Hi guys,

I am a new member here who has come seeking help!
I purchased a (new-to-me) 2006 c6 corvette a few months prior and I learned within a week of owning it, I had lifter/cam issue I didn't notice upon purchase because the car was up to operating temp, but on a cold start it was super evident by the tell-tale lifter Squeak! I was had.. but to make the best of the situation I decided to consider this an opportunity for a high performance cam/head job, along with a short block rebuild, timing chain and cam gears.

The mechanic I chose reccomended the cam package Which I uploaded, LS7 lifters, port and polish heads along with a standard rebuild/refresh while inside. With this cam kit combined with LT Headers, slp cold air intake and exhaust with tuning we made 429whp on a dynojet. I was super happy and all seemed well. I drove it 500 miles then returned for an oil change and inspection. Everything looked good and no issues to note, I discussed with my mechanic about adding a ported FAST manifold to squeeze some extra HP. He agreed this would be worthwhile and I snagged one used off the forums. A Vengeance Racing ported FAST. This is where all the problems began (coincidence or not I'm not sure) hopefully someone can chime in.

After the FAST install and a re tune we made 445whp on the same dyno. This time however the tuner told me he was getting some knock and took away some timing, as well as some smoke out of the exhaust up top in RPMs he thought was due to a bad tank of gas.

Less than a few weeks later I started noticing a faint smell of oil. Which very quickly turned into smoke pouring from the car while on the highway and when I pulled over there was oil on the entire underside of the car and rear wheel wells.

Once back to the shop the mechanic changed the rear main seal and we changed the clutch while in there due to rivets coming apart on the pressure plate. He thought the loose rivets flying around could have damaged the seal causing the failure. unfortunately as soon as we got on the highway after the new seal once again the car started pouring smoke and we were back to square one. Upon further investigation, when pulling the oil dipstick there was TONS of pressure and hissing/spitting oil out of the dipstick tube.

Currently the car is once again getting the rear main changed and I need some advice and help. We cannot figure out why this Is happening and If it is just coincidence or something to do with the ported FAST manifold which the mechanic seems to think is to blame for excess crank case pressure. Any and all help is GREATLY appreciated. Many thanks in advanced!

 

Check your PCV plumbing, lack of proper crankcase venting is your likely cause.

 

I have recommended this to the mechanic as forum research has pointed to however he does not think this is the issue.
with my mods, is there any reason OEM pistons/rings would not support this setup at current power levels?

 

Lack of crank case ventilation will make quick work of your seals as the first responder said as they will not take much pressure.

Check all your spark plus for damage bent electrode, a broke piston will cause this as well though is very rare on an n-a car.

You'll learn trusting other people with your car not a good idea doing your own research and investigation into this highly recommended.

Keep an eye on your oil level.

The valley cover must have a breather hose and the passenger valve cover has another one, is a good idea to install a breather filter cap on the rear driver side valve cover as well where the is plug now.

Your mechanic will gladly keep taking your money he knows what's going on IMO your been framed, is your mechanic the same guy tuning your car?

 

Yes that is exactly why I am here now, to learn enough about engine internals/mechanics to have my own assessment of this situation. I most certainly got a warranty in writing for the engine rebuild and paid with my Amex business card so I have recourse available should it come to that.
He is not the tuner, that is a completely separate shop.
At this point, there is no more money to be taken from me. It is clearly either an internal engine defect or a simple PCV issue. If it is internal I most certainly won't be paying a dime as it's still under warranty. This will make three times the engine has been pulled so I know the mechanic shop doesn't want my car
there any more than I do- especially considering there is no more money to be made on his end. I just am here to truly understand what is going on and how to fix it!

 

pressure test the intake manifold. I do this to every engine, every time. And more frequently on forced induction setups.

https://ls1tech.com/forums/forced-in...l#post19588973

 

Seeing as I'm NA and experiencing these issues, how much pressure should we use to test?

 

If you still have the old manifold, put it back on and see if problem goes away,
if it does you know it's manifold related, if not then start the process of elimination.

 

I would have done that- but I don't have the old manifold and when I got the ported FAST I got retuned . It was a major PITA to get it idling nicely and decel to a stop without choking so I really do not want to have to do a re re tune again for nothing.

how could a FAST manifold be causing excess crank case pressure? Does this even make sense?

 

This should be a very simple problem to find. You pressure test, a couple PSI is fine, more if you need to, in order to find the leak. You are praying there is a leak, i.e. a vacuum hose or something is hooked incorrectly and causing a problem.

If you do not find any leaks, then there is generally only one other place the crankcase pressure can come from: The combustion chamber, passing the rings. Which means your next objective is to do a compression test to find the cylinder with the bad piston(s) seals.

