Is this the same as saying "Porting Heads?"

TIA,
Jason

 

Milling is the removal of the deck material on the combustion chamber side. What is happening is the combustion chamber volume is reduced which is raising compression.

Porting is opening up and reshaping the intake and exhaust ports.

 

Not the same term.

The surface of the head that contacts the head gasket is machined off (the entire surface) a certain amount to raise compression ratio.

Tony

 

Thanks guys, so would milling give me any horsepower?

This is the scenario:

Someone can mill me some heads for free.
What I need to know is it really worth it?
The mill would be done to a 00'WS6, Mac Headers, Borla Exhaust, Cutout, T1 Cam.

When you pull the heads don't you have to buy new head bolts and gaskets? Like $150/$200.00 right? That is why I ask if it is really worth it.

Jason

 

A .050 mill will gain you about one full point on compression ratio. So a stock LS1 will go from 10.1:1 to 11.1:1. Should see some increases in power.

 

about 3% increase in power for each full point of compression ratio.

Going from stock 10.1 up to 11.1 CR should get you about 9 rwhp on a 300 rwhp motor.

Tony

<small>[ March 18, 2002, 02:08 PM: Message edited by: Nine Ball ]</small>

 

I don't know what the numerical limits are, but there are limits to how much you can mill the heads before you run into problems with valve-to-piston clearance, depending on your cam and rocker arm ratio.

By milling the heads, you're putting the valves closer to the pistons at TDC, so be sure you have enough clearance or the result could be ugly.

Just my $.02! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

For the LS1 heads eveery .005" you mill off will give you a small combustion chamber by 1cc, so .050" will give you a 10cc smaller chamber. Making the chmaber in the LS1 that small will net you a gain of 1 1/4 points of compression. That means you'll be running a 11.25:1 compression ratio. To get 11:1 you would do about .040" off of the head. I really wouldn't go over that.

BTW the 1cc per .005" is from Lingenfelter via Marlan Davis in Car Craft

Bret

 

Are there any reasons you would not want to get heads milled by .030 if the heads were already off?

Thanks,
Chris