Piston to valve clearance limits?? Engine guru's please read

[Streamln1]

Got a question for those of you that know specs for milling etc.

Here's the situation -

Over the years my heads have been milled a few times.....Before reassembly this time I measured out the heads, they are at 5.170" height, which is about .020-.015 less than stock.

I knew this was beyond the limit, so I compensate by running head gaskets that are .015" thicker so that brings the spec back to what would be normal limit of about 5.185"


Also the engine block has been milled once, it has about .002" max taken off.

So by my calculations, with the thicker head gaskets I am at about .002" over spec, not a lot but I want to make sure I am not going to run into problems.

I have not done anything to actually measure the piston to valve clearance I/e using molding clay, I do not want to ruin one of my head gaskets by taking it apart again and decompressing the head gasket.

So can we figure by the above specs?

[ItTricky]

With that thicker gasket wouldn't you stand a higher chance of blowing it out as it doesn't have near the integrity the block would normally? I don't know the specs,buttomorrow i can check some service info while at school and see if I can come up with some helpful information.

[Streamln1]

The thicker head gasket just adds 1 layer to the MLS, also the heads have been headlift fixed so they will not flex. I'm not worried about the seal, just the clearance.

The rebuild manual calls the service limit at .008, and the stock heads are anywhere from 5.193" to 5.120" unmilled.

[RealMcCoy]

The factory limit is primarily to maintain cam timing... With the belt crossing the head surface three times before it drives the front cams, it doesn't take much to throw the front cams off a degree or so.

You are in no danger of hitting valves unless you've got some pretty huge lift cams installed.... If you are willing to degree your cams, I wouldn't even bother with the thicker gaskets. ( Cometic I assume? ) I think you'll find the OE gaskets have a better reputation for durability.

[Streamln1]

Cometic is correct.

I have run them for years, no problems here. And they make a 93mm bore gasket which OE doesn't.

I know DSM guys had issues with them because the embossing was not deep enough, but on these it looks as good as stock. I can't find a single 3/S that is running them that has problems when I search.

I suppose we will see with big boost, I also have A1 studs and the head mill was damn near mirror like. I had no problems at 20psi.

Just pulled her apart to do new forged rods and then found out I had some corrosive coolant action going on that needed to be fixed.