302 head gasket - Team Camaro Tech
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post #1 of 25 (permalink) Old Feb 18th, 10, 06:32 PM Thread Starter
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302 head gasket

Hello everyone. I have all gaskets except head gaskets for my stock DZ engine rebuild. Short of asking that proverbial "MAD" magazine stupid question and getting that almost always snappy answer I have seen posted, what Felpro gasket number should I use? My block is not decked and it is within specs according to the machine shop. The 186 head surfaces are nice as well, just had a slight clean up to true them. I also had a set of .030 12.5 Speed Pros cut down to 11's. What is recommended for thickness? Would the .028 (I think it's that one) shim gasket be ok with copper sealer or whatever, be ok? There is 93 octane in my area.

Thanks

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post #2 of 25 (permalink) Old Feb 18th, 10, 08:24 PM
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Re: 302 head gasket

You got to consider QUENCH is best between .035" to .044". You say, other then a .030"+ Bore, the Block is OEM spec meaning it has not been decked and the pistons are .025" down in the Cylinder. The Stock Steel Shim compresses to .019". Now add the 2 together .025" + .019" = .044" = Quench; therefore, you need to use a .019" gasket. NO composite gasket is this thin ;o)

You can paint the Gasket with good old Indian Shellac, Copper Sealer or Hi-Heat Aluminum Paint to use as a sealer.

Quench over .044" can promote ping and possibly detonation because the flame from the explosion escapes the combustion chamber and travels across the top of the piston creating a shock wave rattling the piston. Most of to days engines do not use a quench area and the whole top of the piston is exposed to the initial combustion.

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post #3 of 25 (permalink) Old Feb 18th, 10, 08:52 PM
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Re: 302 head gasket

Gary,
Personally I would use the standard FelPro 7733PT2 composition gasket. If you want to use a steel gasket go with a Cometic or Fel Pro MLS type. I have seen too many shim gaskets on disassembled engines and they almost always show signs of leaking somewhere Cometic will make a MLS gasket in .028, possibly even thinner. The MLS design is completely different than the old stye single layer shims and they really seal well.

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post #4 of 25 (permalink) Old Feb 18th, 10, 10:24 PM
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Re: 302 head gasket

Quote:
The 186 head surfaces are nice
Your one step ahead with a touch up resurfacing. If the Engine Deck is reasonable that is not rust pitted or has rough machine cuts. The Stock GM Steel Shim Head Gasket will do it's job. After all GM used them. The old Indian Shellac applied to the Head Gasket works believe me.

If you are concerned about minor Deck imperfections you can use a Flat Steel Bar or thick piece of Flat Glass wrapped with 400 Grit Wet Sand Paper and Wet Sand, passing over the entire deck surface several times.

Both the Cylinder Head and Deck surfaces have to be spotlessly cleaned with Lacquer Thinner before installing any head Gasket.

The primary cause for failure of a good head gasket installation is the failure of the builder to re-torque the cylinder heads after an hour or so of engine operation and this applies to both the Steel Shim and Composite gaskets.

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post #5 of 25 (permalink) Old Feb 19th, 10, 09:03 AM Thread Starter
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Re: 302 head gasket

I appreciate the replies, thanks.

I didn't have the block decked for the one obvious reason, but I was told it didn't need to be done anyway. All the pistons are .021 down from the deck from my point of view. I first checked at .025 and I could feel the gauge higher then the deck surface so I am assuming it's .021 after checking from .025 to .021. Driverside deck surface looks to have no imperfections and the passenger side has 2 small smooth spots and I can't hardly feel those. They just look darker in color than the rest of the surface.

So with that info is there a concrete answer to what I should use? Or just pick from all the above? It appears there are pros and cons to this. In the past I have just used what my engine builder friend supplied when I got a gasket set, which were composite, but all I need is the head gaskets and I only want to do this once.

I gotta tell ya, this is nerve racking. After spending the cash to do this rebuild, the balancing, getting all the components weighing the same, I don't want anything to go wrong. I'd be afraid to tach it up like some have done. How do you do it?

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post #6 of 25 (permalink) Old Feb 19th, 10, 10:16 PM
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Re: 302 head gasket

Well at 11:1 Static with the appropriate 302 cam your will probably need at least 93 or 94 Octane. Be aware that a quench between .044" to approx .060" crates a shock wave which escapes from the combustion chamber and travels across the top of the piston; hence, knock or ping and rattling the piston. A quench greater then .060" makes a full open chamber which these engines are not designed for. GM designed the engine to use a .019" Gasket and the gasket works providing you follow the procedure to install it.

The other alternative is to "0" deck the block and run a .039" composite Gasket; but then you loose the Engine Stamping, if that's what you are referring to as; "for obvious reasons."

I run a .019" shim gasket in my 10.2:1 Static 600Hp SR MK IV for the very purpose GM designed the QUENCH Area and have no issues with Leaks and no problems with Knock running 91 or 93 Octane.

Clean/use Indian Shellac and Re-Torque after about an hour of run time. Re-Torquing really has nothing to do with the Head Gasket. It Re-Sets and evens the Interface Pressure between the Cylinder Heads and Block caused by Heat Stressing and sets the Head Bolts back to Specs. The Head Gasket just happens to be sandwiched and appreciates even pressure.

Obviously tearing a Hi-Mileage engine down you may find Head Gasket anomalies; but, the Head Gasket was most likely not the reason for rebuilding the engine.

