Head Gasket Steel Shim Style

[COPOZ/28]

This is a head gasket preparation question.  I've received all my OEM '69 302 parts back from the machine shop and the block decks required about 0.008" to clean up, with the resulting deck height coming in at 9.011".  For head gaskets, I can choose between the modern Fel-Pro 0.038" composition part, the Chevy p/n 10105117 0.028" composition part, or the '69 OEM 0.016" steel shim part.  Knowing a tight piston to head quench distance (i.e.: "squish") of 0.036"/0.038" helps to fend off detonation, the 0.016" steel shim gasket gets me to this nice 0.038" squish, but the final actual compression ratio comes out to 11.08:1.  Stepping up to the thicker 0.028" Chevy '117 gasket drops the true CR down to 10.8:1 but increases the squish to 0.050".  Since I have used (and plan to continue to use) ACES IV mixed with 93 octane fuel successfully, I believe I can tolerate the 11.08:1 CR the steel shim gasket gives and plan to use it for this assembly.  My question has to do with how best to prep the "old fashioned" steel shim head gasket to avoid long term future coolant leakage.  Back in the day, the only steel shim head gasket prep I am aware of was spraying a light coating or two of aluminum paint on each side of the gasket, letting it dry and then installing/torquing the heads, followed by a retorque after it's first hot start/cool down.  I've heard of some folks laying on a very thin coating of Perma-Tex Gasket Maker (p/n 51813) around the gasket's coolant holes in addition to the aluminum paint spray.

What have others found that work long term for prepping the old style steel shim head gasket?  Thanks a bunch!

I forgot to mention all the "internals" are OEM '69 302 -- the cam, pistons, intake, carb, etc.
Chuck B.

[Stingr69]

How far down the hole are your piston decks?  Original piston decks are usually about .025" down in the hole before the block is cut.  Assuming a 9" piston deck with a stock compression height piston and an original 9.025" block deck cut .008", you would be about roughly .017" down in the hole at TDC. 

Ignore the compression variance and shoot for .040" minimum clearance quench as ideal.  Too tight quench scares me especially with the 2618 high expansion rate forged pistons. Cold pistons with a typical .005" clearance can get noisy at start up.  The pistons will "slap" a bit until they get to operating temp.  That rocking at TDC when cold might get the pistons too close to the heads.  Anybody else worry about it?

As for steel shim gaskets - I use Permatex Copper Coat spray on both sides of the steel shim gasket.  Hang up the gasket and spray it on.  Let it get tacky before installing it.  Never had a failure.

[Kelley W King]

I have used the copper before. Also used nothing many times except clean surfaces. Never heard of using gasket sealer on them. Only trouble I recall was caused by the holes in the gasket were not exactly correct. Was probably an cheap after market I used when that was all I could afford.

[COPOZ/28]

My pistons all mic'd out at 0.022" +/- 0.001" down the hole.  The piston skirts were treated to the abradable coating from Line2Line in Clarkston, MI for a thumb pressure "push fit" into the cylinder, so that should reduce any piston rocking to the least possible amount and contribute to good, long term ring sealing.  Will follow their recommended dyno break-in cycle to optimize the skirt to wall fit.

[Everett#2390]

I always used steel shim gaskets and I would prepare the head surface and block deck with a new honing stone and WD40 to lube.
Remove dowel pins and hone away until surface scratches are gone all most a mirror finish - very smooooth.
Then file a flat on dowel pins the length as this action lets air escape when installing pin.
Honing stone is the same stone used to sharpen/hone your pocket knife, use the light colored side.
Wipe off WD40 on all surfaces and cylinder bores.

[rszmjt]

I always used steel shim gaskets and I would prepare the head surface and block deck with a new honing stone and WD40 to lube.
Remove dowel pins and hone away until surface scratches are gone all most a mirror finish - very smooooth.
Then file a flat on dowel pins the length as this action lets air escape when installing pin.
Honing stone is the same stone used to sharpen/hone your pocket knife, use the light colored side.
Wipe off WD40 on all surfaces and cylinder bores.

I’m Just wondering why you would file a flat on the dowel pin ? It’s not a blind hole, it goes into the water jacket on SBC, or am I missing something? Not to question, but wondering?

[firstgenaddict]

Above recomendation is great for flattening the deck for a steel shim.
To check truness - There was a long thread on this subject on the NCRS boards a few months ago... basically take a straight flat bar- and a feeler gauge and use to check the truness of the decks.

[Everett#2390]

Apparently, my mistake on GM (Chev) engines). Some manf's are a blind hole for releasing air when driving dowel in place.

Certainly the person is going to check the hole configuration for a relief flat needed or not.
Put dowel pins in freezer for easier insertion.

Let me get the next round of ice cream.

[usa1ti]

Run the .041 Fel Pros for long term reliability and slightly lower compression. Have to be very clean at assembly and really flat deck / head for the steel shims to work well. I don't run those on my high compression race engines anymore. Fel Pro or Cometic only. Ive got a 11:1 302 and 2 12.5:1 427s with the Fel Pros now. All 3 run on premium with 10% ethanol fine. Back a little timing out and the ethanol covers the rest.

[firstgenaddict]

Here is a link to the NCRS discussion on Steel shim
https://www.forums.ncrs.org/showthread.php?126624-Compression-Ratio-Calculations-and-Head-Gaskets

[70z28lt1]

There is also a very nice Chevrolet Performance MLS gasket in 0.028 compressed thickness available that may be worth a look.  Much less cost than Cometic.
https://www.summitracing.com/parts/nal-14096405

[firstgenaddict]

Run the .041 Fel Pros for long term reliability and slightly lower compression. Have to be very clean at assembly and really flat deck / head for the steel shims to work well. I don't run those on my high compression race engines anymore. Fel Pro or Cometic only. Ive got a 11:1 302 and 2 12.5:1 427s with the Fel Pros now. All 3 run on premium with 10% ethanol fine. Back a little timing out and the ethanol covers the rest.

With 10% ethanol you should richen your jets a little and then you may not have to drop the timing out 10% mix is 4-5% lean - running a slight bit more fuel should allow you some more timing.

[TODD]

Chuck; Aren't the 3830711 chevy steel gaskets .021"? If so that would be ideal at .022" in the hole. I was .018" in the hole and went with .028" gaskets. Runs great at 12.5-13.5 afr no detonation.

[dutch]

Fel Pro 1094's? = 0.015"