The thinner head gaskets will give a minimal increase in compression and they are pretty pricey at around $100 a pair for the cometics...depending on machine shop charges usually it would be cheaper to mill heads 0.030 or 0.040" and you pick up substantial compression around like half a point or more..

 

its basically 0.013" difference between the gaskets which is not a TON but should allow better quench. Now, doing BOTH would be best of both worlds.

 

No doubt...just cheaper to mill, them cometics are expensive

 

While the benefits are minimal for either, a .040 gasket will increase compression around .3 and provide a better quench which is beneficial. Milling plus mls gaskets will probably be more expensive than cometics plus milling reduduces flow and can increase valve shrouding. I reccomend both, but fact is fact if its one or the other the thinner gasket is the better option.

 

Even at a 10 or 20 thou its going to make THAT big of a difference on fill? High lift or low lift scenario?

 

An .030" mill isn't going to be enough to shroud the valves to the extent your talking, a stock head gasket is 0.050, so picking up 10 on the head gasket doesn't have near the benefit of compression increase of 3 times that with mill, I didn't think the milling was that much $$...

 

Milling isn't much $. I just wanted a reliable 11:1 that I do not have to worry about detonating on 91 oct which is why I wanted the thinner gasket to increase quench.

 

What would milling the heads cost about roughly? If it's $50 and MLS gaskets are around $50 it would be cheaper to go just the cometic gasket route which are anywhere from $85 to $103 depending on bore size.

Let me edit that, those prices for cometics are for 1 only!! So $85-$103 each. http://www.texas-speed.com/p-2258-co...3910-bore.aspx

 

Remember the pistons are out of the hole about .007-.008".
I think .035" quench is safe. Kind of leaves you with the .045" gasket, and they are spendy.

On 91, I'd concentrate on quench first, CR second.

Just my opinion.

ron

 

I don't mind spending money on gaskets. It is cheaper than chunking a piston and doing a rebuild due to detonation. I value your opinion for sure.

Even a small mill on the head would be a good idea to get the cometic to seal properly. But.. what about the block finish? Will I have to get that decked with a cometic? Or just get some copper spray?

 

90 whp...

 

.030 is good on these engines.

 

It looks like cometic offers thinner gaskets even... 0.027"

http://www.jegs.com/i/Cometic-Gasket...ductId=2848860

Maybe a bit too much quench?

To the poster above, 0.030 total quench?

So since the pistons come out about 7 thou, can run the 0.036 gasket and be around 30 like you say...

 

If this is street then .03x is the tightest I would go.

 

Yup street car. Ill measure how much it comes outs hole. Seems usually 7 thou. 41 gasket @ 7 thou is 34... 36 puts me at 29...