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post #7 of 25 (permalink) Old Feb 20th, 10, 08:29 AM
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Re: 302 head gasket

Gary;
I used the .028 Mr. Gasket Part Number 1134 Ultra-Seal Head Gaskets as my pistons averaged .010" to the deck. This gave me a good quench setting. How low to the deck are your pistons?
Todd

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post #8 of 25 (permalink) Old Feb 20th, 10, 08:36 AM Thread Starter
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Re: 302 head gasket

Quote:
Originally Posted by Z15CAM View Post
Well at 11:1 Static with the appropriate 302 cam your will probably need at least 93 or 94 Octane. Be aware that a quench between .044" to approx .060" crates a shock wave which escapes from the combustion chamber and travels across the top of the piston; hence, knock or ping and rattling the piston. A quench greater then .060" makes a full open chamber which these engines are not designed for. GM designed the engine to use a .019" Gasket and the gasket works providing you follow the procedure to install it.

The other alternative is to "0" deck the block and run a .039" composite Gasket; but then you loose the Engine Stamping, if that's what you are referring to as; "for obvious reasons."

I run a .019" shim gasket in my 10.2:1 Static 600Hp SR MK IV for the very purpose GM designed the QUENCH Area and have no issues with Leaks and no problems with Knock running 91 or 93 Octane.

Clean/use Indian Shellac and Re-Torque after about an hour of run time. Re-Torquing really has nothing to do with the Head Gasket. It Re-Sets and evens the Interface Pressure between the Cylinder Heads and Block caused by Heat Stressing and sets the Head Bolts back to Specs. The Head Gasket just happens to be sandwiched and appreciates even pressure.

Obviously tearing a Hi-Mileage engine down you may find Head Gasket anomalies; but, the Head Gasket was most likely not the reason for rebuilding the engine.
Thanks for the info.

Unless I hear differently I will go with the .019 shim gasket and the Indian Shellac.

I can get the gasket still at GM correct? How about the Shellac, where do I get that?

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post #9 of 25 (permalink) Old Feb 20th, 10, 08:44 AM
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Re: 302 head gasket

Gary;
I didn't read what your piston to deck measurement was? If .036" is ideal quench then whatever your piston to deck is from that is what is ideal. I think Indian head shellac would work fine. But agood modern gasket is ideal also, and gaskets have come a long way. Are you using new head bolts or studs?

Todd

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post #10 of 25 (permalink) Old Feb 20th, 10, 09:10 AM
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Re: 302 head gasket

Use the GM .028" comp gasket. For a stock 30-30, 11:1 pistons, 63CC heads, stock deck they work fine. With good jetting and advance curve they work great on pump 91+ octane. I am pretty sure the original shim was .015". JM recommended the .028: gaskets.

C'mon, Ron. We have been over this.

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post #11 of 25 (permalink) Old Feb 20th, 10, 09:31 AM Thread Starter
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Re: 302 head gasket

Quote:
Originally Posted by VI018DZ View Post
Gary;
I used the .028 Mr. Gasket Part Number 1134 Ultra-Seal Head Gaskets as my pistons averaged .010" to the deck. This gave me a good quench setting. How low to the deck are your pistons?
Todd

They are at .021. At least that's the way I feel it when I checked. Flush with the surface. I haven't had to buy a head gasket set before just complete engine sets. This choice needs alot of thought.

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post #12 of 25 (permalink) Old Feb 20th, 10, 01:32 PM
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Re: 302 head gasket

Gary: Well he's got pretty well a full PIC Gears Heads have when choosing Head Gaskets - Now it's up to him.

Do not think that I do not respect your knowledge when it comes to the 302 engine ;o)

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post #13 of 25 (permalink) Old Feb 20th, 10, 03:38 PM
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Re: 302 head gasket

OK, I'll step in it. What is Indian shellac?

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post #14 of 25 (permalink) Old Feb 20th, 10, 03:44 PM
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Re: 302 head gasket

I was in Advance Auto Parts today picking up some thread sealer when low and behold....there it was right next to it...."Permatex Indian Shellac".

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post #15 of 25 (permalink) Old Feb 20th, 10, 06:53 PM
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Re: 302 head gasket

From what I observed growing up with SBC's, GM never had issues with Head Gaskets until around 74 when Emission Equipped Engines did in fact blow head gaskets in their attempt to meet the EPA STD's implementing EGR, O2 Pumps, Throttle Stops, Charcoal Filters ... etc (In Canada). The engines ran Hotter and used thinner castings particularly in regards to Block Deck and Cylinder Heads. If you had any problems with the Cooling System you more then likely warped Heads and destroyed Head Gaskets. It was also around this time the Modern Composition Gasket evolved and the issue became a concern among Gear Heads.

I agree that the Newer Composite Gasket is superior; however, if you exceed GM's Spec's regarding Quench you risk improper combustion and rattling pistons. I can't see why using a Shim Gasket to meet Design Specs should be a risk if there are NO Emission Devices or Thin Castings and surfaces are smooth; just adhere to the procedure for installing Metal Gaskets followed with the recommended Re-Torquing and there should be no problems.

You would think the topic of Head Gaskets a minor issue but over the years it has enveloped; for example, I point out one and don't get into 13:1 Static or Aluminum castings which I really don't know much about. I believe one should have some history on the issue before making decisions as to what may be a reasonable and safe combination; after all, isn't TC a virtual environment to exchange information and learn about our common interest ;o)

I hope you find my input useful in making decisions about head gaskets. I wish I could use less words.

From the input, I consider this a great thread.

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Last edited by Z15CAM; Feb 20th, 10 at 11:23 PM.
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