out (although I still think the outer diameter is a little off), I had the PCV valve backwards?#&%@!
When I set up new intake and valley pan I somehow put it in the wrong direction so the crankcase was sucking in air from the throttle body and it had no were to go!!
Thanks for the advice, Chad.