Major Blow-By after HG + Cam

QUIKSVT · Nov 3, 2006

OK, I noticed a long time ago a little moisture out the exhuast so I finally dove in and found both head gaskets were slightly blown from the water passages to the cylinder on the #2 #3 #6 #7 cylinders... I replaced head gaskets and dropped a cam in while I was at it. Buttoned the motor up, and now I have HUGE blow by issues. If I get into boost it blows the PCV valve right out of the manifold, and will pump exhaust gas like smoke/steam out the dip stick tube BADLY...

I can't imagine what it is, the only thing I could imagine is the rings aren't sealing... Any ideas as to why the car ran fine when I tore it down, and now its all wacked out? ...

Please give me some input before I yank the motor to do the bottom end.

P.S. its a 63,000 mile longblock.....

BlownFiveLiter · Nov 3, 2006

Since you're running a blower, did you plug the port that goes from the intake tube to the oil fill tube on the valve cover? I'm not very knowledgable on boosted cars, but that was the only thing I could think of, since you'd be boosting the crankcase. Is your PCV clogged up at all? I wouldn't think you'd suddenly have issues related to the PCV with no changes other than headgaskets.

vristang · Nov 3, 2006

^^^yep
On a boosted vehicle the TB/VC hose needs to be relocated to from the TB to before the SC.
You still want the crankcase to get fresh air, so I suggest retaining the line. Just make sure it isn't seeing boost.

Another common issue with boost applications is that a directional valve needs to be installed between the intake manifold and the pcv. Other wise the boost from the intake will be pressurizing the crankcase.

It sounds like this is what you are experiencing ???

Let us know ....

jason

QUIKSVT · Nov 5, 2006

If the PCV is doing its job, the intake charge (positive boost) should not be pressurizing the crankcase. If vacuum is exerted on the PCV valve, it should hold it open to evacuate the crap out of the crank case. Under boost, the PCV valve should be forced shut from the boost pressure in the manifold.

I've now discovered I'm having lower intake problems. It blew the little cork cross gasket out on the backside, so I'm going to go ahead and pull the lower and put new gaskets in. Some how the vacuum leak of the lower not sealing must be causing me problems.

fastranger347 · Nov 5, 2006

dont use the cork pieces, just use a thick (1/4) bead of silicone at either end, if there is any mis alignement of the intake bolt holes or youve had heads milled, the cork pieces can suspend the lower intake from making good contact on the head surfaces

vristang · Nov 6, 2006

QUIKSVT said:
If the PCV is doing its job, the intake charge (positive boost) should not be pressurizing the crankcase. If vacuum is exerted on the PCV valve, it should hold it open to evacuate the crap out of the crank case. Under boost, the PCV valve should be forced shut from the boost pressure in the manifold.

I've now discovered I'm having lower intake problems. It blew the little cork cross gasket out on the backside, so I'm going to go ahead and pull the lower and put new gaskets in. Some how the vacuum leak of the lower not sealing must be causing me problems.

What you described is how the pcv is supposed to work on paper.
However, I have never found one that actually worked that way.

The pcv should seal of manifold pressure from the crankcase, but it doesn't.
You will need a directional valve.

The reason the lower intake gasket blew out, was because of the boost pressure getting into the crankcase.

A directional valve should solve your problems.

jason

89SaleenGT · Nov 6, 2006

vristang said:
What you described is how the pcv is supposed to work on paper.
However, I have never found one that actually worked that way.

The pcv should seal of manifold pressure from the crankcase, but it doesn't.
You will need a directional valve.

The reason the lower intake gasket blew out, was because of the boost pressure getting into the crankcase.

A directional valve should solve your problems.

jason

X2. PCV valves are not 100% air tight when boost is applied.

You probably do not need to tear into that bottom end.

millhouse · Nov 7, 2006

You also need to go out and pick up an appropriate motorcraft pcv valve made from boost. The units off of the 89 supercoupe's work quite well…I believe the part number is E5ZZ-6A666-A.

Mr. Rustypwnz · Nov 7, 2006

svo ones work as well, mine held 25psi quite nicely, never smoked, and I changed hg's all the time, I wonder why? LOL......

Major Blow-By after HG + Cam

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