How can i calculate the head gasket volume ?

To give you a little onfo on what i looking to do is i have a set of forged diamond pistons part#11512 to use on a 6.0 block factory deck,6.125rods,3.622 stroke,.030 over with 11.8 cc head gasket volume and 70 cc chamber heads it make 10.3 compression ratio.
If i want to use fatter head gasket to increase the HGV,can put that motor in like 9.8 compression ratio to use a turbo?

 

Yes it probably can be done. You will need head gaskets approx .020/.025 thicker to achieve your goals.

This will work but not as well as you might imagine. Increasing the "quench" distance this much will seriously degrade detonation resistance. You will be at lower compression but will detonate at a lower boost level than the higher compression motor. You will make less power before it explodes...

Set your quench distance FIRST! I'd target .035-.040 and then remove material in the head to lower your compression ratio. Unshrouding the valves is usually worth something. Choosing valves that have larger "depressions" in them is another possibility. "Sinking" the valves can work as well (but it's not usually good for flow)

Starting with stock 317s might be called for. A serious FI build should be down around 9.0/1 IMO.

Don't destroy the attributes of good quench in an attempt to lower compression. This is the road to a large pile of damaged engine parts IMO.

Better to invest in race gas for the track and turn the boost down for street use.

Looking into an intercooler and/or water-meth injection is another way to "skin the pressurized cat"

Sorry Fast, I think you're shooting yourself in the foot here with the fat HG idea...

 

Head gasket volume is the same as calculating cylinder bore.

Bore*bore*.7854*stroke (thickness of gasket in this case) you will need to check the part number of whatever gasket you will be using as the bore of the gasket varies.

And I agree with the above, quench is where your power lies. Keep it at .035 to .040 and change your chamber/piston volume accordingly to get the desired compression ratio.

 

Thanks so much guys for you advise. Now i think is better to buy a set of pistons to do it the right way!

 

From my experience, boosted/nitrous engines don't care for quench, and wll typically run better with larger quench clearance.. It helps in naturally aspirated engines, but studies have shown it to be even less important as compression ratios are increased.

 

What studies?
Not being snarky here.
Your posts have always been accurate IMO.
I'd really like to see those. I've seen some exceptions to the "quench" rules but they have always been 4 valve "hemi" or pent roof designs where the quench pads were interfering with intake/exhaust flow and due to the spark plug being centrally located detonation was far less critical.

Were these studies applicable to street driven LS head style engines?

I'd really like to see those...

 

A man named Charles Taylor wrote two books titled The Internal Combustion Engine, Volumes 1 and 2. These two books detailed tests he conducted at MIT while he ran the Sloan Labratory there, with combustion being a heavily researched subject for him.

My understanding from the results were that quench was more of a "crutch" for a less than ideal piston and chamber design, with the ideal design often unachievable due to other design constraints. In the tests, no matter the chamber design, a tight quench had a more dramatic effect on 8:1 CR than a 10:1, and continued to diminish as CR increased.

I'll pull the books tonight after work and see if I can expand I this a little more.

 

Cool, fresh reading material to purchase!
Thanks for the info...

What was the dramatic effect? What was measured?

Was detonation intentionally triggered? How?

Being it's from MIT it probably will not have any "spin" on it. That's the type of info I prefer.

I'm going to read those as quickly as I can find them but I still think the LS style head is far from "optimal" in regards to the OPs question of using a thicker head gasket.

I believe the common OHV V8 head design (in-line valves, non cross flow, spark plug offset to one side) burning standard gasoline on a bore greater than 2.5 inches will benefit from some form of quench regardless of compression ratio or boost level.
Removing or reducing it is a mistake IMO.

If I was going to change pistons to reduce compression I'd get a set that maintained the current quench the engine has now (often referred to as D shaped dishes). The flats on the top of the pistons should match the flats present on the heads. I also believe the strongest/lightest piston design are true flat tops and I'd lean toward a larger head casting over replacing pistons. Now for a FI motor forged pistons are not a bad idea. If the OP has stock pistons some nice D shaped dished forged pieces may be a good compromise. Forged pistons will probably require a slightly larger quench distance as heat cycle growth and the required larger bore clearances create the need for more "wiggle" room.

Most current production engines (which now average over 10:1 comp ratio) have some form of quench built into them by design. Reducing burn distance (time) appears to have no negative attributes, reduces fuel consumption and emissions, and improves power output.

Now, I'm old enough to realize that:
I've been wrong before...
I will be wrong again...
And the laws of probability state I'm overdue anyways...

Now, I get to find a copy of the afore-mentioned books, do some reading, and decide if I'm as full of it as my Wife has suggested on many occasions.

Thanks for the references again KCS.

Cheers!

Rick