mrg

A bit OT but here goes. I'm in the process of installing head gaskets (fel pro) on a daily driver. The engine is a 3.1L V6 with aluminum heads.

The head gaskets are the SD (severe duty) type that have the blue teflon coating. My understanding is that this type of head gasket goes on dry.

Question: These gaskets have a stainless steel armor that surrounds the periphery of the cylinder bore holes. The Fel Pro instructions say to 'use sealant on metal faced' gaskets. I'm assuming this is meant for steel shim type head gaskets. Is this correct? ..

Should the stainless steel armor of the gaskets I will be using receive some type of sealer on the metal portion, only? ..

Opinions are appreciated. I did this repair two years ago. I thought sure I wouldn't have to do it again! .. ..

rongold

The only type of head gasket that gets sealer is the original small block steel shim gasket. All late model composition gaskets go on dry. My 427/435 has Fel-Pro composition gaskets on it since 1989, and I installed them dry---still going strong with no leaks. They had the stainless steel bead around the cylinder bore just like yours--So far so good.



Just make sure that the heads and block are straight and not warped.

RON

Plasticman

Ron is correct, and I would add that the surface finish (especially of a newly machined head or deck surface) be checked for compatibility with the head gaskets you plan to use. Too coarse or too smooth a surface is not what most gasket makers recommend (depending on gasket type), but I have had heads that were way too smooth come back from being milled, only to have them redone properly. I have a Fel-Pro surface finish gauge that I use to compare the surface for the appropriate finish. MLS type gaskets require a very smooth surface, but most other composition and shim gaskets do not like it that smooth.

Below was lifted from a Fel-Pro Tips site and may not apply to your particular gasket type:

HEAD GASKETS
Surface Finish
Head and block surfaces can cause sealing problems if they are too smooth or too rough. Too smooth a surface allows excessive lateral motion of the head gasket, which can deform the combustion seal. Too rough a surface creates small leakage paths. Prepare the head and block surface in the 90-110 RMS (80-100 RA) range. That is just enough to feel with your fingernail.

Surface Flatness
To maintain constant contact between the gasket and the head and block, deck surfaces must start out flat and remain flat after the fasteners are torqued. The maximum initial "out of flat" as measured with a straight edge and feeler gauge should not exceed .0025" in any direction. To find out if the surfaces are staying flat during engine operation, it's necessary to "map" the used gaskets. Wipe them off and trace the outline on a piece of paper. Measure the thickness of the gasket body within 1/4" of every bolt hole and at a point midway between bolt holes. In addition, try to find an area of the gasket body that has not been compressed and measure the thickness there as well. The compressed areas should be .003-.004" thinner than the uncompressed areas, and all compressed thicknesses should be within .001-.002" of each other. If the compression is inadequate or uneven, the clamping force can be changed by raising or lowering the torque on the fasteners in those areas 5 lb-ft at a time. This will fine-tune the load on the gasket and result in less flange bending. Examine the gaskets again at the next tear-down. If they are evenly compressed, the head and block are staying flat while the engine is running. This reduces cylinder bore and valve seat distortion which makes more power.

The below was written by Larry Carley (a well known writer for Engine Builder Magazine plus other trade magazines):

HEAD RESURFACING. For years, most aftermarket gasket manufacturers have said surface finishes with a roughness average (RA) of anywhere from 55 to 110 microinches (60 to 125 RMS) are acceptable. The preferred range they have recommended is from 80 to 100 RA. Even so, as long as the surface finish on the head and block end up somewhere between the minimum smoothness and maximum roughness numbers, there shouldn't be any cold sealing or durability problems with the head gasket (assuming everything is assembled correctly and the head bolts are torqued in the proper sequence and to the specified torque).

But like everything else, these numbers have been changing. These recommendations were primarily for older cast iron heads on cast iron blocks. As castings have become lighter and less rigid, the need for smoother, flatter surfaces has become more important. Consequently, some aftermarket gasket manufacturers now recommend a surface finish of 30 to 110 microinches RA (roughness average) for cast iron head and block combinations, with a preferred range of 60 to 100 microinches RA for best results. For aluminum heads, the numbers are even lower. The typical recommendation today for an aluminum head on an OHC bimetal engine is a surface finish of 30 to 60 RA, with the preferred range being from 50 to 60 RA. If the surface finish is too rough (more than about 60 RA), the metal will bite into the gasket and pull it sideways as the head expands and contracts. The cumulative effect over time can cause a delaminating effect in the gasket, literally tearing it apart causing it to leak and fail.

