Thread: FE390 Rebuilt Engine. Problem w/oil spray on drivers side valve cover/little smoking

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Originally Posted by stotzbotz

I wondered if anyone has any other pointers about the excessive oil on the drivers side.

All these motors that we hobbyists are fiddlin' with were produced in a mass production shop, at a rate that would support maximum appreciation of value for the stockholders. It is conceivable, in a maximum production shop, to make a few mistakes along the way that, while not being right, could be pushed through the production line and out the door regardless. One such problem is that in the milling operation that cuts the block decks, a chip from the previous milling operation could miss being cleaned out from the register by the operator, resulting in the block being tipped up by the thickness of the errant chip that could lead to that bank being machined imperfectly, one end of the block to the other, to the centerline of the main bearing bore. The blueprint for the block assumes that all four corners of the block decks should be equidistant from the centerline of the main bearing bore in the block, but when there is a chip in the register, this is not possible. The finish on the block decks will be uphill or downhill side to side and will leave the cylinder heads at a cocked angle to each other. Any reasonable human being can see that this will result in the intake manifold not having a square hole to sit in when it is placed on the cylinder heads. If the gap between the intake manifold and the heads is on the upper side (outside), we can find the gap by spraying a combustible substance onto the intake manifold and listening for the motor rpm's to increase. But when the gap is on the bottom of the intake manifold, there is no way that this same operation with combustible substances will find that there is a gap between the intake manifold and the cylinder heads.

When such a gap exists, it allows the cylinders that are affected, to pull oily crankcase vapors into the cylinders when the intake valves for those cylinders are open and there is nothing that you can do about it except to disassemble the motor and re-machine the block decks to square off the main bearing bores. Now, having said that, I suppose that if a gasket of sufficient thickness or even stacking two gaskets together could be used, that it might achieve sealing up of the space, but doing that will also stack the intake manifold up higher and mis-align the ports between the heads and the intake manifold.

This is something that I try to hit hard when talking to newbie builders on this and other forums. You must begin with the block decks, front to back, being square to the main bearing bore and exactly 90 degrees to each other if you expect to have a quality build. And speaking of that, you must also begin with a straight and round main bearing bore, so what I recommend is checking the main bearing bore for being straight and round first, then cutting the block decks parallel to the main bearing bore after the stack of parts to be used has been determined.

STACK: The crank radius, rod length and piston compression height added together make up the "STACK" of parts that will be used in the cylinder block. Let's say that the crank radius is 1.890", the rod length is 6.490" and the piston compression height is 1.782". If you add these three values together, you find a STACK height of 10.162". Now, if the stock block deck height measures 10.170, then milling the block decks by 0.008" would put the piston crowns at ZERO DECK HEIGHT and allow the compressed thickness of the head gasket used, to be the squish/quench dimension. This approach points to using a composite head gasket, such as the Edelbrock 7337, which compresses to 0.038" and defines the squish/quench at 0.038", just in the middle of the 0.035" to 0.045" that is recommended by most savvy engine builders. Another gasket that will work well is the Fel-Pro 1020, which compresses to 0.041", presenting a 0.041" squish/quench when used with zero deck. Using a composition head gasket will also set the motor up for using aluminum heads if you wish. Using steel shim head gaskets can allow the heads to "fret" against the solid steel gasket and lose material. A thicker composition gasket will allow some "give" as the aluminum grows and shrinks at a different rate than the cast iron of the cylinder block.

Most newbies will shy away from doing any machine work on the block other than the boring and honing of the bores to accept larger pistons, but the cutting of the block decks to square them up costs only about $150 at a good shop. Not only will the heads sit squarely on the block and the intake sit squarely on the heads, but the static compression ratio and thus the "bang" will be closer to the same, cylinder to cylinder.

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