Robert's modified '69 Merc

Quote from: 69 Merc on August 21, 2010, 09:09:11 pm

I just think that with this guys quote's help from Yellowbullet sometime in the past I figured out my problem --

"MEAN_SBC
04-21-2006, 11:03 PM
Just don't run them with mufflers... If there is any back pressure in the exhaust at all, the check valves won't open, and it's like running the engine at WOT with no breathers.... It'll push seals out like crazy..."

My new check valves are fine! It's my 3 chamber Flowmaster mufflers that are creating back-pressure which is closing off my check valves which then is really sealing up the top side of my engine is why my crankcase pressure is rising! Remember that on de-accel I was getting crankcase vacuum.

This has been MY experience and what I have preached all along.

I use the header evac at the track with no issues with the turbo mufflers/tailpipes dropped. I have 2lbs at idle (but have had as much as 5lbs in a previous edition which must have been sealed up real good.) I've used the header evac on the street with turbo mufflers and as long as I do not get frisky and give it high RPM's I have no oil leakage issues. I do not use full throttle in this condition or else the dip stick will pop up 3/4" and I will have oil to clean up off that side of the motor. Can't be good for the seals. I watched the vacuum gauge as I cruised around and confirmed that vacuum decreased to zero quickly as RPM increased with the mufflers on. I attributed it to the backpressure added by the mufflers. I have not watched the vacuum gauge at the track. I have a hard enough time catching the 6400 rpm shift light let alone read a gauge . . . . .

I swap to PCV on the street (with mufflers/tailpies) and it works well and I can do whatever I want. I have also used the PCV at the track with mufflers/tailpipes and did not have dipstick issues when the motor was built right (nearly 150 runs that way last year when I had to slow the car down due to being rollbarless.) This hasn't always been the case though.

I know that header evac can work well when properly installed. I had one motor that I ran a whole season which would blow out the doubled up valve cover gaskets every time the engine was rev'ved up beyond an idle when using a PVC (street or strip.) It also leaked like a sieve out the rear main which I changed twice before realizing through this site that excessive back pressure was the cause. That is when I installed the Mr. Gasket header evac. At first it didn't seem to draw any vacuum, and then I discovered that the included valves did not do a good job of sealing. I ran down to NAPA and bought the good recommended valves and the results were immediate. No more gasket blow out and the rear main seal slowed down to just an annoying quarter sized drop after the car sat a week. I was sold from then on and ran the car solely at the track for the rest of the season. Later found out during the winter build that I had installed the 2nd ring of the piston upside down on several (if not all) pistons which created the excessive blowby. Dumbass.

I can't tell you how many times I look at the rings now when I am preparing to stuff the pistons.

Never, ever trust the valves that come in the cheap evac kits. With the valves found in the Mr Gasket kit, I could blow through both directions. Shaking it "might" allow the inferior disc to center properly once in awhile. The NAPA valves still seal properly and are going on their 3rd year.

Using open breathers offers no evac what-so-ever and tends to give the car an oily spell when driving with the windows down. I don't like that.