Alright I would like to get a few opinions here.

What gaskets are most of you using on SBE with high boost? I'm not looking for someone to just blindly tell me to run an LS9 gasket (I wont run them anyway). I want to know what you like and why you like it. What features or specs made you take that path.

Starting with the bore - How much larger than the bore of the motor would be ideal?
Thickness - How many layers? How much quench do you find ideal for fairly high boost (18-20PSI)? This will be going on an iron 4.8 for reference. Do you not need as many layers on an iron block? I wouldn't think seeing as the block tends to flex less than alum.

Does clamping down on the head studs with increased tq really help? I will also be using stock heads, so lifting a head is somewhat of a concern.

For what its worth I have been leaning toward the .045" cometics which I believe are only a 4 layer gasket. I was thinking 3.91" bore, but I could be convinced a to go larger if there are in fact benefits - talking to a few people I have heard that moving the gasket further away from the bore helps them last longer in extreme examples. Being a smaller bore motor I didnt know if lifting a head becomes less likely as well? Seems to make sense in my own head...

 

I have .040 cometics on an aluminum 5.3L but the engine is not boosted. I believe there only 3 layers thick. The Deck grows approx .007 from what I'm told on the Aluminum block's.

In my opinion more layers would be more of a chance for the boost to creep, but I am no engineer...

 

I hadn't thought of it that way. Frankly, I had always thought the more layers in the gasket the further things can move around without losing solid contact.

 

Throw on some LS9s and party on!

 

Nah... I don't want to run an LS9 on a 4.8. 4.1" bore diameter on a 3.78" bore doesn't sound appealing to me...

That said I ran them on my 4.030" 370 without concern.

 

You may not wanna hear it but LS9 is widely recommended for a reason. I know it looks funny on a 4.8/5.3 bore. I chose to not reinvent the wheel and try it and its working well for me so far. Cant argue with success.

 

I failed a 3 layer LS1 gasket on a 317 headed ls1, torched the head out and catistafice failer. I've uses ls9's on everything ever since, 4.8's, 5.3's, 6L ect... Never failed one.

 

I understand it's a widely used gasket that has had incredible success. But I want to know WHY people love em... not just hear they work.

What 3 layer were you using?

 

more layer longer life span for gasket ,

if 4.8 is iron block ls9 gasket work well .

 

Without getting into the material science details (not that I know them anyway), the extra layers allow the LS9 gasket to withstand more shear stress and deformation before breaking the seal.