Engine block surfacing

[1972ho]

I have been having a problem with oil smoking out the exhaust and I’m trying to figure out if the intake is not sitting true on the head this makes the second intake gasket that I have installed I was first seeing oil on my number 5 and 6 plugs now I’m seeing oil on number 8 plug.Before I assemble the engine I had the block decked by .008 and went with a thinner head gasket going from a .045 thick head gasket to a .038 thick gasket.Would these two changes make a difference in how the intake manifold fit on the head.The last gasket that I removed I could see oil in the two intake ports that had the plugs oiling.

[rustbucket79]

Measure the gasket in multiple places. If it's uniform (and thinner than new) the gasket did its job. If it's stock thickness (in your case at the bottom of the ports) then it's quite possible the gasket was leaking due to improper compression by the intake and head.

[hondo383]

What engine? What manifold and is it new?

I surface and correct every intake for every engine I build, most are way wrong on flatness, port height, angle they all need tweaking

[MadBill]

After checking manifold and head surfaces for flatness, a good test is to put short lengths of solder in existing or purpose-built openings between head and manifold of a pair of used gaskets in various locations top and bottom, front and rear, then torque the intake down, remove and compare solder thicknesses. This will show any discrepancies.

[1972ho]

This is a engine I’ve been running for years I just had a sleeve installed and they had to surface it anyway so I just had them do .008,This is a 351 cleveland with a stock aluminum intake and I just went with a Mr.Gasket head gasket that was thinner than the felpro I was using before.

[PackardV8]

This is a engine I’ve been running for years I just had a sleeve installed and they had to surface it anyway so I just had them do .008,This is a 351 cleveland with a stock aluminum intake and I just went with a Mr.Gasket head gasket that was thinner than the felpro I was using before.

Did they square deck it with a BHJ or similar fixture?

[1972ho]

I forced air into the crank case through the dip stick tube and had air exiting out the carburetor vacuum tube connection,wouldn’t that mean the intake gaskets has a problem at one of the runners.

[superpursuit]

I forced air into the crank case through the dip stick tube and had air exiting out the carburetor vacuum tube connection,wouldn’t that mean the intake gaskets has a problem at one of the runners.

This doesn't mean much if you have an inlet valve open. With cylinder leakage past the rings the air will travel through the open inlet valve to the manifold.

Did you check the clearance on the ends of the manifold to the block before you bolted the manifold on? It's possible it's holding the manifold up there.

[Dave Koehler]

There are several variables at play here and it does not mean that decking the block always needs a thinner gasket.
For instance, I had one case where I had to use a thick Mr gasket piece on one side and a thin one on the other to get the proper crush.
2 thicks was too much, 2 thins was not enough.

[jcisworthy]

Are you over tightening the intake?

[PackardV8]

Since we don't have an answer to my squared deck question, here's the rationale behind it. If the block was .008" out of square and the intake manifold was tightened down on that, aluminum distorts to iron. Heat/cool cycles help it take that set Then if/when the block is squared, the intake is still crooked to the old block. When trying to pull it back square, some distortion may remain.

[1972ho]

The block was square decked many,many years ago but I’m not sure how it was decked after the sleeve was installed.ill know more this morning when I take the intake back off.I really just kind of wanted to know if removing .008 of the deck and going to gasket that is .005 thinner would change how the intake sit on the head.Because everything was fine until I made the changes.

[Newold1]

What thickness intake gasket -uncompressed new-?

Has the intake itself been checked for square, yes aluminum manifolds do tweak and twist.

Are the china rail ends of the intake manifold contacting the block china rails when tightened down?

Try taking of the carb and looking down the intake ports at the intake to head port junctions and see if there is evidence of oil there.

Those dimensions removed with a good .060" gasket and straight square surfaces should seal, less than .015". Measure the same gasket uncompressed and compressed after removal and compare for actual gasket compression and check at various locations on the gasket.

Have you done any leakdowns on the cylinders?

[1972ho]

No leak down but compression test was 5 cylinders at 195 and 2 at 185 and one at 180,I pulled the intake and oil is in all of the cylinders that have the intake valve closed.And it does look like the intake gasket has been compressed it is a Mr.gasket 214.Now what is the procedure for getting the intake squared on the head.

[1972ho]

This is what the intake gasket looks like after removal it .062 thick I measured the top and bottom and the bottom was about .055 in places and the top was .062 or so.