Valve Recession and Fel-Pro's head gasket..

[MasterChiefIDI]

Hi, I was wanting to see if someone could help me with a technical question. I am in the process of assembling my 7.3 idi and am taking protrusion measurements and valve recession measurements. For background, deck was decked .011" and I am using Mahle's .010" reduced pistons. I am using R&D's Stage 1 Cam.

With this combo, my tallest pistons and lowest valve combo is as follows:

Cyl1: Protrusion .031", EX valve recess: .049"
Cyl3: Protrusion .029", EX valve recess: .047"

Here are my questions,

1.) The International service manual calls for the below Valve recession:
- IN: 0.042-0.054
- EX: 0.051-0.063

But the AERA Spec says: (edit, the AERA spec might need to be double checked)
intake..............................(.042 - .052)
exhaust...........................(.046 - .058)

One say I'm OK and the other not OK.. I am more incline to follow international's spec. My very trusted head machinist followed the AERA spec.. But what are others experience here?


2.) Everywhere I read, the Fel-Pro 9047PT head gasket is said to be .010" thicker than factory as to provide some "forgiveness" when decking block for a rebuild. My uncompressed thickness is .072". I called Fel-Pro to ask what the compressed thickness is for this gasket and if it were true it was in fact .010" thicker than stock. They said "compressed thickness is .060" and no, it is not .010" thicker than stock and that .060" was similar to other idi head gasket makers out there.." The .060" sounds more like stock compressed thickness to me and seem hard to believe .072" will compress to .060" but may be not? Is the tech I spoke to mistaken or is this gasket actually .010" thicker?

Reason I ask, is I am concerned my valves may not be recessed enough on Cyl1 and Cyl3 and could collide with piston but if the FP gasket is .010" thicker, I should be golden.. Maybe the best approach is "claying" the valves and seeing that way? Has anyone else done this?

Thank you

 

[MasterChiefIDI]

This thread is so helpful for how to approach the clay piston to valve clearance with clay, solid lifters, and adjustable push rods! I guess I will prepare to to take these measurements and hope for .030" clearance, .015" minimum.

Oilburners.net https://share.google/DZ8bGvnvJEQCCWQ5k

 

[IDIBRONCO]

2.) Everywhere I read, the Fel-Pro 9047PT head gasket is said to be .010" thicker than factory as to provide some "forgiveness" when decking block for a rebuild. My uncompressed thickness is .072". I called Fel-Pro to ask what the compressed thickness is for this gasket and if it were true it was in fact .010" thicker than stock. They said "compressed thickness is .060" and no, it is not .010" thicker than stock and that .060" was similar to other idi head gasket makers out there.." The .060" sounds more like stock compressed thickness to me and seem hard to believe .072" will compress to .060" but may be not? Is the tech I spoke to mistaken or is this gasket actually .010" thicker?

I don't think that I compared them to a stock head gasket, but they ARE .010" thicker than a Victor-Reinz head gasket. Both compressed and uncompressed.

 

[ROCK HARVEY]

How much variation in valve recession do you have across all of them?

When I did my heads I measured how deep all of my valves sat in the same hole so I could sort them thickest to thinnest, then I measured the depth of all of the seats using the same valve so I would know the relative depth of each seat. Then I matched the thick valves to the deep seats so all the cylinders would be as close as possible. Can you do something like this, or are they all already really close together?

 

[ROCK HARVEY]

Another option could be to get a head spacer shim. Rock Auto sells a .020 shim, SBI part #2302140. It’s out of stock right now, hopefully it’s not one of those parts that’s on their website but never in stock.

 

[FrozenMerc]

Clay the pistons to check valve clearance. The Exhaust valve is typically the one that will hit in an over speed or valve float situation as the piston chases the valve close. That said, I doubt you will have a problem.

 

[MasterChiefIDI]

How much variation in valve recession do you have across all of them?

When I did my heads I measured how deep all of my valves sat in the same hole so I could sort them thickest to thinnest, then I measured the depth of all of the seats using the same valve so I would know the relative depth of each seat. Then I matched the thick valves to the deep seats so all the cylinders would be as close as possible. Can you do something like this, or are they all already really close together?

Attached are my recessions and protrusion measurements. The others that have EX valves out have lower protrusion that I don't expect to have issues from. Recession is fairly close together

Another option could be to get a head spacer shim. Rock Auto sells a .020 shim, SBI part #2302140. It’s out of stock right now, hopefully it’s not one of those parts that’s on their website but never in stock.

HOW DID I NOT KNOW THIS EXISTED. Wow. I literally trashed a block because it had .010 too much decked off of it due to machinist error. Had 8 new sleeves in it. Ugh.

Clay the pistons to check valve clearance. The Exhaust valve is typically the one that will hit in an over speed or valve float situation as the piston chases the valve close. That said, I doubt you will have a problem.

Good info on the mechanics! Clay will be next. I can share back here after.

Thank y'all for your thoughts.

 

[MasterChiefIDI]

For anyone interested, I plan to use Comp Cams 7706-1 push rod checkers to take up lash coupled with a few old modified lifters made to be solid lifters, torqued down FP head gasket, and clay from there.