Is is possible to have my heads milled to increase the compression ratio? If so, what would I need to increase it by .5 to make 10:1?

 

Yes.

How much depends upon crown to deck height, head gasket compressed volume, and chamber volume.

 

what do I need to do to figure this out? I'm using standard gasket size as far as i know. The heads are stock 416 heads with bigger valves.

 

Measure the distance from the piston crown to the block deck at TDC.

CC the chambers.

Pick a head gasket that gets you .040" from crown to head. The gasket manufacturer should be able to provide compressed volume.

Mill the heads to get the CC's that give you the CR you want.

 

lol, no guessing then eh? Ok thnx for the info i'll try to get this put together. How do I CC the heads? The heads are stock except the valves, isnt it like 58cc?

 

Like 58cc. Or 56cc. Or 64cc.

Manufacturing variation, don't ya know.

 

Why .040"? A thinner gasket will effectively increase the CR (in addition to milling the heads) and will also help the quench properties.

 

Any tighter than .040 and you risk the piston kissing the head.

Notice he's talking about piston-to-head clearance, not gasket thickness.

 

If you installed larger than stock valves in your 416 heads the chamber is now different than stock. Usually the chamber wall has to be clearanced some to get the valve in.
So the chamber is now larger then stock. (58cc)
The only way to determine the size of the chambers on your modded heads is to cc them. ( its' not hard to do)

You can raise the compression ratio of your motor from what ever it is at now to about .5 a cr higher by just changing the typical .040" replacement head gasket for a thin .015" steel shim head gasket. All that is required is a clean straight block decks and head decks. The pistons must be a minimum of .018" below the top of the block deck @TDC. This clearance combined with the .015" gasket thickness would be .033" total. Thats about as tight as you'd want to run it. Most stock blocks that have not been decked have a .025 to .045" deck clearance.

The only way to accurately determine your exact cr is to measure all the variables and calculate.

You can shave your 416 heads about .060" down to the intake valve seat. If you have 2.02's you cannot shave the heads as much as if you have 1.94's. (smaller seats)
I have reduced the chamber size of modded big valve 416 heads to 52cc's by shaveing them. But they were max shaved right down to the intake valve seat and spark plug boss. Because of the location of the spark plug near the deck theses heads do not lend themselves to angle milling.

But like I said the only way to determine how much to shave your heads is to accuratly determine the exact cr you have now.

 

aftermarket heads will probly ebe cheaper or high comp pistioons

 

It doesn't cost much to have heads milled, less than $100. I think milling my LT1 heads cost $80, but i can't really remember, i'd have to find the receipt.

 

Around here milling is about $30 CDN a head. Milling, valve grinding and assembly is $100 a head.