Well for those unfamiliar I had hi idle on my BG and I did find 2 vacuum leaks in both the right headlight actuator and the windshield relay both which are back ordered. Ilde is 1000 RPM (steady) and with all vacuum tees blocked off including the PCV line I get 850RPM (steady). When I put the PCV line back in it shoots to 1000 regardless of idle speed screw position. Again with PCV disconnected idle speed is completely controlable with the idle speed screws. If I use a breather, the idle issue disappears but when I nail it at WOT the breather spits oil fumes and leave tiny droplets of oil on the valve cover. So the answer could simply be a new breather. My last breather solved this and it did not spew oil fumes until about 3 months when the cotton guaze got over saturated with oil and then started to puke oil spray at WOT. Maybe I could find a breather with removable elements and just change it out every two months. But another problem was I started seeing oil leaks around the manifold to head area which proves LARS statement that engines not running PCV's are more prone to leaks. I have since replaced the intake gasket so that's not an issue but the PCV is allowing too much air at idle. I have tried 4 types of PCV's put a resrictor in the PCV line all of which have failed so I suppose a breather is the answer. Anyone know of a breather with alot of guaze and that is replaceable?

 

thats strange....i wonder why more of us don't have that problem? what kind of vacuum is your engine drawing? after our last discussion i put a restrictor in my line, it is a plastic union fitting for splicing different size hoses together and i just left the smaller diameter fitings on it so it reduces the size of the tubing in two spots... i wonder if you can restrict it again to reduce the vacuum? right now i have a 70 rpm surge/hunt going on so i'm also looking at the vacuum system.

 

16.5" @ 850rpm. I put that restrictor in but after Saturday's autocross event with much of it WOT I opened my engine bay to find oil all over the place ( the engine's pressure overcame the restriction and forced oil between the PCV and the grommet.

 

Have you ever done a compression or leakdown test on the engine?

Brett

 

Hmmmmmm

 

Try installing some OEM valve covers with baffles & routing the PVC & breather lines like the factory did it. The race style v/c breathers always make a mess. I've yet to see an aftermarket company use the same quality valve cover baffles like GM does.

 

Dynamic compression test yields 125psi at all cylinders with no greater than 5 lbs. difference between any 2 cylinders.

 

I get this magazine, "corvette enthusiast". They have a great article this month on this very issue.

Familiar names from NCRS and here write articles.

 

David,

My engine was rebuilt last year. Originally a 10.25:1 compression engine. Rebuilt with only .004" decking. I assume the compression is still around 10.25:1 whcih is loer then what your motor was built at. My dynamic compression is 165PSI per cylinder with no greater then 5PSI difference between any cylinders.

May be you have a bit of blowback past the rings and you are having air pressure come through the oil system?

Squirt some oil in the cylinders (one at a time) and redo your compression test. If it improves greatly then you have bad ring/cylinder seal. Car may still run fine with leaks here but it may be causing your oil problem.

I also agree with the comments about the GM baffles in the valve covers. GM was cheap on what they put on cars. If they did not need the baffles they would have saved money and not put them on. What we get when we buy a car is the best product but produced in the easiest way at the cheapest price.

Hope you find a solution.

Pete

 

That's what I was thinking.....

Brett

 

A leak down test is more accurate and you can isolate on the problem as well by hearing/feeling where the air is going,I would think.

 

I'll be getting a calibrated comp. guage from work next week and retest the compression and tell you all the readings.

 

You said you already checked the compression. You should do a leakdown this time.

Brett

 

Explain the leakdown test process.

David

 

http://www.carcraft.com/techarticles/53599/index.html

 

Next, we fired up the air compressor for the leakdown test. Powerhouse Products’ leakdown tester requires an external air supply to pressurize the cylinder. The tester has two gauges; one measures the supply pressure, and the other measures the resulting cylinder pressure. We set the supply pressure to 100 psi, rotated cylinder No. 1 to TDC, threaded in our tester, and attached the air hose from the compressor. Proceed in the correct firing order and test each cylinder, and rotate the motor 90-degrees clockwise after each test to ensure each cylinder is at TDC with both valves closed. We plugged the observed numbers into the formula %leakdown = [(supply pressure - cylinder pressure) / (cylinder pressure)] x 100 with the following results...

Maybe the picture does bot reveal the guage setup but looking at the gauge pod it appears both guages are on the same line which would give the same readings. Even if your rings were horribly leaking by a good 35 gallon compressor could keep up with a small leak, giving you 100psi no matter what relative position of the piston. I need a better picture of this setup.

How about if air compressor outlet was 100psi and you rigged a tee off my compression guage, charged the cylinder so the compression guage read 100psi and then quickly shut off the compressor outlet valve and checked cylinder pressure over a 1 minute time interval would that work????

Okay never mind I didn't see the guy shutting off the supply valve, yep my setup will work. I have the compressor and the guage al I need is a tee.

 

you know i get a ton of automotive magazines and i'm beginning to think "car craft" is almost the most useful.

 

Car Craft is the best. They got rid of Jef Smith & broght back Freiburger.

 

i read lots of his articles they seem ok...and i think Primedia is doing a great job... of putting different stuff in their magazines, i get chevy hi performance, street rodder, car craft, hot rod, popular hot rodding, hemmings muscle machine ,corvette fever and corvette magazine. of those a bunch are Primedia publications and i'm impressed with them...