 

Ok, I had a similar thing. Pinched PCV line caused my rear main to dump 1.5 quarts on the dyno. I fixed the PCV and also fixed the leak. But I damaged the rings and they always blew by after that. Does this sound about right to you?

That it was the rear main is incidental. Could have been front main, oil pan gasket, any number of seals. Weakest one gives out.

Hears how I figured it out without a **** ton of erasure testing. I drilled a 1/6" hole in the oil cap and ran the engine. After it warmed up I cut the motor and I heard it hissing out the oil cap. Put my finger on the hole and it stopped hissing. Bingo. Crankcase pressurized, PCV not working

 

You did not add a catch can or anything like tat when you did manifold change. If so make sure the in and out hose are not crossed over - backwards thus not letting pressure out. Also on non dry sump cars where do the valve cover hoses vent to. On mine they vent to the dry sump tank. The hoses to the VC must vent somewhere did somebody block those? If you heard a hiss then every hose/vent must be closed so I would check that first.

 

Oh I long since fixed it. I was just trying to help the OP without doing 85 hours worth of tests to determine his PCV isn't drawing down the crankcase.

I'm not afraid to admit when I did something dumb if it helps others out.

 

Thank you guys very much for all of the insight. I will keep you all updated as this progresses.

 

Dear Darth, if you think his vent line is clogged (or yours) why not just take it off and blow into it?

Its not really PCV at WOT unless you still have the OEM filter on the engine. There isn't any pressure drop, it acts more like a vent, pressure PUSHES air out as opposed to vacuum PULLS the air out when there is a pressure drop due to restrictive filter. At least this is how it is on most cars. In any case, he should be able to just blow through the tube, into the crank case, and feel it come out the dipstick hole or other valve cover hole.

 

I don't need to. Per previous post - I had a problem in the past similar to what the OP posted and I fixed it by fixing the PCV

Mine WAS broken. Now it is fixed. Thank you.

Negative ghost rider. If there's no pressure differential, the intake can't draw any air in through the throttle. In a NA engine, the ambient pressure is always slightly higher than the intake manifold. If it wasn't, air would come out the intake, not go in. If you're NA, the fresh air side is vented, and the vacuum side goes to the manifold, you will get PCV. Even at WOT. Works perfectly. How do I know? because that's how I FIXED mine.

Secondly, you can't blow through the tube backwards. The Early LS PCV ran a check valve to prevent air going to wrong direction. There's no guarantee you can blow through it backwards, therefore doing that won't tell you anything.

 

At WOT the pressure in the crank case is higher than atmospheric, thus it exits the tube, even if the tube is vented to the atmosphere. To gain PCV action you need a pressure below atmospheric, significantly more than -0.001psi or -0.01psi or -0.1psi from the manifold. In other words, the manifold "vacuum" is not significant enough to draw on the crankcase, reducing its pressure below atmospheric. To achieve this on a factory engine, typically the tube and filter is designed to be somewhat restrictive (1.5" Hg pressure drop) so that instead of seeing 0.5psi in the crankcase, it may level around -0.5psi. Which won't happen when the manifold pressure is -0.1 or -0.2psi.

You are thinking of the pcv valve maybe? That is a check valve. There is no check valve on the crankcase vent side, at least, I do not detect one on my 5.3 (maybe 5.7 valve cover has two of them?). Next time I see my 5.3L I will check to be 100%. It doesnt make any sense to have a redundant pcv valve though?

 

Looked like you were suggesting blowing backwards through the PCV.

 

Why not just remove the oil fill cap and see if it quits?

 

ah! You should watch my video

During the initial pressure test, you will see the PCV valve leaking. This is part of the air compressor test- it shows you where the air is going, if anywhere. This is NOT the side of the PCV system responsible for removing blow-by gasses during WOT as it typically routes to the intake manifold, whereas the VENT tube (or "fresh air tube" as it may sometimes be called) is routed to a location on the outside of the intake manifold (it could be pre-throttle body, pre-compressor, or just behind the air filter, depends on the vehicle). This is the line that, when clogged or kinked, will cause big trouble (high crankcase pressure) and the line you also suggested correctly to inspect. This is the line that I suggested we "blow" into, for it is a free flowing line to the crankcase, both to, and from, as it exchanges duties depending on the situation (TO the crankcase during idle/cruise and FROM the crankcase during WOT) thus it can not have any check valve.

You know, it crossed my mind as well initially. Then, I imagined trying it (try that) and just imagined the flurry of oil spraying all over the engine bay I realized it wasn't an option.