GX390 compression ratio/fuel

2kdime

New member
So according to Vegas Carts site

Milling the head down requires higher and higher octane fuel, I get it.

But what would I need to run after 91 octane? Alcohol?

Hoping to get at least .100 off the head
 

fredjones

New member
So according to Vegas Carts site

Milling the head down requires higher and higher octane fuel, I get it.

But what would I need to run after 91 octane? Alcohol?

Hoping to get at least .100 off the head

I didn't...but I also took .200 off my head and .100 off the block...then its good to run 91 or higher. But when you do that and have a good cam you will have to fly cut piston for valve relief....no biggy
 

rkcarguy

New member
I think you can, but it leaves the top ring land fairly thin, something I don't like.
Unless you have a mill, better off buying the right piston.
 

2kdime

New member
Ok so milling the piston head flat is ok.

Just haven't looked at how thick the piston head is to see if it can be clearanced for the valves

What's the best way to locate where you need to cut and how much?
 
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