Some engines require an unusually smooth finish. General Motors 2.3L Quad Four, for example, requires a surface finish of 27 to 47 RA for the OEM head gasket. But some aftermarket gaskets can tolerate a rougher finish on these engines.

Ford specifies an even smoother finish for its 4.6L V8 engine. This engine, like many late model Japanese engines, uses a multilayer steel (MLS) head gasket. The MLS gaskets are extremely durable because the multiple layers of metal (each of which is coated with a thin layer of rubber) prevent the gasket from losing torque over time. The design also reduces the amount of torque that's required on the head bolts to seal the gasket, which in turn reduces cylinder bore distortion for better combustion sealing and reduced blowby. The recommended surface finish for the OEM gasket on the 4.6L V8 is 8 to 15 RA! But as in the case of the GM Quad Four, aftermarket gaskets are available that can tolerate a more traditional surface finish.

Though most gasket manufacturers do not specify a minimum smoothness spec for aluminum heads that have MLS head gaskets, they do recommend a minimum of 30 RA for engines with aluminum or cast iron heads that use nonasbestos or graphite head gaskets. The reason for doing so is because soft-faced head gaskets require a certain amount of lateral support from the head and block.

When the head is bolted to the block, the metal on both sides bites into the gasket to help hold it in place.

You don't want too much bite when the head is aluminum and the block is cast iron. Yet a certain amount of support is necessary to keep the combustion gases in the cylinders from distorting the gasket and blowing past it.

This is especially critical in the areas with narrow lands and between the head bolts where there is nothing to keep the gasket in place but the gasket itself. In high output or heavy-duty applications where combustion pressures exert even greater force against the head gasket, a surface finish that's below the minimum smoothness spec might lead to premature gasket failure.

Achieving the smoother surface finishes required for many of today's engines takes careful work - and sometimes new equipment.

Several equipment manufacturers admitted that the spindle and bearings in older milling and grinding equipment may not be able to meet the resurfacing requirements of today's engines.

So new equipment may be needed to produce the super fine finishes required for some of today's applications.

The gasket manufacturers don't care what type of resurfacing techniques or equipment is used as long as the RA numbers end up in the recommended range.

For MLS type gasket applications, though, and even some of the aluminum heads that require a smoother than usual finish (like the 2.3L Quad Four) milling or grinding may be the only way to achieve the lower RA numbers.



Plasticman

mrg

Thanks, Ron and Plasticman. .. The heads were checked for straightness and pressure tested for leaks.
Both heads checked out ok. The old head gaskets appeared to be in good condition, as well. It's looking like one of the intake manifold gaskets failed and that's what allowed coolant to enter the engine.

Interesting read on the Fel Pro tips article. Thanks for posting it, Plasticman.

Shurshot

Hold up a second !!!

You need to confirm the part number of your gasket is not suppose to be used in conjunction with sealant. It is a common mistaken belief that just because it has the blue coating that there us no sealant called for and NOTHING could be further from the truth

FEL PRO MAKES BLUE TEFLON GASKTS THAT REQUIRE SEALANT AS WELL AS BLUE TEFLON GASKETS THAT DO NOT !!!!

On top of that their racing performance ones ones are the ones that call for sealant. When I put my motor together I followed the advice of an engine builder who said the same thing as you have heard and I installed a blue Teflon pan gasket without any sealant. Then I had a "sometime" real bad leak that I could not confirm the source of until last week.

Turns out mine requires it but does not have it. Consequently when I am accelerating after a left turn (and in conjunction with the motor slinging oil to the left), the oil runs up along a windage tray oil right up to where the gasket is that is suppose to have sealant but does not ...... then at a high rpm I suddenly have clouds of smoke as the oil squirts out and hits my headers.

So I checked with Fel Pro and found out that they make two gaskets that look exactly alike but call for different installation procedures regarding sealant.

Fed Ex delivered my new gasket yesterday

Doug