HI i just removed material from my head do you need to cut the same amount into the squish area that you remove from the head thanks when i hit the gas at half throttle it pings and knocks real bad

 

how much did you take off? are you running high enough octane fuel for what you removed?

 

Why did you cut the head to clean it up or to get better hp?

 

I cut mine 20 thousands and didn;t thouch squish.I have no pinging issues on 93. How much did you cut it?

 

I took it all the way down to were it was flat and reshaped the chamber and have some porting done

 

Wow! if it's a 250 you need another head to start with. If it's a 400 then the chamber will have to be opened back up and the squish clearance set at around .055. A lot of times on a stock head you cannot flat mill the head until the squish is right without throwing the compression ratio through the roof.

 

ok it's a 250 and i did open up the chamber so how much squish do i need

 

What are you guys doing about your timing after making these modifications?

 

If the compression is kept within the limits of pump gas then timing doesnt need to be changed. A 250 should have around .045 minimum, but can go up to .060 without ill effects. The before mentioned .055 would be safest minimum for the 400. GOOD LUCK!

 

what are the ill effects that could happen and for high compresion should the timing be retarded or advanced